Prolactin suppresses release of luteinising hormone during lactation in the monkey

STUDIES with rats have shown that during lactation there is an inhibition of luteinising hormone (LH)-dependent physiological events, such as implantation1, and a return to oestrus cyclicity2. This inhibition has been shown to occur only during the intense suckling phase and it has been correlated with the high levels of prolactin present in the circulation at this time. Although exogenous prolactin could substitute for the effects of intense suckling, it could do so only under the permissive influence of minimal suckling stimulus. We have shown that there is, in these conditions, a lowering of LH levels, and that this is due to interference by prolactin with the pituitary responsiveness to LH-releasing hormone (LHRH) (K. Muralidhar, R. M. and N. R. M., unpublished). Using the lactating monkey, we have now demonstrated a similar inhibitory effect of prolactin on pituitary responsiveness to LHRH, suggesting a mechanism by which amenorrhoeic conditions are maintained during lactation.

The ability of prolactin to change the sensitivity of the pituitary of the lactating rat to luteinising hormone releasing hormonein vitro

The ability of prolactin to influence the responsiveness of the lactating rat pituitary to luteinising hormone releasing hormone has been examinedin vitro. The pituitary responsivenessin vivo to luteinising hormone releasing hormone decreased as a function of increase in the lactational stimulus. Prolactin inhibited the spontaneousin vitro release of luteinising hormone and follicle stimulating hormone to a small extent, from the pituitary of lactating rats with the suckling stimulus. However, it significantly inhibited the release of these two hormones from luteinising hormone releasing hormone-stimulated pituitaries. The responsiveness of pituitaries of rats deprived of their litter 24 h earlier, to luteinising hormone releasing hormone was also inhibited by prolactin, although minimal. It was concluded that prolactin could be influencing the functioning of the pituitary of the lactating rat by (a) partially suppressing the spontaneous release of gonadotropin and (b) inhibiting the responsiveness of the pituitary to luteinising hormone releasing hormone.

Effect of diethylstilbesterol and prolactin on the induction of follicle stimulating hormone receptors in immature and cycling rats

Induction of follicle stimulating hormone receptor in the granulosa cells of intact immature rat ovary by diethylstilbesterol, an estrogen, has been studied. A single injection of 4 mg of diethylstilbesterol produced 72 h later a 3-fold increase in follicle stimulating hormone receptor concentration as monitored by [125I]-oFSH binding to isolated cells. The newly induced receptors were kinetically indistinguishable from the preexisting ones, as determined by Lineweaver-Burk plot of the binding data. The induced receptors were functional as evidenced by increased ability of the granulosa cells to incorporate [3H]-leucine into cellular proteins. Neutralization of endogenous follicle stimulating hormone and luteinizing hormone by administering specific antisera had no effect on the ability of diethylstilbesterol to induce follicle stimulating hormone receptors, whereas blockade of endogenous prolactin secretion by ergobromocryptin administration significantly inhibited (∼ 30 %) the response to diethylstilbesterol; this inhibition could be completely relieved by ovine prolactin treatment. However, ovine prolactin at the dose tried did not by itself enhance follicle stimulating hormone receptor level. Administration of ergobromocryptin to adult cycling rats at noon of proestrus brought about as measured on diestrusII, (a) a reduction of both follicle stimulating hormone (∼ 30 %) and luteinizing hormone (∼ 45 %) receptor concentration in granulosa cells, (b) a drastic reduction in the ovarian tissue estradiol with no change in tissue progesterone and (c) reduction in the ability of isolated granulosa cells to convert testosterone to estradiol in response to follicle stimulating hormone. Ergobromocryptin treatment affected only prolactin and not follicle stimulating hormone or luteinizing hormone surges on the proestrus evening. Treatment of rats with ergobromocryptin at proestrus noon followed by an injection of ovine prolactin (1 mg) at 1700 h of the same day completely reversed the ergobromocryptin induced reduction in ovarian tissue estradiol as well as the aromatase activity of the granulosa cells on diestrus II, thus suggesting a role for proestrus prolactin surge in the follicular maturation process.

Role of prolactin(prl) in regulation of the nocturnal surge of testosterone (t) in the bonnet monkey (macaca radiata)

Earlier studies from this lebordory have shown thet adult male bonnet monkeys exhibit nychthemrel rhythmicity la the secretion of serum 'T' the levele reehlng peek by 22OOhr. Of the gonedotropine cnelyeed only serum PRL showed a concommitent increme with T(Biol.of Reprod. 24,814, 1981). In the present study mMinietretion of l rgobromocryptin (EBC) either by i.v.route(2mg)or by naeel l pr~(100~)reeulted in blockade of nocturnal increase of both PRL end T(Controle T-18.6ng/ml: PRL 130=29ng/ml: EBC treated T-2.2&1.2ng/ml; PRL n.d.to 15nng/ml). Adminietretion of N oPRL could not reverse the effect of EBC. Although, increaeed serum PRL induced by injection of Chlorprommine did not result in increase in serum 'T' during the dey time, the nocturnel 'T' surge could not be obeeerved. EBC treeted monkeys, however, showed normal testosterone response to exogenous hCG. These IeSUlte a0 SwgeStive of high levels of PRL me&in6 reeponeiveneee of testes to tonic levels of serum IX. (Aided by grant8 from ICMR, Kew Delhi, WHO, Geneva eld FPF, India).

AE energy release during the fracture of HSC beams

An attempt has been made experimentally to investigate the acoustic emission (AE) energy release in high-strength concrete (HSC) beams subjected to monotonically increasing load. Acoustic emission energy release during the fracture process of the HSC beams is measured. Stress waves released during the fracture process in materials cause acoustic emissions. AE energy released during the fracture of a notched three-point bend plain concrete beam specimens having 28-day compressive strengths of 50.0 MPa, 69.0 MPa and 78.0 MPa and mortar (cement: sand (1: 4) by weight) specimens are studied. Mortar consists of one part cement and four parts sand by weight. The specimens were tested by a material testing system of 1200 kN capacity employing crack mouth opening displacement control at the rate of 0.0004 mm/s. The fracture energy and the AE energy released during the fracture process of all the tested TPB and mortar specimens are compared and discussed. The observations made in the present experimental study have some applications for monitoring the integrity of structures.

Encapsulation and release of rifampicin using poly(vinyl pyrrolidone)-poly (methacrylic acid) polyelectrolyte capsules

Poly(vinyl pyrrolidone) and poly(methacrylic acid) multilayer capsules based on hydrogen bonding have been prepared by the layer-by-layer approach and used to encapsulate and release rifampicin, an antituberculosis drug. Removal of silica core using a buffer of ammonium fluoride and hydrofluoric acid at about pH 3 was found to produce better capsules than hydrofluoric acid alone. An eight-layered capsule had a wall thickness of 20 rim. Maximum encapsulation was found to be about 86 mu g at 40 degrees C with 1 +/- 0.2 x 10(6) capsules. Release studies showed a burst kind of release and maximum release was obtained above pH 7 where the capsules disintegrate rapidly thereby releasing the drug in a short period. Interactions studies with Mycobacterium smegmatis showed that the capsules were cytocompatible and the released drug functioned with the same efficacy as the free drug.

Influence of surface chemistry of mesoporous alumina with wide pore distribution on controlled drug release

The crucial role of the drug carrier surface chemical moeities on the uptake and in vitro release of drug is discussed here in a systematic manner. Mesoporous alumina with a wide pore size distribution (2-7 nm) functionalized with various hydrophilic and hydrophobic surface chemical groups was employed as the carrier for delivery of the model drug ibuprofen. Surface functionalization with hydrophobic groups resulted in low degree of drug loading (approximately 20%) and fast rate of release (85% over a period of 5 h) whereas hydrophilic groups resulted in a significantly higher drug payloads (21%-45%) and slower rate of release (12%-40% over a period of 5 h). Depending on the chemical moiety, the diffusion controlled (proportional to time(-0.5)) drug release was additionally observed to be dependent on the mode of arrangement of the functional groups on the alumina surface as well as on the pore characteristics of the matrix. For all mesoporous alumina systems the drug dosages were far lower than the maximum recommended therapeutic dosages (MRTD) for oral delivery. We envisage that the present study would aid in the design of delivery systems capable of sustained release of multiple drugs.

Cu2+-induced room temperature hydrogen release from ammonia borane

Mechanical stirring of ammonia borane with CuCl2 in the solid state resulted in the release of hydrogen at room temperature through the intermediacy of [NH4](+)[BCl4](-).

Effects of compressibility and heat release on entrainment processes in mixing layers

Characteristics of the process of entrainment in plane mixing layers, and the changes with compressibility and heat release, were studied using temporal DNS with simultaneous fluid packet tracking. Convective Mach numbers of the simulations are 0.15, 0.7 and 1.1. The Reynolds number is quite high (between 11 000 and 37 000 based on layer width and velocity difference), and is above the mixing transition. The study agrees with recent findings in round jets: first, engulfed fluid volume and its growth rate are both very small compared with the volume of the turbulent region and its growth rate, respectively. Secondly, most often, the process occurs close to the turbulent-nonturbulent boundaries. A new finding is that both compressibility and heat release retard the entrainment process so that it takes an O(1) time for vorticity or scalar levels to grow even after growth has been initiated. This delay is manifested as the fall in mixing layer growth rates as compressibility and heat release levels increase.

A real coded genetic algorithm for data partitioning and scheduling in networks with arbitrary processor release time

The problem of scheduling divisible loads in distributed computing systems, in presence of processor release time is considered. The objective is to find the optimal sequence of load distribution and the optimal load fractions assigned to each processor in the system such that the processing time of the entire processing load is a minimum. This is a difficult combinatorial optimization problem and hence genetic algorithms approach is presented for its solution.

Minimizing total weighted tardiness on a batch-processing machine with non-agreeable release times and due dates

This study considers the scheduling problem observed in the burn-in operation of semiconductor final testing, where jobs are associated with release times, due dates, processing times, sizes, and non-agreeable release times and due dates. The burn-in oven is modeled as a batch-processing machine which can process a batch of several jobs as long as the total sizes of the jobs do not exceed the machine capacity and the processing time of a batch is equal to the longest time among all the jobs in the batch. Due to the importance of on-time delivery in semiconductor manufacturing, the objective measure of this problem is to minimize total weighted tardiness. We have formulated the scheduling problem into an integer linear programming model and empirically show its computational intractability. Due to the computational intractability, we propose a few simple greedy heuristic algorithms and meta-heuristic algorithm, simulated annealing (SA). A series of computational experiments are conducted to evaluate the performance of the proposed heuristic algorithms in comparison with exact solution on various small-size problem instances and in comparison with estimated optimal solution on various real-life large size problem instances. The computational results show that the SA algorithm, with initial solution obtained using our own proposed greedy heuristic algorithm, consistently finds a robust solution in a reasonable amount of computation time.