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PubMed2006

Redesign of human carbonic anhydrase II for increased esterase activity and specificity towards esters with long acyl chains.

The effect of modulating the shape and the size of the hydrophobic pocket on the esterase activity and specificity of human carbonic anhydrase II (HCAII) for esters with different acyl chain lengths was investigated. Following an initial screen of 7 HCAII variants with alanine substitutions in positions 121, 143 and 198, detailed kinetic measurements were performed on HCAII and the variants V121A, V143A and V121A/V143A. For some variants, an increased size of the hydrophobic pocket resulted in increased activities and specificities for longer substrates. For V121A/V143A, the rate of hydrolysis for paranitrophenyl valerate was increased by a factor of approximately 3000. The specificities also changed dramatically, for example V121A/V143A is 6.3 times more efficient with paranitrophenyl valerate than paranitrophenyl acetate, while HCAII is >500 times more efficient with paranitrophenyl acetate than paranitrophenyl valerate. An automated docking procedure was performed on these variants with transition state analogues (TSAs) for the hydrolysis reaction. It was possible to correlate the catalytic rate constants to the docking results, i.e. for each variant, efficient hydrolysis was generally correlated to successful TSA-docking. The observations in this paper show that the redesign increased the catalytic rates for substrates with long acyl chains by removal of steric hinders and addition of new favourable binding interactions.

Alanine↗
PubMed1976

The encephalopathic action of five-carbon-atom fatty acids in the rabbit.

1. Five-carbon-atom organic acids (C-5 acids) have been administered intravenously to rabbits with ventriculocisternal perfusion and continuous electroencephalographic recording (EEG). The concentration of the acids in the cerebrospinal fluid (CSF) perfusate have been compared with changes in integrated low-frequency activity in the EEG. 2. The C-5 acids investigated were those accumulating in inborn errors of metabolism, i.e. isovaleric acid, beta-methylcrotonic acid, tiglic acid and alpha-keto- and alpha-hydroxy-isovaleric acid. There activity was compared with that of valeric acid. 3. Valeric acid and isovaleric acid produced coma and pronounced increase in slow-wave electrical activity and these changes paralleled the increase in concentration of the acids in the CSF perfusate. 4. The concentration of beta-methylcrotonic acid and tiglic acid in the CSF perfusate reached values comparable with valeric acid and isovaleric acid but showed less encephalopathic activity. An interaction between beta-methylcrotonic acid and isovaleric acid was observed. 5. Although the concentrations of alpha-ketoisovaleric acid and alpha-hydroxyisovaleric acid rose to the lesser extent in the CSF perfusate, changes in rousability of the animal and in the EEG recording were demonstrated. 6. It is concluded that all the C-5 acids tested have encephalopathic activity although this is lessened by the presence of either a double bond or an oxygenated functional group.

Animals↗
PubMed2001

Radiolabeled cholinesterase substrates: in vitro methods for determining structure-activity relationships and identification of a positron emission tomography radiopharmaceutical for in vivo measurement of butyrylcholinesterase activity.

There is currently great interest in developing radiolabeled substrates for acetylcholinesterase and butyrylcholinesterase that would be useful in the in vivo imaging of patients with Alzheimer's disease. Using a simple in vitro spectrophotometric assay for determination of enzymatic cleavage rates, the structure-activity relationship for a short series of 1-methyl-4-piperidinyl esters was investigated. Relative enzymatic hydrolysis rates for the well-characterized 1-methyl-4-piperidinyl acetate, propionate, and i-butyrate esters were in agreement with literature values. The 4 and 5 carbon esters of 1-methyl-4-piperidinol were specific for butyrylcholinesterase and cleaved in the rank order n-valerate > n-butyrate >> 2-methylbutyrate, iso-valerate. These spectrophotometric results were also in agreement with in vitro hydrolysis rates in mouse blood and with in vivo regional retention of radioactivity in mouse brain of 11C-labeled analogs. Brain uptake and apparent enzymatic rate constants for 1-[11C]methyl-4-piperidinyl n-butyrate and n-valerate were calculated from in vivo measurements in M. nemistrina using positron emission tomography. Based on higher brain uptake of radioactivity and superior pharmacokinetics, 1-[11C]methyl-4-piperidinyl n-butyrate was identified as a new radiopharmaceutical for the in vivo measurement of butyrylcholinesterase activity.

Acetylcholinesterase↗
PubMed1978

Corticosteroid effect on epidermal cell size.

Changes in the epidermis following application of three corticosteroids, betamethasone 17-valerate, hydrocortisone 17-butyrate, and hydrocortisone have been studied histometrically in human volunteers. The reduction in epidermal thickness observed correlated significantly with a reduction in size of the viable epidermal cells. There was no significant reduction in the number of cells constituting the viable epidermis. These findings indicate that thinning of the epidermis is a function of cell size rather than cell number. The epidermal changes developed quickly and were rapidly reversible. It is suggested that measurement of cell size may be an early and sensitive index of atrophogenicity induced by topical corticosteroids. 0.1% Hydrocortisone 17-butyrate and 0.1% betamethasone 17-valerate showed equivalent potency in causing epidermal thinning and reduction in cell size. Reduction in cell size paralleled increasing concentrations of betamethasone 17-valerate, indicating a positive dose-effect relationship.

Adult↗
PubMed1996

Infusion of various short chain fatty acids causes different changes in the blood glucose and insulin concentrations in growing lambs deprived of food overnight.

Glucose and insulin concentrations of jugular blood plasma were monitored in growing lambs over 8 h, following a 2 h infusion of acetate, propionate, n-butyrate, n-valerate and physiological saline into the ruminal vein. Propionate and especially n-valerate infusion significantly increased blood glucose concentration. n-Butyrate induced only a small increase of shorter duration, while acetate failed to exert a pronounced effect on the blood glucose level. SCFA infusion, except for acetate, raised the insulin level in the blood. Relative rise was closely correlated with the length of carbon chain of the SCFA, that is, n-valerate caused the largest elevation of the insulin level, followed by n-butyrate and propionate. At the same time, acetate failed to cause a marked influence on the insulin level. These results of insulin showed agreement with glucose concentration changes, with the exception of n-butyrate treatment, where the increase of plasma insulin concentrations after the infusion proved to be much larger than that of glucose, relative to the preinfusion value.

Acetates↗
PubMed1971

Growth of Escherichia coli on short-chain fatty acids: nature of the uptake system.

Mutants of Escherichia coli K-12 which grow on butyrate and valerate were studied with respect to uptake of these substrates. To utilize short-chain and medium-chain fatty acids, E. coli must synthesize the beta-oxidation enzymes constitutively. In addition, growth on the C(4) and C(5) acids requires a second mutation which permits entry of these substrates. At pH 5, both in the parent and mutant strains, butyrate and valerate penetrate as the undissociated acids but appear not to be activated and thus inhibit growth. At pH 7, the parent strain is not permeable to the anions, whereas the mutant concentrates these substrates. There appear to be two components of the uptake system, a nonspecific diffusion component and an energy-linked activating enzyme. Two mutant types which take up short-chain fatty acids are described. One synthesizes the uptake system constitutively and is inhibited by 4-pentenoate when cultured on acetate. In the other, the uptake system is inducible, and the strain is pentenoate-resistant when grown on acetate but pentenoate-sensitive when cultured on butyrate or valerate.

Acetates↗
PubMed2005

The UV erythema test as a model to investigate the anti-inflammatory potency of topical preparations--reevaluation and optimization of the method.

BACKGROUND: The ultraviolet (UV) erythema test is one of the most frequently used methods to investigate the anti-inflammatory potency of topical dermatological preparations in vivo. METHODS: The following questions were addressed in four separate studies with healthy persons (skin types 2 and 3): (1) the optimal localization was determined by comparing light scales on the back, buttocks and volar forearms; (2) the optimal UV-B dose was determined by comparing the 1-fold, 1.5-fold and 2-fold minimal erythema doses (MEDs); (3) hydrocortisone and prednicarbate were evaluated as positive controls, and a sample size calculation was performed, and (4) betamethasone valerate and pimecrolimus were tested as further positive controls in the optimized study model. RESULTS: The back proved to be the best localization for the UV erythema test. It showed a good correlation between the light scale and the test areas. The 1.5-fold MED was the best irradiation dose. In contrast to prednicarbate and betamethasone valerate, hydrocortisone was a rather weak positive control. However, when the sample size was > or = 40 subjects, significant results were also obtained with hydrocortisone. Pimecrolimus was not effective in the UV erythema test. CONCLUSIONS: The UV erythema test should be performed on the back with at least 40 subjects using the 1.5-fold MED. It may be useful to include a potent corticosteroid, such as prednicarbate or betamethasone valerate, in addition to hydrocortisone. The UV erythema test seems to be suitable only for substances with corticosteroid-like effects, since in this test model the calcineurin inhibitor pimecrolimus was not effective.

Administration, Topical↗
PubMed1984

A randomized trial on the D-homosteroid domoprednate (Ro 12-7024) in the treatment of dermatoses.

39 patients with bilateral dermatoses, mainly psoriasis vulgaris and atopic dermatitis, were treated with 0.1% Ro 12-7024 ointment and 0.1% betamethasone valerate ointment according to a double-blind, right-left, randomized design. Treatment lasted up to 4 weeks. 5 patients did not complete the trial. Assessment of efficacy, expressed as degree of healing in percent of treated skin area and according to an overall assessment of efficacy made by both physician and patient only revealed marginal, mostly statistically insignificant differences, with a trend in favor of betamethasone. Patients' preferences for one of the two treatments favored betamethasone valerate in 17 cases and Ro 12-7024 in 5 cases; 13 cases were ties (p less than 0.001). With the exception of one case of bilateral erythema and itching no side effects were reported. The efficacy of the D-homosteroid Ro 12-7024 is evidently of the same order as that of the group III steroid betamethasone valerate, and the tolerance of the two ointments is good and equal.

Adolescent↗
PubMed2004

Splanchnic metabolism of volatile fatty acids absorbed from the washed reticulorumen of steers.

Six steers fitted with a ruminal cannula and chronic indwelling catheters in the mesenteric artery, mesenteric vein, hepatic portal vein, hepatic vein, as well as in the right ruminal vein were used to study metabolism of VFA absorbed from buffers in the emptied and washed reticulorumen. [2-(13)C]Acetate was infused into a jugular vein to study portal-drained visceral (PDV) uptake of arterial acetate, hepatic unidirectional uptake of acetate, and whole-body irreversible loss rate (ILR). Isobutyrate was infused into the right ruminal vein to calibrate VFA fluxes measured in the portal vein. On sampling days, the rumen was emptied and incubated in sequence with a 0-buffer (bicarbonate buffer without VFA), a VFA-buffer plus continuous intraruminal infusion of VFA, and finally another 0-buffer. Ruminal VFA absorption was determined as VFA uptake from the VFA-buffer and metabolic effects determined as the difference between metabolite fluxes with VFA-buffer and 0-buffers. Steady absorption rates of VFA were maintained during VFA-buffer incubations (4 h; 592+/-16, 257+/-5, 127+/-2, 17+/-<1, 20+/-<1 mmol/h, respectively, of acetate, propionate, butyrate, isovalerate, and valerate). The portal flux of acetate corrected for PDV uptake of arterial acetate accounted for 105+/-3% of the acetate absorption from the rumen, and the net portal flux of propionate accounted for 91+/-2% of propionate absorption. Considerably less butyrate (27+/-3%) and valerate (30+/-3%) could be accounted for in the portal vein. The sum of portal VFA and 3-hydroxybutyrate as well as lactate represented 99+/-3% of total VFA acetyl units and 103+/-2% of VFA propionyl units. Estimates are maximum because no accounting was made for lactate derived from glycolysis in the PDV. The net splanchnic flux of VFA, lactate, 3-hydroxybutyrate, and glucose accounted for 64+/-2% of VFA acetyl units and 34+/-5% of VFA propionyl units. Results indicate that there is a low "first-pass" uptake of acetate and propionate in the ruminal epithelium of cattle, whereas butyrate and valerate are extensively metabolized, though seemingly not oxidized to carbon dioxide in the epithelium but repackaged into acetate, 3-hydroxybutyrate, and perhaps other metabolites. When PDV "second-pass" uptake of arterial nutrients is accounted for, PDV fluxes of VFA, lactate, and 3-hydroxybutyrate represent VFA production in the gastrointestinal tract and thereby VFA availability to the ruminant animal.

Absorption↗
PubMed1992

Ultraviolet B dose-dependent inflammation in humans: a reflectance spectroscopic and laser Doppler flowmetric study using topical pharmacologic antagonists on irradiated skin.

Normal skin responds acutely to ultraviolet (UV) light exposure with complex inflammatory mechanisms. In the present study UVB irradiation ranging from subclinical erythema doses to twice the minimal erythema dose (24 mJ/cm2 to 96 mJ/cm2) was delivered to the skin of 8 volunteers. Pre-irradiated sites were immediately afterwards exposed to a 24-h occlusive patch containing 1 of 4 anti-inflammatory agents or vehicle control. The resultant change in erythema (vascular reaction) was measured objectively using laser Doppler flowmetry (LDF) and reflectance spectroscopy (RS). The 4 anti-inflammatory compounds reduced the UVB-induced vascular reactions in different and dose-dependent ways. Betamethasone-17-valerate and diphenhydramine were most effective at the 24 mJ/cm2 dose site and indomethacin and acetylsalicylic acid were more effective at sites > or = 48 mJ/cm2. Ranking the reduction in oxygenized hemoglobin (OH) content was as follows: betamethasone-17-valerate (OH reduction = 37.4%) > indomethacin (OH reduction = 21.5%) > acetylsalicylic acid (ASA) (OH decrease = 21.0%) > diphenhydramine (OH reduction = 18.4%). Using LDF, the total ranking of the cutaneous blood flow (BF) reduction was: indomethacin (BF reduction = 39.7%) > betamethasone-17-valerate (BF reduction = 32.7%) > acetylsalicylic acid (BF decrease = 17.5%) > diphenhydramine (BF reduction = 12.3%). Diphenhydramine significantly reduced erythema only at the lowest irradiation dose (24 mJ/cm2) and the decrease in OH was associated with an increased amount of deoxygenized hemoglobin (DOH). A similar slight venous dilatation was present at acetylsalicylic acid-exposed sites.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Topical↗
PubMedDate not supplied

[The synthesis of hydroxybutyrate and hydroxyvalerate copolymers by the bacterium Ralstonia eutropha].

The paper deals with the study of the synthesis of 3-hydroxybutyrate (3HB) and 3-hydroxyvalerate (3HV) copolymers by the bacterium Ralstonia eutropha B-5786 grown under different carbon nutrition conditions (growth on carbon dioxide, fructose, and CO2-valerate and fructose-valerate mixtures). The parameters to be analyzed included the yield of biomass, the yield, synthesis rate, and composition of copolymers, the activity of the key enzymes of polyhydroxyalkanoate (PHA) synthesis (beta-ketothiolase, acetoacetyl-CoA reductase, and PHA synthase), the maximum tolerable concentration of valerate to the bacterium, and the conditions that govern the incorporation of hydroxyvalerate to copolymers. This allowed the relationship between cultivation conditions and the proportion of monomers in the copolymers to be deduced. We were able to synthesize a range of 3HB/3HV copolymers and found that the thermal characteristics and the degree of crystallinity of these copolymers depend on the molar fraction of 3HV.

Acetyl-CoA C-Acyltransferase↗
PubMed1998

Corticosteroid contact hypersensitivity screening in Singapore.

BACKGROUND: Topical corticosteroids have been in use since 1957. Two percent to 5% of patients attending patch test (PT) clinics have problems with corticosteroid contact hypersensitivity. Controversies abound with regard to the choice of steroids in the standard battery, the method of patch testing and reading, and the ideal concentration and vehicle. OBJECTIVE: To assess betamethasone 17-valerate (1% pet.), fluocinolone acetonide (0.25% petrolatum [pet.]), and tixocortol pivalate (1% pet.) used in the authors' standard battery. METHODS: Data were analyzed for patients seen between January 1994 and December 1996 who had positive PT reactions to one or more of these steroids. RESULTS: 3,603 patients had standard PTs, of which 20 had positive reactions to one or more of these steroids. There were three positive reactions to betamethasone 17-valerate, 17 to tixocortol, and none to fluocinolone. On further patch testing to the authors' steroid battery, only one tixocortol-positive patient had a positive reaction to hydrocortisone (1% ethanol/ dimethyl sulfoxide [DMSO]). CONCLUSIONS: Corticosteroid allergy is found to be relatively uncommon in Singapore on the basis of this screening series. The frequency of negative reactions to fluocinolone acetonide is sufficiently low for this corticosteroid to be excluded from the authors standard series. The significance of positive tixocortol reactions remains unknown. From the review of other relevant literature, the authors recommend that budesonide be added to their present series. Testing betamethasone 17-valerate in 1% ethanol may yield more positive allergic reactions. Individuals with a positive allergic PT reaction to one corticosteroid should subsequently be tested to a full corticosteroid series.

Administration, Topical↗
PubMed1991

Determination of short-chain fatty acids in equine caecal liquor by ion exchange high performance liquid chromatography after solid phase extraction.

A high performance liquid chromatography (HPLC) method was developed for the determination of seven short-chain fatty acids in equine caecal liquor. Samples were cleaned up on a Sep-pak (C18) cartridge, and the analyte was eluted from the extraction cartridge and filtered through a 0.45 micron cellulose nitrate filter. The analyte was chromatographed by ion exchange HPLC. Detection was by UV at 210 nm. Recovery from phosphate buffer (0.05 M, pH 7.0) and equine caecal liquor was 76.95% (lactic), 76.76% (valeric). The limit of (propionic), 89.35% (isobutyric), 88.73% (butyric), 80.33% (isovaleric) and 72.61% (valeric). The limit of detection of the short-chain fatty acids in phosphate buffer was 0.00006 M (lactic), 0.0001 M (acetic), 0.0002 M (propionic), 0.0001 M (isobutyric), 0.0002 M (butyric), 0.0002 M (isovaleric) and 0.0003 M (valeric). The specificity and sensitivity of this method was sufficiently high to allow the characterization of the pattern of these short-chain fatty acids in equine caecal liquor following intravenous administration of oxytetracycline at the recommended dose rate in a pony.

Animals↗
PubMed2004

Mass spectrometry feedback control for synthesis of polyhydroxyalkanoate granule microstructures in Ralstonia eutropha.

Polyhydroxyalkanoate (PHA) granules with core-shell layered microstructure were synthesized in Ralstonia eutropha using periodic feeding of valeric acid into a growth medium containing excess fructose. The O2 consumption and CO2 evolution rates, determined by off-gas mass spectrometry, have been used as sensitive measures to indicate the type of nutrients utilized by R. eutropha during PHA synthesis. Domains of poly-3-hydroxybutyrate (PHB) were formed during polymer storage conditions when only fructose was present. Feeding of valeric acid (pentanoic acid) resulted in the synthesis of hydroxyvalerate (HV) monomers, forming a poly-3-hydroxybutyrate-co-valerate (PHBV) copolymer. The synthesis of desired polymer microstructures was monitored and controlled using online mass spectrometry (MS). The respiratory quotient (RQ) was unique to the type of polymer being synthesized due to increased O2 consumption during PHBV synthesis. MS data was used as the control signal for nutrient feeding strategies in the bioreactor. The core-shell structures synthesized were verified in cells using transmission electron microscopy after thin sectioning and staining with RuO4. It was demonstrated that the synthesis of core-shell microstructures can be precisely controlled utilizing a MS feedback control system.

3-Hydroxybutyric Acid↗
PubMed1987

Blockade of gamma-aminobutyric acid-receptors of the B-subtype inhibits the dopamine-induced enhancement of the release of cholecystokinin-like immunoreactivity from slices of rat dorsal caudatoputamen.

When slices of rat dorsal caudatoputamen (= neostriatum) are incubated in vitro, cholecystokinin-like immunoreactivity (CCK-LI) is released upon addition of veratridine (3.75 mumol/l). This release is affected by dopamine and by gamma-aminobutyric acid (GABA)-receptor agonists. Dopamine enhances the release by stimulating dopamine D2-receptors and decreases it via D1-receptors. GABAA-receptor agonists enhance the veratridine-induced release of CCK-LI, while GABAB-receptor agonists decrease it. In the present investigation, it was examined whether GABA-receptors are involved in the effect which dopamine exerts via D2-receptors. The GABAA-receptor antagonist bicuculline (10 mumol/l) and the blocker of the GABAA-receptor ionophore picrotoxin (1 mumol/l) did not affect the dopamine (0.1 mumol/l)-induced increase in the release of CCK-LI. However, the GABAA-receptor agonist muscimol (1 mumol/l) not only enhanced the release of CCK-LI, but also prevented a further enhancement by dopamine (0.1 mumol/l). This effect of muscimol was blocked by bicuculline (10 mumol/l). In the presence of delta-amino-n-valeric acid (0.1 mmol/l), which has been described to block GABAB-receptors, dopamine no longer enhanced the veratridine-induced release of CCK-LI. delta-Amino-n-valeric acid also inhibited the pronounced enhancement of the release of CCK-LI caused by dopamine (0.1 mumol/l and 1 mumol/l in the presence of the preferential D1-receptor antagonist SCH 23390. The effect of delta-amino-n-valeric acid persisted in the presence of bicuculline (10 mumol/l and 100 mumol/l).(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids↗
PubMed1987

Metabolism of NG,NG-and NG,N'G-dimethylarginine in rats.

The metabolic fates of NG,NG-and NG,N'G-dimethylarginines in rats were investigated isotopically and novel metabolites, alpha-keto-delta-(N,N-dimethylguanidino)-and alpha-keto-delta-(N,N'-dimethylguanidino)valeric acids and gamma-(N,N-dimethylguanidino)-and gamma-(N,N'-dimethylguanidino)butyric acids were identified. In the case of the rats injected with NG,NG-dimethyl-L-[1,2,3,4,5-14C]arginine, about 13% of the radioactivity was recovered in the first 12-h urine and was distributed in the following metabolites (relative ratios): unchanged NG,NG-dimethyl-L-arginine (35.2%), gamma-(N,N-dimethylguanidino)butyric acid (18.4%), alpha-keto-delta-(N,N-dimethylguanidino)valeric acid (16.4%), and N alpha-acetyl-NG,NG-dimethyl-L-arginine (8.5%). The radioactivity retained in the tissues was found mainly in citrulline and was further distributed in ornithine, arginine, and glutamic acid and even in protein-bound arginine. In the case of NG,N'G-dimethyl-L-[1,2,3,4,5-14C]arginine-injected rats, about 75% of the radioactivity was excreted in the first 12-h urine and was recovered in the following metabolites (relative ratios): N alpha-acetyl-NG,N'G-dimethyl-L-arginine (48.4%), unchanged NG,N'G-dimethyl-L-arginine (23.7%), alpha-keto-delta-(N,N'-dimethylguanidino)valeric acid (20.2%), and gamma-(N,N'-dimethylguanidino)butyric acid (9.6%). In the tissues, most of the radioactivity was associated with unchanged NG,N'G-dimethyl-L-arginine. These findings show that both dimethylarginines are metabolized by a pathway forming the corresponding alpha-ketoacid analogs and the oxidatively decarboxylated products of the alpha-ketoacids in addition to the N alpha-acetyl conjugates identified previously (K. Sasaoka, T. Ogawa, and M. Kimoto (1982) Arch. Biochem. Biophys. 219, 454-458), and NG,NG-dimethyl-L-arginine is catabolized by an additional pathway leading to the formation of citrulline and its metabolically related amino acids. By considering their catabolism, an attempt to use urinary dimethylarginines as an index of in vivo breakdown of tissue proteins is invalid at least in rats.

Animals↗
PubMed1991

Determination of the thickness of the unstirred layers in the moving-drop method for measuring aqueous-nonaqueous interfacial transport rates.

A technique for measuring the thickness of the unstirred layer in the aqueous phase surrounding a rising octanol drop is described. Measurements of the rate of movement of both acetic and valeric acids from the drop into buffered solutions were made using an apparatus previously described (Miller, D.M. (1986) Biochim. Biophys. Acta 856, 27-35). The rate of movement of valeric acid was shown to be dependent on the pH of the buffer while that of acetic acid was not. The thickness of the unstirred layer in the buffered solution (w.u.l.) was found to be 7.0 microns, and the thickness of the unstirred layer in the drop (o.u.l.) was estimated to have an upper limit of 4.6 microns. The rate constant for the movement of valeric acid from the octanol phase to the buffer, kow, has a value restricted to the range 21 to 46 microns s-1 while that for movement in the opposite direction, kwo, ranges from 600 to 1300 microns s-1. The permeability of the w.u.l. is 120 microns s-1, while that of the o.u.l. has a lower limit of 37 microns s-1. Thus diffusion through the w.u.l. was not rate-limiting during movement into the drop, but was during movement outward. The rate of uptake of acetic acid was found to be 39 microns s-1 and was independent of pH, from which it was concluded that the resistance of the w.u.l. was negligible for this compound.

Acetates↗
PubMed1991

Effect of estradiol treatment on beta-endorphin content and release in the female rat hypothalamus.

The purpose of the present study was to determine whether an injection of estradiol valerate or chronic estradiol treatment alters beta-endorphin-immunoreactive (IR) material in the hypothalamus. Hypothalamic beta-endorphin-IR material was significantly reduced (by 47%) 2 months following an estradiol valerate injection. In addition, both the basal and veratridine-evoked release of beta-endorphin-IR material from hypothalamic slices incubated in vitro were decreased 48% and 52%, respectively. The net release of beta-endorphin-IR material was decreased by 50% compared to control animals. Chronic estradiol treatment (2 months) did not alter the tissue content of beta-endorphin-IR material. Although, we noted a significant decrease (48%) of the basal release and a significant increase (45%) of the evoked release, the net release of beta-endorphin-IR material from slices was not altered (107% of control). The present results suggest that estradiol valerate treatment decreases the capacity of beta-endorphin neurons in the hypothalamus to synthesize and maintain the release of beta-endorphin.

Animals↗