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B J Baum

Publications and source records attributed to B J Baum.

At least 91 records · Page 5Linked to original sources
PubMed1996

Aquaporin 1 expression during the cell cycle in A5 cells.

Aquaporin 1 is an integral membrane protein which functions as a water channel. It is reportedly (Lanahan et al., 1992) encoded by a delayed early response gene. We asked if the expression of aquaporin 1 varied during the cell cycle in an epithelial cell line (A5) in which its is constitutively expressed. A5 cells were synchronized by double thymidine block and cell cycle stages defined by flow cytometric analysis. AQP1 mRNA and protein levels were highest when most cells were in G0/G1, then decreased approximately 40-60% when the cells moved into the S and G2/M phases. These results provide the first demonstration that constitutive aquaporin 1 expression can fluctuate during the cell cycle.

Animals↗
PubMed1996

Evidence for the systemic delivery of a transgene product from salivary glands.

The aim of this study was to assess the feasibility of using gene transfer to salivary glands to direct the systemic delivery of therapeutic proteins in vivo. We used a replication-deficient recombinant adenovirus vector (Ad alpha 1AT) that encodes human alpha 1-antitrypsin (h alpha 1-AT), which we used as a marker protein. Ad alpha 1AT (5 x 10(9) pfu) was administered by retrograde ductal instillation to the submandibular glands of male rats. The amount of h alpha 1-AT found in the salivary glands, saliva, serum, and other tissues was analyzed by a sensitive enzyme-linked immunosorbent assay (ELISA). Maximal levels of the marker protein were detected at 24-48 hr post-virus administration for glands (274 ng/mg protein), saliva (approximately 313 ng/ml), and serum (approximately 5 ng/ml). Serum levels remained elevated for 96 hr, whereas the measured half-life for the marker protein was approximately 2 hr. Generally little to no h alpha 1-AT was detectable in most other organs. However, we were able to measure low levels of marker protein in tissues immediately surrounding infected glands. In all animals studied, levels of h alpha 1-AT were higher in the glandular venous effluent than in arterial blood. Similar results were found with parotid glands. The aggregate data demonstrate that salivary glands may be a target for the nonsurgical, systemic delivery of transgene-encoded therapeutic proteins for diseases that require relatively low circulating protein levels.

Adenoviruses, Human↗
PubMed1996

Adenovirus-mediated expression of aquaporin-5 in epithelial cells.

A recombinant adenovirus coding for rat aquaporin-5 was constructed and plaque purified. The recombinant adenovirus (AdrAQP5) mediated the expression of aquaporin-5 in rat and human salivary cell lines and in dog kidney cells in vitro as demonstrated by Northern blot and Western blot analyses, and by confocal microscopy after immunofluorescent labeling. In kidney cells, expression of the transgene was optimal if cells were infected at their basolateral surface, a phenomenon associated with the distribution of integrin receptors on these cells. The expressed aquaporin-5 protein was functionally active because viral-mediated gene transfer resulted in a significant increase in the osmotically directed net fluid secretion rate across monolayers of kidney cells. AdrAQP5 should provide an efficient and useful means to impart facilitated water permeability to cells lacking such a pathway.

Adenoviridae↗
PubMed1996

Immediate inflammatory responses to adenovirus-mediated gene transfer in rat salivary glands.

Although replication-deficient adenoviruses can efficiently transfer genes to the salivary glands, the current vectors precipitate an immediate, transient decrease in salivary function. To study the cause of this salivary hypofunction, 10(6)-10(10) plaque-forming units (pfu) of the vector AdCMV beta gal were delivered by retrograde ductal infusion to the submandibular glands (SMGs) of rats. Microscopic analysis of infected glands showed a dose-related, rapidly developing inflammatory response, which at the highest amount of virus was characterized by a predominantly neutrophil-containing infiltrate, focal necrosis, and edema. Moreover, the glands of nude rats developed similar morphologic changes to those of immunocompetent rats. After 3 days, the volume of stimulated saliva secreted from SMGs receiving AdCMV beta gal (6.75 x 10(9) pfu) was approximately 20% that of controls. UV-inactivated virus caused a similar decrease in saliva output. We evaluated to what extent the anti-inflammatory glucocorticoid, dexamethasone, could suppress inflammation and preserve salivary function. Three days after infusion with a high dose of AdCMV beta gal (6.75 x 10(9) pfu), the glands from dexamethasone-treated animals showed markedly less inflammation and no necrosis. Furthermore, there was no significant difference in the average amount of saliva secreted from the infected glands (105 +/- 17 microliters) compared to the control glands (123 +/- 18 microliters). In addition, dexamethasone extended the expression of beta-galactosidase in the SMGs. These results suggest that the adenovirus-mediated acute inflammation in rat SMG is responsible for diminished gland function and transgene expression. Furthermore, we demonstrate a useful role for glucocorticoids in controlling acute inflammation during experimental gene transfer with current adenovirus vectors.

Adenoviridae↗
PubMed1996

Interferon-gamma induced cell death in a cultured human salivary gland cell line.

Increased levels of several cytokines, including interferon-gamma (IFN-gamma) and tumor necrosis factor-alpha (TNF-alpha), have been demonstrated in the salivary gland microenvironment of patients with Sjögren's syndrome (SS). How these cytokines may be contributing to the pathogenesis of the disease is not well understood. This study examined the role of IFN-gamma +/- TNF-alpha on cellular death in a cultured human salivary gland cell line (HSG). Cells treated long-term with IFN-gamma +/- TNF-alpha demonstrate a profound antiproliferative effect with a decrease in cell number to below that initially plated. Treatment of HSG cells with TNF-alpha alone did not have any significant effects on growth but did increase the expression of the IFN-gamma receptor. Cells labelled with propidium iodide and anti-digoxigenin dUTP/dATP were examined by flow cytometry to determine the percentage of cells exhibiting low DNA content and DNA strand breaks. The percentage of cells exhibiting subdiploid DNA and DNA strand breaks increased with increased time of exposure to the cytokines. The maximum percentage of cells exhibiting DNA degradation at 12 days was 58% for cells treated with IFN-gamma + TNF-alpha, 31% for IFN-gamma treated cells, and < 5% for TNF-alpha-treated and untreated cells. The cells with subdiploid ( < 2n) DNA were subsequently demonstrated to represent two populations, both with evidence of increased DNA strand breaks but with differing light scatter characteristics. One population had features of cells undergoing necrosis, whereas the second population exhibited features of apoptosis. These findings were confirmed by transmission electron microscopy. Cells not exposed to cytokines did not exhibit significant evidence of either death process. We conclude that long-term exposure of a human salivary gland epithelial cell line to IFN-gamma +/- TNF-alpha leads to increased DNA degradation and subsequent cell death. This suggests a potential SS disease mechanism and implicates the role of the epithelial cell in this disease as an important area for future study.

Cell Count↗
PubMed1996

A 2 week pair-fed study of early X-irradiation effects on rat major salivary gland function.

Salivary gland function is affected shortly after irradiation of the head and neck. An intense oral mucositis develops after exposure and may interfere with ingestion. The effects of restricted food and water intake on the secretory output of rat major salivary glands were examined. Parotid and submandibular salivary output and body weight were measured in rats at 4, 8, 11 and 14 days after 15 Gy X-irradiation of the head and neck. Comparisons were made with two groups: a non-irradiated group with food and water intake restricted to that of the irradiated group (pair-fed), and a non-irradiated, ad libitum-fed control group. Parotid saliva output was significantly decreased in the irradiated group at 4, 8, and 11 days compared with the control group. The pair-fed rats also had significantly decreased parotid output at these time points and their parotid function did not differ from that of the irradiated animals. At 14 days, all three groups demonstrated similar parotid function. Submandibular salivary output was not affected to the same extent. Only at a single time point (11 days) was flow significantly decreased in the irradiated group. Total body weight was less than that of control rats for both the irradiated and pair-fed animals at all time points. These results suggest that the early effects of radiation on salivary glands are due, in part, to limited intake of food and water during the immediate post-irradiation period.

Analysis of Variance↗
PubMed1996

The dental curriculum: what should be new in the 21st century?

Dental education is at a critical juncture. The success of water fluoridation has reduced the caries burden of Americans and, consequently, has raised questions about the disproportionate technical emphasis on treating the sequelae of caries in US dental schools. Additionally, several powerful external factors-such as changing demographics, advances in biological science, fundamental changes in our health care delivery system, and a modest US economy-are forcing dental educators to question the appropriateness of retaining the current dental curriculum into the 21st century. The author considers these factors, suggests what type of dentist will be needed by society in approximately 20 years, and concludes that today's dental educational system is inadequate to produce such a dentist. Several elements, in addition to technical excellence, are required for the dental curriculum, including major changes in pedagogy, relevant science training, practical fluency in medicine, an increased mix of stomatologic skills, and broader contact with other health care providers.

Biological Science Disciplines↗
PubMed1996

Interferon-gamma induces persistent depletion of internal Ca2+ stores in a human salivary gland cell line.

Interferon-gamma (IFN-gamma), in the presence of tumor necrosis factor-alpha (TNF-alpha), decreases proliferation of a human salivary gland ductal cell line, HSG (Wu, A., R. Kurrasch, J. Katz, P. Fox, B. Baum, and J. Atkinson. J. Cell. Physiol. 161:217-226, 1994). We examined the possible effects of these cytokines (1,000 U/ml IFN-gamma +/- 20 U/ml TNF-alpha for 7 days) on Ca2+ mobilization in HSG cells. In HSG cells, fetal bovine serum (10%) or carbachol (100 microM) stimulated rapid increases in cytosolic Ca2+ concentration ([Ca2+]i), apparently mobilized from different thapsigargin-sensitive intracellular Ca2+ stores. Serum induced a proliferative effect on HSG cells, which was suppressed (> 90%) by treatment with IFN-gamma +/- TNF-alpha, but not with TNF-alpha alone. Serum-, carbachol-, and thapsigargin-stimulated [Ca2+]i elevations were reduced by 90, 60, and > 65%, respectively, in cells treated with IFN-gamma +/- TNF-alpha and 30, 45, and 45%, respectively, in cells treated with TNF-alpha. Removal of the cytokines from the growth medium induced recovery of both cell proliferation and Ca2+ mobilization responses within 7 days. Treatment of HSG cells with thapsigargin (0.02-2 nM) induced a dose-dependent decrease in cell proliferation. Additionally, acute treatment (< 10 min) of cells with IFN-gamma did not affect [Ca2+]i or alter carbachol-, thapsigargin-, or serum-induced changes in [Ca2+]i. These data demonstrate that prolonged treatment of HSG cells with IFN-gamma +/- TNF-alpha leads to a persistent depletion of intracellular Ca2+ stores. We suggest that this may have a role in cell growth.

Blood Physiological Phenomena↗
PubMed1995

Decreased m3-muscarinic and alpha 1-adrenergic receptor stimulation of PIP2 hydrolysis in parotid gland membranes from aged rats: defect in activation of G alpha q/11.

m3-Muscarinic cholinergic receptor (m3-AChR) and alpha 1-adrenergic receptor (alpha 1-AR) stimulation of phosphatidylinositol 4,5-bisphosphate (PIP2) hydrolysis (by a PIP2-specific phospholipase C, PLC) in rat parotid gland membranes is mediated via activation of alpha subunits of the Gq/11 family of G-proteins. This study examines m3-AChR and alpha 1-AR stimulation of PIP2 hydrolysis in membranes isolated from parotid glands of old (24 months) and young (3 months) rats (old and young rat membranes). Old rat membranes exhibited reduced stimulation of PIP2 hydrolysis in response to the addition of guanosine-5'-O-(3-thiotrisphosphate) (GTP gamma S) alone or GTP gamma S plus either carbachol (m3-AChR agonist) or epinephrine (alpha 1-AR agonist). This reduction in receptor-stimulated PIP2 hydrolysis was not due to a decrease in PLC activity per se since cholate-solubilized PLC activity was similar in old and young rat membranes. Additionally, these membranes exhibited comparable, immunologically detectable, levels of PLC beta 3, G alpha q/11, and G beta. In the presence of 10 microM AlCl3 and 10 mM NaF, stimulation of PIP2 hydrolysis in both old and young rat membranes was similar. Preincubation of membranes from old rats with GTP gamma S induced a time-dependent increase in the rate of PIP2 hydrolysis and, with 20 min preincubation, the rates of hydrolysis in old and young rat membranes were not statistically different. In aggregate, these data indicate that there is a defect in the activation of G alpha q/11 in parotid gland membranes from old rats.

Adenylyl Cyclases↗
PubMed1995

Alpha 1-adrenergic and m3-muscarinic receptor stimulation of phosphatidylinositol 4,5-bisphosphate-specific phospholipase C are independently mediated by G alpha q/11 in rat parotid gland membranes.

Stimulation of m3-muscarinic cholinergic receptors (m3AChR) in the rat parotid gland increases the hydrolysis of phosphatidylinositol 4,5-bisphosphate (PIP2) via activation of the G alpha/11 family of G-proteins (Sawaki et al. (1993) Arch. Biochem. Biophys., 546-550). Herein we report that alpha 1-adrenergic receptor (alpha 1-AR) stimulation of PIP2 hydrolysis is also mediated via alpha subunits of the G q/11 family of G-proteins. The alpha 1-AR agonist, epinephrine, induced a dose-dependent increase (1.5-fold maximum) of exogenously added PIP2 in the presence of guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S), which was inhibited by the alpha 1-AR antagonist, phentolamine, but not by the beta-adrenergic receptor antagonist, propranolol. The epinephrine-stimulated component of PIP2 hydrolysis was significantly inhibited by pretreating the membranes with an antiserum against G alpha q/11. When carbachol and epinephrine were present simultaneously (with GTP gamma S), the increase in PIP2 hydrolysis obtained was not significantly different from the sum of the increases in PIP2 hydrolysis obtained with each agonist alone. PIP2 hydrolysis stimulated in the presence of carbachol and epinephrine was inhibited by alpha 1-AR and m3AChR antagonists, phentolamine and atropine respectively, to the level obtained with each agonist alone. Notably, in the presence of both agonists the inhibition of PIP2 hydrolysis by anti-G alpha q/11 antiserum was not significantly different from the sum of the inhibitions obtained with each agonist alone. These results indicate that m3AChR and alpha 1-AR stimulation of PIP2 hydrolysis in rat parotid gland membranes are independently mediated by the G alpha q/11 family of G-proteins.

Animals↗
PubMed1995

Evidence for the presence of a Hg-inhibitable water-permeability pathway and aquaporin 1 in A5 salivary epithelial cells.

The molecular basis of water-permeability in salivary and other exocrine glands is not understood. We have examined two well-studied salivary epithelial cell lines for evidence of a Hg-inhibitable water-permeability pathway. A5 and HSG cells are derived from rat and human submandibular glands, respectively. Only A5 cells demonstrated such a pathway. The rate of A5 cell osmotic shrinkage was inhibited about fivefold in the presence of 300 microM HgCl2. To determine if this activity was associated with the expression of the prototypical water channel (aquaporin, AQP) AQP1, we used three separate experimental approaches; Northern analysis and reverse transcription-polymerase chain reaction (RT-PCR) analysis of isolated mRNA, and Western analysis of cell membranes. All three methods yielded positive results with A5 cells and negative results with HSG cells. The approximately 800 bp product of RT-PCR was analyzed further by sequencing and restriction enzyme digestion. The results were consistent with the previously reported coding region sequence for rat kidney AQP1. The aggregate data demonstrate that marked differences in water-permeability and water channel expression exist in these two salivary epithelial cell lines.

Animals↗
PubMed1995

Extended stimulated parotid and submandibular secretion in a healthy young and old population.

BACKGROUND: Previous morphological studies have shown that both the human parotid and submandibular glands display age-related reductions in the proportion of fluid secreting acinar cells. In contrast, short-term functional studies of fluid secretion do not show such a consistent disparity among different-aged persons. This study compared the ability of a population of healthy young and old individuals to secret saliva from the parotid and submandibular glands for an extended period of time under conditions of intense gustatory stimulation. METHODS: Saliva was collected over 30 minutes from 30 healthy, unmedicated individuals using 10% citric acid as a gustatory stimulus. Of the 30 subjects, 15 were young (age range 27-40 years) and 15 were old (age range 60-97 years). Parotid salivary flow rates were determined every minute, and submandibular flow rates were determined at 2, 10, 20, and 30 minutes. A comparison was made between the slopes of the two groups. The slopes were derived from the average salivary flow rate at each time point. RESULTS: There was no difference in the ability of the parotid glands of young and old individuals to secrete saliva. In contrast, the submandibular glands of the elderly individuals did not show the same pattern of secretion when compared to their younger counterparts, who demonstrated increasing flow rates over the test period. CONCLUSIONS: The parotid glands of young and old persons are able to maintain high secretory ability under the stress of intense stimulation for an extended period of time. Conversely, the submandibular gland demonstrates an age-related, statistically significant difference in the pattern of fluid secretion with an intense gustatory stimulus.

Adult↗
PubMed1995

Facilitated DNA transfer to rat submandibular gland in vivo and GRP-Ca gene regulation.

The internalization of DNA can be facilitated by adenovirus infection. Using the replication-deficient adenovirus, Ad-dl312, and a plasmid-based firefly luciferase gene as a reporter, we have optimized the uptake and expression of DNA in rat submandibular glands in vivo. Luciferase expression is transient and peaked at approximately 18 h after infection. Luciferase activity increased with plasmid concentration and was greatest at 10(9) to 10(10) plaque-forming units of Ad-dl312 per gland. We next examined the expression in vivo of plasmids containing deletions of the glutamine/glutamic acid-rich protein (GRP-Ca isoform) gene upstream region linked to a chloramphenicol acetyltransferase (CAT) reporter. Constructs with 9.4, 6.3, and 2.7 kb and 17 base pairs of upstream sequence gave relative CAT activities of 100, 30, 7.6, and 38.5, respectively. With the 9.4-kb GRP-Ca construct, CAT was preferentially expressed in acinar cells, which is characteristic of GRP. This gene transfer approach should prove useful in the further study of gene expression in salivary glands and other organs.

Adenoviridae↗
PubMed1995

Kinetic analysis of muscarinic receptors in human brain and salivary gland in vivo.

Previous studies in rats have suggested that the muscarinic acetylcholine receptor (mAChR) antagonist (S)-3-quinuclidinyl-(S)-4-[123I]iodobenzilate [(SS)-IQNB] may be useful for the in vivo evaluation of mAChRs in humans as a control for the higher-affinity compound (RR)-IQNB. We have directly tested this hypothesis and examined the distribution of mAChRs in brain regions and parotid glands of healthy human volunteers in vivo using (RR)- and (SS)-IQNB (relatively high- and low-affinity antagonists, respectively), planar imaging, and pharmacokinetic analysis. This is the first in vivo study of mAChRs in humans that has employed stereoisomeric ligands and metabolic analysis to determine specific receptor binding. We observed that (SS)-IQNB showed much faster clearance from blood than (RR)-IQNB and different metabolite profiles. Also, the transport kinetics of the enantiomers were different. The estimated binding potential (approximately Bmax/Kd) of (RR)-IQNB was highest in two cortical regions, intermediate in parotid gland, and lowest in cerebellum. The aggregate results show that in humans (SS)-IQNB does not act as an ideal general probe to measure the nonspecific IQNB distribution. However, (RR)-IQNB does appear to have value when used for studies of human brain mAChRs.

Adult↗
PubMed1995

The impact of gene therapy on dentistry.

To the casual observer, gene therapy--an emerging science--appears likely to have little impact on dentistry. However, even in these early research stages, it is clear that gene therapy will have a broad effect on dentistry. This article is designed to provide the practitioner with a general understanding of gene therapy, as well as several examples of how it is being used today in efforts to manage dental and oral problems better.

Animals↗
PubMed1994

Effect of tumor necrosis factor-alpha and interferon-gamma on the growth of a human salivary gland cell line.

Interferon-gamma (IFN-gamma) is a product of activated T-lymphocytes, and tumor necrosis factor-alpha (TNF-alpha) is a product of both lymphocytes and macrophages. These cell types are often present at sites of tissue damage secondary to chronic infection or autoimmune disease. The purpose of this study was to characterize the effects of TNF-alpha and IFN-gamma on a human submandibular gland epithelial cell line (HSG). IFN-gamma caused a concentration-dependent decrease in HSG cell growth (approximately 70% in 6 days). Conversely, TNF-alpha alone had little effect on the growth of these cells. When these cytokines were added in combination (20 units/ml TNF-alpha and 1,000 units/ml of IFN-gamma), there was a synergistic antiproliferative effect; no apparent cell growth was observed. The cytokine-induced antiproliferative effect was reversible. After the apparent cessation of cell growth for 3-6 days, removal of the cytokines permitted complete growth recovery. Further, cells that recovered and exhibited growth patterns that were similar to control cells remained susceptible to the antiproliferative effects of the cytokines. Flow cytometry revealed that the percentage of cells in G0/G1 with the combination of cytokines was significantly increased by 24 h. The antiproliferative effect of IFN-gamma alone and that of IFN-gamma and TNF-alpha in combination were blocked completely using an antibody to the IFN-gamma receptor. A hypothesized mechanism of tissue damage in autoimmune inflammatory disorders is via up-regulation of cell surface markers such as intercellular adhesion molecule type I (ICAM-1) and histocompatibility antigen HLA-DR which can exacerbate the inflammatory process. Treatment of HSG cells with IFN-gamma, with or without TNF-alpha, resulted in increased levels of ICAM-1 and the acquisition of HLA-DR expression. These aggregate data suggest that IFN-gamma alone can regulate the expression of cell surface markers involved in the inflammatory process as well as cause a potent yet reversible inhibition of HSG cell growth that is modulated by the presence of TNF-alpha.

Antibodies↗