A Cohort of 469 Mayer-Rokitansky-Küster-Hauser Syndrome Patients-Associated Malformations, Syndromes, and Heterogeneity of the Phenotype

The Mayer-Rokitansky-Küster-Hauser syndrome is characterized by aplasia of the uterus and upper two-thirds of the vagina. While it can appear as an isolated genital malformation, it is often associated with extragenital abnormalities, with little still known about the pathogenetic background. To provide an overview of associated malformations and syndromes as well as to examine possible ties between the rudimentary tissue and patient characteristics, we analyzed a cohort of 469 patients with MRKHS as well as 298 uterine rudiments removed during surgery. A total of 165 of our patients (35.2%) had associated malformations (MRKHS type II). Renal defects were the most common associated malformation followed by skeletal abnormalities. Several patients had atypical associated malformations or combined syndromes. Uterine rudiments were rarer in patients with associated malformations than in patients without them. Rudiment size ranged from 0.3 cm3 to 184.3 cm3 with a mean value of 7.9 cm3. Importantly, MRKHS subtype or concomitant malformations were associated with a different frequency of uterine tissue as well as a different rudiment size and incidence of endometrial tissue, thereby indicating a clear heterogeneity of the phenotype. Further research into the associated molecular pathways and potential differences between MRKHS subtypes is needed.

Tissue-preserving treatment with non-invasive physical plasma of cervical intraepithelial neoplasia-a prospective controlled clinical trial

Objective

Cervical cancer represents the fourth leading cause of cancer among women and is associated with over 311,000 annual deaths worldwide. Timely diagnosis is crucial given the lengthy pre-cancerous phase, which is typified by cervical intraepithelial neoplastic lesions. However, current treatment methods are often tissue-destructive and can be accompanied by severe side effects. To address these concerns, our study introduces a novel, gentle approach for the tissue-preserving treatment of CIN lesions.

Results

We present findings of a controlled, prospective, single-armed phase IIb clinical trial performed at the Department for Women’s Health, Tübingen, Germany. From September 2017 to March 2022 we assessed 570 participants for study eligibility. Of the screened patients, 63 participants met with CIN1/2 lesions met the inclusion criteria and were treated with non-invasive physical plasma (NIPP). Assessment of treatment efficacy was based on a comprehensive analysis of histological and cytological findings, along with high-risk HPV infection load at 3 and 6 months post-treatment. Comparative analyses were performed retrospectively with data obtained from 287 untreated patients in the control group. Our findings indicate that patients treated with NIPP experienced an 86.2% rate of full remission, along with a 3.4% rate of partial remission of CIN lesions, which compares favorably to the control group’s rates of 40.4% and 4.5%, respectively. Additionally, we observed a twofold reduction in high-risk HPV infections following NIPP treatment. Minor side effects were observed, such as mild pain during treatment and short-term smear bleeding or increased vaginal discharge within 24 h after treatment. Given the experimental nature of NIPP treatment and the availability of established standard treatments, our study was designed as a non-randomized study.

Conclusion

NIPP treatment offers a highly flexible and easy-to-apply method for treating pre-cancerous CIN1/2 lesions. This non-invasive approach is notable for its tissue-preserving nature, making it a promising alternative to current excisional and ablative treatments. CIN1/2 lesions were employed as preliminary in vivo models for the targeted treatment of CIN3 lesions.

Clinical trial registration

https://www.clinicaltrials.gov, identifier NCT03218436.

Tumor-Free Resection Margin Distance in the Surgical Treatment of Node-Negative Squamous Cell Cancer of the Vulva Has No Impact on Survival: Analysis of a Large Patient Cohort in a Tertiary Care Center

BACKGROUND

The aim of this study was to evaluate the impact of pathological tumor-free margin distance on survival in SCC patients treated with surgery alone.

METHODS

This retrospective study included 128 patients with node-negative disease that received no adjuvant treatment. Disease-free and overall survival were analyzed according to pathological tumor-free margin distance.

RESULTS

The patients were subclassified into three resection margin category groups: "1 to 3 mm" (n = 42), ">3 to 8 mm" (n = 47) or ">8 mm" (n = 39). Thirty-nine of the 128 patients (30.5%) developed recurrent disease. Median follow-up for disease-free survival (DFS) was 6.49 years (95% CI 5.16 years; 7.62 years), and median follow-up for overall survival (OS) was 6.29 years (95% CI 5.45 years; 7.33 years). The 5-year DFS rate was 0.70 (95% CI: 0.62-0.79), and the 5-year OS rate was 0.79 (95% CI: 0.71-0.87). Regarding the survival outcome, there were no independent significant differences in either disease-free survival (DFS) (p = 0.300) or overall survival (p = 1.000) among patients within the three tumor-free resection margin categories. Multivariate analyses did not show any statistically significant association between tumor-free resection margin distance and recurrent disease or death, either when analyzed as a categorical variable or when analyzed as a continuous variable.

CONCLUSION

The present study did not show a significant impact of pathological tumor-free resection margin distance following surgery in patients with node-negative SCC of the vulva (that did not receive adjuvant treatment) on disease-free and overall survival.

Laparoscopic Supracervical Hysterectomy and Laparoscopic Total Hysterectomy in Patients with Very Large Uteri: a Retrospective Single-Center Experience at a Major University Hospital

Objective The main objectives of our study were to demonstrate that laparoscopic supracervical hysterectomy (LSH) or total laparoscopic hysterectomy (TLH) can be performed safely even in patients with a uterine weight ≥ 500 g, to analyze the rate of conversions to laparotomy due to uterine size and to estimate the incidence and type of intraoperative and long-term postoperative complications. Study Design Retrospective open, single-center, comparative interventional study of LSH and TLH. Results The present study comprised a total of 138 patients that underwent laparoscopic hysterectomy with a uterine weight ≥ 500 g; 109 patients (79.0 %) underwent LSH and 29 patients (21.0 %) underwent TLH. Median uterine weight across the entire cohort was 602 g, with the largest uterus weighing 1860 g. A total of 24 cases (17.4 %) among the 138 hysterectomies were converted to a laparotomy due to lack of adequate intraabdominal space and size of the uterus. Mean uterine weight of the patients in the LSH group that underwent conversion was 883 g (SD 380 g, n = 13) and 757 g (SD 371 g, n = 11) in the TLH group. The rate of conversion to laparotomy due to the uterine weight was significantly lower in the LSH group (11.9 %) compared to the TLH group (37.9 %) (p = 0.002). Intraoperative complications requiring laparotomy for other reasons but uterine size occurred in 6 patients of the study cohort (6/138; 4.3 %). Long-term postoperative complications occurred in 2 patients (2/138, 1.4 %), both patients from LSH group had to be re-operated on due to adhesions. Conclusions Our study adds further insight in the limited data set of laparoscopic hysterectomy for increased uterine weight and shows that LSH and TLH are safe and feasible even in patients with very large uteri (≥ 500 g).

Decidualization is Impaired in Endometrial Stromal Cells from Uterine Rudiments in Mayer-Rokitansky-Küster-Hauser Syndrome

BACKGROUND/AIMS

Uterine rudiments from patients with Mayer-Rokitansky-Küster-Hauser syndrome (MRKHS) contain all tissues typically found in the uterus. Endometrium from the rudiments predominantly exhibits basalis-like features, and endometrial proliferative capacity in patients' epithelium and stroma is significantly lower.

METHODS

This single-center, prospective study conducted at a major German university hospital compared in-vitro decidualization in cultured ESCs from MRKHS patients and hysterectomy controls. Primary ESC cultures were established from both sources. Hormone-induced prolactin and IGFBP-1 secretion served as a measure of their ability to undergo decidualization in response to hormonal stimulation. Expression levels of 8 key marker genes of decidualization were also determined.

RESULTS

At day 9, mean secretion of prolactin and IGFBP-1 was significantly reduced by 89.0% and 99.5%, respectively, in MRKHS ESCs vs. hysterectomy controls, both indicating impaired decidualization of MRKHS ESCs. Key decidual markers confirmed impaired decidualization in MRKHS patients.

CONCLUSION

Our results indicate that the ESCs from MRKHS patients lack hormone responsiveness as a potential sign of dysfunctional hormone receptor function, which may also play a role in the onset of MRKHS. Further studies are needed to corroborate our findings, directly address receptor function, and elucidate the role of other potential determinants of uterine development and adult function.

The impact of HER2 phenotype of circulating tumor cells in metastatic breast cancer: a retrospective study in 107 patients

Background

In metastatic breast cancer (MBC), antigen profiles of metastatic tissue and primary tumor differ in up to 20 % of patients. Reassessment of predictive markers, including human epidermal growth factor receptor 2 (HER2) expression, might help to optimize MBC treatment. While tissue sampling is invasive and often difficult to repeat, circulating tumor cell (CTC) analysis requires only a blood sample and might provide an easy-to-repeat, real-time “liquid biopsy” approach. The present retrospective study was conducted to compare HER2 expression in primary tumors, metastatic tissue, and circulating tumor cells (CTCs) from MBC patients and to analyze the potential impact of HER2 overexpression by CTCs on progression-free (PFS) and overall survival (OS) in MBC.

Methods

CTC-positive (five or more CTCs/7.5 mL blood; CellSearch®, Janssen Diagnostics) MBC patients starting a new line of systemic treatment were eligible for the study. HER2 status of CTCs was determined by immunofluorescence (CellSearch®). HER2 status of primary (PRIM) and metastatic (MET) tumor tissue was determined by immunohistochemistry. Data were analyzed using descriptive statistics and Kaplan–Meier plots.

Results

One hundred seven patients (median age (range) 57 (33–81) years) were included. 100/107 (93 %) patients were followed-up for a median [95 % confidence interval (CI)] of 28.5 [25.1–40.1] months. Of 37/107 (35 %) CTC-HER2-positive patients only 10 (27 %) were PRIM-HER2-positive. 6/46 (13 %) patients were MET-HER2-positive; only 2/10 (20 %) CTC-HER2-positive patients were MET-HER2-positive. Overall accuracy between CTC-HER2 expression and PRIM-HER2 and MET-HER2 status was 69 % and 74 %, respectively. Kaplan–Meier plots of PFS and OS by CTC-HER2 status revealed significantly longer median [95 % CI] PFS of CTC-HER2-positive versus CTC-HER2-negative patients (7.4 [4.7–13.7] versus 4.34 [3.5–5.9] months; p = 0.035). CTC-HER2-positive status showed no significant difference for OS (13.7 [7.7–30.0] versus 8.7 [5.9–15.3] months; p = 0.287).

Conclusions

HER2 status can change during the course of breast cancer. CTC phenotyping may serve as an easy-to-perform “liquid biopsy” to reevaluate HER2 status and potentially guide treatment decisions. Further, prospective studies are needed.

Serial enumeration of circulating tumor cells predicts treatment response and prognosis in metastatic breast cancer: a prospective study in 393 patients

BACKGROUND

To prospectively assess circulating tumor cell (CTC) status at baseline (CTCBL) and after one cycle of a new line of systemic therapy (CTC1C), and changes from CTCBL to CTC1C (CTC kinetics, CTCKIN) for their utility in predicting response, progression-free (PFS) and overall survival (OS) in metastatic breast cancer (MBC).

METHODS

CTCBL and CTC1C status was determined as negative (-) or positive (+) for < 5 or ≥ 5 CTCs/7.5 ml blood using CellSearch™ (Veridex). CTCKIN was categorized as favorable (CTC1C-) or unfavorable (CTC1C+). Tumor response was to be assessed every 2-3 months using the Response Evaluation Criteria in Solid Tumors (RECIST) criteria. Statistical analysis focused on the relation between CTC status and CTCKIN, and response, PFS, and OS.

RESULTS

133/393 (34%) patients enrolled were CTCBL+. CTC1C status after one cycle and radiological tumor response were assessed after median (range) periods of 1.2 (0.5-3.2) and 2.9 (0.5-4.8) months, respectively. 57/201 (28%) were CTC1C+. Median [95% confidence interval] PFS and OS (months) were significantly reduced in CTCBL+ vs. CTCBL- patients (PFS 4.7 [3.7-6.1] vs. 7.8 [6.4-9.2]; OS 10.4 [7.9-15.0] vs. 27.2 [22.3-29.9]), and for CTC1C+ vs. CTC1C- patients (PFS 4.3 [3.6-6.0] vs. 8.5 [6.6-10.4]; OS 7.7 [6.4-13.9] vs. 30.6 [22.6-not available]). Unfavorable CTCKIN was significantly associated with progressive disease. Multivariate Cox regression analysis revealed prognostic factors for shorter PFS (CTCBL+, persistent CTCs after one cycle, ≥ 3rd-line therapy, and triple-negative receptor status) and shorter OS (CTCBL+, persistent CTCs after one cycle, bone-and-visceral/local metastases, ≥ 3rd-line therapy, and triple-negative receptor status).

CONCLUSIONS

CTCBL, CTC1C, and CTCKIN are predictive of outcome in MBC. Serial CTC enumeration is useful in tailoring systemic treatment of MBC.

TRIAL REGISTRATION

Not applicable.

Cervical Detachment Using Monopolar SupraLoop™ Electrode versus Monopolar Needle in Laparoscopic Supracervical Hysterectomy (LSH): An Interventional, Comparative Cohort Study

Objective: Currently available monopolar loop electrodes are difficult to handle in laparoscopic supracervical hysterectomy (LSH) and are entirely disposable devices, generating additional operating costs. The aim of this interventional study was the comparison of the efficiency and safety of cervical detachment with a newly developed monopolar loop electrode (SupraLoop™) with a conventional method of cervical detachment in LSH. Material and Methods: Our study sample included 1598 patients; 1070 patients that underwent LSH with cervical detachment using the monopolar SupraLoop™ (study group) and 528 patients that underwent LSH with cervical detachment using the monopolar needle (control group). We also assessed cervical detachment time and total device application and cutting time in a subgroup of 49 patients (23 patients from the study group and 26 patients from the control group). Results: Total operation time for LSH was significantly shorter among SupraLoop™ patients (93 ± 41 minutes) when compared to patients in whom cervical detachment was performed with the needle (105 ± 44 minutes) (p < 0.001). Cervical detachment time and total device application including cutting time was significantly shorter for the SupraLoop™ group (SupraLoop vs. needle; 0.12 ± 0.21 min vs. 5.1 ± 4.4 min [p < 0.001]; 2.3 ± 1.8 min vs. 5.4 ± 2.4 min [p < 0.001]). There were no major or minor complications directly related to the use of the SupraLoop™ device, whereas two intraoperative complications were directly related to the application of the monopolar needle. Conclusion: The newly developed monopolar loop electrode (SupraLoop™) is both an effective and safe instrument for cervical detachment in laparoscopic supracervical hysterectomy, and performed better than the needle, offering a significantly shorter operating time and less complications for the hysterectomy compared to the conventional method.

[Reproducibility of readings of ISO C 3D and CT lumbar pedicle screw scans]

PURPOSE

This study was conducted to evaluate the reproducibility of the reading of lumbar pedicle screw scans using a C-arm-based imaging system in comparison to computed tomography. The influence of the technique and the experience of the rater should be determined.

MATERIALS AND METHODS

The lumbar spines of 23 patients were stabilized using 102 pedicle screws. The position of the screws was controlled intraoperatively using an Arcadis Orbic 3D scanner. All scans were evaluated independently by three raters. The position of the implants in reference to the pedicle walls was described. Additionally, another 100 lumbar pedicle screws in 16 patients were evaluated postoperatively with a multirow CT. Kappa according to Fleiss was calculated for the reproducibility of the rater statements. Each rater repeated the analysis of 24 screws to assess the intraobserver variance.

RESULTS

The reports of the CT scans showed significantly less variation. The consent of all 3 raters was achieved in 79.4 vs. 65.1 % of cases. The Kappa values were 0.56 and 0.29, respectively. Poor results were obtained especially for the medial pedicle wall (consent 70.0 vs. 50.0 %). The influence of the experience of the rater was not able to be verified.

CONCLUSION

The image quality of the ISO C 3D is worse than that of multirow CT scans for the evaluation of lumbar pedicle screws. This causes greater variance among the rater reports. We stopped using the ISO C 3D technique intraoperatively for the implantation of lumbar pedicle screws.

Adenosine stress cardiac magnetic resonance imaging for the assessment of ischemic heart disease

AIMS

This prospective study was designed to determine the diagnostic value of adenosine stress cardiac magnetic resonance imaging (CMRI) in patients referred to elective coronary angiography.

METHODS AND RESULTS

Myocardial perfusion measurements at rest and adenosine stress were performed in 141 patients (105 men, 36 women, mean age 63.4 years) at 1.5 T with a Turbo Flash sequence. Stress-induced perfusion deficits were correlated to angiographic stenoses > or =75%. The overall sensitivity for CMRI depicting coronary artery disease (CAD) with relevant stenoses was 90.4%, the specificity was 77.4%, the positive predictive value was 85.9%, the negative predictive value was 84.2% and the accuracy 85.2%. Subgroup analysis was performed for 3-vessel disease (n = 44, sensitivity 92.3%, specificity 75.0%), 2-vessel disease (n = 43, sensitivity 92.6%, specificity 92.9%), 1-vessel disease (n = 27, sensitivity 93.1%, specificity 71.4%) and patients without CAD (n = 27, specificity 70.4%) as well as for patients with prior myocardial infarction (n = 44, sensitivity 92.9%, specificity 86.7%), prior coronary artery bypass surgery (n = 21, sensitivity 88.2%, specificity 66.7%), prior coronary interventions (n = 88, sensitivity 91.9%, specificity 75.0%), or diabetics (n = 27, sensitivity 90.5%, specificity 83.3%).

CONCLUSION

Our study shows that stress perfusion CMRI can accurately predict relevant CAD and contributes to the identification of hemodynamic relevant stenoses in patients scheduled for coronary angiography.

Analysis of risk factors determining prognosis of cutaneous squamous-cell carcinoma: a prospective study

BACKGROUND

Cutaneous squamous-cell carcinomas (SCC) are among the most common cancers capable of metastasis. Current Tumour Node Metastasis (TNM) staging includes horizontal tumour size, involvement of extradermal structures, and degree of differentiation. The aim of this study was to prospectively analyse the key factors predicting metastasis and local recurrence in cutaneous SCC.

METHODS

We assessed prospectively investigated potential risk factors for metastasis or local recurrence of SCC, previously suggested by retrospective studies and small case series, in 615 white patients. Between Jan 1, 1990, and Dec 31, 2001, all patients underwent surgery for cutaneous SCC with complete histological examination of the three-dimensional excision margins (3D-histology) in one centre. Univariate and multivariate analysis included tumour thickness, horizontal size, body site, histological differentiation, desmoplastic growth, history of multiple SCC, and immunosuppression. Primary endpoints were time to metastasis and time to local recurrence, defined as the time from date of diagnosis of the primary tumour to the date of diagnosis of metastasis or local recurrence, respectively.

FINDINGS

653 patients were enrolled in the study. 38 patients were lost to follow-up leaving 615 assessable patients (median age 73 years [range 27-98]). During a median follow-up period of 43 months (range 1-165), 26 (4%) of 615 patients developed metastases and 20 patients developed local recurrence (3%). Tumours 2.0 mm or less in thickness did not metastasise. Metastases occurred in 12 (4%) of 318 tumours between 2.1 mm and 6.0 mm in thickness, and in 14 (16%) of 90 tumours with a thickness greater than 6.0 mm. On multivariate analysis, key prognostic factors for metastasis were increased tumour thickness (hazard ratio 4.79 [95% CI 2.22-10.36]; p<0.0001), immunosuppression (4.32 [1.62-11.52]; p=0.0035), localisation at the ear (3.61 [1.51-8.67]; p=0.0040), and increased horizontal size (2.22 [1.18-4.15]; p=0.0128). The risk of local recurrence depended on increased tumour thickness (6.03 [2.71-13.43]; p<0.0001) and desmoplasia (16.11 [6.57-39.49]; p<0.0001).

INTERPRETATION

Only SCC greater than 2.0 mm in thickness are associated with a significant risk of metastasis. Tumours greater than 6.0 mm are associated with a high risk of metastasis and local recurrence. Desmoplastic growth is an independent risk factor for local recurrence. Studies should assess the role of follow-up visits and sentinel-lymph-node biopsy in high-risk patients.

Quantitative analysis of prion-protein degradation by constitutive and immuno-20S proteasomes indicates differences correlated with disease susceptibility

The main part of cytosolic protein degradation depends on the ubiquitin-proteasome system. Proteasomes degrade their substrates into small peptide fragments, some of which are translocated into the endoplasmatic reticulum and loaded onto MHC class I molecules, which are then transported to the cell surface for inspection by CTL. A reliable prediction of proteasomal cleavages in a given protein for the identification of CTL epitopes would benefit immensely from additional cleavage data for the training of prediction algorithms. To increase the knowledge about proteasomal specificity and to gain more insight into the relation of proteasomal activity and susceptibility to prion disease, we digested sheep prion protein with human constitutive and immuno-20S proteasomes. All fragments generated in the digest were quantified. Our results underline the different cleavage specificities of constitutive and immunoproteasomes and provide data for the training of prediction programs for proteasomal cleavages. Furthermore, the kinetic analysis of proteasomal digestion of two different alleles of prion protein shows that even small changes in a protein sequence can affect the overall efficiency of proteasomal processing and thus provides more insight into the possible molecular background of allelic variations and the pathogenicity of prion proteins.

Discrete cleavage motifs of constitutive and immunoproteasomes revealed by quantitative analysis of cleavage products

Proteasomes are the main proteases responsible for cytosolic protein degradation and the production of major histocompatibility complex class I ligands. Incorporation of the interferon gamma--inducible subunits low molecular weight protein (LMP)-2, LMP-7, and multicatalytic endopeptidase complex--like (MECL)-1 leads to the formation of immunoproteasomes which have been associated with more efficient class I antigen processing. Although differences in cleavage specificities of constitutive and immunoproteasomes have been observed frequently, cleavage motifs have not been described previously. We now report that cells expressing immunoproteasomes display a different peptide repertoire changing the overall cytotoxic T cell--specificity as indicated by the observation that LMP-7(-/-) mice react against cells of LMP-7 wild-type mice. Moreover, using the 436 amino acid protein enolase-1 as an unmodified model substrate in combination with a quantitative approach, we analyzed a large collection of peptides generated by either set of proteasomes. Inspection of the amino acids flanking proteasomal cleavage sites allowed the description of two different cleavage motifs. These motifs finally explain recent findings describing differential processing of epitopes by constitutive and immunoproteasomes and are important to the understanding of peripheral T cell tolerization/activation as well as for effective vaccine development.

Ring vaccination

Based on the description of an outbreak of foot-and-mouth disease (FMD), a particle model is developed describing the most important properties of this epidemic. Also control measures (mass and ring vaccination) are implemented. This model shows the expected behavior in simulations. Since it is impossible to treat this model analytically, we use ideas of branching processes on two levels to derive a caricature of the particle model. In simulations it is shown that this caricature exhibits similar behavior as the particle system. It is possible to analyze the caricature and, in this way, to obtain expressions for the most important quantities like the reproduction number or the expected final number of infected individuals etc. In this way mass vaccination and ring vaccination can be compared and control strategies can be optimized.

Biogenesis of the yeast frataxin homolog Yfh1p. Tim44-dependent transfer to mtHsp70 facilitates folding of newly imported proteins in mitochondria

Tim44 is an essential component of the mitochondrial inner membrane protein import machinery. In this study we asked if Tim44 is of relevance in intramitochondrial protein folding. We investigated the role of Tim44 in the biogenesis of the authentic mitochondrial protein Yfh1p, the yeast homolog of mammalian frataxin, which was recently implicated in Friedreich ataxia. After inactivation of Tim44, binding of mitochondrial heat shock protein (mtHsp)70 to translocating Yfh1p and subsequent folding to the native state was nearly completely blocked. Residual amounts of imported Yfh1p showed an increased tendency to aggregate. To further characterize the functions of Tim44 in the matrix, we imported dihydrofolate reductase (DHFR) as a model protein. Depletion of Tim44 allowed import of DHFR, although folding of the newly imported DHFR was delayed. Moreover, the depletion of Tim44 caused a strongly reduced binding of mtHsp70 and Mge1 to the translocating polypeptide. Subsequent dissociation of mtHsp70 from imported DHFR was delayed, indicating that mtHsp70-substrate complexes formed independently of Tim44 differ from the complexes that form under the control of Tim44. We conclude that Tim44 not only plays a role in protein translocation but also in the pathways of mitochondrial protein folding.

Synchronous and asynchronous updating in cellular automata

We analyze the properties of a synchronous and of various asynchronous methods to iterate cellular automata. Asynchronous methods in which the time variable is not explicitly defined, operate by specifying an updating order of the cells. The statistical properties of this order have significant consequences for the dynamics and the patterns generated by the cellular automata. Stronger correlations between consecutive steps in the updating order result in more, artificial structure in the patterns. Among these step-driven methods, using random choice with replacement to pick the next cell for updating, yields results that are least influenced by the updating method. We also analyse a time-driven method in which the state transitions of single cells are governed by a probability per unit time that determines an exponential distribution of the waiting time until the next transition. The statistical properties of this method are completely independent of the size of the grid. Consecutive updating steps therefore show no correlation at all. The stationary states of a cellular automaton do not depend on whether a synchronous or asynchronous updating method is used. Their basins of attraction might, however, be vastly different under synchronous and asynchronous iteration. Cyclic dynamics occur only with synchronous updating.

Separation of structural and dynamic functions of the mitochondrial translocase: Tim44 is crucial for the inner membrane import sites in translocation of tightly folded domains, but not of loosely folded preproteins

The essential gene TIM44 encodes a subunit of the inner mitochondrial membrane preprotein translocase that forms a complex with the matrix heat-shock protein Hsp70. The specific role of Tim44 in protein import has not yet been defined because of the lack of means to block its function. Here we report on a Saccharomyces cerevisiae mutant allele of TIM44 that allows selective and efficient inactivation of Tim44 in organello. Surprisingly, the mutant mitochondria are still able to import preproteins. The import rate is only reduced by approximately 30% compared with wild-type as long as the preproteins do not carry stably folded domains. Moreover, the number of import sites is not reduced. However, the mutant mitochondria are strongly impaired in pulling folded domains of preproteins close to the outer membrane and in promoting their unfolding. Our results demonstrate that Tim44 is not an essential structural component of the import channel, but is crucial for import of folded domains. We suggest that the concerted action of Tim44 and mtHsp70 drives unfolding of preproteins and accelerates translocation of loosely folded preproteins. While mtHsp70 is essential for import of both tightly and loosly folded preproteins, Tim44 plays a more specialized role in translocation of tightly folded domains.

Anisotropy in cellular automata

Time-dependent and stationary patterns produced by standard cellular automata used for various qualitative modeling purposes show various geometric features that reflect the anisotropy of the underlying grid and neighborhood rather than the properties of the physical model itself. We investigate several modifications of cellular automata such as random grids, stochastic local functions, asynchronous evaluations that are designed to avoid anisotropy. We apply these tools to a class of simple totalistic automata simulating contact processes. It appears that random grids are most useful.

The mitochondrial ClpB homolog Hsp78 cooperates with matrix Hsp70 in maintenance of mitochondrial function

The mitochondrial heat shock protein Hsp78 is a member of the Hsp104/Clp family with unknown function. Saccharomyces cerevisiae deletion mutants of HSP78 show wild-type like growth. We report that deletion of the HSP78 gene in yeast strains with point mutations in the SSC1 gene (encoding matrix Hsp70) led to loss of mitochondrial DNA, indicating that at least one of the heat shock proteins Hsp78 and mt-Hsp70 is needed to maintain a rho+ state of the mitochondrial genome. Mitochondria isolated from these double mutants had a strongly reduced membrane potential, explaining defects in the rate of preprotein import. The lack of Hsp78 led to aggregation of the mutant mt-Hsp70 while other matrix chaperones stayed soluble. We conclude that Hsp78 is required to keep mutant forms of mt-Hsp70 soluble and suggest a cooperation of Hsp78 and mt-Hsp70 in maintenance of essential mitochondrial functions.