Contraception and sexuality.

Contraception has changed female sexuality. The possibility of sex without pregnancy is taken for granted by most women and facilitates sexual availability. Potential consequences to female sexual response are linked to the various contraceptive methods in use today. This is a comprehensive review article of existing literature that explores the impact of current contraceptive methods upon the female sexual response cycle with potential sexual dysfunction. The definitions and classifications of female sexual response and female sexual dysfunction are also reviewed. Combination estrogen and progesterone contraceptive products decrease testosterone and increase sex hormone binding globulin without consistent impact upon libido. Progesterone only methods can in small numbers decrease libido and cause vaginal dryness and dyspareunia. Bleeding irregularities contribute to vaginal dryness and vulvar irritation. In the postpartum period and during lactation, these changes are exacerbated. Overall, IUD users have no significant effect on libido. Female sterilization generally has a positive impact upon sexuality unless the woman has been ambivalent over the procedure. Barrier and natural family planning methods are neutral. The freedom of sexual activity without pregnancy must be balanced with known side effects, risks and benefits to sexual health. The impact of contraceptive methods upon sexual function is not often discussed with women prior to initiation of a selected method or at subsequent visits. It is important that as clinicians we recognize the impact of contraceptive methods to sexual functioning and counsel our patients appropriately.

Leucas aspera: A review.

Leucas aspera commonly known as 'Thumbai' is distributed throughout India from the Himalayas down to Ceylon. The plant is used traditionally as an antipyretic and insecticide. Medicinally, it has been proven to possess various pharmacological activities like antifungal, antioxidant, antimicrobial, antinociceptive and cytotoxic activity. Further, studies reveal the presence of various phytochemical constituents mainly triterpenoids, oleanolic acid, ursolic acid and b-sitosterol, nicotine, sterols, glucoside, diterpenes, phenolic compounds (4-(24-hydroxy-1-oxo-5-n-propyltetracosanyl)-phenol). These studies reveal that L. aspera is a source of medicinally active compounds and have various pharmacological effects; hence, this drug encourage finding its new therapeutic uses.

R-curve behavior and micromechanisms of fracture in resin based dental restorative composites.

The fracture properties and micromechanisms of fracture for two commercial dental composites, one microhybrid (FiltekZ250) and one nanofill (FiltekSupreme Plus), were studied by measuring fracture resistance curves (R-curves) using pre-cracked compact-tension specimens and by conducting both unnotched and double notched four point beam bending experiments. Four point bending experiments showed about 20% higher mean flexural strength of the microhybrid composite compared to the nanofill. Rising fracture resistance was observed over approximately 1 mm of crack extension for both composites, and higher overall fracture resistance was observed for the microhybrid composite. Such fracture behavior was attributed to crack deflection and crack bridging toughening mechanisms that developed with crack extension, causing the toughness to increase. Despite the lower strength and toughness of the present nanofill composite, based on micromechanics observations, large nanoparticle clusters appear to be as effective at deflecting cracks and imparting toughening as solid particles. Thus, with further microstructural refinement, it should be possible to achieve a superior combination of aesthetic and mechanical performance using the nanocluster approach for dental composites.

Fragmentation and plasmid strand breaks in pure and gold-doped DNA irradiated by beams of fast hydrogen atoms.

The results of an investigation into the damage caused to dry plasmid DNA after irradiation by fast (keV) hydrogen atoms are presented. Agarose gel electrophoresis was used to assess single and double strand break yields as a function of dose in dry DNA samples deposited on a mica substrate. Damage levels were observed to increase with beam energy. Strand break yields demonstrated a considerable dependence on sample structure and the method of sample preparation. Additionally, the effect of high-Z nanoparticles on damage levels was investigated by irradiating DNA samples containing controlled amounts of gold nanoparticles. In contrast to previous (photonic) studies, no enhancement of strand break yields was observed with the particles showing a slight radioprotective effect. A model of DNA damage as a function of dose has been constructed in terms of the probability for the creation of single and double strand breaks, per unit ion flux. This model provides quantitative conclusions about the effects of both gold nanoparticles and the different buffers used in performing the assays and, in addition, infers the proportion of multiply damaged fragments.

R-curve behavior and toughening mechanisms of resin-based dental composites: effects of hydration and post-cure heat treatment.

OBJECTIVES: To test the hypothesis that the fracture resistance of two different particulate resin composites degrade after water hydration and improve after post-cure heat treatment, and to correlate those changes with salient failure micromechanisms. METHODS: Two composites with different filler morphology were selected, denoted microhybrid (Filtek Z250) and nanofill (Filtek Supreme plus). Following initial light curing, hydrated samples were aged in water for 60 days at room temperature while post-cured samples were heat treated at 120 degrees C for 90 min. Fracture resistance was assessed using fracture resistance curves (R-curves) utilizing pre-cracked compact tension, C(T), specimens. The flexural strength of the hydrated composites also was evaluated in four-point bending using unnotched beams. Scanning electron microscopy (SEM) of crack paths and fracture surfaces was performed to determine the micromechanisms of fracture and toughening. The results were compared by two-way ANOVA and Tukey's multiple comparison test (p< or =0.05). RESULTS: SEM observations revealed a predominantly interparticle matrix crack path for all cases except the hydrated nanofill composite, which showed evidence of particle matrix debonding. Hydration lowered the strength for both composites and the peak toughness for the nanofill composite. The strength decrease was attributed to resin matrix plasticization and hydrolytic degradation in both cases, with additional interfacial degradation causing a larger strength decline and concomitant peak toughness decrease in the nanofill composite. The post-cure heat treatment noticeably changed the R-curve shape causing the peak toughness to be reached after shorter amounts of crack extension. Such changes help explain the increases in strength reported in other studies and is attributed to improved resin matrix properties. SIGNIFICANCE: Results from this study provide new insight into the micromechanisms of fracture in resin-based dental composites which should aid the future development and improvement of these materials.

Mechanistic aspects of fatigue crack growth behavior in resin based dental restorative composites.

OBJECTIVE: To test the hypothesis that a commercial microhybrid resin based composite (Filtek Z250) has superior fatigue resistance to a nanofill composite (Filtek Supreme Plus) and to determine the related micromechanisms involved in the fatigue process. METHODS: After 60 days of water hydration, the fatigue crack growth resistance of two different resin composites, one microhybrid (Filtek Z250) and one nanofill (Filtek Supreme Plus), was measured in wet conditions using compact-tension, C(T), specimens at a load ratio of 0.1 and frequency of 2Hz. Cyclic fatigue behavior was quantified in terms of the fatigue crack growth rate, da/dN, as a function of the stress intensity range, DeltaK. RESULTS: A sigmoidal da/dN-DeltaK curve with three different fatigue crack growth regimes was identified for both composites. In general, fatigue crack growth ranged from approximately 10(-9) to 10(-5)m/cycle over DeltaK of 0.54-0.63MPa radicalm for the Z250 composite and DeltaK of 0.41-0.67MPa radicalm for the Supreme Plus composite. The Supreme Plus composite showed a lower fatigue threshold, DeltaK(th), by approximately 0.13MPa radicalm compared to the Z250 composite, while also showing a plateau in the fatigue crack growth curve that is likely related to environmental attack. SEM observations of the fatigue crack paths and fracture surfaces revealed an interparticle crack path and extrinsic toughening mechanisms of crack deflection and crack bridging. No fatigue degradation of reinforcing particles or clusters was found, but cluster-matrix debonding was evident in the Supreme Plus composite, also indicative of environmental attack due to water. SIGNIFICANCE: This study increases the understanding of both the fatigue behavior and the micromechanisms of fatigue in resin based dental composites.

Variation of strand break yield for plasmid DNA irradiated with high-Z metal nanoparticles.

Using agarose gel electrophoresis, we measured the effectiveness of high-Z metal particles of different sizes on SSB and DSB yields for plasmid DNA irradiated with 160 kVp X rays. For plasmid samples prepared in Tris-EDTA buffer, gold nanoparticles were shown to increase G'(SSB) typically by a factor of greater than 2 while G'(DSB) increased by a factor of less than 2. Similar dose-modifying effects were also observed using gold microspheres. Addition of 10(-1) M DMSO typically decreased damage yields by a factor of less than 0.5. Plasmid samples prepared in PBS showed significantly different damage yields compared to those prepared in Tris-EDTA (P < 0.001) with G'(SSB) and G'(DSB) increasing by factors of 100 and 48, respectively. Furthermore, addition of gold nanoparticles to samples prepared in PBS decreased G'(SSB) and G'(DSB) by factors of 0.2 and 0.3, respectively. The results show plasmid damage yields to be highly dependent on differences in particle size between the micro- and nanometer scale, atomic number (Z) of the particle, and scavenging capacity of preparation buffers. This study provides further evidence using a plasmid DNA model system for the potential of high-Z metal nanoparticles as local dose-modifying agents.

Water fragmentation and energy loss by carbon ions at the distal region of the Bragg peak.

Time-of-flight mass spectrometry was used to investigate fragmentation and energy transfer processes in water by C ions at the distal part of the Bragg peak. Measurements of the positive ion fragments from ionization, electron capture, electron loss, transfer-loss and loss-ionization channels have allowed us for the first time (a) to obtain a quantitative determination of the energy lost by C ions in water and (b) to show that total water fragment ion production has a much flatter profile with projectile energy than would be expected if the water radical formation was assumed to follow the energy-loss profile obtained from available stopping power models.

Magnetically quantized continuum distorted waves.

A new derivation of continuum distorted-wave theory is presented. It is generalized to magnetically quantized continuum distorted waves. The context is analytic continuation of hydrogenic-state wave functions from below to above threshold, using parabolic coordinates and quantum numbers including m the magnetic quantum number. This continuation applies to excitation, charge transfer, ionization, and double and hybrid events for both light- and heavy-particle collisions. It is applied to the calculation of double-differential cross sections for the single ionization of the hydrogen atom and for a hydrogen molecule by a proton for electrons ejected in the forward direction at a collision energy of 50 keV and 100 keV respectively.

The evaluation of the safety and tolerability of two formulations of cyclosporine: neoral and sandimmune. A meta-analysis.

BACKGROUND: Neoral, a microemulsion formulation of cyclosporine, was approved for use in the United States in 1995. Many studies comparing Neoral and Sandimmune have been conducted, and although most state that Neoral is the superior cyclosporine formulation, results have failed to conclusively demonstrate this claim. The aim of this meta-analysis was to compare the safety and efficacy of Neoral and Sandimmune. METHODS: Publications comparing the use of Neoral and Sandimmune were reviewed for demographic variables, adverse events, rejection incidence, graft losses, and serum creatinine. Neoral and Sandimmune were compared in all patients and in the following subgroups: (1) age (adult or pediatric), (2) transplant type (kidney, liver, or heart), (3) indication (de novo or stable), and (4) study design (randomized prospective trials versus nonrandomized, blinded versus open-labeled studies). RESULTS: The rate of graft loss was similar when comparing Neoral and Sandimmune in all analyses. The incidence of rejection was lower in Neoral-treated de novo renal, liver, and cardiac transplants (P<0.05). There were significantly more adverse events in Sandimmune-treated de novo liver transplants than Neoral-treated de novo liver transplants (P<0.00001). When considering only randomized prospective trials, the incidence of rejection was lower in Neoral-treated de novo and stable patients (P<0.05). However, there were more adverse events in Neoral-treated stable patients (P<0.00001). When considering only blinded studies, there were more adverse events in Neoral-treated patients (P<0.05), whereas in open-labeled studies there was no difference in adverse events comparing Neoral and Sandimmune (P=NS). CONCLUSIONS: Considering all published trials, the data seem to indicate that Neoral therapy is preferred because of a lower rejection incidence, with a trend toward less adverse events. However, when limiting the analysis to only randomized prospective trials, and specifically assessing blinded studies, the data become less clear. Neoral use was associated with more adverse events in blinded studies, and Sandimmune use was associated with more adverse events in open-labeled studies. Careful individual consideration must be given in choosing the best possible cyclosporine formulation.

An editing environment for DNA sequence analysis and annotation (extended abstract).

This paper presents a computer system for analyzing and annotating large-scale genomic sequences. The core of the system is a multiple-gene structure identification program, which predicts the most "probable" gene structures based on the given evidence, including pattern recognition, EST and protein homology information. A graphics-based user interface provides an environment which allows the user to interactively control the evidence to be used in the gene identification process. To overcome the computational bottleneck in the database similarity search used in the gene identification process, we have developed an effective way to partition a database into a set of sub-databases of "related" sequences, and reduced the search problem on a large database to a signature identification problem and a search problem on a much smaller sub-database. This reduces the number of sequences to be searched from N to O ([square root of] N) on average, and hence greatly reduces the search time, where N is the number of sequences in the original database. The system provides the user with the ability to facilitate and modify the analysis and modeling in real time.

Stereoacuity testing in patients with retinal and optic nerve disorders.

A study comparing the relative sensitivity for detecting abnormal stereoacuity in patients with retinal or optic nerve disease on clinically used stereoacuity tests is not available. It is also not apparent from the ophthalmic literature if optic nerve or retinal diseases are likely to have a greater impact on stereoacuity performance. We were also interested in determining a level of visual acuity loss that would likely results in an impairment of stereoacuity on these clinical tests. Forty-two patients with various retinal and optic nerve disorders and eighteen normal subjects were evaluated for stereoacuity using three tests: Titmus Stereoacuity Test (TST), Randot Stereoacuity Test (RST), and TNO Stereoacuity Test (TNO). The performance on these three stereoacuity tests was compared with the normal subjects. Additionally, TST scores from our patients were compared to predicted TST scores derived from a previously published nomogram. For patients with retinal and optic nerve disease, an abnormal score on one clinical test of stereoacuity was likely to predict an abnormality on the other tests. Performance on the TST relative to the predicted value derived from a nomogram was not significantly different for patients with retinal vs. optic nerve disease. With some exceptions, patients with visual acuities of 20/30 or worse in at least one eye were likely to show abnormal stereoacuity.

Generation of a pH gradient in an immobilized enzyme system.

Several examples of two-step sequential reactions exist where, because of the poor equilibrium conversion by the first reaction, it is desirable to conduct the two reactions simultaneously. In such a scheme, the product of the first reaction is continuously removed by the second reaction, thus not allowing the first reaction to approach chemical equilibrium. Therefore, the first reaction is allowed to proceed in the desired direction at an appreciable rate. However, in many biochemical applications where enzyme catalysts are involved, the enzyme's activities are strong functions of pH. Where the pH optima of the first and second reaction differ by three to four units, the above reaction scheme would be difficult to implement. In these cases, the two reactions can be separated by a thin permeable membrane across which the desired pH gradient is maintained. In this article, it was shown, both by theory and experiment, that a thin, flat membrane of immobilized urease can accomplish this goal when one face of the membrane is exposed to the acidic bulk solution (pH(b) = 4.5) containing a small quantity of urea (0.01 M). In this particular case, the ammonia that was produced in the membrane consumed the incoming hydrogen ions and thus maintained the desired pH gradient. Experimental results indicate that with sufficient urease loading, the face of the membrane opposite to the bulk solution could be maintained at a pH that would allow many enzymes to realize their maximum activities ( approximately 7.5). It was also found that this pH gradient could be maintained even in the presence of a buffer, which greatly enhances the transport of protons into the membrane.

Electron microscope tomography of Balbiani Ring hnRNP substructure.

Three-dimensional (3-D) reconstructions, by electron microscope tomography, of selectively stained, contrast enhanced Balbiani Ring (BR) hnRNP granules reveal a complex spatial arrangement of RNA-rich domains. This particulate substructure was examined by volume rendering computer graphics. Modeling the arrangement of RNA-rich domains is made difficult by apparent structural flexibility and/or heterogeneity of composition. Formulation of a consensus 3-D arrangement of RNA-rich domains will require an expanded data base of reconstructed BR granules and the development of new image manipulation and analysis techniques. This study demonstrates the potential for ultrastructural cell biology of combining several new techniques: selective nucleic acid staining, electron spectroscopic imaging to enhance contrast, electron microscope tomography and volume rendering computer graphics.