Phase transitions: jumping between liquid states
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Journal Article↗
Biomedical subjects
P McMillan
Publications and source records attributed to P McMillan.
A comparative study of root-end induction using osteogenic protein-1, calcium hydroxide, and mineral trioxide aggregate in dogs.
Calcium hydroxide has been the material of choice for apexification. The purpose of this study was to compare the efficacy of osteogenic protein-1 and mineral trioxide aggregate with that of calcium hydroxide in the formation of hard tissue in immature roots of dogs. Sixty-four roots of premolars were used. After induction of periradicular lesions, the canals were debrided and filled with calcium hydroxide for 1 wk. After the removal of calcium hydroxide, the root canals received one of the treatment materials in a balanced design. The animals were euthanized 12 wk later. The degree of hard tissue formation and amount of inflammation were evaluated histomorphically. Data were statistically evaluated using ANOVA, chi 2, and Kruskal-Wallis. Mineral trioxide aggregate produced apical hard tissue formation with significantly greater consistency. The difference in the amount of hard tissue produced among the three test materials was not statistically significant. Furthermore, the degree of inflammation was not significantly different between the various test groups.
Aluminum Compounds↗
Macrophage trafficking in the uterus and cervix precedes parturition in the mouse.
Immune activation is implicated in the etiology of preterm labor, but little is known about macrophage number or distribution in the uterus or cervix at term. This study tested the hypothesis that macrophages migrate into the reproductive tract before the onset of parturition. Paraffin-embedded sections from the mid-uterine horn and cervix of C3/HeN mice on Days 15 and 18 of pregnancy, the day of birth (Day 19), and 1 day postpartum were stained with a pan-macrophage marker to analyze cell numbers and distribution. During pregnancy, uterine macrophages were dispersed in endometrium, usually associated with vasculature and subluminal epithelium. In myometrium, macrophages were clustered in stromal connective tissue; near term and postpartum, cells appeared to surround the muscle bundles. Total macrophage numbers were increased on Day 15 relative to those in nonpregnant controls, declined before birth, and increased postpartum. In the cervix, macrophages congregated in subepithelium, often perivascular or near ganglia. Macrophage numbers in the cervix peaked on Day 18, then declined to nonpregnant levels by the day after birth. Thus, macrophage numbers in the uterus were inversely related to those in the cervix. These findings raise the possibility that macrophages and their products may be involved in uterine contractility and cervical remodeling during the processes of parturition.
Animals↗
Altered formation and bulk absorption of cerebrospinal fluid in FGF-2-induced hydrocephalus.
Upregulation of certain growth factors in the central nervous system can alter brain fluid dynamics. Hydrocephalus was produced in adult Sprague-Dawley rats by infusing recombinant basic fibroblast growth factor (FGF-2) at 1 microg/day into a lateral ventricle for 2, 3, 5, or 10-12 days. Lateral and third ventricular enlargement progressively increased from 2 to 10 days. Ventriculomegaly was also induced by a 75% reduced dose of FGF-2. At 10-12 days, there was a 29% attenuation in cerebrospinal fluid (CSF) formation rate, from 2. 5 to 1.8 microliter/min (P < 0.01). Choroid plexus, the main site of CSF secretion, had an augmented number of dark epithelial cells, which have previously been associated with decreased choroidal fluid formation. The twofold elevated resistance to CSF absorption, i.e., 0.8 to 1.7 mmHg. min(-1). microliter(-1), was attributable, at least in part, to enhanced fibrosis and collagen deposits in the arachnoid villi, a major site for CSF absorption. Normal CSF pressure (2-3 mmHg) was consistent with a patent cerebral aqueduct and reduced CSF formation rate. The FGF-2-induced ventriculomegaly is interpreted as an ex vacuuo hydrocephalus brought about by an altered neuropil and interstitium of the brain.
Absorption↗
Apparently new syndrome of sensorineural hearing loss, retinal pigment epithelium lesions, and discolored teeth.
We report on a family with early-onset sensorineural hearing loss, abnormal retinal pigment epithelium granularity, accumulation of creamy-white lesions at the level of the retinal pigment epithelium particularly superior to the arcade, and selective discoloration (brown) of molars or canine deciduous teeth that follows an apparent autosomal recessive inheritance pattern. This appears to be a new syndrome that can be distinguished from the known otodental, oculo-acoustic and flecked retina syndromes by the occurrence of distinct dental and ocular abnormalities.
Child, Preschool↗
Effects of resorbable membrane placement and human osteogenic protein-1 on hard tissue healing after periradicular surgery in cats.
Periradicular surgeries were performed on the maxillary cuspid teeth of twelve cats. Before reapproximation of the surgical flaps, eight of the osteotomies were covered with a resorbable membrane and eight were filled with human osteogenic protein-1 (hOP-1) on a collagen carrier. The remaining eight sites received no further treatment and served as controls. The animals were euthanized after 12 wk, and the specimens were examined histomorphometrically for the presence or absence of osseous regeneration, inflammation, and cementum formation on the root ends. The results showed that the sites treated with the membrane exhibited significantly more inflammation adjacent to the resected root ends (p < 0.05), and that the use of the membrane had no statistically significant effect on osseous healing or new cementum formation. The use of hOP-1 was associated with a significant decrease in the thickness of new cementum formed on the resected root ends (p < 0.05), but had no statistically significant effect on osseous healing or degree of inflammation. Based on these results, it seems that neither the use of hOP-1 nor resorbable membranes have a positive effect on periradicular tissue healing in endodontic surgery.
Absorbable Implants↗
The temporal profile and morphologic features of neuronal death in human stroke resemble those observed in experimental forebrain ischemia: the potential role of apoptosis.
Although neuronal death has been studied in experimental models of ischemia, the precise mechanisms regulating cell death remain unclear. Furthermore, the timing and pattern of neuronal death in human stroke has not been extensively studied. To further our understanding of ischemia-induced neuronal death, we examined the temporal profile of histochemical and morphologic characteristics of hippocampal neuronal death following experimental forebrain ischemia and compared these findings to human brain specimens obtained from subjects suffering cerebral infarction. Transient forebrain ischemia (TFI) was induced in normothermic adult rats by bilateral carotid artery occlusion combined with hypotension. Animals were sacrificed at 6, 12, 18, 24, 48, and 72 h and 7, 14, and 28 days following ischemia (n = 4 at each time point). Experimental tissue was analyzed using light and electron microscopy as well as TUNEL histochemistry. A total of 27 human brain specimens with neuropathological confirmation of ischemic damage and appropriate controls were also examined using light microscopy and TUNEL histochemistry. Dense TUNEL staining in hippocampal CA-1 neurons was present at 48 and 72 h following experimental ischemia. Prior to these times, little or no nuclear staining was noted and after 72 h nuclear staining diminished rapidly. Ultrastructural findings at these time points demonstrated many features similar to those seen in cells undergoing apoptosis, such as cell shrinkage with increased electron density, chromatin condensation with formation of heterochromatin, intact plasma membranes, and intact intracellular organelles. In a similar fashion, human stroke specimens during the subacute period showed dense nuclear TUNEL staining in penumbral neurons, whereas in the acute or chronic stages little or no staining was noted. Our results demonstrate that the timing of morphologic changes and TUNEL histochemistry following human stroke resembles that observed in experimental TFI. Furthermore, neuronal death in both experimental ischemia and human stroke share several features characteristic of apoptotic cell death.
Adolescent↗
Uracil misincorporation in human DNA detected using single cell gel electrophoresis.
Poor folate status may be important in the aetiology of several epithelial cell malignancies including cancer of the uterine cervix. Folic acid is essential in the synthesis of purine nucleotides and the pyrimidine nucleoside thymidine and it is probable that imbalances in these DNA precursors negatively effect DNA stability and may ultimately lead to malignant transformation. The development of a modified 'comet assay' using the bacterial DNA repair enzyme uracil DNA glycosylase, to detect misincorporated uracil in human DNA is reported here. The effect of perturbing folic acid and deoxyuridine levels on uracil misincorporation in normal human lymphocytes and cultured human tumour cells was investigated using this assay. HeLa cells and peripheral human lymphocytes incubated as agarose-embedded nucleoids, with 1 unit of uracil DNA glycosylase per microg of DNA, contained low levels of uracil in their DNA. Both HeLa cells and stimulated human lymphocytes cultured in folate-deficient medium were growth arrested. Incubating human lymphocytes in folate-deficient medium significantly increased the level of uracil detected compared with control cells. HeLa cells showed an increase in non-specific DNA damage (strand breaks). Deoxyuridine (100 microM) significantly increased the level of uracil detected in the DNA of both folate-deficient and control HeLa cells. It appears that this modified comet assay specifically detects misincorporated uracil in single human cells. It should, therefore, prove valuable in determining the role of folic acid status in DNA instability and cancer.
Cell Division↗
Measurement of blood flow with radiolabeled microspheres in reflected mucogingival flaps in cats.
To quantify and compare blood flow in maxillary mucogingival flaps, a total of 16 cats (32 mucogingival specimens) were divided into two groups. In group I the blood flow in attached or reflected maxillary tissues were measured. In Group II the effects on blood flow were measured in reflected tissues after the injection of the following solutions: (1) saline solution; (2) 2% lidocaine plain; (3) 2% lidocaine with 1:50,000 epinephrine; (4) no injection. After an injection of 153 Gadolinium microspheres into the left ventricle of the heart, the tissues were harvested and placed in a gamma counter. Group I had a mean blood flow value of 34.4 ml/min/100 gm of tissue for the unreflected samples and 152.3 ml/min/100 gm of reflected tissue. The levels of blood flow in tissue samples in group II results were: no injection (control), 41.2 ml/min/100 gm; saline solution, 46.8 ml/min/110 gm; 2% lidocaine with 1:50,000 epinephrine, 60.6 ml/min/100 gm; and 2% lidocaine plain, 90.2 ml/min/100 gm. On the basis of these results it appears that reflection of gingival tissue and injection of 2% lidocaine plain induces increased blood flow 90 minutes postoperatively.
Adrenergic beta-Agonists↗
Identification of the thyrotropin-releasing hormone precursor, its processing products, and its coexpression with convertase 1 in primary cultures of hypothalamic neurons: anatomic distribution of PC1 and PC2.
The processing of pro-TRH, has been extensively studied in our laboratory using a corticotropic cell line, AtT20, transfected with the pro-TRH gene. We have also demonstrated that the convertases PC1 and PC2 process pro-TRH to cryptic peptides in vitro. However, although these processing pathways have been well characterized in vitro, little is known about the processing and subcellular distribution of pro-TRH and its derived peptides in hypothalamic neurons, an endogenous source of pro-TRH and PC enzymes. In this study we used multiple approaches to identify, both biochemically and anatomically, the presence and localization of pro-TRH (26 kDa) and its processing products. We also investigated the presence of PC1 and PC2 enzymes and the coexpression of pro-TRH and PC1 messenger RNAs. Identification of the TRH precursor was demonstrated by 1) Western blot analysis of cellular extracts, 2) immunoprecipitation of radiolabeled pro-TRH followed by analysis on acrylamide gel electrophoresis, 3) fluorescence immunocytochemistry, and 4) immunoelectron microscopy. The presence of the convertases PC1 and PC2 was determined by Western blot analysis of cellular extracts and fluorescence immunocytochemistry. The coexpression of pro-TRH with PC1 was shown by double in situ hybridization. Our findings support three main conclusions. First, this primary culture system of hypothalamic neurons is suitable for characterizing pro-TRH processing as well as identifying the anatomical location of its processing products. Second, prohormome processing takes place during axonal transport after removal of the signal peptide in the endoplasmic reticulum, and subsequent cleavages of the prohormone occur as intermediate peptides move down the axon toward the nerve terminal. This coupled transport-processing phenomenon may provide the necessary mechanism to ensure flexibility in differential processing of specific protein sequences that are determined by the secretory needs of cells. It appears that certain intermediate peptides differ in their subcompartmental distribution, suggesting the possibility of a differential processing and maturation of pro-TRH-derived peptides. Thirdly, the 87-kDa form of PC 1 may initiate the processing of pro-TRH at the Golgi complex level, which then continues to be processed by PC1 and PC2 in later stages of the secretory pathway.
Animals↗
Role of T cells in the pathogenesis of periapical lesions. A preliminary report.
The pulps of mandibular molars of 15 athymic and 15 conventional rats were surgically exposed and left open to their oral flora. Each group was divided into three subgroups of five animals each. The rats were killed after their pulps were exposed for 2, 4, or 8 weeks. After fixing, decalcifying, and embedding, the specimens were sectioned and stained with hemotoxylin and eosin. They were then examined under a microscopic grid and quantified by percentages of surface areas of bone, connective tissue, bone marrow, intrabony spaces, periapical lesions, and numbers of osteoclasts, with the use of a DataVoice computerized data collection and analysis system. Statistical analysis showed no significant difference between periapical tissue responses of the conventional and athymic groups. The results indicate that the pathogenesis of periapical lesions is a multifactorial phenomenon and is not totally dependent on the presence of T-cell lymphocytes.
Analysis of Variance↗
Raman spectroscopic studies of hen egg-white lysozyme at high temperatures and pressures.
In situ high-temperature, high-pressure Raman experiments on 3 mM (pH 5) aqueous solutions of hen egg-white (HEW) lysozyme show a decrease in the relative height of the 505 cm-1 band associated with S-S stretching vibrations at 72 degrees C (1 bar). The peak height changes are accompanied by significant band broadening, and the integrated band intensity does not change within experimental error. The effect of increased pressure at 72 degrees C was to hinder broadening of the 505 cm-1 band. HEW lysozyme (2.4 mM, pH 5) was also heated at 76 degrees C, 80 degrees C, and 95 degrees C for different periods of time, and aliquots were quenched to room temperature for Raman and enzymatic activity measurements. After 9 hr at 76 degrees C, the protein exhibits enzyme activity less than 50% of the initial value, and approximately 50% reduction in activity is achieved after 3 hr at 80 degrees C or 1 hr at 95 degrees C. The Raman results suggest that different irreversibly denatured conformations are attained during prolonged exposures at these different temperatures. It is apparent from these studies that the S-S stretch intensity is decreased irreversibly.
Amino Acid Sequence↗
Tissue reaction to intraperitoneal polymer implants: species difference and effects of corticoid and doxorubicin.
The peritoneal cavity is a convenient site for implantation of encapsulated hormone-secreting tissue. However, host tissue organization around such implants may affect solute exchange and viability of the encapsulated tissue. The reaction to polyvinyl chloride acrylic copolymer capsules implanted in the peritoneal cavity of rats and mice was therefore studied. Some animals received a slow release dexamethasone pellet, others were pretreated with doxorubicin, in an attempt to minimize the tissue reaction. The tissue reaction was significantly thicker in rats than in mice at both 2 and 6 weeks after implantation. In rats, corticoids decreased significantly the thickness of the reactive layer as compared to control at all time points studied, but doxorubicin had no effect. The tissue reaction in mice was not significantly affected by corticoid treatment. In both species the thickness of the tissue reaction did not increase significantly between 2 and 6 weeks. At 3 days the tissue reaction consisted of an interrupted single layer of macrophages in mice, whereas in rats the reaction consisted of two or three layers of macrophages and polymorphonuclear cells. At both 2 and 6 weeks, several cell layers surrounded the implants: a single layer of macrophages lying along the polymer, a variable number of layers of fibroblasts interspersed with collagen fibrils (fewer in mice than in rats, and fewer in corticoid treated rats than control rats) and an outer monolayer of mesothelial cells. We conclude that the intensity of tissue reaction to polymer implants in the peritoneal cavity is species dependent and can be decreased by the administration of corticoids but not doxorubicin.
Adrenal Cortex Hormones↗
Use of semipermeable polyurethane hollow fibers for pituitary organ culture.
A new model for organ culture of endocrine tissue is described. Rat anterior pituitary fragments were cultured for 4 wk within semipermeable polyurethane isocyanate hollow fibers. Growth hormone and prolactin, two of the anterior pituitary hormones, were released into the medium during the entire culture period. Electron microscopy of the pituitary fragments after 2 wk in culture showed a rim of viable tissue in all specimens examined. Individual cells, from this outer rim, exhibited excellent organelle preservation and numerous secretory granules. Experiments involving potassium depolarization and 10(-6) M dopamine provided evidence for the normal responsiveness of the cultured pituitary tissue to both stimulatory and inhibitory factors. These studies illustrate the potential utility of the described organ culture system for further investigations of endocrine physiology.
Animals↗
Electron microscopic identification of parvovirus virions in erythroid-line cells in fatal hydrops fetalis.
Intrauterine infection with parvovirus B19 may lead to fatal hydrops fetalis. Intranuclear particles, consistent with parvovirus virions, within erythroid cells were readily identified on transmission electron microscopy of formalin-preserved material obtained at necropsy from a neonate and two fetuses in whom clinical and light microscopic criteria for parvovirus B19 infection were met. No such particles were seen in similar material from a neonate and two fetuses with erythroblastosis fetalis due to alpha-thalassemia, maternofetal Rh incompatibility, and an erythrocyte membrane protein defect. When other means of investigation are impracticable transmission electron microscopy is widely available and easily performed and may be of value in establishing a diagnosis of parvovirus B19 infection.
Adult↗
Long-term plasma glucose normalization in experimental diabetic rats with macroencapsulated implants of benign human insulinomas.
Permselective tubular membranes (1 mm i.d.) were filled with fragments of nine freshly resected human insulinomas, closed at both ends, and implanted in the peritoneal cavity of 30 streptozocin-induced diabetic rats. In 14 animals, nonfasting plasma glucose (PG) and insulin levels were normalized by these immunoprotected transplants for up to 1 yr (PG from 520 +/- 12 to 142 +/- 3 mg/100 ml; insulin from 6 +/- 0.5 to 44 +/- 3 microU/ml). These animals showed the same weight gain after 12 mo of observation as 20 controls. The remaining 16 animals showed an incomplete or transient correction of their diabetes and survived 4-6 mo, versus less than 8 wk in untreated animals. Removal of the membrane-encapsulated insulin-secreting tissue from 8 successfully treated rats led to hyperglycemia and death within 10 days. Histology and electron microscopy of insulinoma tissue retrieved after long-term implantation showed functionally active endocrine cells and no evidence of graft rejection. In vitro perifusion gave similar results for encapsulated and nonencapsulated insulinoma tissue. The amount of insulin secreted was quite variable, and responsiveness of the insulinoma to changes in glucose concentration of the surrounding medium was observed in three out of the five tumors studied. These observations establish the effectiveness of immunoseparation by a synthetic membrane in a pancreatic xenograft model.
Adenoma, Islet Cell↗
Encapsulated human islet transplants in diabetic rats.
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Animals↗
[Anatomic and functional study of endocrine pancreatic tissue enclosed in hollow fibers].
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Animals↗