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PubMed2006

Testosterone stimulates the primary to secondary follicle transition in bovine follicles in vitro.

The mechanisms controlling the initiation and early stages of follicular growth are poorly understood. Our laboratory developed a serum-free culture system that supports spontaneous and wholesale activation of primordial follicles in pieces of cortex dissected from the ovaries of fetal calves and fetal baboons. However, very few follicles activated in vitro progressed to the secondary stage. To determine whether androgens can promote the primary to secondary follicle transition, pieces of fetal bovine ovarian cortex were cultured in serum-free medium in the absence or presence of testosterone (T, 10(-7) and 10(-6) M) or estradiol (E(2), 10(-6) M) for 10 days. Cortical pieces were then fixed and embedded in plastic for serial sectioning and morphometric analysis; fresh cortical pieces fixed on Day 0 served as uncultured controls. Freshly isolated cortical pieces contained mostly primordial follicles, whereas after 10 days in vitro, most primordial follicles had activated, differentiating into primary follicles as expected. Neither T nor E(2) affected the number of primordial and primary follicles compared with controls (P > 0.05). However, T (10(-7) and 10(-6) M) increased the number of secondary follicles (P < 0.05), whereas E(2) had no effect, suggesting that the effect of T was not due to conversion of T to E(2). In the second experiment, the optimal concentration of T for preantral follicle growth was determined. A range of lower doses of T (10(-10)-10(-7) M) increased the number of secondary follicles in cultured cortical pieces in a dose-dependent manner, with 10(-7) M T being the most effective (P < 0.05). In the third experiment, addition of a specific androgen receptor blocker, flutamide, inhibited the stimulatory effects of T on the primary to secondary follicle transition (P < 0.05), suggesting a receptor-mediated action of T. Localization of androgen receptors by immunohistochemistry revealed immunostaining for the androgen receptor in ovarian stromal cells and increasing immunoreactivity in follicle cells as follicular development progressed from primordial and primary to secondary to antral follicles, suggesting the involvement of the androgen receptor in bovine folliculogenesis. In summary, our results show that T promotes the growth of bovine follicles activated in vitro and suggest that its stimulatory effect is mediated through androgen receptors in the stroma and/or follicular cells.

Androgen Antagonists↗
PubMed2005

Does the investing layer of the deep cervical fascia exist?

BACKGROUND: The placement of the superficial cervical plexus block has been the subject of controversy. Although the investing cervical fascia has been considered as an impenetrable barrier, clinically, the placement of the block deep or superficial to the fascia provides the same effective anesthesia. The underlying mechanism is unclear. The aim of this study was to investigate the three-dimensional organization of connective tissues in the anterior region of the neck. METHODS: Using a combination of dissection, E12 sheet plastination, and confocal microscopy, fascial structures in the anterior cervical triangle were examined in 10 adult human cadavers. RESULTS: In the upper cervical region, the fascia of strap muscles in the middle and the fasciae of the submandibular glands on both sides formed a dumbbell-like fascia sheet that had free lateral margins and did not continue with the sternocleidomastoid fascia. In the lower cervical region, no single connective tissue sheet extended directly between the sternocleidomastoid muscles. The fascial structure deep to platysma in the anterior cervical triangle comprised the strap fascia. CONCLUSIONS: This study provides anatomical evidence to indicate that the so-called investing cervical fascia does not exist in the anterior triangle of the neck. Taking the previous reports together, the authors' findings strongly suggest that deep potential spaces in the neck are directly continuous with the subcutaneous tissue.

Aged↗
PubMed2000

Histomorphometry of parietal bones versus age and race.

Surgeons are used to obtaining bone grafts of calvaria, which are abundant and available. The outer table of the parietal bone can be split, usually at the level of the diploic interstice, with an osteotome. Inadvertently violating the inner table and the dura leads some surgeons to avoid using the outer table in the elderly. Sullivan and Smith measured the thickness of the outer tables, diploe, and inner table of 37 cadavers (average age, 59 years) and found each layer to be well preserved distinctly. However, they suggested that calvaria become brittle in patients older than 50 years of age. The current authors hypothesized that diploic composition is not changed, even in the elderly. The thickest part of the parietal bone of 49 Koreans and 30 whites were acquired, and undecalcified slides were made. Via light microscopy, using the National Institutes of Health image, the following measurements were made: the thickness of the parietal bone (PT), outer table (OT), diploe (DT), and inner table (IT); trabecular bone volume percent (TBV); trabecular thickness (TT); and trabecular separation (TS). There was no significant difference in the thickness of the OT, DT, and IT of the PT, TBV, TT, and TS among different ages. The PTs of women were thicker than men's. The PTs of whites were significantly thicker than Koreans'. This study disclosed that the DT is not different among varying age groups and is not sclerosed in the persons older than 80 years, and the OT of these individuals is not brittle. Thus, surgeons do not need to hesitate when taking the OT of the PT in older patients. However, the selection of the site is attentive to PT. The thickest posteromedial part of the PT is favorable and safe as a donor.

Adolescent↗
PubMed2006

Apoptotic changes of Middle East jaw lymphoma.

Jaw lymphoma a highly malignant tumor affects children between two and eight years, duration of illness between two and three weeks, and the general condition of severe toxicity, and the death rate is 91.9%. The aim of this cellular study is to show the apoptotic changes associated with these tumors. Twenty-four children, 13 boys and 11 girls, were reported with jaw lymphoma and studied for apoptotic detection of the tumor through morphological assessment by using ground section and electron microscopy. Ground section shows lymphoblastic lymphoma, darkly-stained of ribonucleic acid, also apoptotic changes seen in some of the cells. Electron microscopy showed high mitotic figures, lymphoblast transformed to plasma cell, high nucleocytoplasmic ratio, some cells showed double nuclei, some nuclei are crested in shape or convoluted, degenerative changes seen in some of the cells, chromatin clumps near the nuclear membrane, mitochondria showing homogenous and degenerative changes, virus like particles seen in this nucleus and cytoplasm. The presence of low-level of apoptosis is a poor prognostic feature of jaw lymphoma due to homogeneity and degenerative changes of the mitochondria and disruption of the cell surface.

Apoptosis↗
PubMed1995

Origin of posterior pituitary high intensity on T1-weighted magnetic resonance imaging. Immunohistochemical, electron microscopic, and magnetic resonance studies of posterior pituitary lobe of dehydrated rabbits.

RATIONALE AND OBJECTIVES: To investigate the origin of posterior pituitary high intensity (PPHI) seen on T1-weighted magnetic resonance (MR) images. METHODS: Six rabbits, including four rabbits deprived of drinking water for 4 days and two control rabbits, were examined by MR imaging. Plasma vasopressin levels were sequentially measured by radioimmunoassay. Pituitary glands were immunostained with guinea pig anti-rabbit vasopressin antibody, and ultrathin sections of Epon/Araldite-embedded specimens were observed with a transmission electron microscope. RESULTS: In control rabbits, PPHI was noted on T1-weighted MR images, and the posterior pituitary lobe was positively immunostained with anti-vasopressin antibody. At the ultrastructural level, nerve terminals contained numerous neurosecretory granules bearing vasopressin. Conversely, plasma vasopressin levels gradually increased and PPHI was absent in 4-day dehydrated rabbits. The posterior lobe was scarcely stained with anti-vasopressin antibody, and neurosecretory granules were rarely observed. However, a number of small dispersed vesicles, possibly derived from the fragmentation of neurosecretory granule envelopes, were seen in the nerve terminal. CONCLUSIONS: Posterior pituitary high signal seen on T1-weighted MR images is attributed to neurosecretory granules bearing vasopressin.

Animals↗
PubMed1999

The effect of aging on pars compacta of the substantia nigra in rhesus monkey.

This aim of this study was to re-evaluate the types of neurons present in pars compacta of the substantia nigra in the rhesus monkey, and then to determine the effects of aging on the morphology of both the neurons and neuroglial cells. The substantia nigra was therefore examined in Golgi impregnated material, in sections labeled with antibodies to tyrosine hydroxylase and to GABA, and in tissue embedded in plastic for light and electron microscopy. Three types of neurons were encountered: (1) large multipolar neurons with prominent Nissl bodies, (2) bipolar neurons that are medium sized and spindle-shaped, with Nissl bodies confined to the poles of the deeply indented nuclear envelopes, and (3) small multipolar cells with sparse Nissl substance. The large and medium neurons are believed to be dopaminergic and the small neurons GABA-ergic. With age, all of the neurons accumulate lipofuscin, especially the small multipolar neurons. In addition, Marinesco bodies appear within the nuclei of the large multipolar neurons. The dendrites are most severely affected by age; many of them lose organelles and their cytoplasm can become filled with vacuoles, membranous whorls, and dense bodies. In old monkeys many of the astrocytes have inclusions and in the neuropil there is a striking increase in the number of astrocytic processes. Also large spheroids appear. These appear to be derived from astrocytes and they have a core of dense granular material surrounded by a paler peripheral zone of cytoplasm from which processes can extend. Most of the oligodendrocytes have dense inclusions in their cytoplasm and many of the myelin sheaths break down. Microglial cells can become enormously swollen by phagocytosed material. Although both neurons and neuroglial cells are affected by age, no entities that could be construed to be dying neurons were encountered.

Aging↗
PubMed1990

Pathogenesis of small-intestinal mucosal lesions in chronic diarrhea of infancy: I. A light microscopic study.

In an effort to increase our understanding of the pathogenesis of chronic protracted diarrhea in infants, we examined 44 jejunal mucosal specimens. Only 3 of the 44 specimens showed a normal mucosa (grade 1). Partial villous atrophy was seen in 17 mucosal specimens (grade 2) with marked patchiness in all of the specimens. Subtotal or total villous atrophy (grade 3) was found in the remaining 24 mucosal biopsies. Plasma cells and macrophages were variably increased and intraepithelial lymphocytes were moderately increased in grades 2 and 3. Eight of ten mucosal biopsy specimens embedded in plastic material and cut at 1-2-mm thickness, showed bacteria of unidentified nature, situated either above the microvillous layer or on the mucosal surface. Both adherent and nonadherent bacteria could be identified in the same specimen. We concluded that severe pathological mucosal changes are common in young infants with protracted diarrhea and that the presence of bacteria may be more common than has previously been documented.

Atrophy↗
PubMed1999

Glutamate-like immunoreactivity during hair cell recovery after gentamicin exposure in the chinchilla vestibular sensory periphery.

OBJECTIVE: Determine the expression of glutamate by immunohistochemistry in normal and recovering vestibular hair cells in the chinchilla crista ampullaris after gentamicin ototoxicity. STUDY DESIGN: In five groups of three animals each, ototoxicity was produced by placing gentamicin (50 microg)-impregnated Gelfoam pellets within the perilymphatic space of the superior semicircular canal. Animals were sacrificed at 1, 2, 4, 8, and 16 weeks after treatment. A group of normal (n=3) animals was also processed. METHODS: For the detection of glutamate the inner ears of these animals were dissected, and the horizontal cristae ampullaris embedded in plastic. Two-micron-thick tissue sections were obtained and incubated with monoclonal antibodies against glutamate. The immunoreaction was detected using the avidinbiotinylated-complex technique and diaminobenzidine was the chromogen. RESULTS: Normal sensory epithelia demonstrated type I and type II hair cells with moderate glutamate-like immunoreactivity. Supporting cells demonstrated no glutamate-like immunoreactivity. Afferent nerve fibers and calyxes surrounding type I hair cells demonstrated strong glutamate-like immunoreactivity. At 1 and 2 weeks after treatment the few type II hair cells surviving ototoxic treatment (15%-18%) contained moderate glutamate-like immunoreactivity, supporting cells showed no immunoreactivity, and nerve terminals and fibers displayed strong immunoreactivity. At 4 and 8 weeks after treatment, recovered hair cells (80%) had greater glutamate-like immunoreactivity when compared with normal hair cells, supporting cells displayed no glutamate-like immunoreactivity, and afferent fibers contained strong glutamate-like immunoreactivity. At 16 weeks, glutamate-like immunoreactivity in hair cells returned to normal level. CONCLUSION: Glutamate may be used as an indicator of hair cell differentiation and as an index of the molecular recovery of hair cells after ototoxicity.

Animals↗
PubMed1999

Mandibular reconstruction using bone morphogenetic protein 2: long-term follow-up in a canine model.

OBJECTIVE: To determine the degree of bone resorption and stability of 3-cm, full-thickness canine mandibular defects reconstructed with recombinant human bone morphogenetic protein 2 (rhBMP-2) and a bioerodible particle carrier followed for 30 months after reconstruction. STUDY DESIGN: Nine dogs, divided into three groups, underwent reconstruction of surgically created 3-cm, full-thickness defects of the body of the mandible. METHODS: Mandibular reconstruction was performed via a combined intraoral and extraoral approach. Using standard plating techniques, a unilateral full-thickness, 3-cm defect was created in the body of the mandible. After stabilizing the defects with titanium reconstruction plates, test implants composed of rhBMP-2 and poly(lactide-co-glycolide) bioerodible particles were placed in the mandibular defects of six animals. Reconstruction plates were removed from test animals at 10 weeks. Three short-term test animals were sacrificed 3 months after reconstruction. Three long-term test animals were sacrificed 30 months after reconstruction to determine the degree of resorption and long-term stability of the rhBMP-2-induced bone. Control implants (carrier without rhBMP-2) were used in three animals and were sacrificed at 3 months. At 9 months, long-term animals were advanced to a solid diet. Masticatory function and body weight were monitored periodically to assess diet tolerance. Roentgenographic photodensitometry was performed on serial dental roentgenograms of the reconstructed segments to determine bone density and the degree of bone resorption over 30 months. After sacrifice, reconstructed segments were harvested and embedded in plastic for histological analysis and histomorphometry to determine the percentage of the defect replaced by mineralized bone (area density) and degree of resorption from 3 to 30 months after reconstruction. The main outcome measures were bone density and bone height determined from serial roentgenograms and percentage of the reconstructed segment replaced by mineralized bone (area density) determined from histomorphometry. RESULTS: Control animals without rhBMP-2 showed no evidence of bone formation across the defect. Histological examination revealed good bone formation in two of three of the short-term test animals with a mean area density of 41.0%. The long-term test animals treated with rhBMP-2 demonstrated good bone formation that was comparable to that of normal host bone by 3 months. The roentgenographic photodensity measurements stabilized at 5 months without evidence of persistent bone resorption. The height of the reconstructed segment (rhBMP-2-induced bone) initially decreased, then stabilized by 11 months after reconstruction with no indication of resorption or failure. Histological examination of the long-term test animals revealed good bone formation across the mandibular defects. However, there were localized areas of thinning of the cortical bone as compared with the short-term test animals sacrificed at 3 months. Histological examination verified the loss of height of the bone in the reconstructed segments. The area density (mean) of the long-term test animals was 56.5%. Despite the decrease in height of the induced bone, there was an increase in area density of the bone over time. CONCLUSIONS: This study demonstrated that rhBMP-2 in a bioerodible particle carrier induced new host bone formation across critical-size mandibular defects. The newly formed bone successfully integrated with existing host bone creating a stable union capable of withstanding the forces of masticatory function in a canine. There was some evidence of early bone resorption (thinning of the cortical bone and decrease in height) in the rhBMP-2-induced bone. The rhBMP-2-induced bone stabilized by 11 months after reconstruction and no further resorption was noted. The percentage of area of the defect replaced by rhBMP-2-induced bone (area density) increased over 30 months. (ABSTRACT TRUNCATED)

Animals↗
PubMed2003

Unbiased stereologic type I and type II hair cell counts in human utricular macula.

OBJECTIVE: The objective of the study was to obtain unbiased estimates of the total number of type I and type II hair cells in human utricular macula from individuals with documented normal vestibular function. STUDY DESIGN: Application of unbiased stereology using microdissected human temporal bone specimens was conducted in an observational study. METHODS: Postmortem temporal bones were obtained from 10 normal patients (age range, 42-96 y; mean age, 82 y). The utricular maculae were microdissected, embedded in plastic, and cut into serial 2-microm sections. Unbiased estimates of the total number of type I and type II hair cells were obtained using the physical fractionator technique of stereology. RESULTS: The average total number of hair cells was 27,508 (CV = 11%) consisting of 17,326 (coefficient of variation [CV] = 11%) type I hair cells and 10,182 (CV = 13%) type II hair cells. The ratio of type I to type II hair cells was 1.70:1. In the age range of the study, there was no statistically significant correlation between hair cell counts and age. CONCLUSIONS: Morphometric studies of the human utricular sensory epithelium can be accomplished using unbiased stereology on microdissected specimens. There was no effect of age on total hair cell counts or on the ratio of type I to type II hair cells in the age range of the study. Further studies on younger subjects are needed to establish the effect of age. The results from the present study are closely aligned with prior studies that estimated total hair cell counts using surface mount preparations. The current data represent the first total type I and type II hair cell counts in human utricular neuroepithelium.

Adult↗
PubMed2004

Location and timing of initial osteoid deposition in postmeningitic labyrinthitis ossificans determined by multiple fluorescent labels.

OBJECTIVES/HYPOTHESIS: Variable amounts of fibrosis and neo-ossification fill the cochlea following bacterial meningitis. The purpose of the study was to delineate the timing and location of initial ossification following pneumococcal meningitis, as well as subsequent remodeling and resorption, over the 3-month period after infection. STUDY DESIGN: Randomized, double-blind study. METHODS: Fluorochromes are compounds that specifically incorporate into ossifying bone. Sequential addition of different colored fluorochromes during osteoneogenesis define the timing and location of osteoid deposition and mineralization. Mongolian gerbils were infected by intrathecal injection of Streptococcus pneumoniae type 3, and control gerbils received saline. Both groups were injected with calcein on postoperative day 3, followed by xylenol orange, oxytetracycline, and alizarin red on days 7, 14, and 28 respectively. Ten experimental gerbils were killed 24 hours after each label, and an additional group at 84 days after infection. Two groups of 10 control gerbils were killed at 29 and 84 days after treatment. The temporal bones and tibias were harvested, embedded in plastic, and sliced with a diamond saw. Wafers at a thickness of 200 microm were mounted in sequence and examined. RESULTS: Sixteen of 49 experimental animals (33%) were positive for at least one of the fluorescent labels. Fluorescent labeled osteoid was present at all sampling times. Label extended from the endosteal wall into the lumen of the scala tympani between the vestibule and the round window membrane. Discrete sites of fluorescence varied among specimens and were associated with the opening of the cochlear aqueduct, the scala tympani, organ of Corti, and the stria vascularis and spiral ligament in all turns from base to apex. CONCLUSION: The results indicate that osteoid is deposited and begins mineralization by day 3 after infection, at least, and continues, at least, through the first 28 days after infection. There was no apparent resorption of new bone and remodeling by 84 days after infection.

Animals↗
PubMed2001

Transforming growth factor beta-coated platinum coils for endovascular treatment of aneurysms: an animal study.

OBJECTIVE: To test the hypothesis that coating platinum coils with transforming growth factor beta (TGFbeta) would improve the cellular proliferation within experimental aneurysms relative to uncoated coils. MATERIALS AND METHODS: Elastase-induced saccular aneurysms were created in 12 New Zealand White rabbits. These aneurysms were embolized with platinum coils, either "control" (unmodified) coils or "test" (coated with TGFbeta) coils. Subjects were killed either 2 weeks (n = 3, control; n = 3, test) or 6 weeks (n = 3, control; n = 3, test) after embolization. Aneurysm tissue was embedded in plastic, sectioned, and stained with hematoxylin and eosin. The thickness of tissue covering the coils at the coil-lumen interface was measured by use of a digital microscope, and was compared between groups by use of the Student's t test (P < or = 0.05). RESULTS: Two-week implantation samples demonstrated mean thickness of tissue overlying TGFbeta-coated coils of 36+/-15 microm and mean thickness of overlying control coils of 3+/-5 microm, indicating significantly thicker tissue growth covering test versus control coils (P = 0.02). Six-week implantation samples demonstrated mean thickness of tissue overlying TGFbeta-coated coils of 86+/-74 microm versus mean thickness overlying control coils of 37+/-6 mu; this difference did not reach statistical significance (P = 0.30). Thickness of tissue covering TGFbeta-coated coils did not change significantly from 2 to 6 weeks (P = 0.31). Tissue thickness over control coils increased significantly between 2 and 6 weeks (P = 0.002). CONCLUSION: TGFbeta-coated platinum coils undergo earlier cellular coverage than standard platinum coils, but differences in coverage between coated and control coils are no longer present at later time points. These data suggest that improvements in intra-aneurysmal cellular proliferation resulting from coil modifications, although significant in the early postembolization phase, may dissipate over time.

Animals↗
PubMed2000

Plaster of Paris as an osteoconductive material for interbody vertebral fusion in mature sheep.

STUDY DESIGN: In adult female sheep, histologic and biomechanical criteria were used to determine whether the osteoconductive performance of plaster of paris would promote the incorporation of the tubular titanium mesh implants used for interbody vertebral fusions. OBJECTIVES: To compare the osteogenicity of plaster of paris with that of autogenous iliac crest bone and bone marrow 6 months after they were loaded into tubular titanium mesh cages and implanted as L3-L5 bridges after L4 corpectomies. SUMMARY OF BACKGROUND DATA: One of the aims of surgery for vertebral pathology is to stabilize the spine by interbody fusions. The morbidity associated with the use of iliac crest autograft bone for fusion grafts prompted trials using plaster of paris as an osteoconductive substrate. METHODS: The total volume of bone that invested the L3-L5 mesh cages after 6 months was quantitated by computed tomography scans. All specimens subsequently were cut into fusion mass segments for biomechanical testing in flexion, extension, compression, and torsion, and then embedded in plastic for sectioning and histomorphometry to determine the trabecular bone volume within the titanium mesh. RESULTS: In each experimental model, implants of plaster of paris were the osteoconductive equal of autogenous iliac crest bone/marrow preparations. The volumes of bone formed around and within the titanium mesh were identical, and the tissues were biomechanically indistinguishable. A partial mechanism was determined by modifying the system for midshaft femoral defects. CONCLUSIONS: In the sheep, a tubular titanium mesh packed with plaster of paris forms an osteoconductive conduit to achieve a biomechanically stable interbody lumbar vertebral fusion.

Animals↗
PubMed1989

Electron microscopy of hyalin bodies in the human intraosseous endolymphatic sac.

Hyalin bodies are amorphous, eosinophilic masses protruding from the subepithelial connective tissue into the lumen of the intraosseous endolymphatic sac (ES). We studied hyalin bodies at the electron microscopic level. Celloidin- embedded temporal bone sections known to have hyalin bodies were re-embedded into plastic and cut into thin sections appropriate for electron microscopy. The results revealed that the hyalin bodies are composed predominantly of thick bundles of collagenous fibers arranged in various directions. Fibroblasts and disintegrated macrophages were occasionally observed among the collagen fibers. Concentric calcific structures found within the hyalin bodies were composed of multiple smaller, concentric, lamellar calcifications. The results of this study support the hypothesis that the hyalin bodies are a repository of membranous cellular debris phagocytized by the macrophages.

Calcinosis↗
PubMed2005

The histologic effects of pulsed and continuous radiofrequency lesions at 42 degrees C to rat dorsal root ganglion and sciatic nerve.

STUDY DESIGN: Experimental histologic study of the effects of radiofrequency (RF) or convective heating of the rat dorsal root ganglion or sciatic nerve to 42 degrees C. OBJECTIVE: To determine whether treatment causes neuropathologic changes in an effort to explore the mechanisms and safety of pulsed RF pain therapy. SUMMARY OF BACKGROUND DATA: Clinical data suggest that low temperature pulsed RF energy delivered to the DRG is a safe and effective form of therapy for low back pain. However, the mechanism by which this treatment modifies pain is unclear. METHODS: A total of 118 Sprague-Dawley rats were divided into five groups for different RF and thermal treatments. All treatments increased tissue temperature to 42 degrees C. Treatments of the DRG included pulsed RF, continuous RF, and conductive heat. The generator output was increased until 42 degrees C was obtained in the tissue and was then maintained for 120 seconds. As a positive control, some rat sciatic nerves were treated with continuous RF lesions at 80 degrees C. Animals were killed for histologic study at 2, 7, or 21 days after treatment. Tissue was fixed in gluteraldehyde and embedded in plastic resin for detailed light microscopic neuropathologic evaluation. RESULTS: The methods used to heat the tissue to 42 degrees C caused no significant difference in pathology. However, subclinical changes included endoneurial edema caused by alterations in the function of the blood-nerve barrier, fibroblast activation, and collagen deposition. Tissue returned to normal conditions by 7 days in nerve and 21 days in the DRG. These minor structural changes observed at the light microscopic level in normal animals do not exclude the possibility that there would be nonstructural changes in gene expression or cytokine upregulation in injured tissue. Lesions at 80 degrees C caused consistent thermal injury characterized by Wallerian degeneration of nerve fibers. CONCLUSIONS: The data support the hypothesis that pulsed RF treatment does not rely on thermal injury of neurologic tissue to achieve its effect.

Animals↗
PubMed2004

Disorganization of cortical microtubules stimulates tangential expansion and reduces the uniformity of cellulose microfibril alignment among cells in the root of Arabidopsis.

To test the role of cortical microtubules in aligning cellulose microfibrils and controlling anisotropic expansion, we exposed Arabidopsis thaliana roots to moderate levels of the microtubule inhibitor, oryzalin. After 2 d of treatment, roots grow at approximately steady state. At that time, the spatial profiles of relative expansion rate in length and diameter were quantified, and roots were cryofixed, freeze-substituted, embedded in plastic, and sectioned. The angular distribution of microtubules as a function of distance from the tip was quantified from antitubulin immunofluorescence images. In alternate sections, the overall amount of alignment among microfibrils and their mean orientation as a function of position was quantified with polarized-light microscopy. The spatial profiles of relative expansion show that the drug affects relative elongation and tangential expansion rates independently. The microtubule distributions averaged to transverse in the growth zone for all treatments, but on oryzalin the distributions became broad, indicating poorly organized arrays. At a subcellular scale, cellulose microfibrils in oryzalin-treated roots were as well aligned as in controls; however, the mean alignment direction, while consistently transverse in the controls, was increasingly variable with oryzalin concentration, meaning that microfibril orientation in one location tended to differ from that of a neighboring location. This conclusion was confirmed by direct observations of microfibrils with field-emission scanning electron microscopy. Taken together, these results suggest that cortical microtubules ensure microfibrils are aligned consistently across the organ, thereby endowing the organ with a uniform mechanical structure.

Arabidopsis↗
PubMed1975

Compartmentation in Vicia faba Leaves: II. Kinetics of C-Sucrose Redistribution among Individual Tissues following Pulse Labeling.

Leaflets of Vicia faba L. were pulse labeled with (14)CO(2) and the kinetics of (14)C-sucrose redistribution among individual tissues was followed. Sucrose specific activity in the whole leaf peaked about 15 minutes after labeling and declined with a half-time of about 80 minutes. In one experiment, leaflet discs taken at various times during the (12)CO(2) chase were quick frozen, freeze-substituted, and embedded in plastic. The tissue was sectioned paradermally and sections of palisade parenchyma, of spongy parenchyma, and of spongy parenchyma that contained veins were collected. Water extracts from these sections were assayed for sucrose specific activity. Sucrose specific activity in the palisade parenchyma was higher than that of the spongy parenchyma and reached a maximum in both tissues 9 to 15 minutes after labeling. Sucrose specific activity initially declined rapidly in the palisade parenchyma followed by a period during which little or no loss occurred. Sucrose specific activity in sections containing veins peaked at 15 minutes with a maximum value substantially higher than either mesophyll tissue, indicating that recently synthesized sucrose was preferentially exported from the mesophyll. Decline of activity in these sections containing veins continued for the remainder of the experiment. Sucrose specific activity in lower epidermal peels peaked several minutes after that of the whole leaflet and remained lower. Sucrose specific activity in upper epidermal peels was variable (probably due to contamination), but the limited data suggest that the sucrose specific activity there reached somewhat higher values than those of the lower epidermis. The experiments indicate that each leaf tissue contains a kinetically identifiable sucrose pool (which we refer to as "histological compartmentation"), and that further compartmentation may occur at the intracellular level. A simulation of leaf sucrose compartmentation is presented.

Journal Article↗
PubMed2004

Microwave exposure increases bone demineralization rate independent of temperature.

There is a long-standing controversy regarding an effect of microwaves, independent of increasing temperature, on the rate of bone demineralization. In this study, we exposed standardized samples of gerbil femur to constant microwave exposure while maintaining the demineralizing solution (ethylenediamine tetraacetic acid, EDTA) at 20 degrees C. Random samples were selected at 3 h intervals, embedded in plastic and sectioned for histological evaluation to determine the extent of demineralization. The time to complete demineralization was significantly faster with microwave exposure (33 h) compared to non-exposure on a tissue rotator (45 h) in a limited amount (5 mL/24 h) of EDTA. The presence of bone marrow was a significant barrier to the rate of demineralization and resulted in an asymmetrical pattern of mineral extraction. Samples without bone marrow were completely demineralized after 21 h of exposure to microwaves and EDTA. Additional comparisons were made between samples exposed to an effectively infinite supply of demineralizing agent (bone marrow intact). There was a significant increase in rate with unlimited demineralizing agent with (24 h) or without (30 h) microwaves when compared to tissue demineralized on the rotator. Our results establish a positive effect of microwaves on the rate of bone demineralization which is independent of temperature.

Animals↗