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Biomedical subjects

D A Edwards

Publications and source records attributed to D A Edwards.

At least 19 recordsLinked to original sources
PubMed2001

Inhalation delivery of proteins from ethanol suspensions.

To circumvent inherent problems associated with pulmonary administration of aqueous-solution and dry-powder protein drugs, inhalation delivery of proteins from their suspensions in absolute ethanol was explored both in vitro and in vivo. Protein suspensions in ethanol of up to 9% (wt/vol) were readily aerosolized with a commercial compressor nebulizer. Experiments with enzymic proteins revealed that nebulization caused no detectable loss of catalytic activity; furthermore, enzyme suspensions in anhydrous ethanol retained their full catalytic activity for at least 3 weeks at room temperature. With the use of Zn(2+)-insulin, conditions were elaborated that produced submicron protein particles in ethanol suspensions. The latter (insulin/EtOH) afforded respirable-size aerosol particles after nebulization. A 40-min exposure of laboratory rats to 10 mg/ml insulin/EtOH aerosols resulted in a 2-fold drop in the blood glucose level and a marked rise in the serum insulin level. The bioavailability based on estimated deposited lung dose of insulin delivered by inhalation of ethanol suspension aerosols was 33% (relative to an equivalent s.c. injection), i.e., comparable to those observed in rats after inhalation administration of dry powder and aqueous solutions of insulin. Inhalation of ethanol in a relevant amount/time frame resulted in no detectable acute toxic effects on rat lungs or airways, as reflected by the absence of statistically significant inflammatory or allergic responses, damage to the alveolar/capillary barrier, and lysed and/or damaged cells.

Administration, Inhalation↗
PubMed2001

The effect of a receptor layer on the measurement of rate constants.

Many cellular reactions involve a reactant in solution binding to or dissociating from a reactant attached to a surface. Most studies assume that the reactions occur on this surface, when in actuality the receptors usually lie in a thin layer on top of it. The effect of this layer is considered, particularly as it relates to the BIAcore measurement device, though the results are applicable to biological systems. A dimensionless parameter measuring the strength of the effect of the receptor layer is found. Asymptotic and singular perturbation techniques are used to analyse association and dissociation kinetics, though the effect of the receptor layer need not be small. Linear and nonlinear integral equations result from the analysis; explicit and asymptotic solutions are constructed for physically realizable cases. In addition, effective rate constants are derived that illustrate the combined effects of transport and the receptor layer on the measured rate constants. All these expressions provide a direct way to estimate rate constants from BIAcore binding data.

Cell Membrane↗
PubMed2000

Antiangiogenic and antitumor activities of cyclooxygenase-2 inhibitors.

We provide evidence that cyclooxygenase (COX)-2-derived prostaglandins contribute to tumor growth by inducing newly formed blood vessels (neoangiogenesis) that sustain tumor cell viability and growth. COX-2 is expressed within human tumor neovasculature as well as in neoplastic cells present in human colon, breast, prostate, and lung cancer biopsy tissue. COX-1 is broadly distributed in normal, as well as in neoplastic, tissues. The contribution of COX-2 to human tumor growth was indicated by the ability of celecoxib, an agent that inhibits the COX-2 enzyme, to suppress growth of lung and colon tumors implanted into recipient mice. Mechanistically, celecoxib demonstrated a potent antiangiogenic activity. In a rat model of angiogenesis, we observe that corneal blood vessel formation is suppressed by celecoxib, but not by a COX-1 inhibitor. These and other data indicate that COX-2 and COX-2-derived prostaglandins may play a major role in development of cancer through numerous biochemical mechanisms, including stimulation of tumor cell growth and neovascularization. The ability of celecoxib to block angiogenesis and suppress tumor growth suggests a novel application of this anti-inflammatory drug in the treatment of human cancer.

Animals↗
PubMed2000

A mechanistic analysis of carrier-mediated oral delivery of protein therapeutics.

This article summarizes the results of a theoretical analysis of protein absorption into the systemic circulation from the small intestine, with and without molecular 'carriers' designed to enhance absorption. The predictions are compared with experimental systemic protein concentrations following intraduodenal delivery of insulin, interferon alpha-2b, and human growth hormone. The results show that, from the standpoint of improving oral absorption, the primary consequence of carrier molecules is to increase epithelial membrane permeability, thereby leading to higher bioavailability. Several possible mechanisms of this permeability enhancement are discussed.

Absorption↗
PubMed1999

Colocalization of androgen receptors and mating-induced FOS immunoreactivity in neurons that project to the central tegmental field in male rats.

Bilateral lesions of the central tegmental field (CTF) in male rats virtually eliminate mating behavior. This study examined if mating-induced Fos expression (a measure of neuronal activation) and androgen receptors (AR) are colocalized in brain and spinal cord neurons which project to the CTF. Animals received unilateral injections of the retrograde tracer Fluorogold (FG) in the lateral part of the CTF (CTFl), and 10 days later were killed after ejaculating with females. Brains and spinal cords were examined for FG transport, AR-immunoreactivity (AR-ir), and Fos-immunoreactivity (Fos-ir). AR-ir and Fos-ir were visualized with fluorescence microscopy using cyanine-conjugated and fluorescein-conjugated secondary antibodies. The CTFl received projections from AR-containing neurons in forebrain structures (bed nucleus of stria terminalis, medial preoptic area, lateral and ventromedial hypothalamus), in the central amygdala and various mid- and hindbrain structures (dorsolateral tegmentum, superior and inferior colliculi, pedunculopontine nucleus), and in the lumbosacral spinal cord (lamina X). Some of the AR-containing neurons in bed nucleus of stria terminalis and in the dorsal part of the medial preoptic area with projections to the CTFl were activated by mating. Most AR-containing neurons in spinal lamina X with projections to the CTFl were also activated by mating. Information from spinal cord and pontine nuclei and from outputs descending from the forebrain may be relayed in the CTFl. Thus, as part of a network of hormone-sensitive neurons linking brain and spinal cord mechanisms for mating, the CTFl could participate in the integration of visceral and somatic information relevant for sexual behavior.

Animals↗
PubMed1999

Transport effects on surface-volume biological reactions.

Many cellular reactions involve a reactant in solution binding to or dissociating from a reactant confined to a surface. This is true as well for a BIAcore, an optical biosensor that is widely used to study the interaction of biomolecules. In the flow cell of this instrument, one of the reactants is immobilized on a flat sensor surface while the other reactant flows past the surface. Both diffusion and convection play important roles in bringing the reactants into contact. Usually BIAcore binding data are analyzed using well known expressions that are valid only in the reaction-limited case when the Damköhler number Da is small. Asymptotic and singular perturbation techniques are used to analyze dissociation of the bound state when Da is small and O(1). Linear and nonlinear integral equations result from the analysis; explicit and asymptotic solutions are constructed for physically realizable cases. In addition, effective rate constants are derived that illustrate the effects of transport on the measured rate constants. All these expressions provide a direct way to estimate the rate constants from BIAcore binding data.

Biological Transport, Active↗
PubMed1999

Large porous particles for sustained protection from carbachol-induced bronchoconstriction in guinea pigs.

PURPOSE: To determine whether a new formulated albuterol aerosol could sustain inhibition to bronchoconstriction for approximately one day in guinea pigs challenged with carbachol. METHODS: Large and porous particles, comprising a combination of endogenous or FDA-approved excipients and albuterol sulfate, were prepared by spray drying using a NIRO portable spray drier. The anesthetized animals inhaled 5 mg of large porous or small nonporous particles by forced ventilation via cannulae inserted in the lumen of their exposed tracheae. At regular intervals over a period of 36 hours after drug delivery, airway resistance was determined in response to carbachol challenge dose. RESULTS: Whereas inhalation of small nonporous albuterol particles protected from the carbachol-induced bronchoconstriction for up to 5 hours, inhalation of large porous albuterol particles produced a significant inhibition of carbachol-induced bronchoconstriction for at least 16 hours. CONCLUSIONS: The absence of substantial side effects, verified over a period of 24 hours by evaluating cardio-respiratory parameters as well as pulmonary inflammation, supports the utility of large porous albuterol particles for sustained therapies in asthma and other types of lung disease.

Administration, Inhalation↗
PubMed1999

Formulation and physical characterization of large porous particles for inhalation.

PURPOSE: Relatively large (>5 microm) and porous (mass density <0.4 g/cm3) particles present advantages for the delivery of drugs to the lungs, e.g., excellent aerosolization properties. The aim of this study was, first, to formulate such particles with excipients that are either FDA-approved for inhalation or endogenous to the lungs; and second, to compare the aerodynamic size and performance of the particles with theoretical estimates based on bulk powder measurements. METHODS: Dry powders were made of water-soluble excipients (e.g., lactose, albumin) combined with water-insoluble material (e.g., lung surfactant), using a standard single-step spray-drying process. Aerosolization properties were assessed with a Spinhaler device in vitro in both an Andersen cascade impactor and an Aerosizer. RESULTS: By properly choosing excipient concentration and varying the spray drying parameters, a high degree of control was achieved over the physical properties of the dry powders. Mean geometric diameters ranged between 3 and 15 microm, and tap densities between 0.04 and 0.6 g/cm3. Theoretical estimates of mass mean aerodynamic diameter (MMAD) were rationalized and calculated in terms of geometric particle diameters and bulk tap densities. Experimental values of MMAD obtained from the Aerosizer most closely approximated the theoretical estimates, as compared to those obtained from the Andersen cascade impactor. Particles possessing high porosity and large size, with theoretical estimates of MMAD between 1-3 microm, exhibited emitted doses as high as 96% and respirable fractions ranging up to 49% or 92%, depending on measurement technique. CONCLUSIONS: Dry powders engineered as large and light particles, and prepared with combinations of GRAS (generally recognized as safe) excipients, may be broadly applicable to inhalation therapy.

Administration, Inhalation↗
PubMed1999

Inhalation of estradiol for sustained systemic delivery.

Large porous estradiol particles were formulated by spray drying estradiol in combination with various U.S. Food and Drug Administration (FDA)-approved or endogenous excipients. The powders were characterized in terms of their geometrical size, mass density, and aerosolization properties. Small nonporous particles were also prepared using the same excipients and were physically characterized to insure that they possessed a similar mean aerodynamic size as the large porous particles. The two powders were aerosolized into the lungs of rats via an endotracheal tube or subcutaneously injected as a control to assess relative bioavailability. Two different large porous particle formulations were found to produce elevated systemic estradiol concentrations upon inhalation for approximately 5 days, with relative bioavailabilities of 59.7% and 86.0%. Systemic estradiol concentrations following inhalation of two different small nonporous particle powders remained elevated for only approximately 1 day, with relative bioavailabilities of 18.3% and 38.7%. Bronchoalveolar lavage was performed up to 96 hours after inhalation of porous and nonporous estradiol powders. Small changes in neutrophil and macrophage populations were observed following inhalation of both the porous and nonporous powders.

Administration, Inhalation↗
PubMed1999

Analysis of stained objects in histological sections by spectral imaging and differential absorption.

We describe a new light microscopic imaging system and method to perform high through put color image analysis on histological tissue sections. The system features a computer-controlled, random-access liquid crystal tunable filter and high-resolution digital camera on a conventional brightfield microscope. For any combination of stains, the method determines the spectral transmittance of each stain on the slide and selects two or more wavelengths at which the differential absorption between stain and counterstain is greatest and the exposure time is reasonably short. Flatfield corrected digital images at these wavelengths are acquired and divided to produce a gray scale ratio image. The ratio image is calculated such that the stained features of interest are highlighted above a uniform background and the counterstained features are highlighted below background. Image threshold procedures using either visual inspection or a threshold value determined by the image mean intensity and standard deviation are used to segment the stained features of interest for subsequent morphometry. Results are presented for peroxidase-AEC-labeled tumor tissue and trichrome-stained biomaterial implant tissues. In principle, the method should work for any combination of colored stains. (J Histochem Cytochem 47:1307-1313, 1999)

Animals↗
PubMed1999

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Complementary Therapies↗
PubMed1998

Androgen receptor and mating-induced fos immunoreactivity are co-localized in limbic and midbrain neurons that project to the male rat medial preoptic area.

Two studies were designed to document neuronal colocalization of androgen receptor immunoreactivity and mating-induced Fos immunoreactivity (AR-ir, Fos-ir) in brain of male rats and to examine the extent to which limbic and midbrain neurons that project to the preoptic area are androgen sensitive and activated by mating. Brains from male rats, killed 1 h after ejaculating with receptive females, were examined for Fos-ir and AR-ir and compared with those from control rats not given access to females. PG21 anti-AR and anti-c-fos primary antibodies were visualized by fluorescence microscopy using cyanine-conjugated and fluorescein-conjugated secondary antibodies. In mated males (Expt. 1), Fos-ir and AR-ir were colocalized in neurons of the medial preoptic nucleus (MPN), the dorsal medial amygdala (dMEA), the central tegmental field (CTF), the bed nucleus of the stria terminalis, the anterior hypothalamus, the lateral hypothalamus, and the ventral premamillary nucleus. In Expt. 2, male rats received a unilateral injection of the retrograde tracer FluoroGold (FG) in the preoptic area and four days later were killed after ejaculating with receptive females. Brains were subsequently examined for FG transport, Fos-ir and AR-ir. Fluorogold-containing neurons were present in dMEA and CTF as well as in other hypothalamic and limbic regions known to project to the MPN. In dMEA and CTF, nuclear colocalization of AR-ir and mating-induced Fos-ir was present in a proportion of FG-containing neurons. Sexually relevant information may be carried through the brain by an interconnected network of hormone-sensitive neurons.

Animals↗
PubMed1998

Fos induced by mating or noncontact sociosexual interaction is colocalized with androgen receptors in neurons within the forebrain, midbrain, and lumbosacral spinal cord of male rats.

This study was designed to determine the extent to which Fos immunoreactivity (induced either by mating or noncontact sociosexual interaction) and androgen receptor (AR) immunoreactivity are colocalized in brain and spinal cord of male rats. Some males (Mated) were allowed to mate to ejaculation; others (Social Controls) were placed with females but physical contact was prevented by a wire mesh screen; remaining males (Isolated) were placed alone in the test jar for the duration of the test period. After testing, brains and spinal cords were examined for AR and Fos immunoreactivity (ir). PG21 anti-AR and anti-c-fos primary antibodies were visualized by fluorescence microscopy using cyanine-conjugated and fluorescein-conjugated secondary antibodies. In both brain and spinal cord, the number of Fos-ir neurons varied according to group: Mated males > Social Controls > Isolated males. Fos was highly localized in subsets of AR-ir neurons within the medial preoptic nucleus, bed nucleus of the stria terminalis, dorsomedial nucleus of the amygdala, and central tegmental field. Fos was also localized in subsets of AR-ir neurons within the L5, L6, and S1 segments of the spinal cord. Spinal cord concentrations of AR-ir and Fos-ir neurons were greatest in Lamina X, and the vast majority of Fos-ir neurons in the dorsal part of Lamina X were also AR-ir. Thus, in both brain and spinal cord, androgen-sensitive neurons are active during mating, and transmission of sexually relevant information from cord to brain is probably accomplished via hormone-sensitive spinal neurons.

Animals↗
PubMed1998

Recent advances in pulmonary drug delivery using large, porous inhaled particles.

The ability to deliver proteins and peptides to the systemic circulation by inhalation has contributed to a rise in the number of inhalation therapies under investigation. For most of these therapies, aerosols are designed to comprise small spherical droplets or particles of mass density near 1 g/cm3 and mean geometric diameter between approximately 1 and 3 micron, suitable for particle penetration into the airways or lung periphery. Studies performed primarily with liquid aerosols have shown that these characteristics of inhaled aerosols lead to optimal therapeutic effect, both for local and systemic therapeutic delivery. Inefficient drug delivery can still arise, owing to excessive particle aggregation in an inhaler, deposition in the mouth and throat, and overly rapid particle removal from the lungs by mucocilliary or phagocytic clearance mechanisms. To address these problems, particle surface chemistry and surface roughness are traditionally manipulated. Recent data indicate that major improvements in aerosol particle performance may also be achieved by lowering particle mass density and increasing particle size, since large, porous particles display less tendency to agglomerate than (conventional) small and nonporous particles. Also, large, porous particles inhaled into the lungs can potentially release therapeutic substances for long periods of time by escaping phagocytic clearance from the lung periphery, thus enabling therapeutic action for periods ranging from hours to many days.

Administration, Inhalation↗
PubMed1998

Androgen receptors and estrogen receptors are colocalized in male rat hypothalamic and limbic neurons that express Fos immunoreactivity induced by mating.

Conversion of testosterone into estradiol is important for male rat sexual behavior, and both steroids probably contribute to mating. The distributions of neurons containing androgen receptors (AR) and estrogen receptors (ER) overlap, and many AR-immunoreactive (AR-ir) neurons express Fos immunoreactivity (Fos-ir) induced by mating. Because mating-induced Fos-ir in the male rat occurs mainly in AR-ir neurons, and because both steroids are important for mating, we hypothesized that (i) AR-ir and ER-ir are colocalized and that (ii) some of these neurons are activated during mating. We examined, in adjacent sections from the medial preoptic area (MPN) through the central tegmental field (CTF), the expression of ER-ir in: (i) AR-ir-containing neurons, and (ii) Fos-ir-expressive neurons. PG21 anti-AR, OA-11-824 anti-c-fos, H222 or 1D5 anti-ER primary antibodies were visualized, respectively, with cyanine-conjugated, fluorescein- or cyanine-conjugated, and fluorescein-conjugated secondary antibodies in male rats which were killed 1 h after ejaculating with a receptive female. In MPN, bed nucleus of the stria terminalis (BNST), and medial amygdala (MEA), 80-90% of ER-ir labeling occurred in AR-ir-positive neurons but only about 30% of AR-ir neurons were ER-ir-positive. No ER-ir was found in the CTF. This suggests the presence of three types of brain neurons sensitive to gonadal steroid hormones: neurons sensitive to androgens only, neurons sensitive to both androgens and estrogens, and neurons sensitive to estrogens only. About 50% of ER-ir labeling occurred in cells expressing mating-induced Fos-ir but only about 30% of Fos-ir neurons were ER-ir-positive. These findings suggest that, in the MPN, at least two different neuronal populations are activated during mating: the first contains AR-ir only and the second contains AR-ir and ER-ir. In the BNST and MEA, at least three hormonally sensitive populations are activated during mating: the two described above plus a third population which expresses ER-ir only.

Animals↗
PubMed1997

Large porous particles for pulmonary drug delivery.

A new type of inhalation aerosol, characterized by particles of small mass density and large size, permitted the highly efficient delivery of inhaled therapeutics into the systemic circulation. Particles with mass densities less than 0.4 gram per cubic centimeter and mean diameters exceeding 5 micrometers were inspired deep into the lungs and escaped the lungs' natural clearance mechanisms until the inhaled particles delivered their therapeutic payload. Inhalation of large porous insulin particles resulted in elevated systemic levels of insulin and suppressed systemic glucose levels for 96 hours, whereas small nonporous insulin particles had this effect for only 4 hours. High systemic bioavailability of testosterone was also achieved by inhalation delivery of porous particles with a mean diameter (20 micrometers) approximately 10 times that of conventional inhaled therapeutic particles.

Administration, Inhalation↗
PubMed1997

Deafferentation of the olfactory bulbs of male rats reduces erection to remote cues from females.

If male rats are paired with a receptive, soliciting female rat in a setting that prevents physical contact, but permits auditory, visual, and olfactory contact, some will have erections of the penis--noncontact erections (NCE). Surgical deafferentation of the olfactory bulbs from all the known chemosensory systems of the nasal septum renders rats anosmic, decreases sexual performance in copulation tests with females, and substantially reduces the frequency of NCE. Thus, NCE appear to be primarily regulated though the olfactory perception of volatile chemosensory cues from receptive females.

Animals↗