Biomedical subjects

Ralf Dittrich

Publications and source records attributed to Ralf Dittrich.

44 records · Page 3Linked to original sources

PubMed2002

Circulating microemboli in 33 patients with intracranial arterial stenosis.

BACKGROUND: Intracranial arterial stenosis is a rare cause of stroke in Caucasians. Detection of clinically silent circulating microemboli by transcranial Doppler sonography is now widely investigated in patients with carotid artery disease in the hope to identify patients at increased risk for stroke. METHODS: In 33 patients with intracranial internal carotid (n = 12), middle cerebral (n = 18), posterior cerebral (n = 2), or basilar artery stenosis (n = 1), we performed a 1-hour microembolus detection downstream to the stenosis in the middle or in the posterior cerebral artery, respectively. The stenosis was assessed by transcranial Doppler and duplex ultrasound. 18 patients had been symptomatic in the dependent territory. RESULTS: Five patients with ischaemic symptoms within the last 8 days and with a peak systolic flow velocity of > or =210 cm/s in the stenosis showed microembolic signals at a rate of 3-25 events/h, despite effective anticoagulation. All these 5 patients had a lesion pattern on cranial CT or MRI scan suggesting embolic origin. All the asymptomatic patients (n = 15) and all the patients with a peak systolic intrastenostic velocity of 160 to <210 cm/s (n = 13) did not show microembolic signals at all. CONCLUSION: Microembolic signals occur in recently symptomatic patients with high-grade intracranial arterial stenosis indicated by a sonographically measured stenotic peak flow velocity of > or =210 cm/s. Therapeutic anticoagulation was not sufficient to suppress microemboli formation.

Adult↗

PubMed2002

Contrast transcranial Doppler ultrasound in the detection of right-to-left shunts: comparison of Echovist-200 and Echovist-300, timing of the Valsalva maneuver, and general recommendations for the performance of the test.

BACKGROUND AND PURPOSE: Cardiac right-to-left shunts (RLS) can be identified by transesophageal echocardiography (TEE) as well as by transcranial Doppler ultrasound (TCD) using contrast agents, such as Echovist-200 or Echovist-300 in conjunction with a Valsalva maneuver (VM) as provocation procedure. Both Echovist preparations are in use. Currently, the appropriate timing of the VM is still under debate. METHODS: Sixty-four patients were investigated by both TEE and bilateral TCD of the middle cerebral arteries. The following protocol was applied in a randomized way: (1) no VM, (2) VM for 5 s starting with the beginning of Echovist-300 injection, (3) VM for 5 s starting 5 s after the beginning of Echovist-300 injection, (4) VM for 5 s starting 10 s after the beginning of Echovist-300 injection, and (5) VM for 5 s starting 5 s after the beginning of Echovist-200 injection. RESULTS: In 27 patients, an RLS was demonstrated by both TEE and contrast TCD (shunt-positive). Twenty-two patients were negative in both investigations, no patient was positive on TEE but negative on TCD, 15 patients were only positive on at least one TCD investigation but negative on TEE. Tests 3 and 5 were the most appropriate ones; test 3 was slightly superior to test 5. CONCLUSIONS: TCD using Echovist-300 or Echovist-200 is a sensitive method to identify TEE-proven cardiac RLS. To achieve the best diagnostic accuracy, the VM should be performed for a duration of 5 s starting at 5 s following the beginning of contrast injection.

Adult↗

PubMed2002

Optimizing the technique of contrast transcranial Doppler ultrasound in the detection of right-to-left shunts.

BACKGROUND AND PURPOSE: A cardiac right-to-left shunt (RLS) can be identified by transesophageal echocardiography and transcranial Doppler ultrasound (TCD) with contrast agents and a Valsalva maneuver (VM) as a provocation procedure. This article applies the modalities of these tests detailed in previous studies to a large patient cohort and compares 2 contrast agents (saline and Echovist-300). METHODS: Eighty-one patients were investigated by both transesophageal echocardiography and bilateral TCD of the middle cerebral arteries. The following protocol with injections of 10 mL agitated saline was applied in a randomized way: (1) no VM, (2) VM for 5 seconds starting 5 seconds after the beginning of contrast injection, and (3) repetition of the test with VM if the first test with VM was negative. The VM was performed for 5 seconds starting exactly 5 seconds after the beginning of saline injection. Thereafter, the same protocol was repeated with 10 mL Echovist-300 instead of saline. RESULTS: Thirty-one patients had a cardiac RLS. The Echovist-300 investigation disclosed all these 31 shunts, but saline disclosed only 29 of them. Twenty-two had an RLS only in at least 1 of the above TCD tests, some of them even with a considerable shunt volume. CONCLUSIONS: Contrast TCD performed with Echovist-300 but not with saline yields a 100% sensitivity to identify transesophageal echocardiography-proven cardiac RLSs. The TCD test should be repeated if negative the first time. This article gives detailed information for the optimization of the contrast TCD technique. Extracardiac shunts detected only during contrast TCD can have a considerable shunt volume and may allow for paradoxical embolism.

Adult↗

PubMedDate not supplied

Influence of inflammation and pump dynamic on cerebral microembolization in patients with Continuous-Flow DeBakey LVAD.

Microembolic signals (MES) have shown to be associated with increased risk of ischemic stroke in patients with pulsatile left ventricular assist devices (LVADs) in contrast to continuous-flow DeBakey LVAD. The pathogenesis of microembolization in LVAD-patients is still not known. We investigated whether systemic markers of inflammation or pump dynamic correlate with cerebral microembolization in nine patients with DeBakey LVAD. We performed transcranial Doppler (TCD) for MES-detection and evaluated parameters of inflammation (i.e. Leukocytes, CRP, Fibrinogen) and pump dynamic (i.e. power, speed, flow). During a mean LVAD duration of 203.7 +/- 179 days, thromboembolic events occurred in five patients with an incidence of 0.38% (approximately 0.38 events/100 LVAD-days). We performed 290 TCD monitorings with a MES mean count of 50.4 +/- 346 signals/hour (0-5042) and prevalence of 42.8%. There was no association between individual microembolic activity and the markers of inflammation or pump dynamic. In patients with DeBakey LVAD, a high load of clinically silent cerebral microemboli can be detected. However, there is no correlation between markers of inflammation or pump dynamic and the individual amount of microembolization. We hypothesize that a gaseous nature of the majority of detected microemboli in the DeBakey LVAD may be the underlying reason for this discrepancy.

Adult↗

PubMedDate not supplied

Development of sex cord stromal tumors after heterotopic transplantation of cryopreserved ovarian tissue in rats.

Chemoradiotherapy has substantially improved life expectancy in young women with cancer, but these treatments often cause infertility. One method of preserving fertility is to cryopreserve ovarian tissue, with subsequent autotransplantation of the tissue after successful anticancer therapy. This study examined the long-term effect of heterotopic transplantation of cryopreserved ovarian tissue on the histology. Ovarian tissue from rats was cryopreserved using a slow-freezing protocol. After thawing, the tissue pieces were transplanted under the splenic capsule in 14 rats of the same inbred strain and remained there for 210 or 300 days. Sex cord stromal tumors, consisting mainly of granulosa cells, were found in all of the rats. Although the hormonal situation in rats cannot be directly compared to that in humans, the development of sex cord stromal tumors in this animal model may be worth considering when cryopreserved ovarian tissue is transplanted heterotopically in fertility-preserving programs for cancer patients.

Animals↗

PubMedDate not supplied

The role of albumin in the calculation of free and bioavailable testosterone in women with hyperandrogenemia.

BACKGROUND: The aim of this study was to assess the role of albumin in the calculation of free testosterone (cFT) and bioavailable testosterone (cBT). PATIENTS AND METHODS: Ninety-two healthy women, who presented at our fertility center for evaluation of possible hyperandrogenemia, were included in the study. Total blood testosterone (TT), free testosterone (FT) and sex hormone-binding globulin (SHBG) were measured using commercially available enzyme immunoassays in one serum sample. cFT and cBT were then calculated, taking into account the individual albumin concentration, but without taking account of each individual albumin serum concentration. RESULTS: No differences were observed in the calculated values for FT and BT, with or without taking into account the individual albumin concentration. A correlation between the two was demonstrated. CONCLUSION: For clinical routine work, it is not necessary to estimate the individual albumin concentration in hyperandrogenic women in order to calculate the FT and BT concentrations from TT and SHBG serum concentrations, when the albumin concentration is in the physiological range of 40-50 g/L.

Adult↗

PubMedDate not supplied

Effects of the antiestrogens tamoxifen and raloxifene on the estrogen receptor transactivation machinery.

The influence of 17beta-estradiol (E2), tamoxifen (TAM) and raloxifen (RLX) on the proliferation of breast (BC) and endometrial carcinoma cell lines (EC) and the expression of different compounds of the estrogen receptor (ER)-transactivation machinery were studied. E2 stimulated the proliferation of BC, but had no effect on the EC. TAM showed a biphasic effect on ER-positive cell lines. RLX showed an antagonistic suppression or no effect. The expression of ERalpha was down-regulated by E2, but not affected by selective estrogen receptor modulators. ERbeta and progesterone receptor expressions were up-regulated by E2, TAM and OHT. This supports the hypothesis that ERbeta expression is also regulated via the ERalpha-pathway. The steroid receptor coactivator (SRC) AIB1 expression was slightly decreased by E2 but not by antiestrogens (antiE). TIF2 expression was increased by E2, TAM and RLX, but SRC-1 expression was not. In comparison, the expressions of ERbeta and progesterone receptor were strongly influenced by antiE, while the expression of SRCs was only slightly affected.

Breast Neoplasms↗

PubMedDate not supplied

Xenotransplantation of human ovarian tissue pieces in gonadotropin-stimulated SCID mice: the effect of ovariectomy.

The number of follicles were compared in different developmental stages after the cryopreservation of human ovarian tissue by open freezing system followed by xenotransplantation into severe combined immunodeficient (SCID)-mice under stimulation, with and without ovariectomy. Ovarian tissue, cryopreserved for fertility preservation was partly examined by LIVE/DEAD viability staining or was transplanted in the neck muscle of 32 SCID-mice. The development of follicles, estradiol production, vaginal cytology and uterus weight was assessed after 15 weeks under gonadotropin stimulation, with or without ovariectomy. Viable follicles were detected in all frozen/thawed specimens using the LIVE/DEAD assay. Ovariectomy caused a significant improvement of survival of follicles in the preantral and antral stages in the gonadotropin-stimulated animals (p < 0.001), whereas there was no significant effect on the primordial and primary follicle counts. In the non-ovariectomised group, only isolated primordial and primary follicles could be detected. The total follicle amount was significantly higher in the ovariectomised group (n=17, 9.2 +/- 7.8, mean +/-SD) than in the non-ovariectomized group (n=15, 0.3 +/- 1.0). This study demonstrates that ovariectomy of stimulated recipient SCID-mice is essential for the development of follicles after xenotransplantation of cryopreserved human ovarian grafts.

Animals↗