Structure and function of animal cryptochromes

Cryptochrome (CRY) is a photolyase-like flavoprotein with no DNA-repair activity but with known or presumed blue-light receptor function. Animal CRYs have DNA-binding and autokinase activities, and their flavin cofactor is reduced by photoinduced electron transfer. In Drosophila, CRY is a major circadian photoreceptor, and in mammals, the two CRY proteins are core components of the molecular clock and potential circadian photoreceptors. In mammals, CRYs participate in cell cycle regulation and the cellular response to DNA damage by controlling the expression of some cell cycle genes and by directly interacting with checkpoint proteins.

Analysis of risk factors associated with uterine perforation by intrauterine devices

OBJECTIVE

To determine the risk factors for intrauterine devices (IUDs) being displaced into the abdominal cavity.

METHODS

This prospective follow-up study was conducted between 1996 and 2002, at the family planning clinic of a referral hospital. All 8343 women who had a copper T-380A IUD inserted underwent ultrasound examination after 1 year. Relative risk estimates and logistic regression analyses were performed to determine the risk factors associated with uterine perforation by intrauterine devices.

RESULTS

Eighteen uterine perforations occurred during the study, giving an incidence of 2.2 per 1000 insertions. When the time elapsed after the last delivery until IUD insertion is considered, postplacental insertion and insertion after 6 months postpartum were found not to increase the risk of uterine perforation. However, IUD insertion 0-3 months postpartum increased the risk of uterine perforation (odds ratio (OR) 11.7, 95% confidence interval (CI) 2.8-49.2) as did insertions at 3-6 months postpartum (OR 13.2, CI 2.8-62). Increasing parity decreased the risk (OR 0.04, CI 0.01-0.1) and increasing number of abortions increased the risk (OR 2.1, CI 1.2-3.6).

CONCLUSION

It is safer to postpone IUD insertion until 6 months after delivery.

Inhibition of force and shortening in smooth muscle by vanadate

We have investigated the effects of vanadate (Vi) on force generation by, and shortening of, chemically skinned smooth muscle preparations from guinea-pig taenia coli at 22 degrees C. A method, using phosphatase inhibitors, was introduced to obtain stable, long-lasting contractions in thiophosphorylated preparations. Vi (10-1000 microM) dose-dependently inhibited active force, to about 20% of its maximum level. At a higher temperature (30 degrees C), the rate of inhibition was faster but the extent of inhibition was less. The rate of contraction following photolytic release of ATP to fibres in rigor was not affected by Vi (30 microM). The maximal shortening velocity (Vmax) was inhibited in a similar manner as active force by Vi (30 microM). In conclusion, the results suggest that Vi interacts with a force-generating actomyosin-ADP (AMADP) state reached after phosphate release. The rate of inhibition of smooth muscle contraction was markedly lower than in skeletal muscle, suggesting differences either in properties of the Vi-bound states or, more likely, in the concentration of AMADP states capable of binding Vi. This suggests that the long duty cycle in smooth muscle is not associated with a higher relative population of AMADP states reached immediately after Pi release, but rather by an increase in the population of subsequent force-generating cross-bridge states. The Vi-bound cross-bridges introduce an internal load to shortening, possibly acting in a similar manner as cross-bridge states introduced at low levels of activation.

Passive mechanical properties of the guinea pig aorta and portal vein: a comparison in the low-frequency range

The study was carried out to determine the differences in the low-frequency dynamic mechanical properties of the guinea pig aorta and portal vein. Experiments were performed at five passive load levels in the aorta and at four levels in the portal vein. Sudden stretches 65 s in duration were imposed on the muscles, and the resulting force responses were recorded. After the experiments, the Fourier transformations of the force responses and the length perturbations were calculated. The results of the transformation were used to find the dynamic stiffness values in the range of 0-3 Hz. The quotient of the dynamic to the static stiffness (Ed/Es) obtained for the aorta and portal vein was the higher the higher was the frequency. At a given frequency and load level, the quotient Ed/Es was significantly greater for the portal vein than that for the aorta. Furthermore, the quotient value obtained for the portal vein varied with the passive load, whereas the same quotient obtained for the aorta did not vary significantly with the load levels. The phase difference between force and length was small and constant over the frequency range of 0-3 Hz, in both vessels. The differences in the dynamic characteristics are discussed in relation to the shortening capacity of the muscle cells in the two vessels.

Alteration of tension response to stretch with spontaneous contraction frequency in the guinea pig taenia coli and stiffness-work characteristics

Previously we developed a data acquisition procedure to measure the tension responses of smooth muscles during their spontaneous contraction. This study was undertaken to determine whether the time course of the tension responses to stretches was altered with the ongoing spontaneous contractions. In addition, the stiffness, phase and work characteristics were evaluated from the tension responses in order to see how these characteristics were affected by the changes in the tension responses. The tension responses of the spontaneously contracting taenia coli to stretches had four phases. However, the latencies of the phases changed with the type of the spontaneous contractions during which the measurement was carried out. In the responses recorded during the slow spontaneous contractions (40-70 s), the second phase reached the minimum at 2.26 +/- 1.12 s and the third phase had the peak tension at 9.56 +/- 3.08 s. These latencies were 0.89 +/- 0.30 s and 3.91 +/- 1.10 s, respectively, when the experiments were undertaken during high frequency contractions (10-30 s). Besides, the maxima and minima in the stiffness, phase and work characteristics were also shifted to higher frequencies as the spontaneous contraction became faster. Work had a positive peak around 0.03 Hz for the slowly contracting taenia coli. The peak shifted to 0.1 Hz when the taenia coli contracted at higher frequency. The results show that the time course of the tension responses is determined by the contractile state of the taenia coli.

The efficacy of a five-drug antiemetic combination during chemotherapy regimens containing cisplatin or cyclophosphamide-doxorubicin

A five-drug combination, including metoclopramide, thiethylperazine, diphenhydramine, dexamethasone, and diazepam, was given to 32 patients during three consecutive treatments with chemotherapy. Eighteen patients (group A) were treated with a cisplatin-containing regimen, and 14 patients (group B) were treated with a cyclophosphamide- and doxorubicin-containing chemotherapy. In group A, complete responses were lower on the first day than on the second and third days (P < 0.015 and P < 0.041, respectively), during the first and second courses. The five-drug antiemetic regimen seems safe and effective. These results show that clinical trials that evaluate antiemetic efficacy in cisplatin-containing chemotherapy regimens should evaluate at least two consecutive courses.

Human long-latency potentials evoked by monaural interruptions of a binaural click train: connection to sound lateralization based on interaural intensity differences

In 9 subjects with normal hearing, monaural offset (MO) responses in the long-latency range were recorded with and without an ongoing sound (click train at a rate of 250/s) at the opposite ear. In the latter case MOs were perceived simply as termination of a sound. In the former case, however, the abrupt transition from binaural to monaural (BM) stimulation was perceived as a shift of the fused image from the center to either side. Therefore, the fairly large difference potential obtained by subtracting the MO response from the BM response was evaluated as the cortical response to stimulation of the sound lateralization mechanism based on interaural intensity differences. These center-to-side responses, which could be characterized by an N1-P2 wave sequence at latencies of 120 and 220 ms, respectively, were compared with the auditory onset responses also recorded from the same subjects by means of a sequential stimulation paradigm. The scalp topography of the N1 components in all these responses recorded simultaneously from frontocentral, parietocentral and two superior temporal electrodes with a neck reference is discussed.