The role of exogenous calcium for gonadotropin-stimulated progesterone production by human granulosa-luteal cells

Previous studies of cells from various species have indicated that exogenous calcium is necessary for gonadotropic stimulation of steroidogenesis. To determine whether this requirement for exogenous calcium is a universal attribute of steroidogenic cells, we studied baseline and stimulated progesterone (P) production by cultured human granulosaluteal cells obtained at the time of oocyte retrieval for in vitro fertilization (IVF). During 4 hours in culture, both cholera toxin (1.25 micrograms/mL) and human chorionic gonadotropin (hCG, 1 IU/mL) stimulated a significant (P less than 0.05) 2- to 4-times increase in P production. Both baseline and stimulated (cholera toxin or hCG) increases in P were unaffected when cellular uptake of exogenous calcium was inhibited by the calcium channel blocker nitrendipine (10 microM), or by culturing the cells in calcium-free medium or in calcium-free medium with [ethylenebis(oxyethylenenitrilo)]-tetra-acetic acid (EGTA, to chelate any possible free extracellular calcium). At later time points (24 and 48 hours), lack of available exogenous calcium began to have an inhibitory effect on P production, and the hCG effect was more sensitive to the lack of exogenous calcium than was the cholera toxin effect. We speculate that this apparent independence from exogenous calcium over a short culture period is due to the prior stimulation of these cells by exogenous gonadotropins employed in IVF cycles.

Recovery of forensically important entomological specimens from human cadavers in Malaysia--an update

A total of 101 entomological specimens recovered from human cadavers were processed and studied. Analysis of the data indicated that about 95% of these specimens were maggots of flies. Maggots of the blowfly Chrysomya (Family: Calliphoridae) especially Ch. rufifacis and Ch. megacephala were predominantly found in 77 cases (76.2%) while larvae of several other flies of the genera Sarcophaga, Calliphora, Lucilia and hermetia were also recovered. It was notable that Musca domestica or other related flies were not found in all these specimens. The age of these larvae was useful in the determination of the minimum time lapsed after death. However, more biological studies on animal carcases should be conducted for more accurate determinations. Methods of collection, preservation and despatching of specimens were also discussed.

A versatile computational method for the determination of areas under the curve and moment curve following multidose drug administration

The accurate determination of area under the biologic fluid concentration-time curve (AUC) and area under the first moment curve (AUMC) are important in the calculation of a compound's pharmacokinetic parameter estimates. Although numerous mathematical methods exist for the calculation of both AUC and AUMC under varying conditions, some permit direct computation of areas, whereas others only approximate the true areas. In this study, we describe an alternative mathematical method which allows the direct calculation of either the AUC or AUMC after any dose of drug administered by any route. Simulated data with known areas were used to assess the accuracy of the proposed method and compared to area calculations obtained from widely used published methods. Experiments were also performed under conditions of varying elimination half-lives and reduced numbers of concentration-time values. Under any experimental condition, the newly proposed method was the most accurate in determining both the AUC and AUMC. Percent deviations from exact area values were less than or equal to 0.11% with the proposed method, whereas as much as 30% deviation was observed using other methods of calculation. These findings support the accuracy of the proposed method in calculating the AUC or AUMC and its utility in data analysis.

Mass screening models for contagious diseases with no latent period

In this paper, a simplified model describing the stochastic process underlying the etiology of contagious and noncontagious diseases with mass screening is developed. Typical examples might include screening of tuberculosis in urban ghetto areas, venereal diseases in the sexually active, or AIDS in high risk population groups. The model is addressed to diseases which have zero or negligible latent periods. In the model, it is assumed that the reliabilities of the screening tests are constant, and independent of how long the population unit has the disease. Both tests with perfect and imperfect reliabilities are considered. It is shown that most of the results of a 1978 study by W.P. Pierskalla and J.A. Voelker for noncontagious diseases can be generalized for contagious diseases. A mathematical program for computing the optimal test choice and screening periods is presented. It is shown that the optimal screening schedule is equally spaced for tests with perfect reliability. Other properties relating to the managerial problems of screening frequencies, test selection, and resource allocation are also presented.

The glucagonoma syndrome in a Chinese man

The glucagonoma syndrome is a rare clinical condition. In this syndrome there is a pancreatic islet cell tumour which secretes glucagon, associated with a distinctive skin eruption--migratory necrolytic erythema. We describe a 79 year old Chinese man who presented with the typical skin features of this condition and on investigation had a pancreatic islet cell tumour. Serum glucagon levels were markedly elevated. He had a partial pancreatectomy and the skin rash improved dramatically. However he had liver metastases and responded poorly to streptozotocin. The skin features recurred and the patient died 9 months after diagnosis. As far as we are aware, this is the first report of a Glucagonoma syndrome in a Chinese.

Equilibrium analysis of disaggregate facility choice systems subject to congestion-elastic demand

This paper considers the impact of congestion on the spatial distribution of customer utilization of service facilities in a stochastic-dynamic environment. Previous research has assumed that the rate of demand for service is independent of the attributes of the facilities. We consider the more general case in which facility utilization is determined both by individual facility choice (based on the stochastic disaggregate choice mechanism) and by the rate of demand for service. We develop generalized results for proving that equilibria exist and describe sufficient conditions for the uniqueness and global stability of these equilibria. These conditions depend upon the elasticity of demand with respect to the level of congestion at the facilities, and on whether customers are congestion-averse or are congestion-loving. Finally, we examine special cases when these conditions are satisfied.

The determinants of spatial distribution of hospital utilization in a region

This article presents a series of models for explaining hospital utilization. The models belong to the multinomial logit class, which relate the probability of hospital selection to factors that include travel time between patients and hospitals, hospital attractiveness factors, physician characteristics, and patient characteristics. Separate models for different population groups (sex, age, socioeconomic classes) and medical services (general medicine, obstetrics, pediatrics, psychiatry, and general surgery) are estimated and compared with the general hospital model. The results, which are based on an extensive data base and new estimation procedures, are superior to those of past studies. A number of differences between utilization patterns for the various populations are also observed.

Role of food characteristics in behavioral change and weight loss

A behaviorally oriented correspondence course was completed by 517 subjects. All subjects received the behavioral course but were sorted into four groups: (a) behavioral instruction only, (b) recommend soup for lunch, (c) recommend soup for any meal or snack, and (d) recommend yogurt for meals or snacks. Subjects lost an average of 3.8 kg. in 10 weeks. There was a marked association between rate of eating and total caloric consumption for the meal. Eating soup as part of lunch or dinner led to both decreased consumption of kilo-calories and a slower rate of eating.

Properties of a new carvable composite dental filling material

The chemical principles and physical properties of a new composite system, which apparently cures in a two-step process to allow time for hand carving to the proper anatomic contours, are described. The new material appears to have better in vitro wear resistance than an older composite filling material.

A comparison of ultraviolet-curing and self-curing polymers in preventive, restorative and orthodontic dentistry

Both self-cured and UV-cured resin-base dental materials are used in preventive, restorative, and orthodontic dentistry. Polymerization is initiated in both systems by free radicals. Self-curing materials generate free radicals by means of chemical compounds included in their formulation. UV-curing systems rely upon externally-supplied, long wavelength, ultraviolet radiation to produce free radicals within the material. Therefore, although the major chemical components of both systems are similar in many respects, each system has particular advantages and disadvantages over the other, which must be recognized by the practitioner. Substantial differences exist, for example, in the color stability of these two types of materials, because of the fact that the UV-cured system cannot include UV absorbers, which protect the self-cured systems from discoloration after exposure to sunlight. UV-cured systems require a limitation on the maximum depth of filled restorative that can be cured at one time, since the filler particles attenuate UV radiation. The limit-layer is generally established as 1-1-5 mm maximum thickness. Therefore, UV-cured filled systems are more time-consuming in restorations of deeper cavities. This liability is also in evidence as it affects the degree of polymerization of UV-cured filled systems. The uncertainty of complete polymerization is apparently responsible for highly erratic compressive strength data found with UV-cured restoratives. Normally, the amount of unpolymerized monomer is much less predictable in UV-cured systems, over that which is obtained in self-cured materials. The presence of a larger fraction of unpolymerized monomer creates a greater potential for pulpal injury from UV-cured restorative materials. The catalyst used in several UV-cured systems is benzoin methyl ether, a compound of rather high toxicity (LD50:300 mg/kg). The safety of using UV radiation in the vicinity of oral mucosa has not been firmly established. The design of the UV lamp should provide for focusing all radiation onto hard tissue. However, UV-cured systems do offer several advantages over self-cured systems. They normally are one-component systems and therefore are more convenient to use in certain types of applications, e.g., fissure sealing. UV-cured systems also provide an unlimited working time, an important advantage for specific applications.

Synthesis of lysophosphatidylethanolamine analogs that inhibit renin activity

A series of lysophosphatidylethanolamine analogs containing saturated and methylene-interrupted cis-olefinic fatty chains was synthesized by phosphorylation and phosphonylation of respective fatty alcohols. Arachidonyl- and linolenylphosphorylethanolamines (12, 13), arachidonyl (2-phthalimidoethyl)phosphonate (17), and arachidonyl (2-aminoethyl)phosphonate (18) were found to be effective inhibitors of the renin-renin substrate reaction in vitro; lysophosphatidylethanolamine analogs 14-16 of lesser unsaturation were either weakly active or inactive. In a preliminary study, intramuscular administration of 25 mg/kg/day of arachidonyl (2-aminoethyl)phosphonate (18) to the hypertensive rat caused pronounced reduction (50 mm) in blood pressure within 3 days; upon continued dosage (15 mg/kg/day) of 18 for an additional 4 days, plasma renin activity was found to be 16 ng/0.1 ml/15 hr as compared with 69 ng/0.1 ml/15 hr before initial drug administration. Arachidonic acid (3), arachidonyl alcohol (8), and several corresponding tetraenoid ester, amide, mesylate, and glyceryl ether derivatives (4-7, 10, 11), that are not phosphate or phosphonate esters, were found to exhibit negligible or modest inhibition of renin activity in vitro.

Histological studies of an adhesive paint-on restorative for cervical erosions

A histological study of the response in the pulps of human teeth to cervical restorations made with a composite resin following etching of the enamel for 2 minutes with 50 per cent phosphoric acid showed moderate inflammation after 14 days. Three specimens showed normal structure after 98 days. Teeth restored without etching showed only slight inflammation.

Surface roughness of composite filling materials

Seven commercial composite filling materials were studied as regards 1) differences in their ability to take a smooth polish as measured by an electronic roughness gauge and 2) their relative loss in smoothness due to toothbrushing. A series of test formulations indicated that polishability and ability to retain a good polish are interrelated and are functions of filler particle size and filler hardness. Optimization in the filler particles from the point of view of polishability also results in improved wear resistance to toothbrushing.

Effects of acid etchants on dentin

The ability of acid etchants to penetrate dentin was tested under simulated clinical conditions. No penetration of the dentinal tubules by acid was detected by use of two different test methods, although pronounced roughening of the treated surfaces was observed.

An adhesie dental restorative material

Development of elastomeric polyurethane resins for use as adhesive liners under composite restorative materials is reviewed. The elastic nature of these adhesive films appears to provide a marginal seal despite dimensional changes of the restorative material. Adhesive strengths of 1,500 psi to enamel have been maintained after thermal cycling and after storage for one year in water.

Sealing of developmental pits and fissures. I. In vitro study

Development and laboratory evaluation of a thermosetting polyurethane resin designed for use as a pit and fissure sealant was conducted. The material exhibited adhesion to enamel in excess of 1,300 psi. Radioautographs and scanning electron photomicrographs did not indicate leakage of isotope and showed an intimate contact between the resin and the fissure walls. The resin appeared to penetrate into the deepest fissures. The material is hydrolysis resistant; 90% of the original adhesive strength was retained after one year in 37 C water.

Scanning electron microscope study of composite restorative materials

The relatively new class of dental restoratives, termed composites, contain thermosetting resin binders and various concentrations of several different types of inert fillers. Because of the difference in types and amounts of resins and fillers present in these materials, each restorative has unique surface characteristics. In addition, the various resin types and filler loading volumes cause differences in polymerization shrinkage and adaptation to the margins of cavity preparations. A combination of radioisotope leakage studies and scanning electron microscopy studies was used to investigate the surfaces and adaptation of four of these composite materials in comparison to an amalgam, silicate, and unfilled poly ( methyl methacrylate).

Physical properties of four thermosetting dental restorative resins

Four aromatic, thermosetting, composite dental restorative materials were evaluated for their mechanical and physical properties. The properties of two materials approached those of dentin and dental amalgams. One of the materials tested appeared to have the necessary requirements for use as both an anterior and posterior restorative material.