Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Absorption”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,369 records · Page 76Linked to original sources
PubMed1988

Comparison of human jejunal and ileal fat absorption by electron microscopy.

Morphologic and physiologic experiments in rodents have demonstrated differences between jejunal and ileal fat absorption. Compared with the rat jejunum, absorbed lipid particles within rat ileal absorptive cells are larger and exit at a slower rate. To evaluate the relevance of these observations to humans, we studied jejunal and ileal ultrastructure in 3 volunteers, each of whom had an intact small intestine and an ileostomy postcolectomy for ulcerative colitis. Proximal jejunal biopsy specimens were obtained via a hydraulic tube after an overnight fast and again after a 20-min intrajejunal lipid infusion. On a separate day, terminal ileal biopsy specimens were taken via the stoma with a small steerable suction biopsy tube after an overnight fast and again after a 20-min intraileal infusion of the same lipid mixture. One volunteer underwent biopsy after a 60-min ileal infusion of a digested meal of higher lipid content. Electron microscopy of fasting human jejunal absorptive cells revealed obvious smooth endoplasmic reticulum in the extreme apical region beneath the terminal web; very low density lipoprotein particles were observed within smooth endoplasmic reticulum and Golgi cisternae. In contrast, fasting human ileal absorptive cells contained less apical smooth endoplasmic reticulum and fewer or no very low density lipoprotein particles. After the 20-min infusion of lower-lipid content, human jejunal and ileal absorptive cells were indistinguishable because they contained fat particles of the same size and number within smooth endoplasmic reticulum, Golgi cisternae, and extracellular spaces. After the 60-min ileal infusion of higher-lipid content, human ileal absorptive cells appeared to be the same as those of the human jejunum after similar lipid infusions. Our observations of the ultrastructural similarity in human jejunal and ileal absorptive cells after lipid infusions contrasts with those in rodents and may reflect species-specific differences in mechanisms of fat absorption.

Adult↗
PubMed1989

Short-chain fatty acids stimulate active sodium and chloride absorption in vitro in the rat distal colon.

Studies were performed to determine the mechanism by which short-chain fatty acids increase colonic Na and Cl absorption by determining unidirectional 22Na and 36Cl fluxes across isolated stripped mucosa from the rat distal colon under voltage clamp conditions. Mucosal butyrate (25 mM, in the absence of bicarbonate) significantly enhanced both net Na and net Cl absorption by 7.0 +/- 1.3 and 6.9 +/- 1.0 microEq/h.cm2, respectively, without increasing the short-circuit current. Net Na and Cl absorption in butyrate-Ringer's solution and HCO3-Ringer's solution were identical. Butyrate stimulation of Na (and Cl) absorption was Cl-dependent and prevented by 1 mM mucosal amiloride, an inhibitor of Na-H exchange, but was HCO3-independent and not inhibited by acetazolamide, a carbonic anhydrase inhibitor. In contrast, bicarbonate-stimulated Na (and Cl) absorption was also Cl-dependent and amiloride-sensitive, but was significantly inhibited by acetazolamide. The effect of mucosal butyrate on net Na and Cl absorption was substantially greater than serosal butyrate, which in the presence of bicarbonate did not alter ion transport. The stimulation of Na and Cl absorption by mucosal butyrate was significantly greater than by propionate and acetate, whereas mucosal formate did not alter Na transport. The results of this study permit the following model: short-chain fatty acid stimulation of active Na and Cl absorption involves uptake of the nonionized form of butyrate and the coupling of Na-H and Cl-butyrate exchanges.

Acetazolamide↗
PubMed1992

Intestinal absorption of ursodeoxycholic acid in patients with extrahepatic biliary obstruction and bile drainage.

Ursodeoxycholic acid (UDCA) dissolves cholesterol gallstones and improves liver function test results in patients with cholestatic liver diseases. Its absorption was studied in patients who had complete extrahepatic biliary obstruction caused by pancreatic carcinoma but no intestinal or liver disease. Six patients received 500 mg chenodeoxycholic acid (CDCA) or 250-2000 mg UDCA in capsules in single oral doses in random order, with an interval of 2 days between the different treatment regimens. In the control period the patients excreted into bile 382.3 +/- 108.0 mumol CDCA (mean +/- SD) and 1866.7 +/- 172.6 mumol cholic acid per 24 hours. After administration of 1273.6 mumol (500 mg) CDCA, biliary excretion of this bile acid increased to 1370.9 +/- 185.7 mumol/24 h, indicating an intestinal absorption rate of 77.6% +/- 9.8%. After oral administration of 636.8 mumol (250 mg), 1273.6 mumol (500 mg), 2547.2 mumol (1000 mg), and 5094.4 mumol (2000 mg) of UDCA, the respective absorption rates were 60.3% +/- 7.4%, 47.7% +/- 9.0%, 30.7% +/- 7.5%, and 20.8% +/- 3.9%, and whereas in the control period no UDCA was detected in the bile, the UDCA percentages measured were 14.6% +/- 8.2%, 19.6% +/- 9.1%, 23.1% +/- 11.3%, and 27.4% +/- 12.1%. The coadministration of CDCA did not enhance the absorption of UDCA. The data indicate that absorption of orally administered CDCA is almost complete, whereas UDCA absorption is incomplete. With increasing doses UDCA absorption decreases. To achieve absorption of adequate amounts of UDCA, high and/or multiple doses are needed.

Administration, Oral↗
PubMed1992

Effect of CO2 on rat colonic Na absorption: studies with nystatin.

An increase in ambient CO2 tension from 3% to 11% augments colonic Na absorption in the rat. The membrane site of action of CO2 was examined by measuring colonic Na absorption in the Ussing chamber when nystatin was used to permeabilize the luminal (apical) membrane. The equal rates of ouabain-sensitive Na absorption at 3% and 11% CO2 in the presence of nystatin and at 11% CO2 in its absence suggested that CO2 acted at the luminal membrane. This finding was also observed at a submaximal rate of Na absorption (produced by lowering bathing solution Na from 140 to 27 mmol/L) and in a Cl-free solution (to prevent cell swelling). The basolateral membrane was indeed rate limiting for Na absorption in the presence of nystatin, because methylprednisolone (3 mg/kg SC for 3 days to increase sodium-potassium--stimulated adenosine triphosphatase activity) increased Na absorption measured in the presence of nystatin and because CO2 increased absorption in steroid-treated rats in the absence of nystatin. These results validate the protocol and confirm the luminal site of action of CO2 and nystatin on colonic Na absorption.

Absorption↗
PubMed1991

Jejunal and ileal absorptive function after a model of canine jejunoileal autotransplantation.

The effects of intestinal transplantation on the physiologic functions of the gut are not well understood. Our aim was to determine the effect of a large animal model of small intestinal transplantation (disruption of all neural and lymphatic continuity) on selected absorptive functions of the jejunoileum. Seven dogs were studied before and at 1, 4, and 12 weeks after a model of jejunoileal autotransplantation, which avoids confounding factors of immune rejection, immunosuppression, and harvest ischemia. Jejunal function was assessed by quantitative [3H]-folate and D-xylose absorption and ileal function by quantitative 57Co-vitamin B12 absorption. The role of lymphatic continuity was assessed by fecal fat recovery following 5 days of a controlled, high fat diet (75 g/day). All dogs developed a profuse, watery diarrhea that persisted for 6 to 12 weeks and lost about 15% body weight; however, absorption of D-xylose, folate, and vitamin B12 was unaffected at any time point. Fat absorption postoperatively was only mildly abnormal (less than or equal to 8 g/day) at all time points in five of seven dogs despite complete lymphatic disruption. We concluded that jejunoileal autotransplantation does not markedly affect these specific jejunoileal absorptive functions. Fat absorption in most dogs surprisingly remains almost normal. Anatomic and physiologic consequences of intestinal transplantation do not appear to induce global abnormalities in all absorptive functions in the nonrejecting jejunoileum.

Absorption↗
PubMed1981

The kinetics of peritoneal insulin absorption.

This study examined the relationship between the delivery of insulin into the peritoneal space and its absorption into the peripheral circulation. Studies were performed in conscious dogs receiving somatostatin (5.0 microgram/min) to suppress endogenous insulin secretion, and intravenous glucose (50 mg/min) to prevent hypoglycemia. The biologic effectiveness of the absorbed insulin was determined by its hypoglycemic effect. The possibility of direct absorption of insulin into the portal circulation from the peritoneal space in anesthetized, portal vein-catheterized dogs was examined with radiolabeled I125 insulin. Our results suggest that absorption of insulin from the peritoneal space is volume, concentration, and time-dependent. Maximal absorption of insulin was observed at 50 min when 1.92 U of insulin in a volume of 3 ml was infused intraperitoneally over 30 min. More rapid absorption was observed at 30 min when this quantity of insulin was given in a 1-min intraperitoneal bolus, compared to 30 min of intraperitoneal infusion. Least rapid absorption of insulin followed the delivery of 1.92 U of insulin in a volume of 15 ml. Intermediate absorption of insulin was observed at 40 min when the 1.92 U was delivered in a volume of 0.6 ml. Peripheral intravenous insulin delivery of 1.92 U reached a maximal plasma concentration at 20 min, which was more than three times the concentration observed with intraperitoneal insulin. Isotopic tracer studies, in which radioiodinated insulin was placed into the peritoneal space in anesthetized dogs, demonstrated greater radioactivity in the portal vein than in the aorta throughout a 30-min observation period. These studies demonstrate that intraperitoneal administration of insulin results in absorption of insulin which is volume, concentration, and time-dependent. Thus, the peritoneal space may be an appropriate site for insulin delivery through a transcutaneous catheter.

Absorption↗
PubMed1991

Gastrointestinal absorption of paraquat in the isolated mucosa of the rat.

The gastrointestinal absorption of paraquat (1,1'-dimethyl-4,4'-bipyridylium) was studied using the isolated mucosa from different regions of the gastrointestinal tract of rats. Tissues were stripped of their muscle layers and the viability of the mucosa was maintained in flux chambers by bathing both serosal and luminal membranes with separate oxygenated solutions. Paraquat absorption, transmucosal potential difference (PD), and permeability of the mucosa were studied. Exposure of the luminal side of isolated mucosae to paraquat (100 mg/ml) resulted in greater paraquat absorption across the small intestine compared to other regions of the gastrointestinal tract. The descending order of tissue absorption (as %/cm2 mucosa) was jejunum (17.6 +/- 0.8%), ileum (10 +/- 2.7%), colon (5.7 +/- 3.2%), duodenum (5.5 +/- 1.3%), stomach (2 +/- 0.8%), and esophagus (0.5 +/- 0.7%). Mucosal uptake of paraquat in the ileum was nonlinear over a luminal concentration range 2-200 mg/ml. Three phases to paraquat absorption were identified in this region of the small intestine: (i) a rate which was faster than diffusion (2-20 mg/ml paraquat); (ii) a rate which was slower than diffusion and obeyed saturation kinetics, with an apparent Km = 116 mM and Vmax = 11.3 mumol/g/hr, at paraquat concentrations up to 150 mg/ml: and (iii) a rate similar to that of diffusion at 200 mg/ml paraquat. Paraquat absorption at 200 mg/ml was also associated with an increase in mucosal permeability and reduction in PD. Inhibition of tissue metabolism resulted in a linear or diffusional paraquat absorption over a wide luminal concentration range (2-200 mg/ml). It is suggested, therefore, that paraquat absorption in the rat occurs principally in the small intestine and by a mechanism which consists of facilitated, saturable, and diffusional components. Knowledge of the mechanism by which paraquat gains entry to the bloodstream may offer new approaches to the development of safer formulations of the herbicide.

Animals↗
PubMed1990

Calbindin D28k in mammalian intestinal absorptive cells: immunohistochemical evidence.

Calbindin D28k and D9k are two cytosolic calcium-binding proteins abundant in intestinal absorptive cells which appear to play a role in calcium translocation. Until today, calbindin D28k was found in avian and reptilian absorptive cells but not in mammalian ones. We have described the presence of calbindin D28k-immunoreactivity in intestinal absorptive cells of pig and jerboa (Jaculus jaculus). Pig calbindin D28k-immunoreactive absorptive cells were prominent in duodenum, they were scattered along the villi and nearly absent in the crypts. Jerboa labelled absorptive cells were located along the colonic mucosal surface. No calbindin D28k could be detected in mouse, rat and goat absorptive cells. Topography of calbindin D28k absorptive cells was compared with calbindin D9k distribution. Our results confirmed the data of the literature showing a gradient of labelling increasing from the crypt to the top of the villus and no positive endocrine cell. Young (48 h old) pigs did not expressed calbindin D28k in absorptive cells although calbindin D9k was detected. Calbindin D28K was also observed in endocrine cells which were numerous in pig and goat duodenum and very rare in mouse and jerboa. Western blot experiments confirmed the presence of calbindin D28k in the adult pig intestine, in the jerboa colon and the absence of cross-reactivity between calbindin D28k antibody and calbindin D9k.

Animals↗
PubMed1992

In vivo and in vitro percutaneous absorption and skin evaporation of isofenphos in man.

Studies were done to determine the percutaneous absorption of isofenphos in human volunteers from whom informed consent had been obtained. In vivo absorption in man was 3.6 +/- 3.6% of applied dose for 24-hr exposure and 3.6 +/- 0.5% for 72-hr exposure. Skin wash recovery data show that isofenphos evaporates from in vivo skin during the absorption process; the surface dose is minimal (< 1%) by 24 hr. Skin stripping showed no residual isofenphos in stratum corneum. This explains the similar absorption for 24 and 72-hr dose prewash exposures. Skin surface recovery in vivo with soap and water was 61.4 +/- 10.4 for the first dosing time (15 min). Time-recovery response declined with time to 0.5 +/- 0.2% at 24 hr. In vitro absorption utilizing flow-through diffusion methodology with human cadaver skin and human plasma receptor fluid gave 2.5 +/- 2.0% dose absorbed, an amount similar to in vivo studies. An additional 6.5 +/- 24% was recovered in the skin samples (total of 9%). Skin surface wash at 24 hr recovered 79.7 +/- 2.2% and skin content was 6.5 +/- 2.4% (total dose accountability of 88.7 +/- 4.6%). Thus, isofenphos was available for absorption during the whole dosing period. Neither in vitro absorption nor in vitro evaporation studies predicted the potential skin evaporation of isofenphos. Published dermal studies in the rat had predicted isofenphos absorption at 47% of applied dose (12-fold greater than actual in man). Subsequent toxicokinetic modeling predicted possible concern with the use of isofenphos.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1990

Percutaneous absorption of benzyl acetate through rat skin in vitro. 1. Validation of an in vitro model against in vivo data.

The percutaneous absorption in vitro of the fragrance agent benzyl acetate has been evaluated in flow-through diffusion cells using shaved full-thickness skin from male Fischer 344 rats. After the application of neat [methylene-14C]benzyl acetate to the epidermal surface of the skin and occlusion with parafilm 1.3 cm above the skin surface, the absorption of the chemical across the skin and into the receptor fluid was rapid and extensive, commencing within 1 hr of application, and reaching 49.8 +/- 3.2% (mean +/- SD, n = 4) of the applied dose after 48 hr. The coefficient of variation for absorption at 48 hr between four identical experiments was 6.4%. The extent of absorption at 48 hr of benzyl acetate applied in 50% (v/v) ethanol was not significantly different from that after application neat, although absorption at earlier times was enhanced, with a maximum increase of 8.5% of the applied dose at 12 hr. Over the dose range studied there was a linear relationship (r = 0.996) between the amount of benzyl acetate applied to the skin (1.66-33.13 mg benzyl acetate/cm2) and the amount absorbed into the receptor fluid at 24 hr (0.66 +/- 0.04-10.27 +/- 0.51 mg/cm2). The extent of absorption of benzyl acetate through rat skin in vitro was compared with the extent of absorption in vivo at 24 hr and a correlation coefficient of 0.993 was obtained. These data support the use of this in vitro system as a model to predict in vivo absorption and indicate the suitability of the system to study factors influencing the disposition of topically applied benzyl acetate.

Animals↗
PubMed2004

Self-absorption correction for beta radioactivity measurements in water samples.

Two methods were used to apply self-absorption corrections for the determination of beta radioactivity in water samples (either for an identified radionuclide or for monitoring trends). One method was performed by estimating the absorption coefficient by assuming an exponential behaviour of absorption using external absorbers, while the other method was performed by preparing empirical curves using standards of different mass. In the first method, a relationship between absorption coefficient and maximum beta energy was also derived. In the second method, self-absorption curves for 90Sr/90Y standard were prepared with several sodium salts (carbonate, nitrate and sulphate salts) and, for 40K standard using a potassium salt. Both beta emitters are usually necessary to calibrate detectors for beta radioactivity measurements. This study showed that, for 90Sr/90Y, results using standards of different mass were more accurate than using external absorbers. Furthermore, it is highly recommended to melt sodium nitrate salts in order to perform a self-absorption curve for 90Sr/90Y because standards were stable in time and homogeneously distributed. For 40K, a self-absorption curve may be easily derived using paper absorbers of different thickness, instead of performing a time consuming self-absorption curve using a set of varying thickness of 40K standards. In order to test the two methods, the gross beta activity of several environmental water samples was analysed.

Absorption↗
PubMed2004

Absorption characteristics of compounds with different molecular weights after application to the unilateral kidney surface in rats.

The aim of the present study is to clarify the absorption mechanism of a drug from the kidney surface membrane in rats. We studied the absorption characteristics of phenolsulfonphthalein (PSP) and other compounds with different molecular weights after their application to the rat kidney surface in vivo, employing a cylindrical diffusion cell (i.d. 6 mm, area 0.28 cm(2)). The time course of free PSP amounts remaining in the diffusion cell obeyed first-order kinetics at a dose of 1 mg, and its rate constant k(a) was calculated to be 0.0137 min(-1). Absorption ratios of PSP in 4 h were calculated (from the amount recovered from the diffusion cell) to be 91.4, 96.4 and 97.7% at doses of 0.5, 1 and 1.5 mg, respectively. The area under the curve for the plasma concentration profile of free PSP was proportional to the application dose. It is thus suggested that the absorption process of PSP from the rat kidney surface does not approach saturation at a dose of 1.5 mg. Also, no significant difference was seen in the k(a) values within the dose range of 0.5-1.5 mg, which were estimated by curve-fitting the plasma concentration profiles of free PSP in a two-compartment model with first-order absorption. Furthermore, we examined the importance of molecular weight on the absorption from the kidney surface using fluorescein isothiocyanate-dextrans (FDs) with molecular weights of 4400 (FD-4), 11,000 (FD-10), 40,500 (FD-40) or 69,000 (FD-70), including the organic anions bromphenol blue and bromosulfonphthalein. The absorption ratios of FDs from the rat kidney surface in 6 h decreased with an increase in the molecular weight (76.1% for FD-4, 54.4% for FD-10, 11.5% for FD-40 and 3.9% for FD-70). A linear relationship was observed between k(a) and the reciprocal value of z the square root of the molecular weight of these compounds. The limit of absorption from the rat kidney surface was extrapolated to be at a molecular weight of approximately 130,000.

Absorption↗
PubMed2004

Intestinal solute carriers: an overview of trends and strategies for improving oral drug absorption.

A large amount of absorptive intestinal membrane transporters play an important part in absorption and distribution of several nutrients, drugs and prodrugs. The present paper gives a general overview on intestinal solute carriers as well as on trends and strategies for targeting drugs and/or prodrugs to these carriers in order to increasing oral bioavailability and distribution. A number of absorptive intestinal transporters are described in terms of gene and protein classification, driving forces, substrate specificities and cellular localization. When targeting absorptive large capacity membrane transporters in the small intestine in order to increase oral bioavailabilities of drug or prodrug, the major influence on in vivo pharmacokinetics is suggested to be dose-dependent increase in bioavailability as well as prolonged blood circulation due to large capacity facilitated absorption, and renal re-absorption, respectively. In contrast, when targeting low-capacity transporters such as vitamin transporters, dose independent saturable absorption kinetics are suggested. We thus believe that targeting drug substrates for absorptive intestinal membrane transporters could be a feasible strategy for optimizing drug bioavailability and distribution.

Administration, Oral↗
PubMed2004

The role of biopharmaceutics in the development of a clinical nanoparticle formulation of MK-0869: a Beagle dog model predicts improved bioavailability and diminished food effect on absorption in human.

MK-0869 (aprepitant), a potent substance P antagonist, is the active ingredient of EMEND which has recently been approved by the FDA for the prevention of chemotherapy-induced nausea and vomiting. Early clinical tablet formulations of MK-0869 showed significant food effects on absorption, suggesting that formulation could have a significant role in improving bioavailability. A Beagle dog model was developed in an effort to guide novel formulation development. Using the suspension of the micronized bulk drug used for the tablet formulations, the food effect on absorption was confirmed in the dog at a similar magnitude to that observed in humans. Further dog studies demonstrated a clear correlation between particle size and in vivo exposures, with the nanoparticle (NanoCrystal) colloidal dispersion formulation providing the highest exposure, suggesting dissolution-limited absorption. The NanoCrystal dispersion also eliminated the food effect on oral absorption in the dog at a dose of 2mg/kg. Regional absorption studies using triport dogs indicated that the absorption of MK-0869 was limited to the upper gastrointestinal tract. These results provided strong evidence that the large increase in surface areas of the drug nanoparticles could overcome the narrow absorption window and lead to rapid in vivo dissolution, fast absorption, and increased bioavailability. In addition, the dog model was used for optimizing formulation processes in which the nanoparticles were incorporated into solid dosage forms, and for selecting excipients to effectively re-disperse the nanoparticles from the dosage units. The human pharmacokinetic data using the nanoparticle formulation showed excellent correlations with those generated in the dog.

Absorption↗
PubMed2006

Rapid-onset intranasal delivery of metoclopramide hydrochloride. Part I. Influence of formulation variables on drug absorption in anesthetized rats.

Intranasal (IN) administration is a promising approach for rapid-onset delivery of medications and to circumvent their first-pass elimination when taken orally. Metoclopramide (MCP) is a potent antiemetic, effective even for preventing emesis induced by cancer chemotherapy. The feasibility of developing an efficacious intranasal formulation of metoclopramide has been undertaken in this study. The nasal absorption of MCP was studied in anesthetized rats over 60min using the in vivo in situ technique. The influence of several formulation variables, vis., pH and the addition of preservative, viscosity and absorption enhancing agents on the nasal MCP absorption was examined. The data obtained showed that MCP was well absorbed nasally where almost 90% of the drug was absorbed after 60min from the rat nasal cavity. The MCP absorption was pH-dependant such that the apparent first-order rate constant of absorption (K(app)) was almost tripled when the pH of the solution was increased from 5 to 8. However, deviation from the classical pH-partition theory was observed pointing to the role of aqueous pore pathway in MCP nasal absorption. The K(app) was significantly increased (P<0.05) by incorporation of 0.01% of the preservative benzalkonium chloride. Conversely, increasing the solution viscosity by the use of hydroxylpropyl methylcellulose adversely affected the rate of absorption. The use of enhancers namely sodium deoxycholate, sodium cholate, chitosan low and high molecular weight, protamine sulphate and poly-l-arginine resulted in significant increase in MCP absorption. The highest promoting effect was observed with the bile salt sodium deoxycholate where about 92% of the drug was absorbed in 25min from the rat nasal cavity and the K(app) showed more than two-fold increase as compared to control (from 0.0452 to 0.1017min(-1)).

Absorption↗
PubMed2006

Novel oral formulation safely improving intestinal absorption of poorly absorbable drugs: utilization of polyamines and bile acids.

In order to develop a novel oral formulation that can safely improve the intestinal absorption of poorly absorbable drugs, polyamines such as spermine (SPM) and spermidine (SPD) was examined as an absorption enhancing adjuvant in rats. The absorption of rebamipide, classified into BCS Class IV, from colon was significantly improved by SPM or SPD, and the enhancing ability of SPM was larger than that of SPD. As a possible mixing and/or interaction of polyamines with bile acids were expected, the combinatorial use of sodium taurocholate (STC) with polyamines was also examined. The absorption of rebamipide was drastically improved by the combinatorial use of SPM or SPD with STC. As STC itself did not enhance the absorption of rebamipide so much, it was considered that polyamines and STC had a synergistic enhancing effect. In-vivo oral absorption study was also performed to investigate the effectiveness and safety of polyamines and their combinatorial use with STC in rats. Although the enhancing effect slightly attenuated comparing with the in-situ loop study, the absorption of rebamipide was significantly improved and the combinatorial use of 10 mM SPM with 25 mM STC showed the largest enhancing effect. Histopathological studies clearly showed that any significant change in stomach and duodenum was not caused by SPM (10 mM), SPD (10 mM) or their combinatorial use with STC (25 mM) at 1.5 or 8.0 h after oral administration. Taken all together, polyamines, especially SPM, and its combinatorial use with STC could improve the absorption of poorly absorbable drugs without any significant changes in gastrointestinal tract after oral administration in rats.

Adjuvants, Pharmaceutic↗
PubMed2004

Optical absorption of 1H-pyrazolo[3,4-b]quinoline and its derivatives.

The results of experimental studies and quantum chemical simulations of the absorption spectra of 1H-pyrazolo[3,4-b]quinoline and its derivatives are presented. The quantum chemical calculations (semi-empirical AM1 and PM3 methods) show similarity in the absorption spectra of 1H-pyrazolo[3,4-b]quinoline and 1,3-dimethyl-1H-pyrazolo[3,4-b]quinoline which are characterized by five strong absorption bands in the spectral range 200-500 nm. A substitution of the methyl groups by at least one phenyl group causes the drastic changes of the absorption spectra mainly within the spectral range 240-370 nm. We attribute these differences to additional molecular double bonding segments C=C of the substituted phenyl groups, i.e. to pi --> pi* transitions. A comparison of measured and the calculated absorption spectra manifests quite satisfactory agreement for all compounds in the part regarding the spectral position of the first oscillator (absorption threshold). At the same time, the measured spectra demonstrate the considerable broadening practically of all absorption bands and even complete damping some of them in the case of phenyl derivatives. The experiments performed with highly and weakly polar organic solvents shows that the solvent effect on the absorption spectra is small. For this reason the discrepancies between the calculated and the measured spectra are attributed to electron-vibronic coupling as well as to rotational dynamics of phenyl rings.

Absorption↗
PubMed2006

Optical absorption of sodium copper chlorophyllin thin films in UV-vis-NIR region.

The optical absorption studies of sodium copper chlorophyllin thin films (SCC), prepared by spray pyrolysis, in the UV-vis-NIR region was reported for the first time. Several new discrete transitions are observed in the UV-vis region of the spectra in addition to a strong continuum component in the IR region. The spectra of the infrared absorption allow characterization of vibration modes for the powder and thin films of SCC. The absorption spectrum recorded in the UV-vis region showed different absorption bands, namely the Soret (B) in the region 340-450 nm and Q-band in the region 600-700 nm and other band labeled N in the 240-320 region. Some important spectral parameters namely optical absorption coefficient (alpha), molar extinction coefficient (epsilon(molar)), oscillator strength (f), electric dipole strength (q(2)) and absorption half bandwidth (Deltalambda) of the principle optical transitions were evaluated. The analysis of the absorption coefficient in the absorption region revealed direct transitions and the energy gap was estimated as 1.63 eV. Discussion of the obtained results and their comparison with the previous published data are also given.

Absorption↗