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PubMed1993

Laboratory and animal model evaluation of the Cryotech LCS 2000 in hepatic cryotherapy.

Hepatic cryotherapy is increasingly used in the treatment of patients with multiple hepatic metastases, particularly from colorectal cancer. The Cryotech LCS 2000 system, with insulated shaft-circulated liquid nitrogen probes, was designed for this purpose and was evaluated on the bench and in an animal model. The 9-mm probe was considerably more effective than the 5-mm probe when judged on time to create an iceball of a given diameter. The use of thawing gas reduced the time until the probe could be removed from 25 to 5 min but heated gas only produced a further reduction of 2 min. In the animal model, significant reduction in treatment times occurred with vascular inflow occlusion. The zone of necrosis as a percentage of the original iceball diameter was significantly higher following a twin freeze/thaw cycle. The relationship of the edge of the iceball to the eventual zone of hepatic necrosis was studied using different unabsorbable markers. India ink and sutures proved unreliable but a Teflon cannula was more successful and the margin was only of the order of 2 mm. The discrepancy between this observation and the percentage of the original iceball diameter which apparently becomes necrotic (64 and 82%) for single- and double-freeze lesions, respectively, suggests that the cryolesion undergoes shrinkage within 1 month and that the diameter of necrosis underestimates the true zone of destruction.

Animals↗
PubMed2001

Do denervated peripheral nerve trunks become ischemic? The impact of chronic denervation on vasa nervorum.

The long-term relationship between the peripheral nerve trunk and its vascular supply, the vasa nervorum, has not been considered in the context of denervation and regeneration. While the microvessels of peripheral nerve are not thought to influence Wallerian degeneration itself, in this work we explored how vasa nervorum respond to denervation of the nerve trunk. Our hypotheses were that the presence of axons had a significant impact on the vasa nervorum and that the absence of reinnervation might eventually lead to an unfavorable ischemic regenerative microenvironment. We studied rat sciatic nerve trunks for up to 6 months following transection and either prevented regeneration or allowed it to proceed. Vasa nervorum were studied in several ways: (i) measurements of local endoneurial blood flow using microelectrode hydrogen clearance polarography; (ii) measurements of erythrocyte flux (flow) in the extrinsic nerve plexus using laser Doppler flowmetry; (iii) India ink perfusion of microvessels in unfixed nerve; (iv) mRNA expression of vascular endothelial growth factor (VEGF) using reverse transcription polymerase chain reaction. Early after injury, there were rises in endoneurial and extrinsic flow, microvessel numbers, and VEGF mRNA expression. Angiogenesis was apparently confined to the epineurial and perineurial compartments. Later, however, there were substantial declines in flow observed in long-term (6-month) denervated sciatic nerve trunks associated with declines in the caliber of new microvessels. Reinnervated sciatic nerves had restored endoneurial blood flow. The findings confirm important relationships between axon presence and local blood flow. Angiogenesis is a feature of the injured peripheral nerve, but long term denervated nerve trunks have declines of flow despite retaining new microvessels.

Animals↗
PubMed1993

Inhalation toxicity of 1,6-hexanediamine dihydrochloride in F344/N rats and B6C3F1 mice.

1,6-Hexanediamine (HDA) is a high production volume chemical which is used as an intermediate in the synthesis of paints, resins, inks, and textiles and as a corrosion inhibitor in lubricants. Two- and 13-week studies of the toxicity of the dihydrochloride salt of HDA (HDDC) were conducted in male and female Fischer 344/N rats and B6C3F1 mice using whole-body inhalation exposure. Both species were evaluated for histopathologic and reproductive effects, and rats were examined for clinical chemistry and hematologic changes. In the 2-week inhalation studies, animals were exposed to 10-800 mg HDDC/m3, 6 hr per day. All rats, all female mice, and two of five male mice in the high-exposure group died before the end of the study. Surviving mice in this group had a dose-dependent depression in body weight gain. Clinical signs were primarily related to upper respiratory tract irritation and included dyspnea and nasal discharge in both species. Treatment-related histopathologic lesions included inflammation and necrosis of the laryngeal epithelium of both species and the tracheal epithelium of mice, as well as focal inflammation and ulceration of the respiratory and olfactory nasal mucosa. In the 13-week inhalation studies, animals were exposed to HDDC at concentrations of 1.6-160 mg/m3 for 6 hr per day, 5 days per week. In addition to the base study groups, a supplemental group of rats at each exposure level was included to assess the effect of HDDC on reproduction. No treatment-related changes in organ weights or organ-to-body-weight ratios occurred in rats, and no treatment-related clinical signs or gross lesions were seen in either species. Chemical-related microscopic lesions were limited to the upper respiratory tract (larynx and nasal passages) in the two highest exposure groups and were similar in both species. These lesions included minimal to mild focal erosion, ulceration, inflammation, and hyperplasia of the laryngeal epithelium, in addition to degeneration of the olfactory and respiratory nasal epithelium. HDDC caused no significant changes in sperm morphology or vaginal cytology and no significant adverse effects on reproduction in rats or mice. Hematologic and clinical chemistry changes in rats were minor and sporadic and were not accompanied by related histologic findings. HDDC did not increase the frequency of micronucleated erythrocytes in mice.(ABSTRACT TRUNCATED AT 400 WORDS)

Administration, Inhalation↗
PubMed1996

Groin dissection practices among gynecologic oncologists treating early vulvar cancer.

OBJECTIVE: To survey the surgical practice of gynecologic oncologists regarding the extent of groin dissection for early vulvar cancer. METHODS: A 14-item questionnaire was developed and presented to the Annual Meeting of the Felix Rutledge Society. Gynecologic oncologists were asked to describe in descriptive, categorical, and visual terms the groin procedure that they perform as part of management of early vulvar cancers. Three ink-line drawings were created by a medical illustrator for the purpose. Fifty returned surveys were evaluable. RESULTS: The most commonly performed procedures were removal of the lymph nodes above the cribriform fascia and those medial to the femoral vein (40%), removal of lymph nodes above the cribriform fascia (34%), and removal of all nodes above and below the cribriform fascia (22%). Respondents performing the first procedure termed it "superficial inguinal lymphadenectomy" (40%), "inguinal femoral lymphadenectomy" (25%) and a variety of other names (35%). Respondents performing the second two procedures were much more consistent in the figure and name that they matched with their description of the nodes removed. When respondents were asked to match the figures with categorical definitions based on their understanding of the literature, the figure depicting Scarpa's triangle following removal of the superficial inguinal and medial femoral nodes was named superficial inguinal lymphadenectomy by 24% despite the fact that the femoral vein was clearly visible and labeled. CONCLUSIONS: We conclude that (1) among this group of gynecologic oncologists superficial inguinal and medial femoral lymphadenectomy is the most commonly performed procedure for women with early vulvar cancer and that the procedure is frequently called superficial inguinal lymphadenectomy; (2) publications and protocols on this topic must provide complete descriptions of procedures performed, and investigators must assure that individual surgeons are performing the same procedure; and (3) treatment results with superficial inguinal and medial femoral lymphadenectomy are poorly described and a fertile area for further study.

Female↗
PubMed2001

A Study on the Adsorption Characteristics of Orthophosphates on Rutile-Type Titanium Dioxide in Aqueous Solutions.

Rutile-type titanium dioxide is widely used as a pigment for paint, coating ink, paper, plastic products, and cards because of its very whiteness and outstanding hiding property. It has two weak properties to be improved, however, one being its coagulation in compounding and the other its decreasing whiteness owing to poor heat resistance. To solve these problems, a study on the treatment of titanium dioxide surfaces by adsorption technology has been performed. Experiments have been carried out to establish the adsorption isotherms of orthophosphates on titanium dioxide and to investigate the effect of organic solvents on adsorption. It is shown that the adsorption isotherms vary with pH. A Freundlich adsorption isotherm is suitable for the acidic and basic regions, while a Langmuir adsorption isotherm is suitable for the region of pH 5-8 where a maximum adsorption has been achieved. In aqueous solutions containing organic solvents, the adsorption was strongest with aqueous solutions containing 1 wt% toluene and weakest with those containing 1 wt% ethanol. Among the alcohols used, the adsorption was strongest with the aqueous solution containing 1 wt% butanol and weakest with that containing 1 wt% ethanol, thus showing a correlation with the molecular weight of the alcohol. Copyright 2001 Academic Press.

Journal Article↗
PubMed2001

The Effects of Void Geometry and Contact Angle on the Absorption of Liquids into Porous Calcium Carbonate Structures.

The absorption (permeation) of alcohols into porous blocks of calcium carbonate has been studied experimentally and with a computer model. The experimental measurement was of change in apparent weight of a block with time after contact with liquid. The modeling used the previously developed 'Pore-Cor' model, based on unit cells of 1000 cubic pores connected by cylindrical throats. To gain some insight into absorption into voids of complex geometry, and to provide a representation of heterogeneities in surface interaction energy, the cylindrical throats were converted to double cones. Relative to cylinders, such geometries caused hold-ups of the percolation of nonwetting fluids with respect to increasing applied pressure, and a change in the rate of absorption of wetting fluids. Both the measured absorption of the alcohols and the simulated absorption of the alcohols and of water showed significant deviations from that predicted by an effective hydraulic radius approximation. The simulation demonstrated the development of a highly heterogeneous wetting front, and of preferred wetting pathways that were perturbed by inertial retardation. The findings are useful in the design of high-performance, low-waste pigments for paper coatings, and environmentally friendly printing inks, as well as in wider industrial, environmental, and geological contexts. Copyright 2001 Academic Press.

Journal Article↗
PubMed2002

Surface adsorption effects in the inkjet printing of an aqueous polymer solution on a porous oxide ceramic substrate.

The inkjet printing of a polymeric solution into a porous substrate was studied, with the focus on phenomena occurring within the pore space during infiltration. Lines of aqueous polyacrylic acid (PAA) solution were printed onto the surface of porous, high-green-density ceramic powder beds. The PAA is a binder for the ceramic particles, allowing removal of the printed line structure ("primitive") and characterization of the extent of polymer penetration. Large differences in cross section of the retrieved printed structure were observed between ceramic systems and for different specific surface area powders. A mechanism for "filtration" of the polymer by adsorption onto the ceramic particle surfaces during infiltration was proposed. The adsorption of PAA onto Al2O3, SiO2, and TiO2 was characterized via adsorption isotherms, and the trend of primitive cross section with PAA adsorption was consistent with the filtration hypothesis, as was the variation with powder-specific surface area. These results can be generalized to other systems where a solution is inkjet printed onto a porous substrate (e.g., inks on plain paper, porous coated papers, etc.) Utilization of the adsorption effects may allow confinement of the solute molecules (e.g., colorant) to a small region near the substrate surface.

Journal Article↗
PubMed2002

Adsorption of a polymeric siloxane surfactant on carbon black particles dispersed in mixtures of water with polar organic solvents.

The adsorption of a rake-type polymeric siloxane surfactant (polydimethylsiloxane-graft-polyether copolymer) on carbon black (CB) particles dispersed in mixtures of water with polar organic solvents (ethanol, formamide, or glycerol) has been investigated. The adsorption obeys the Langmuir isotherm at low surfactant concentrations (below the critical micelle concentration, CMC). At these conditions, the average surface area occupied by one siloxane surfactant follows the sequence water+glycerol mixture >plain water >water+ethanol mixture. At higher surfactant concentrations in the solution in contact with the particles, a sharp increase in the adsorbed amount is observed. The adsorbed layer thickness has been determined by dynamic light scattering. Below the CMC the adsorbed layer thickness is less than 10 nm. Above the CMC, the adsorbed layer thickness increases to 20-30 nm, a length scale comparable to the diameter of the siloxane surfactant micelles in aqueous solution. This fact, together with SANS data that we have obtained in the absence of added polar organic solvent, indicates that the structure of the adsorbed layer is similar to that of micelles. The findings presented here are relevant to waterborne coatings and ink formulations, where polymeric surfactants are used in conjunction with polar organic solvents.

Journal Article↗
PubMed1998

Persistent and heterogenous expression of the cyclin-dependent kinase inhibitor, p27KIP1, in rat hearts during development.

We have previously shown that there were differential and dramatic decreases of cyclin and cyclin-dependent kinase (CDK) activities in cardiomyocytes during the neonatal period. The activity of CDKs control cell cycle progression, and this activity is regulated positively and negatively by association of CDKs with cyclins and cyclin-dependent kinase inhibitors (CKIs), respectively. While the INK family (p15(INK4B)/p16(INK4A)/p18(INK4C)/p19(INK4D)) of CKIs is not detectable in hearts, the KIP/CIP family (p21(CIP1), p27(KIP1) and p57(KIP2)) of CKIs is detectable in most organs including the heart. Differential and dramatic changes of the KIP/CIP family (p21(CIP1), p27(KIP1) and p57(KIP2)) of CKIs were detected in rat hearts during development. The mRNA and protein levels of p21(CIP1) and p57(KIP2) were readily detectable in hearts at gestational and early postnatal periods and decreased thereafter. The mRNA levels of p27(KIP1) in ventricles were high during the gestational period, and did not change until day 30 postnatal, then were decreased slightly in 90-day-old rats. The protein levels of p27(KIP1) increased significantly in the early postnatal period, then were expressed persistently, although levels decreased slightly in the adult period. However, protein levels of p27(KIP1) in atria did not change during development. Variable immuno-staining patterns of p27(KIP1) were observed at different periods of development and in various locations in myocardium. During the gestational period, approximately 35-50% of myocardial cells in the cardiac wall were p27(KIP1) immuno-positive and were distributed diffusely. These p27(KIP1) immunopositive cells increased predominantly in endocardial and mid-portion areas of ventricular myocardium at the early postnatal period. This heterogenous pattern of p27(KIP1) protein expression persisted to adult hearts though the percentage of p27(KIP1) immuno-positive cells decreased slightly. High magnification revealed that more than 50% of adult cardiomyocytes were p27(KIP1) immuno-positive and that p27(KIP1) was located solely in nuclei. These results indicate that p27(KIP1) may be an important inhibitor of CDK activities in cardiomyocytes during early postnatal development and may block the re-entrance of adult cardiomyocytes into the cell cycle after injury.

Animals↗
PubMed2001

Sarcolemmal blebs and osmotic fragility as correlates of irreversible ischemic injury in preconditioned isolated rabbit cardiomyocytes.

The hypothesis that irreversible ischemic injury is related to sub-sarcolemmal blebbing and an inherent osmotic fragility of the blebs was tested by subjecting isolated control and ischemically preconditioned (IPC) or calyculin A (CalA)-pretreated (protected) rabbit cardiomyocytes to ischemic pelleting followed by resuspension in 340, 170 or 85 mosmol medium containing trypan blue. At time points from 0-240 min, osmotic fragility was assessed by the percentage of trypan blue permeable cells. Membrane blebs were visualized with India ink preparations. Bleb formation, following acute hypo-osmotic swelling, developed by 75 min and increased with longer periods of ischemia. Osmotic fragility developed only after 75 min. Cells resuspended in 340 mosmol media did not form blebs and largely retained the ability to exclude trypan blue, even after 240 min ischemia. Although the latent tendency for osmotic blebbing preceded the development of osmotic fragility, most osmotically fragile cells became permeable without evident sarcolemmal bleb formation. The onset of osmotic fragility was delayed in protected cells, but protection did not reduce the bleb formation. It is concluded that blebbing and osmotic fragility are independent manifestations of ischemic injury. The principal locus of irreversible ischemic injury and the protection provided by IPC may lie within the sarcolemma rather than at sarcolemmal attachments to underlying adherens junctions.

Animals↗
PubMed1998

Separation and enrichment of the active component of carbon based paramagnetic materials for use in EPR oximetry.

Carbon based paramagnetic materials are frequently used for EPR oximetry, especially in vivo, but the EPR spectra of these materials often have more than one paramagnetic center and/or relatively low signal intensity. To determine whether the multi-components of carbon based materials could be separated and enriched in the active component, we used density gradient centrifugation to separate the materials into several fractions. We studied two types of coals, gloxy and Pocahontas, and found these materials to have large density distribution. The separated density fractions had very different EPR spectra and intensities. The active component from the coal material had a more homogeneous EPR signal and significantly increased EPR signal intensity, whereas for India ink, only slight changes were observed. This result can be very useful in the development of better probes for EPR oximetry.

Carbon↗
PubMed1995

Ischemic time-dependent microvascular changes and reperfusion injury in the rat small intestine.

The significance of the reperfusion period in the pathophysiology of complete occlusion of the intestinal circulation is controversial. Our study was designed to evaluate the exact magnitude of reperfusion-induced intestinal mucosal damage in a standardized rat model of complete segmental arterial ischemia as a function of the occlusion time. Intestinal ischemia was maintained for 15, 30, or 60 min, or ischemia was followed by a 30-min reperfusion period. Intraarterial India ink perfusion was applied to visualize the mucosal vascularity changes induced by ischemia or ischemia-reperfusion. The height of the distributing arterioles of the villi and the average mucosal thickness were recorded by an image analysis system, and the degree of mucosal damage was established on a semiquantitative 0 to 5 grade scale. Ischemia induced erythrocyte obstructions at the villus tip, a progressive decrease in carbon-filled arteriole height, and a concomitant 7, 23, or 35% reduction of the mucosal thickness. The percentage decrease in perfused arteriole height/percentage mucosal thickness reduction ratio was 2.2, 1.5, or 1 during the 15-, 30-, or 60-min ischemia, respectively. Extravasation of the carbon tracer was observed in the 60-min ischemia group. During reperfusion, the mucosal layer was reduced by 27, 38, or 57%, respectively, compared with the baseline values. The arteriole height reduction/mucosal thickness reduction ratio was 1:1 in all ischemic-reperfused groups. The degree of mucosal damage was significantly increased during reperfusion after the 15-min ischemia. Microvessel obstruction is initiated at the villus tip following the onset of arterial occlusion, with subsequent destruction of the surrounding tissues during reperfusion. The reperfusion component of the net mucosal damage may be very significant in early forms of complete occlusion of the mesenteric circulation.

Animals↗
PubMed1996

Hepatotoxins and liver transplantation decrease pulmonary metastases in rats with hepatoma.

Results following liver transplantation for hepatocellular carcinoma have been dismal, attributed largely to recurrent disease locally or at distance sites. Undetected micrometastases or tumor that embolizes at the time of liver transplant from manipulation of the liver may account for these recurrences. A model and treatment protocol were developed to address this clinical problem. The protocol is modeled on the concept of bone marrow transplantation for leukemia. Hepatotoxins that are lethal to both normal hepatocytes and hepatoma cells are administered followed by liver transplantation to "rescue" the failing liver. The feasibility of this protocol was examined in a rat model. Male Buffalo rats were injected with 1 million Morris hepatoma MH-7777 cells intravenously at Day 0 as a model for micrometastatic disease. Three treatment groups were established. Group 1 received no treatment. Group 2 received 5% dextrose in water (D5W) followed by a syngeneic orthotopic liver transplant (OLTX). Group 3 received the hepatotoxin pyrazofuin (10 mg/kg) followed by OLTX. Animals were followed to Day 35, at which time they were sacrificed and examined for evidence of pulmonary metastases and quantitation of nodules with India ink insufflation. There was a significant decrease in the number with pulmonary nodules as well as the number of animals with pulmonary metastatic disease in the pyrazofurin-treated group compared with groups 1 and 2 (4.8 +/- 4.0 nodules/animal vs 45.2 +/- 11.2 nodules/animal--no treatment and 60.8 +/- 21.4 nodules animal--D5W/OLTX group) These data indicate that this model is reliable for examining metastatic hepatoma and that pyrazofurin is effective in preventing hematogenous micrometastases of hepatoma cells. Other hepatotoxins and the effect of allogeneic transplantation and immunosuppression could be examined in this model.

Amides↗
PubMed2001

A novel method of studying wound healing.

In order to study wound healing, it is often necessary to administer various wound-active substances by the systemic route. It is unclear whether the observed effects are the result of local or systemic influence of the agent administered. Furthermore, high systemic doses are often required to achieve activity at the wound level. Direct intrawound administration of substances is traumatic and disruptive to the fragile wound environment and increases the risk of infection. We devised a system for continuous atraumatic delivery of substances directly to subcutaneously implanted polyvinyl alcohol sponges, an adaptation of a well-established model of wound healing. Sponge-catheter constructs were fashioned by feeding identical lengths of silicone catheters through two 40-mg sponge disks (on edge). The distal sponge was fixed 0.5 cm from the distal, ligated end of the catheter and centered over two 1-mm holes in the catheter tubing. The proximal sponge was fixed over nonperforated catheter with its edge 2 cm proximal from the close edge of the distal sponge. Each construct was connected to a mini-osmotic pump (infusion rate 1 microl/h) loaded with an appropriate infusate and inserted subcutaneously on the dorsum of anesthetized male Sprague-Dawley rats. Hydroxyproline (OHP) content of sponges, a measure of collagen deposition, was determined at 7 days postwounding. Infusion of India ink confirmed selective delivery to the distal sponge. Saline infusion alone significantly elevated OHP content compared to noninfused sponges (450 +/- 43 vs 328 +/- 36 microg OHP/100 mg sponge, P < 0.05). Infusion of S-methylisothiourea (a selective iNOS inhibitor, 84 microg/sponge/24 h) successfully inhibited NO production (35.9 +/- 3.1 vs 49.6 +/- 3.6 microM, P < 0.05) and decreased sponge OHP content (385 +/- 60 vs 568 +/- 70 microg OHP/100 mg sponge, P < 0.05) without the toxic side effect (i.e., weight loss) seen with systemic administration. Infusion of an adenoviral solution containing mouse iNOS cDNA resulted in successful transduction of wound cells demonstrating the ability to deliver genes to a healing wound model. The data demonstrate that manipulation of wound physiology is possible by local delivery of low doses of wound-active compounds to the wound site. This promises to be a powerful tool for the study of both normal and impaired wound healing.

Adenoviridae↗
PubMed2000

In vivo adenovirus-mediated suicide gene therapy of orthotopic bladder cancer.

These studies were undertaken to determine the feasibility, safety, and efficacy of suicide gene therapy using adenoviral-mediated herpes simplex virus thymidine kinase (ADV/RSV-tk) and the prodrug ganciclovir (GCV) in an orthotopic murine bladder cancer model. We utilized a replication-defective adenoviral construct containing the beta-galactosidase gene as a control and the herpes simplex virus thymidine kinase gene as the therapeutic vector under the transcription control of the Rous sarcoma virus long terminal repeat promoter. Intravesically created, orthotopic bladder tumors were established in syngeneic C3H/He female mice. India ink injection and beta-galactosidase studies were performed to determine if transurethral administration, direct tumor injection, or the combination was the most efficient route of virus administration. Optimal dosing of ADV/RSV-tk was determined by direct tumor injection with increasing viral doses and treatment with GCV. Treatment efficacy, long-term survival, and toxicity were determined in separate but similar controlled experiments. Growth curve studies demonstrated reliable tumor formation by 14 days. Direct transvesical tumor injection resulted in the best distribution and intratumor gene expression as measured by X-gal staining. Dose-ranging experiments demonstrated an optimal viral dose of 5 x 10(8) plaque-forming units and a greater than twofold reduction in tumor growth for the animals treated with ADV/RSV-tk compared to controls. Efficacy studies demonstrated a greater than threefold reduction in tumor growth. No clinical or gross pathologic toxicity was detected. Long-term survival results suggested a survival benefit for the treatment animals compared to controls. We conclude that ADV/RSV-tk in combination with GCV provides effective therapy for orthotopic murine bladder cancer by significantly inhibiting tumor growth with limited toxicity to the host. These data provide further support for testing this suicide gene therapy strategy in human Phase I trials.

Adenoviridae↗
PubMed1997

Vessels supplying septa and tendons as functional shunts in perfused rat hindlimb.

An assessment was made of the relationship between vasoconstrictor-mediated changes in metabolism and the apparent flow in putative nonnutritive vessels of muscle located on tendon. Surgically isolated rat hindlimbs were perfused at constant flow while monitoring perfusion pressure and venous pO2. In addition exposed tibial tendon vessels of the biceps femoris muscle of the perfused leg were positioned either under a surface fluorometer probe to monitor signal strength when pulses of fluorescein isothiocyanate dextran were infused or over the objective lens of an inverted microscope for photography when pulses of India ink were infused. Measurements were conducted under steady state with vehicle, norepinephrine, or serotonin infused. Norepinephrine increased perfusion pressure and oxygen uptake (VO2), but decreased fluorescence signal from the tendon vessels. Photomicroscopy confirmed that the vessels had generally decreased in diameter. Serotonin also increased perfusion pressure but decreased VO2 and increased fluorescence signal from the tendon vessels. Photomicroscopy confirmed that serotonin infusion had led to a marked increase in diameter of the vessels. It is concluded that a reciprocal relationship exists between resting muscle metabolism as controlled by vasoconstrictors and flow-through muscle tendon vessels.

Animals↗
PubMed1999

The lymphatic vessels and the so-called "lymphatic stomata" of the diaphragm: a morphologic ultrastructural and three-dimensional study.

We studied the absorbing peripheral lymphatic vessel with the light microscope, the transmission electron microscope, the scanning electron microscope, and three-dimensional models of the diaphragm of several rodents and insectivores under normal and experimental conditions (lymphatic stasis and dehydration). To clarify the delicate and complex mechanism that permits drainage of the abdominal cavity contents into the lymphatic circulatory system, we introduced Polystyrene latex spherules, China ink, and Trypan blue into the abdominal cavities. After anatomical comparisons of the superficial and deep networks of absorbing peripheral lymphatic vessels at the tendinous and muscular portions of the diaphragm and after classification of lymphatic vessels into absorbing and conducting functions, we examined the stomata, which, owing to morphologic and topographic findings, we defined as stable structures. Furthermore, we observed that the stomata and submesothelial connective channel are fundamental elements that facilitate the flow of the corpuscular and liquid contents of the peritoneal cavity to the submesothelial absorbing lymphatic vessel wall. Also, we underlined that the genesis of the connective channel depends on the secondary cytoplasm extensions of two distinct adjacent endothelial cells, which, to facilitate the flow of the absorbed abdominal contents, completely coat this channel. Additionally, our observations illustrate that the secondary cytoplasm extensions do not engage in continuous relationships with the basal lamina of the mesothelium and with the margins of the stoma, and, hence, the hypothesis of "lymphatic stomata" as an expression of the anchoring of the borders of the open interendothelial junctions to the orifice margins of the stoma cannot be confirmed. Moreover, we describe the presence and formation of intraendothelial channels in the lymphatic endothelial wall. We affirm that this morphological entity is a dynamic unit, because its numerical density varies according to different physiological and experimental conditions to degrees of hydrostatic and colloidal osmotic pressure and, perhaps, also to the particular characteristics of the substances that the connective channel liberates into the endothelial wall of the lymphatic vessel. In conclusion, we affirm that the absorbing peripheral lymphatic vessels of the diaphragm, by way of intraendothelial channel formations, membrane diffusion, and the vesicular path of the endothelial cells, constitute the fundamental draining elements for the corpuscular and liquid contents of the abdominal cavity.

Absorption↗
PubMed2002

Experimental performance assessment of SPM for SPECT neuroactivation studies using a subresolution sandwich phantom design.

The validity domain of voxel-based statistical analysis of SPECT neuroactivation studies with statistical parametric mapping (SPM) has been investigated by a limited number of theoretical and simulation studies. In this work, an experimental setup is described with an assessment of its activation detection performance together with the influence of acquisition and processing parameters. A subresolution sandwich phantom was constructed using a printed high-resolution digital Hoffman phantom with a (99m)TcO(4)-ink mixture. Activations of 8, 16, and 24 mm diameter, with an intensity ranging from 5 to 60%, were constructed in the right frontal cortex, anterior and posterior cingulate, and left striatum. Triple-headed SPECT acquisitions were carried out using both fan-beam and parallel beam geometry. The impact of activation characteristics (size, intensity and location), study size, physical degradation factors, and reconstruction technique were studied using SPM99 in a group comparison design with correction for multiple comparisons. For a 15 x 15 design, all 24-mm activations of 5% intensity were detected for the fan-beam data. Decreased focus or study size, lower SPECT resolution, absence of scatter, and attenuation correction resulted in an increase in minimally detectable activation. For a single study referred to 15 control studies, only 24-mm activation foci with a minimal intensity of 10% were detected in the optimal configuration. This approach allows experimental parameter optimization of SPM-based group or single-subject SPECT activation studies compared to normal data, as used in clinical applications. In principle, these findings can be extended to SPECT receptor studies or PET data.

Algorithms↗