Search PubMed⌕ Search

Biomedical subjects

B J Baum

Publications and source records attributed to B J Baum.

At least 109 records · Page 6Linked to original sources
PubMed1994

Examination of rat salivary glands for the presence of the aquaporin CHIP.

The aquaporin CHIP, AQP-CHIP, is a 28-kDa integral membrane protein that functions as a water channel in kidney and red blood cells. We have examined rat salivary glands for the presence of this molecule. In Northern blot analyses an AQP-CHIP cDNA hybridized to rat kidney mRNA approximately 20-fold more than to mRNA from the rat parotid gland. Western blot analyses, using antisera against human AQP-CHIP, showed that AQP-CHIP was present in crude membranes from rat salivary glands to a much lesser extent than in rat kidney membranes. A 2.8 kb cDNA encoding AQP-CHIP was also isolated from an adult rat parotid gland cDNA library. Immunolocalization studies using thin and ultrathin cryosections and light and electron microscopy, however, revealed that no glandular epithelium was labeled. In contrast, significant immunolabeling was present in microvascular endothelial cells. Non-fenestrated endothelia of capillaries and venules exhibited labeling on both their apical and basolateral membranes. The present study demonstrates that AQP-CHIP is not involved directly in fluid secretion from salivary epithelial cells. Further, this study provides strong evidence that AQP-CHIP is an endothelial cell water channel found within salivary gland tissue which may contribute to water permeability in the capillary beds.

Animals↗
PubMed1994

Rat salivary gland blood flow and blood-to-tissue partition coefficients following X-irradiation.

Effects of a single high dose of X-irradiation (15 Gy) to the head and neck region in adult male rats were examined. Three days after radiation, rats were infused with [14C]-iodoantipyrine (IAP) via the femoral vein. Animals were killed at designated times thereafter and the three major salivary glands removed. The uptake of IAP by these tissues was analysed using a pharmacokinetic model. Radiation had relatively modest effects on all measured variables when compared with results from the non-irradiated control and pair-fed groups.

Animals↗
PubMed1994

Interaction of iodinated quinuclidinyl benzilate enantiomers with M3 muscarinic receptors.

We examined the interaction of 3-quinuclidinyl-4-iodobenzilate enantiomers, (RR)- and (SS)-IQNB, relatively receptor-active and -inactive, respectively, with M3-muscarinic receptors (mAChRs) in rat parotid acinar cells in vitro. This stereospecific antagonist pair has often been used for in vivo studies of mAChRs. There was a 16-fold difference in the ability of (RR)- and (SS)-IQNB to bind in vitro to mAChRs; Ki values estimated by competition with N-methylscopolamine were 5.3 and 84.2 nM, respectively. However, the ability of these antagonists to inhibit carbachol-stimulated inositol trisphosphate formation (Ki values determined by Schild analyses) was more similar, 16.3 and 47.7 nM, respectively for (RR)- and (SS)-IQNB. These data suggest that while it may be useful to employ this antagonist pair to evaluate some mAChR subtypes in vivo, it is difficult to use them in studies of M3-mAChRs.

Animals↗
PubMed1994

Direct in vivo adenovirus-mediated gene transfer to salivary glands.

Gene transfer to the salivary glands holds the potential for the therapy of salivary gland disorders and for delivery of therapeutic proteins to the mouth and upper gastrointestinal tract. Administration of the recombinant adenovirus vectors Ad.RSV beta gal [coding for the intracellular protein beta-galactosidase (beta-Gal)] and Ad alpha 1AT [coding for human alpha 1-antitrypsin (alpha 1-AT), a secreted protein] to salivary gland cell lines in vitro demonstrated exogenous gene expression. Retrograde ductal injection of the Ad.RSV beta gal vector to rat salivary glands in vivo resulted in beta-Gal expression in acinar and ductal cells. Exposure of submandibular glands in vivo to Ad alpha 1AT resulted in expression of alpha 1-AT mRNA transcripts, de novo synthesis of alpha 1-AT, and secretion in the saliva. To evaluate the feasibility of adenovirus-mediated gene transfer to human glands, human minor salivary glands were infected ex vivo with Ad.RSV beta gal, and implanted into severe combined immunodeficient mice. Evaluation of the human tissue demonstrated beta-Gal activity. These observations demonstrate that adenovirus vectors are capable of direct delivery of genes to the salivary glands, suggesting a variety of possible gene therapy applications.

Adenoviridae↗
PubMed1994

Kinetic analysis of rat exocrine gland muscarinic receptors in vivo.

Recently we employed two enantiomers of the muscarinic antagonist quinuclidinyl iodobenzilate (IQNB), and pharmacokinetic analyses, to define and quantitate nonspecific and specific binding to rat parotid gland muscarinic acetylcholine receptors (mAChRs) in vivo (Hiramatsu et al., 1993). The present studies were designed to utilize this same approach for evaluating mAChRs in three other morphologically different rat exocrine glands: the submandibular, sublingual and lacrimal glands. The metabolism and tissue distribution of the intravenously injected IQNB enantiomers were determined, and the resulting data were assessed in terms of their goodness of fit to several multicompartmental models. All three exocrine glands showed substantial nonspecific ligand distribution as measured with the receptor-inert enantiomer (SS)-IQNB. Nonspecific distribution represented 45, 21 and 36% of total ligand distribution in submandibular, sublingual and lacrimal glands, respectively, as measured with the receptor-active enantiomer (RR)-IQNB. The rank order of the binding potential, kinetically equivalent to Bmax/Kd, for (RR)-IQNB and these mAChRs was lacrimal > sublingual > submandibular glands (674 +/- 235 > 575 +/- 109 > 345 +/- 29). These results demonstrate that specific mAChRs in the exocrine glands can be measured in vivo with the (RR)-IQNB enantiomer and that despite some small quantitative differences, the distribution of (RR)- and (SS)-IQNB is similar in the three exocrine glands but is substantially different from that in brain and heart.

Animals↗
PubMed1993

Involvement of G alpha q/11 in m3-muscarinic receptor stimulation of phosphatidylinositol 4,5 bisphosphate-specific phospholipase C in rat parotid gland membranes.

Carbachol stimulation of phosphatidylinositol 4,5-bisphosphate (PIP2) hydrolysis by rat parotid gland membranes is dependent on the presence of GTP gamma S and is a result of m3-muscarinic receptor regulation of G-protein coupled, PIP2-specific phospholipase C (PLC). The PLC activity (> 80%) was solubilized with 1% Na-cholate but the solubilized enzyme was not stimulated by GTP gamma S and carbachol. Immunoblotting of rat parotid membranes with polyclonal antiserum, which recognizes alpha-subunits of the Gq/11 family, indicated the presence of two immunoreactive proteins of approximate molecular weights 41 and 42 kDa. Incubation of membranes with the common G alpha q/11 antiserum attenuated the stimulation of PIP2 hydrolysis, induced by GTP gamma S alone and by carbachol, in the presence of GTP gamma S. The antiserum had no effect on PIP2 hydrolysis in unstimulated membranes or in the cholate extract, where it is uncoupled from the G-protein. Antiserum against G alpha i, which is also coupled to the m3-muscarinic receptor in this tissue, had no effect on either basal or stimulated PIP2 hydrolysis. These results demonstrate that in rat parotid gland, activation of PIP2-specific PLC by m3-muscarinic receptor stimulation is mediated via alpha-subunits of the Gq/11 family of G-proteins.

Animals↗
PubMed1993

The functions of saliva.

Oral health is determined to a considerable extent by our ability to produce saliva. Not only must adequate amounts be produced, but a large number of specific proteins also must be secreted for the mouth to function properly. This brief review is directed at describing (1) how saliva is secreted, (2) the consequences of decreased salivary function, (3) the components necessary for oral homeostasis, and (4) the common causes of salivary hypofunction.

Homeostasis↗
PubMed1993

Old age in health and disease. Lessons from the oral cavity.

It is not clear if aging distinctions can be made at the level of an organ or organism. The purpose of this study was to determine if a general definition of systemic aging, primary aging (influence of the passage of time), versus secondary aging (influence of extrinsic factors), can be used to discriminate the functional status of an individual organ system, the oral cavity. Thirty healthy, nonmedicated subjects (that is, those who exhibit primary aging) and 42 persons being treated for medical problems and taking prescription medications (that is, those who exhibit secondary aging), aged 75 to 96 years, from the oral physiology component of the Baltimore Longitudinal Study of Aging were evaluated. A standardized examination assessed gingival, periodontal, dental, and oral mucosal tissues. There were few substantive differences in oral health and function between primary and secondary aging subjects. Thus use of broad definitions of aging in an organism did not lead to meaningful predictions of the health or function of an individual organ system. Furthermore, the similarity in the oral condition between both groups studied here suggests substantial resiliency of the oral cavity during aging.

Aged↗
PubMed1993

Cross-sectional and longitudinal analyses of stimulated parotid salivary constituents in healthy, different-aged subjects.

BACKGROUND: Salivary gland dysfunction has traditionally been associated with old age, and complaints of xerostomia are common in an elderly population. Measurement of certain salivary constituents can provide information about the functional ability of discrete areas of the salivary gland. To our knowledge, this is the first longitudinal study to examine levels of salivary constituents in stimulated parotid saliva in a population of different-aged persons. METHODS: The levels of five salivary constituents (total protein, lactoferrin, proline-rich proteins, sodium, and potassium) were measured in stimulated parotid saliva of 47 healthy, unmedicated men and women over a 10.5 year period. RESULTS: There were no significant age-related decreases in the presence of total protein, lactoferrin, proline-rich proteins, sodium, and potassium in this exocrine secretion. CONCLUSIONS: These data confirm and extend previous cross-sectional studies of salivary constituents, indicating that parotid gland function is maintained in healthy aging individuals.

Adult↗
PubMed1993

Human neoplastic submandibular intercalated duct cells express an acinar phenotype when cultured on a basement membrane matrix.

Culture of the human neoplastic submandibular gland intercalated duct cell line, HSG, on the basement membrane extract Matrigel induces dramatic morphologic changes and cytodifferentiation. Transmission electron microscopy demonstrated an acinar cell phenotype with polarized cells containing a well-developed Golgi apparatus, multiple microvilli-like projections from the apical surfaces into a lumenal-like area, and numerous granule-like organelles. Amylase, an acinar cell marker, was detected by both immunocytochemical and Northern blot analyses. A 50% reduction in [3H]thymidine incorporation by cells cultured on Matrigel, as compared to cells cultured on tissue culture plates, confirmed the differentiated phenotype of the cells. Multiple components of Matrigel appear to contribute to the morphologic differentiation of the HSG cells since antibodies to both laminin and collagen IV, as well as the laminin-derived bioactive peptide containing SIKVAV, have potent inhibitory effects on HSG cell organization on Matrigel. Collectively, these data indicate that culture of HSG cells on Matrigel is a useful model to study salivary gland acinar development.

Amylases↗
PubMed1993

Kinetic analysis of rat parotid gland muscarinic receptors in vivo: comparison with brain and heart.

(RR)- and (SS)-quinuclidinyl iodobenzilate enantiomers [(RR)- and (SS)-IQNB, active and inert, respectively] have been synthesized for quantitative evaluation of muscarinic acetylcholine receptor (mAChR) binding. Pharmacokinetic approaches have not been used previously to assess in vivo IQNB binding in nonexcitable tissues. We have applied this method to examine mAChRs in rat parotid gland in comparison to those in brain and heart. Short-term infusion studies in vivo showed that the "instantaneous" reversible binding of (RR)- and (SS)-IQNB was high in the parotid (greater nonspecific binding potential), intermediate in the heart, and lowest in cortex and cerebellum. Long-term bolus injection experiments showed that the parotid gland mAChRs possessed a binding potential for receptor specific sites (380), which was intermediate between that of parietal cortex (930) and cerebellum (10) and greater than that of heart (165). In vitro binding to plasma membranes was generally consistent with the in vivo findings. In aggregate, these studies show that mAChRs can be evaluated in vivo in a nonexcitable tissue with the use of stereospecific ligands and a pharmacokinetic approach. The data suggest that IQNB, a mAChR antagonist, can identify characteristics of specific binding sites, which may reflect tissue differences.

Animals↗
PubMed1993

Relationship between muscarinic receptor occupancy and response in rat parotid acinar cells.

To determine whether spare muscarinic cholinergic receptors (mAChRs) exist in rat parotid acinar cells, we examined the effect of propylbenzilylcholine mustard (PBCM) on agonist (carbachol)-stimulated inositol trisphosphate (IP3) formation and on mAChR number, using l-[N-methyl-3H]scopolamine methyl chloride (NMS)-binding assays. Treatment with PBCM (1, 3, 10, 30, 50 nM) for 15 min caused a 5, 22, 60, 66, and 72% decrease, respectively, in maximal IP3 formation stimulated by carbachol as well as a large reduction in the potency of carbachol in eliciting this response. Using these data, equilibrium constants (Ka) for activation of the mAChRs by carbachol were calculated. These Ka values agreed well with Kd values of high-affinity mAChR binding sites determined from carbachol displacement of [3H]NMS binding in parotid acinar cells. Reduction in mAChR number after PBCM treatment was determined by Scatchard analysis of specific [3H]-NMS binding sites and compared with the expected reduction (q values) calculated from dose-response curves for carbachol-stimulated IP3 formation before and after PBCM treatment. PBCM (1, 3, 10, 30 nM) decreased mAChR maximal binding in cells 47.5, 68.9, 82.4, and 85.3%, respectively, which did agree with the approximately 38, 70, 90, and 92% decrease in receptor number expected from the calculated q values. Data demonstrate that PBCM irreversibly inactivates mAChRs in rat parotid cells, and the decrease in receptor number, measured directly from [3H]NMS binding or calculated from receptor theory, is greater than that observed for stimulated IP3 production. These results suggest that a modest (30-40%) population of spare receptors exists for mAChR-mediated IP3 production in rat parotid glands.

Animals↗
PubMed1993

New approaches for determining the site of salivary fluid secretory disorders.

Considerable progress has been made in understanding the events which underlie salivary fluid secretion. We have utilized novel approaches to evaluate the functional status of three distinct sites in the secretory cascade. First, salivary sympathetic nerve function studies used isotopic dopamine to measure catecholamine uptake and metabolism in vivo. Second, salivary muscarinic-cholinergic receptors were characterized in vivo by use of stereo-specific ligands and pharmacokinetic analyses. Finally, microfluorometric methods were used to study intracellular Ca2+ signaling in dispersed cells prepared from biopsied tissue. We conclude that it is possible to determine the functional status of key steps in salivary fluid generation with isotopic and fluorometric imaging techniques.

Animals↗
PubMed1993

Signaling mechanisms that regulate saliva formation.

The precipitating event in the formation of saliva is the binding of neurotransmitter molecules to cell surface receptor proteins. The principal neurotransmitters involved are acetylcholine and norepinephrine that bind, respectively, to muscarinic-cholinergic, and alpha- and beta-adrenergic receptors. The transduction of the extracellular signal requires an integral membrane protein capable of binding GTP, a G protein, that specifically interacts with the receptor. The components of G protein transduction systems are fairly well studied, but the pathways by which signals are routed are just being recognized. Delineation of such routing pathways is essential to understanding the regulation of saliva formation.

Animals↗
PubMed1993

Acute effects of X irradiation on the function of rat salivary glands.

Radiation-induced damage to salivary glands has been recognized for over 80 years. However, the mechanisms responsible for the destruction of gland parenchyma are still not known. The purpose of this study was to describe alterations in salivary function in the rat within the first 24 h after irradiation. Saliva was collected from the parotid and submandibular glands during radiation treatment and at four times (0.5, 1, 4, and 24 h) after 15 Gy X irradiation delivered to the head and neck. Total body weight, submandibular gland weight, and food and water intake were monitored and the total protein, sodium, and potassium content of the salivas was analyzed. The effects of radiation on salivary glands of the rat could be demonstrated by 24 h. Parotid salivary flow was reduced and the sodium concentration was significantly less than that in control animals. Submandibular gland weights declined markedly by 24 h. These effects appear to be influenced significantly by the animals' limited intake of food and water during this period, as well as the anesthesia administered.

Animals↗