Using Graphdiyne Nanoribbons for Molecular Electronics Spectroscopy and Nucleobase Identification: A Theoretical Investigation.

In pursuit of fast, cost-effective, and reliable DNA sequencing techniques, a variety of two-dimensional (2D) material-based nanodevices such as solid-state nanopores and nanochannels have been explored and established. Given the promising potential of graphene for the design and fabrication of nanobiosensors, other 2D carbon allotropes such as graphyne and graphdiyne have also attracted a great deal of attention as candidate materials for the development of sequencing technology. Herein, employing the 2D electronic molecular spectroscopy (2DMES) method, we investigate the capability of graphdiyne nanoribbons (GDNRs) as the building blocks of a feasible, precise, and ultrafast sequencing device. Using first-principles calculations, we study the adsorption of four canonical nucleobases (NBs), i.e., adenine (A), cytosine (C), guanine (G), and thymine (T) on an armchair GDNR (AGDNR). Our calculations reveal that compared to graphene, graphdiyne demonstrates more distinct binding energies for different NBs, indicating its more promising ability to unambiguously recognize DNA bases. Utilizing the 2DMES technique, we calculate the differential conductance (Δg) of the studied NB-AGDNR systems and show that the resulting Δg maps, unique for each NB-AGDNR complex, can be used to recognize each individual NB without ambiguity. We also investigate the conductance sensitivity of the proposed nanobiosensor and show that it exhibits high sensitivity and selectivity toward various NBs. Thus, our proposed graphdiyne-based nanodevice would hold promise for next-generation DNA sequencing technology.

Structural, Electronic, and Magnetic Characteristics of Graphitic Carbon Nitride Nanoribbons and Their Applications in Spintronics.

The development of quantum information and quantum computing technology requires special materials to design and manufacture nanosized spintronic devices. Possessing remarkable structural, electronic, and magnetic characteristics, graphitic carbon nitride (g-C3N4) can be a promising candidate as a building block of futuristic nanoelectronics and spintronic systems. Here, using first-principles calculations, we perform a comprehensive study on the structural stability as well as electronic and magnetic properties of triazine-based g-C3N4 nanoribbons (gt-CNRs). Our calculations show that gt-CNRs with different edge conformation exhibit distinct electronic and magnetic characteristics, which can be tuned by the edge H-passivation rate. By investigating gt-CNRs with various possible edge configurations and H-termination rates, we show that while the ferromagnetic (FM) ordering of gt-CNRs stays preserved for all of the studied configurations, half metallicity can only be achieved in nanoribbons with specific edge structure under full H-passivation rate. For spintronic application purposes, we also study spin-transport properties of half-metal gt-CNRs. By determining the suitable gt-CNR configuration, we show the possibility of developing a perfect gt-CNR-based spin filter with a spin filter efficiency (SFE) of 100%. Considering the above-mentioned notable electronic and magnetic characteristics as well as its high thermal stability, we show that gt-CNR would be a remarkable material to fabricate multifunctional spintronic devices.

DNA/RNA sequencing using germanene nanoribbons via two dimensional molecular electronic spectroscopy: an ab initio study.

Developing fast, reliable, and cost effective, yet practical DNA/RNA sequencing methods and devices is a must. In this regard, motivated by the recently introduced two-dimensional electronic molecular spectroscopy (2DMES) technique for molecular recognition, and the compatibility of 2D layers of group IV elements with the current technology of manufacturing electronic devices, we investigate the capability of germanene nanoribbons (GeNRs) as a feasible, accurate, and ultra-fast sequencing device under the application of 2DMES. We show that by employing 2DMES, not only can GeNRs unambiguously distinguish different nucleobases to sequence DNA/RNA, they are also capable of recognizing methylated nucleobases that could be related to cancerous cell growth. Our calculations indicate that, compared to frequently used graphene layers, germanene provides more distinct adsorption energies for different nucleobases which implies its better ability to recognize various molecules unambiguously. By calculating the conductance sensitivity of the system for experimental purposes, we also show that the introduced sequencing device possesses a high sensitivity and selectivity characteristic. Thus, our proposed system would be a promising device for next-generation DNA sequencing technologies and would be realizable using the current protocols of fabricating electronic devices.

A high performance N-doped graphene nanoribbon based spintronic device applicable with a wide range of adatoms.

Designing and fabricating nanosize spintronic devices is a crucial task to develop information technology of the future. However, most of the introduced spin filters suffer from several limitations including difficulty in manipulating the spin current, incapability in utilizing a wide range of dopants to provide magnetism, or obstacles in their experimental realization. Here, by employing first principles calculations, we introduce a structurally simple and functionally efficient spin filter device composed of a zigzag graphene nanoribbon (ZGNR) with an embedded nitrogenated divacancy. We show that the proposed system, possessing a robust ferromagnetic (FM) ordering, exhibits perfect half metallic behavior in the absence of frequently used transition metals (TMs). Our calculations also show that the suggested system is compatible with a wide range of adatoms including basic metals, metalloids, and TMs. It means that besides d electron magnetism originating from TMs, p electrons of incorporated elements of the main group can also cause half metallicity in the electronic structure of the introduced system. Our system exploiting the robustness of doping-induced FM ordering would be beneficial for promising multifunctional spin filter devices.

Graphene and Graphene Analogs toward Optical, Electronic, Spintronic, Green-Chemical, Energy-Material, Sensing, and Medical Applications.

This spotlight discusses intriguing properties and diverse applications of graphene (Gr) and Gr analogs. Gr has brought us two-dimensional (2D) chemistry with its exotic 2D features of density of states. Yet, some of the 2D or 2D-like features can be seen on surfaces and at interfaces of bulk materials. The substrate on Gr and functionalization of Gr (including metal decoration, intercalation, doping, and hybridization) modify the unique 2D features of Gr. Despite abundant literature on physical properties and well-known applications of Gr, spotlight works based on the conceptual understanding of the 2D physical and chemical nature of Gr toward vast-ranging applications are hardly found. Here we focus on applications of Gr, based on conceptual understanding of 2D phenomena toward 2D chemistry. Thus, 2D features, defects, edges, and substrate effects of Gr are discussed first. Then, to pattern Gr electronic circuits, insight into differentiating conducting and nonconducting regions is introduced. By utilizing the unique ballistic electron transport properties and edge spin states of Gr, Gr nanoribbons (GNRs) are exploited for the design of ultrasensitive molecular sensing electronic devices (including molecular fingerprinting) and spintronic devices. The highly stable nature of Gr can be utilized for protection of corrosive metals, moisture-sensitive perovskite solar cells, and highly environment-susceptible topological insulators (TIs). Gr analogs have become new types of 2D materials having novel features such as half-metals, TIs, and nonlinear optical properties. The key insights into the functionalized Gr hybrid materials lead to the applications for not only energy storage and electrochemical catalysis, green chemistry, and electronic/spintronic devices but also biosensing and medical applications. All these topics are discussed here with the focus on conceptual understanding. Further possible applications of Gr, GNRs, and Gr analogs are also addressed in a section on outlook and future challenges.

Lower Electric Field-Driven Magnetic Phase Transition and Perfect Spin Filtering in Graphene Nanoribbons by Edge Functionalization.

Perfect spin filtering is an important issue in spintronics. Although such spin filtering showing giant magnetoresistance was suggested using graphene nanoribbons (GNRs) on both ends of which strong magnetic fields were applied, electric field controlled spin filtering is more interesting due to much easier precise control with much less energy consumption. Here we study the magnetic/nonmagnetic behaviors of zigzag GNRs (zGNRs) under a transverse electric field and by edge functionalization. Employing density functional theory (DFT), we show that the threshold electric field to attain either a half-metallic or nonmagnetic feature is drastically reduced by introducing proper functional groups to the edges of the zGNR. From the current-voltage characteristics of the edge-modified zGNR under an in-plane transverse electric field, we find a remarkable perfect spin filtering feature, which can be utilized for a molecular spintronic device. Alteration of magnetic properties by tuning the transverse electric field would be a promising way to construct magnetic/nonmagnetic switches.

Late umbilical cord clamping, neonatal hematocrit and Apgar scores: a randomized controlled trial.

OBJECTIVE: Based on current evidence, there is a little agreement on the best timing for after birth umbilical cord clamping. This study was designed to compare the impact of using two different times for cord clamping on hematocrit concentration and Apgar scores of the neonate. STUDY DESIGN: Fifty-six healthy full-term vaginally born neonates were allocated to early (10 seconds after delivery) and late (3 minutes after delivery) umbilical cord clamping groups in this randomized clinical trial. We recorded the length of the 3rd stage of labor and Apgar score at 5 minutes. Infant's hematocrit was measured at 2 and 18 hours of age. RESULTS: Neonatal hematocrit differed between the two groups. Late cord clamping group had greater hematocrit at 2 hours (45.5 ± 4 vs. 49.5 ± 4.4, P = 0.0003) and 18 hours (47.7 ± 5.5 vs. 52.9 ± 4.3, P = 0.0002). Apgar scores at 5 minutes (9.3 ± 0.6 vs. 9.4 ± 0.6, p = 0.5) and duration of delivery 3rd stage (10.2 ± 3.7 min vs. 8.9 ± 5 min, P = 0.2) did not differ between early and late cord clamping groups respectively. CONCLUSION: Late cord clamping leads to a significant increase in the hematocrit of the neonate but it does not have effects on Apgar score and duration of the 3rd stage of labor.

Effect of formulation and processing variables on the characteristics of tolmetin microspheres prepared by double emulsion solvent diffusion method.

The aim of this study was to evaluate microencapsulated controlled release preparations of tolmetin sodium using ethylcellulose as a retardant material. Microspheres were prepared by using water-in-oil-in-oil (W/O(1)/O(2)) double-emulsion solvent diffusion method, using different ratios of ethylcellulose to tolmetin sodium. Span 80 was used as the droplet stabilizer and n-hexane was added to harden the microspheres. The prepared microspheres were characterized for their micromeritic properties, drug content, loading efficiency, production yield, and particle size. Fourier transform infrared spectroscopy, differential scanning calorimetry, X-ray powder diffractometry and scanning electron microscopy were used to characterize microparticles. The in vitro release studies were performed in pH 1.2 and 7.4. The prepared microspheres were spherical in shape. The drug-loaded microspheres showed near to the theoretical of entrapment and release was extended up to 24. The X-ray diffractogram and differential scanning thermographs showed amorphous state of the drug in the microspheres. It was shown that the drug: polymer ratio, stirring rate, volume of dispersing medium and surfactant influenced the drug loading, particle size and drug release behavior of the formed microparticles. The results showed that, generally, an increase in the ratio of drug: polymer (0.5:1) resulted in a reduction in the release rate of the drug which may be attributed to the hydrophobic nature of the polymer. The in vitro release profile could be modified by changing various processing and formulation parameters to give a controlled release of drug from the microparticules. The release of tolmetin was influenced by the drug to polymer ratio and particle size and was found to be diffusion and erosion controlled. The best-fit release kinetic was achieved with Peppas model.

Eleven years prospective follow-up of the tension-free vaginal tape procedure for treatment of stress urinary incontinence.

The aim of this study was to evaluate the long-term effectiveness and safety of the tension-free vaginal tape (TVT) procedure. In a Nordic three-center prospective observational cohort study, 90 women with primary stress incontinence had a TVT operation performed in local anesthesia. Assessment included a 24-h pad test, a stress test, physical examination, and a visual analog scale for assessing the degree of bother. Patient's global impression of cure was obtained, and condition specific quality of life questionnaires were used. Seventy-seven percent of the initial cohort of 90 women and 89% of those alive and capable of cooperating were assessed 11.5 years after the TVT operation. Ninety percent of the women had both a negative stress test and a negative pad test being objectively cured. Subjective cure by patients global impression was found in 77%, 20% being improved and only 3% regarded the operation as a failure. No late-onset adverse effects of the operation were found, and no case of tape erosion was seen. The TVT procedure is safe and effective for more than 10 years.

Expression of estrogen receptor-alpha and -beta in anterior vaginal walls of genuine stress incontinent women.

Our objective was to study the expression of estrogen receptor (ER) isoforms, ER-alpha and ER-beta, in the anterior vaginal wall of menopausal and fertile women with genuine stress incontinence (SI) by immunohistochemistry and Western blot analysis. Eighteen menopausal women with SI who either were or were not taking estrogen/progestin replacement therapy and 14 fertile women with SI who either were or were not taking contraceptives were enrolled in the study. Biopsies from the suburethral anterior vaginal wall were obtained at tension-free vaginal tape (TVT) operation. Monoclonal antibody to ER-alpha and polyclonal antibody to ER-beta were used to stain frozen sections of vaginal tissue. The receptor expressions were scored based on percentage of positive cells. ER-alpha was detected in vaginal epithelial, stromal and smooth muscle cells. In menopausal SI women ER-alpha was detected significantly more frequently in the vaginal walls of estrogen/progestin-treated patients than in those who were untreated. Fertile SI women had significantly higher expression of ER-alpha than menopausal SI women. ER-alpha was not observed in vaginal blood vessels. ER-beta was detected in epithelial and vascular smooth muscle cells of the vagina. No significant difference in ER-beta expression was observed between different groups of patients. The expression of ER-alpha was not correlated with that of ER-beta. Both ER-alpha and -beta were detected, indicating a potential role for both types of estrogen receptor in the human vaginal wall. The expression of ER-alpha, but not of ER-beta, in menopausal SI women was regulated by estrogen/progestin replacement therapy. The presence of ER-beta in vaginal vascular smooth muscle cells raises the possibility of vascular effects of estrogen on the human vaginal wall.

Tension-Free vaginal tape (TVT) in stress incontinent women with intrinsic sphincter deficiency (ISD)--a long-term follow-up.

In a prospective long-term study 49 women with stress incontinence and ISD (intrinsic sphincter deficiency) were followed for a mean of 4 years (range 3-5) after TVT operation. Preoperatively all patients underwent urodynamic investigations, quality of life evaluation, a 24-hour pad test and a gynecologic examination to properly verify the incontinence symptoms. The same protocol was used for postoperative evaluation. The mean age of the women was 66 years (+/- 11) and mean parity 2 (range 0-4). A standard TVT operation was performed under local anesthesia. At the postoperative evaluations 36 patients (74%) were completely cured of their incontinence problems. In addition, 6 women (12%) were significantly improved. In 7 patients (14%) no improvement was found. The majority of these not cured patients were >70 years of age and had urethral resting pressure of <10 cmH2O. Few intra- and postoperative complications occurred. It is concluded that TVT can be used for surgical treatment of patients with ISD and stress incontinence. However, older patients (>70 years) with a very low resting urethral pressure and an immobile urethra seem to constitute a risk group where TVT surgery is less successful.

Tension-Free vaginal tape (TVT) in women with mixed urinary incontinence--a long-term follow-up.

In a prospective long-term study we evaluated the effect of TVT surgery in 80 women suffering from mixed urinary incontinence. Their mean age was 59 +/- 11 years with a mean parity of 2 (range 0-6). Mean follow-up was 4 years (range 3-5). The preoperative evaluation included a 24-hour pad test, quality of life evaluation, gynecologic examination and urodynamic investigations, including simultaneous urethrocystometry. From the patient history 96 patients were initially tentative candidates for TVT operation. Sixteen of these had only minor symptoms and signs of stress incontinence but significant symptoms and signs of detrusor instability, and were not considered suitable for TVT surgery. In the remaining 80 women the urodynamic investigation with filling urethrocystometry demonstrated stress incontinence and urge incontinence concomitant with urethral relaxation and/or 'premature micturition' reflex. At the postoperative long-term follow-up 85% of the patients were completely cured. Another 4% were significantly improved. In 11% of the patients the operation failed. Few intra- or postoperative complications occurred. Based on these results, we conclude that TVT surgery can be used for treatment of female mixed urinary incontinence. A proper urodynamic assessment is recommended before surgery is performed.

Long-term results of the tension-free vaginal tape (TVT) procedure for surgical treatment of female stress urinary incontinence.

In a prospective long-term Nordic multicenter study, 90 consecutive patients who had a tension-free vaginal tape (TVT) operation performed because of stress urinary incontinence were evaluated according to a strict protocol after approximately 5 years (range 48-70 months). Eighty-five patients could be evaluated according to the protocol. Another 5 elderly patients had to be interviewed by telephone at the final check-up after 5 years. The study protocol involved pre- and postoperative objective and subjective evaluation. The median follow-up time was 56 months. Seventy-two of the 85 patients who were fully evaluated (84.7%) were both objectively and subjectively completely cured. Another 9 patients (10.6%) were significantly improved and 4 (4.7%) were regarded as failures. No patient complained of long-term voiding difficulties and there were no signs of defective healing or rejection of the tape material. All patients had suffered from primary stress incontinence, and 25 also had preoperative complaints of urge. In 14 of these (56%) the urge symptoms were relieved postoperatively. We conclude that the TVT procedure seems to fulfil the expectations of high long-term cure rates, as suggested in previous short-term reports.

Tension-Free vaginal tape (TVT) in women with recurrent stress urinary incontinence--a long-term follow up.

In a prospective long-term follow-up study we evaluated the results of TVT surgery in 34 women with recurrent stress urinary incontinence in whom previous traditional surgical procedures had failed. The women were followed for a mean of 4 years (range 3-5) after TVT surgery. The mean age was 58.9 +/- 10 years and the mean parity 2 (0-4). Pre- and postoperative evaluation was performed according to a protocol which included gynecologic examination, urodynamic investigations, quality of life evaluation and 24-hour pad test. According to the protocol 28 patients (82%) were cured, 3 (9%) were significantly improved, and the operation failed in 3 cases (9%). There were no significant intra- or postoperative complications. All patients were operated on under local anesthesia with a short hospitalization and had no long-term postoperative voiding problems.

Multiple connexins localized to individual gap-junctional plaques in human myometrial smooth muscle.

The synchronous contractions of the uterus in labour depend on electrical coupling of myometrial smooth muscle cells by gap junctions. In the human myometrium, gap junctions are scarce in the non-pregnant uterus, but become abundant at term in preparation for labour. We have previously demonstrated that in the human myometrium at term, three different gap-junctional proteins are expressed, connexins 43, 45, and 40. These connexins are known to have distinctive functional capacities in in vitro expression systems but whether, in the human myometrium in vivo, they are co-assembled into the same gap junction or form different types of gap junction has previously been unclear. By applying triple immunogold labelling to sections of Lowicryl-embedded tissue for electron microscopy, together with complementary immunoconfocal microscopy, we demonstrate here that connexins 43, 45, and 40 are commonly present as mixtures within the same gap-junctional plaque. While all gap junctions contain connexin43, the relative signal for each connexin type varies between individual junctions. The presence within single gap-junctional plaques of three different connexins, each with the potential for conferring distinctive channel properties, suggests an inherent versatility for modulation of smooth muscle cell intercellular communication properties during human parturition.

A three-year follow up of tension free vaginal tape for surgical treatment of female stress urinary incontinence.

OBJECTIVE: To study the long term results of tension-free vaginal tape, a new ambulatory surgical procedure for treatment of female stress urinary incontinence. STUDY DESIGN: A prospective open study using a standardised protocol for pre- and post-operative evaluation. PARTICIPANTS: Fifty consecutive women participated in the study. All suffered from genuine stress incontinence. The mean age was 57 years (SD 11), 42 women (84%) were multiparous, 8 (16%) nulliparous. SURGICAL METHOD: Tension-free vaginal tape implies the implantation of a prolene tape around mid-urethra via a minimal vaginal incision. The procedure is carried out under local anaesthesia, allowing the surgeon to check intra-operatively that continence has been obtained. RESULTS: All the women except one could be operated on an ambulatory basis under local anaesthesia. Mean operation time was 29 minutes (range 1647). Ninety percent of the women were able to micturate spontaneously within 24 hours with insignificant residual volumes. In another 10% of the women an in-dwelling catheter had to be used temporarily. There was no need for long term postoperative catheterisation (> 14 days). Post-operative evaluation was carried out after 2 to 6, 12, 24 and 36 months. According to the protocol, 86% of the women were completely cured and another 11% were significantly improved. No signs of deterioration of the results over time were observed. No defect in healing or rejection of the tape occurred. CONCLUSION: We consider the tension-free vaginal tape operation to be a safe and effective surgical procedure for the treatment of female urinary stress incontinence. The technique can be considered as an ambulatory procedure performed under local anaesthesia, allowing the majority of the women to be discharged from the clinic the same day or the day after the procedure.

Identification of two further gap-junctional proteins, connexin40 and connexin45, in human myometrial smooth muscle cells at term.

The powerful synchronous contractions of the uterus in labor depend on electrical coupling of myometrial smooth muscle cells by gap junctions. In humans and other mammals, gap junctions are scarce in the myometrium of the non-pregnant uterus, but become abundant at term and/or with the onset of labor. Previous work has shown that the gap-junctional protein (connexin) expressed by human myometrial smooth muscle cells is connexin43, the same connexin type that predominates in cardiac muscle. Here we show that two further gap junctional proteins, connexin40 and connexin45, are expressed by the myometrial smooth muscle cells of the human uterus at term. Transcripts encoding the human isoforms of these connexins were demonstrated by Northern blot analysis, and immunoconfocal microscopy enabled precise localization of the corresponding proteins to punctate contact points (i.e., gap junctions) between interacting smooth muscle cells. Double labeling demonstrated that, while some fluorescent spots comprise only connexin43, both connexin40 and connexin45 predominantly colocalize to connexin43-positive fluorescent spots. Triple labeling revealed that where all three connexin types were expressed, they frequently localized to the same gap junction spot. As gap-junctional channels composed of different connexin types have been demonstrated in vitro to have different functional properties, multiple connexin expression may contribute to modulation of gap junction function in human myometrial smooth muscle cells in vivo.

Sex steroid receptors and human parturition.

OBJECTIVE: To investigate the correlation between sex steroid hormones and their receptors during normal and dysfunctional labor. METHODS: Myometrial and decidual biopsies along with maternal and cord blood samples were taken from women with or without labor activity. Estrogen and progesterone receptor contents in myometrium and decidua were determined by enzyme immunoassay, and hormone concentrations were analyzed by radioimmunoassay. RESULTS: In the lower segment of the uterus, the progesterone receptor concentrations of myometrium were significantly lower in oxytocin-resistant dystocia compared with those of normal labor and before labor (P < .04, P < .005, respectively). No significant difference was found in the estrogen receptors contents in the groups studied. The progesterone receptors of myometrium from the upper segment showed higher concentrations in active labor compared with those before labor and oxytocin-resistant labor (P <.01, P < .05, respectively). Estrogen receptors from the upper segment showed no significant difference in these regards. There was no difference in peripheral and myometrial sex hormone levels in the groups studied. CONCLUSION: These data suggest that, in the human, 1) oxytocin-resistant labor is associated with low levels of progesterone receptors, 2) estrogen receptors content in myometrium might have no or little relation to labor, and 3) functional labor seems not to be related to a decreased progesterone activity in the myometrium.

Quantitative immunoconfocal analysis of human myometrial gap junction connexin43 in relation to steroid hormone concentrations at term labour.

The aim of this study was to quantify gap junction expression in the human myometrium in relation to progesterone and oestradiol concentrations, and to establish whether oxytocin-resistant dystocia is due to an abnormality in gap junction expression. Three groups of patients were investigated: (i) before labour (at term), (ii) normal labour and (iii) oxytocin-resistant dystocia (eight patients per group). For each patient, the concentrations of oestradiol and progesterone in maternal blood and in myometrial tissue were measured, and the number and area of immunostained connexin43 gap junctions per unit volume of tissue determined by quantitative analysis of digital images obtained by confocal microscopy. No significant difference in connexin43 gap junction content was observed between the three patient groups. When all groups were pooled, there was a significant positive correlation (P < 0.05) between the quantity of immunolabelled gap junctions and the oestradiol:progesterone ratio, but there was no significant difference in this correlation between the groups. Gap junction immunolabelling was not correlated with the progesterone or oestradiol concentration in the maternal blood or the myometrium. These data suggest that in human myometrium: (i) dystocia is not due to a reduced level of immunodetectable connexin43 gap junctions, (ii) onset of labour is not associated with a sudden increase in immunodetectable gap junction protein and (iii) gap junctions can be expressed in the presence of high progesterone concentrations.

Effects of progesterone and oxytocin on intracellular elemental composition of term human myometrium in vitro.

OBJECTIVE: To study the effects of progesterone and oxytocin on contractile activity related to the intracellular elemental composition of human pregnant myometrium. STUDY DESIGN: Myometrial strips were mounted in tissue baths and superfused with plain buffer, oxytocin or progesterone. Progesterone was initially added to the tissue bath or at the onset of spontaneous contraction of the strips. The myometrial contractile activities were recorded isometrically and the results were analyzed by a specific computer program. The effects of oxytocin and progesterone on the intracellular elemental composition were studied by X-ray microanalysis in an electron microscope. RESULTS: The contractile activity in terms of frequency and tonus of the muscle strips was increased by oxytocin and progesterone. This increase was more pronounced if progesterone was added to the bath at the start of the experiment. After 120 min of incubation with oxytocin and progesterone the total intracellular concentration of calcium was significantly higher (P < 0.0001 and P < 0.002, respectively) compared to buffer. CONCLUSIONS: (i) Oxytocin increases total intracellular calcium concentration concomitant with an increase in uterine contractile activity. (ii) Progesterone increases the myometrial tone and frequency of contractions, simultaneously with an increase in total intracellular calcium.