Effect of starvation on gonadotrophin secretion and on in vitro release of LRH from the isolated median eminence of the male rat

1983 ◽  
Vol 103 (3) ◽  
pp. 293-301 ◽  
Author(s):  
Michael Warnhoff ◽  
Gunter Dorsch ◽  
Karl M. Pirke
Keyword(s):  
In Vitro Release ◽  
Basic Mechanism ◽  
Male Rat ◽  
Gonadotrophin Secretion ◽  
Significant Difference ◽  
Lh Release ◽  
And Control ◽  
Vitro Release

Abstract. A perfusion system was developed in which isolated median eminences (ME) were stimulated in vitro by depolarizing agents such as potassium and veratridine. Potassium concentrations between 30 and 80 mm released increasing amounts of luteinizing hormone-releasing hormone (LRH) from the MEs of starved and control rats. Veratridine at a concentration of 50 μm caused a more prolonged LRH release in both starved and control animals. LRH secretion in vitro was slightly, though not under all conditions, significantly greater in rats starved for 5 days. The testosterone (T)-LH feedback was studied by castrating the animals and substituting various doses of T through implantation of T-releasing capsules of different sizes. The concentration in plasma, which can prevent the castration-induced much smaller in starved than in control rats. The in vitro release of LRH evoked by 80 mm potassium was not different for starved and fed rats under various feedback conditions. Both groups revealed decreased in vitro release of LRH when castrated animals were not substituted with T. The effect of castration was studied from 1 to 28 days. The plasma LH values rapidly increased in starved and control animals, indicating that the hypothalamic responsestration is not delayed by starvation. The release in vitro of LRH decreased from the first to the fifth day and remained constant thereafter. No significant difference between starved and fed rats was observed. The experiments indicate that the 'releasable pool' of LRH in vitro is greater under conditions of reduced LH release in vivo. The basic mechanism of depolarization-induced exocytosis of LRH from the ME is intact in starved animals.

Reliability of a Single β-Thromboglobulin Measurement in a Diabetic Population : Importance of PGE1 in Anticoagulant Mixture

1987 ◽  
Vol 57 (02) ◽  
pp. 201-204 ◽  
Author(s):  
P Y Scarabin ◽  
L Strain ◽  
C A Ludlam ◽  
J Jones ◽  
E M Kohner
Keyword(s):  
In Vitro Release ◽  
Mean Value ◽  
Reliable Estimate ◽  
Diabetic Patients ◽  
Single Measurement ◽  
Diabetic Population ◽  
The Difference ◽  
Vitro Release

SummaryDuring the collection of samples for plasma β-thromboglobulin (β-TG) determination, it is well established that artificially high values can be observed due to in-vitro release. To estimate the reliability of a single β-TG measurement, blood samples were collected simultaneously from both arms on two separate occasions in 56 diabetic patients selected for a clinical trial. From each arm, blood was taken into two tubes containing an anticoagulant mixture with (tube A) and without (tube B) PGE!. The overall mean value of B-TG in tube B was 1.14 times higher than in tube A (p <0.01). The markedly large between-arms variation accounted for the most part of within-subject variation in both tubes and was significantly greater in tube B than in tube A. Based on the difference between B-TG values from both arms, the number of subjects with artifically high B-TG values was significantly higher in tube B than in tube A on each occasion (overall rate: 28% and 14% respectively). Estimate of between-occasions variation showed that B-TG levels were relatively stable for each subject between two occasions in each tube. It is concluded that the use of PGEi decreases falsely high B-TG levels, but a single measurement of B-TG does not provide a reliable estimate of the true B-TG value in vivo.

Development, in vitro and in vivo Evaluations of Solid-Lipid Microparticles based on Solidified Micellar Carrier System for Oral Delivery of Cefepime

2017 ◽  
Vol 10 (1) ◽  
pp. 3582-3593
Author(s):  
Chukwuebuka Umeyor ◽  
Uchechukwu Nnadozie ◽  
Anthony Attama
Keyword(s):  
Oral Delivery ◽  
In Vitro Release ◽  
Carrier System ◽  
Solid Lipid ◽  
Solid Lipid Microparticles ◽  
Release Study ◽  
Lipid Microparticles ◽  
Vitro Release

This study seeks to formulate and evaluate a solid lipid nanoparticle-based, solidified micellar carrier system for oral delivery of cefepime. Cefepime has enjoyed a lot of therapeutic usage in the treatment of susceptible bacterial infections; however, its use is limited due to its administration as an injection only with poor patient compliance. Since oral drug administration encourage high patient compliance with resultant effect in improved therapy, cefepime was formulated as solid lipid microparticles for oral delivery using the concept of solidified micellar carrier system. The carrier system was evaluated based on particle yield, particle size and morphology, encapsulation efficiency (EE %), and thermal analysis using differential scanning calorimeter (DSC). Preliminary microbiological studies were done using gram positive and negative bacteria. In vitro release study was performed using biorelevant media, while in vivo release study was performed in white albino rats. The yield of solid lipid microparticles (SLM) ranged from 84.2 – 98.0 %. The SLM were spherical with size ranges of 3.8 ± 1.2 to 42.0 ± 1.4 µm. The EE % calculated ranged from 83.6 – 94.8 %. Thermal analysis showed that SLM was less crystalline with high potential for drug entrapment. Microbial studies showed that cefepime retained its broad spectrum anti-bacterial activity. In vitro release showed sustained release of cefepime from SLM, and in vivo release study showed high concentration of cefepime released in the plasma of study rats. The study showed that smart engineering of solidified micellar carrier system could be used to improve oral delivery of cefepime.

Formulation and Evaluation of Itopride Hydrochloride Floating Beads for Gastroretentive Delivery

2013 ◽  
Vol 6 (4) ◽  
pp. 2269-2280
Author(s):  
Nagratna Dhople ◽  
P N Dandag ◽  
A P Gadad ◽  
C K Pandey ◽  
Masthiholimath V S
Keyword(s):  
Sustained Release ◽  
In Vitro Release ◽  
Entrapment Efficiency ◽  
Sustained Release Formulation ◽  
Prokinetic Drug ◽  
Drug Entrapment Efficiency ◽  
Itopride Hydrochloride ◽  
Vitro Release

A gastroretentive sustained release system of itopride hydrochloride was formulated to increase the gastric residence time and modulate its release behavior. Itopride hydrochloride is a prokinetic drug used in the treatment of gastroeosophageal reflux disease, Non-ulcer dyspepsia and as an antiemetic. Hence, itopride hydrochloride beads were prepared by emulsion gelation method by employing low methoxy pectin and sodium alginate as sustained release polymers in three different ratios alone and in combination and sunflower oil was used to enable floating property to the beads. The effect of variation in polymer and their concentration was investigated. The beads were evaluated for production yield, particle size, swelling index, density measurement, buoyancy, drug content, drug entrapment efficiency, in vitro release characteristics and release kinetic study. Based on drug entrapment efficiency, buoyancy, swelling and in vitro release, F9 was selected as the optimized formulation. F9 was further subjected to surface morphology by SEM, in vitro release comparison with marketed formulation, in vivo floating study in rabbits and stability study for 90 days. In vitro release follows zero order and fitted in Korsmeyer peppas model (Non-Fickian release). Therefore, the rate of drug release is due to the combined effect of drug diffusion and polymer swelling. The in vivo X-ray studies revealed that the beads were floating in the rabbit stomach up to 10 hours. Thus, it was concluded that the sustained release formulation containing itopride hydrochloride was found to improve patient compliance, minimize the side effects and decrease the frequency of administration.

Medicament Release from Ointment Bases: III. Ibuprofen: In Vitro Release and In-Vivo Absorption in Rabbits

1986 ◽  
Vol 12 (14) ◽  
pp. 2521-2540 ◽  
Author(s):  
A. Muktadir ◽  
A. Babar ◽  
A. J. Cutie ◽  
F. M. Plakogiannis
Keyword(s):  
In Vitro Release ◽  
In Vivo Absorption ◽  
Vitro Release

Preparation, Characterization and In Vitro Release Kinetics of Vancomycin Carried β-TCP/Chitosan Composite Microspheres Used as Bone Tissue Engineering Scaffolds

2012 ◽  
Vol 512-515 ◽  
pp. 1821-1825
Author(s):  
Lin Zhang ◽  
Xue Min Cui ◽  
Qing Feng Zan ◽  
Li Min Dong ◽  
Chen Wang ◽  
...  
Keyword(s):  
Tissue Engineering ◽  
Release Kinetics ◽  
In Vitro Release ◽  
Cross Linking ◽  
Tissue Engineering Scaffolds ◽  
Composite Microspheres ◽  
Chitosan Composite ◽  
Vitro Release

A novel microsphere scaffolds composed of chitosan and β-TCP containing vancomycin was designed and prepared. The β-TCP/chitosan composite microspheres were prepared by solid-in-water-in-oil (s/w/o) emulsion cross-linking method with or without pre-cross-linking process. The mode of vancomycin maintaining in the β-TCP/chitosan composite microspheres was detected by Fourier transform infrared spectroscopy (FTIR). The in vitro release curve of vancomycin in simulated body fluid (SBF) was estimated. The results revealed that the pre-cross-linking prepared microspheres possessed higher loading efficiency (LE) and encapsulation efficiency (EE) especially decreasing the previous burst mass of vancomycin in incipient release. These composite microspheres got excellent sphere and well surface roughness in morphology. Vancomycin was encapsulated in composite microspheres through absorption and cross-linking. While in-vitro release curves illustrated that vancomycin release depond on diffusing firstly and then on the degradation ratio later. The microspheres loading with vancomycin would be to restore bone defect, meanwhile to inhibit bacterium proliferation. These bioactive, degradable composite microspheres have potential applications in 3D tissue engineering of bone and other tissues in vitro and in vivo.

Diadermatic Dose Forms Of Testosterone: In-Vitro Release Studies and in-Vivo Absorption In A Human Male

1989 ◽  
Vol 15 (9) ◽  
pp. 1405-1422
Author(s):  
A. Babar ◽  
R. A. Khaleque ◽  
A. J. Cutie ◽  
F. M. Plakogiannis
Keyword(s):  
In Vitro Release ◽  
Human Male ◽  
Release Studies ◽  
In Vivo Absorption ◽  
Vitro Release
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