Biomedical subjects

Frank Riedel

Publications and source records attributed to Frank Riedel.

At least 37 records · Page 2Linked to original sources

PubMed2005

TGF-beta antisense oligonucleotides reduce mRNA expression of matrix metalloproteinases in cultured wound-healing-related cells.

The pathology of chronic dermal ulcers is characterized by excessive proteolytic activity which degrades extracellular matrix. The transforming growth factor-beta (TGF-beta) has been identified as an important component of wound healing. Recent developments in molecular therapy offer exciting prospects for the modulation of wound healing, specifically those targeting TGF-beta. We investigated the effect of TGF-beta antisense oligonucleotides on the mRNA expression of matrix metalloproteinases in cultured human keratinocytes, fibroblasts and endothelial cells using multiplex RT-PCR. The treatment of keratinocytes and fibroblasts with TGF-beta antisense oligonucleotides resulted in a significant decrease of expression of mRNA of MMP-1 and MMP-9 compared to controls. Accordingly, a decreased expression of MMP-1 mRNA in endothelial cells was detectable. Other MMPs were not affected. Affecting all dermal wound-healing-related cell types, TGF-beta antisense oligonucleotide technology may be a potential therapeutic option for the inhibition of proteolytic tissue destruction in chronic wounds. Pharmaceutical intervention in this area ultimately may help clinicians to proactively intervene in an effort to prevent normal wounds from becoming chronic.

Cell Line↗

PubMed2005

Plasma level and tissue expression of angiogenic factors in patients with hereditary hemorrhagic telangiectasia.

The value of angiogenic factors interleukin-8 (IL-8) and vascular endothelial growth factor (VEGF) was determined in patients with hereditary hemorrhagic telangiectasia (HHT) to evaluate their role in HHT pathogenesis. IL-8 and VEGF were measured in plasma of 41 HHT patients and healthy controls by ELISA technique. In both groups, the IL-8 and VEGF tissue expression in cryostat sections of the nasal mucosa were then compared. VEGF plasma levels were significantly increased in HHT patients compared to healthy controls. In contrast, the IL-8 plasma levels in both groups did not show any significant difference. Compared to healthy controls, HHT tissue samples showed a weak IL-8 staining, whereas the VEGF staining was very strong. The plasma levels of VEGF and IL-8 could not be correlated to the patients' clinicopathological findings. Additionally to the angiogenic pro-inflammatory cytokine IL-8, the angiogenic factor VEGF seems to play a major role in HHT pathogenesis.

Humans↗

PubMed2005

Up-regulation of beta-catenin in external auditory canal cholesteatoma.

The external auditory canal cholesteatoma (EACC) is a rare disease with hyperproliferation and destructive growth in the adjacent structures. Down-regulation of beta-catenin (key component of the zonula adherens) is a pivotal factor for loose tissue integrity and invasiveness. Transforming growth factor beta1 (TGF-beta1) was reported to decrease beta-catenin in mammary epithelium. We investigated the abrogation of TGF-beta1 and beta-catenin expression in EACC culture cells. Cultured EACC-specimens were incubated with 6 micromol TGF-beta1 antisense. After 48 h, expression of beta-catenin was determined by means of immunohistochemistry. The cells showed an increased mural reactivity to beta-catenin, and intracellular reactivity was unchanged. The untreated cells showed a loss of beta-catenin expression at the membranes. The predominant membranous location after treatment with TGF-beta1 antisense suggests increased tendency of the cells for tissue formation and strong cell-cell adhesion rather than migratory and invasive character, and thus TGF-beta1 antisense application is a useful therapeutical strategy.

Cells, Cultured↗

PubMed2005

Tissue engineering with adult stem cells in reconstructive surgery (review).

Tissue engineering is a multidisciplinary field combining biology and engineering along with clinical application to design, manufacture, modify, grow and maintain living tissue. This field has enjoyed tremendous growth in the past 10 years fueled by its potential role in regenerating new tissues and naturally healing injured or diseased organs. Many approaches to tissue engineering have been explored, including ex vivo de novo construction of tissues and strategies of in vivo induction of tissue regeneration. Interventions are hindered by factors such as rejection by the immune system, limited blood supply or morbidity of the donor site. Regardless of the approach, most researchers and clinicians agree that any successful tissue engineering construct will derive from a single unit, the cell. Because the engineering of tissue necessitates a sufficient number of tissue-specific cells with minimal donor site morbidity, a great deal of scientific effort has been directed towards stem cell research and the use of stem cells as a source of cells for new tissues. This review aims at outlining the role of stem cells in tissue engineering, focusing on the use of adult-derived stem cells as applied to the research and practice of plastic surgery.

Animals↗

PubMed2005

Patients with hereditary hemorrhagic telangiectasia have increased plasma levels of vascular endothelial growth factor and transforming growth factor-beta1 as well as high ALK1 tissue expression.

BACKGROUND AND OBJECTIVES: Hereditary hemorrhagic telangiectasia (HHT), an inherited vascular dysplasia, is caused by mutations in endoglin or activin receptor-like kinase (ALK)-1. Haploinsufficiency for these genes is thought to result in an imbalanced angiogenic activity. The aim of this study was to evaluate the plasma levels and the expression profiles of angiogenic and angiogenesis-related factors in the context of HHT. DESIGN AND METHODS: Vascular endothelial growth factor (VEGF) and transforming growth factor (TGF)-beta1 plasma concentrations were determined in 31 HHT patients and 40 healthy controls by ELISA. VEGF and TGF-beta1 plasma concentrations were correlated with the patients' clinicopathological features. Tissue expression of angiogenic and angiogenesis related proteins was determined by immunostaining on nasal cryostat sections from 13 HHT patients and 5 healthy controls. RESULTS: Of the 31 patients, 29 had statistically significantly raised plasma concentrations of VEGF and TGF-beta1 but there was no correlation with specific clinicopathological features. Increased VEGF, TGF-beta1 and ALK1 immunostaining was seen in all 13 investigated patients. beta-smooth muscle actinin immunostaining was increased in 12 patients. Increased endoglin immunostaining was seen in only 9 patients. INTERPRETATION AND CONCLUSIONS: This study provides evidence of the role of VEGF and TGF-beta1 in the pathogenesis of HHT. Plasma concentrations of these two factors may serve as further diagnostic criteria for HHT. For the first time, we report increased TGF-beta1 plasma concentrations and increased TGF-beta1 and ALK1 tissue expression in HHT, which appear not to be specifically associated with either endoglin or ALK1 mutations. The data suggest that HHT is an angiogenic disorder characterized by an over-expression of VEGF, TGF-beta1 and ALK1.

Activin Receptors↗

PubMed2005

In-vitro analysis of the expression of TGFbeta -superfamily-members during chondrogenic differentiation of mesenchymal stem cells and chondrocytes during dedifferentiation in cell culture.

Traditional surgical methods for the reconstruction of cartilage defects rely on the transplantation of autologous and allogenous tissues. The disadvantages of these techniques are the limited availability of suitable tissues and the donor site morbidity of transplants. In addition, in cultured chondrocytes, the dedifferentiation of cells seems unavoidable during multiplication. In this study, we investigated the expression of distinct markers during the dedifferentiation of human chondrocytes (HC) and human mesenchymal stem cells (MSC) in cell culture using microarray technique, immunohistochemistry and RT-PCR. Transforming growth factor beta (TGFbeta) is a multifunctional peptide that plays play a crucial role in inducing and maintaining chondrogenic differentiation. In dedifferentiating chondrocytes, the gene for TGFbeta1 was constantly expressed, while the gene for TGFbeta2 was never expressed. The genes for TGFalpha, TGFbeta4 and TGFbetai were activated with ongoing dedifferentiation. TGFbeta-receptor 3 was constantly expressed, while the genes for the TGFbeta-receptors 1 and 2 were never expressed. Immunohistochemical staining for TGFbeta beta 3 revealed upregulation in the course of dedifferentiation. The genes for LTBP1 and LTBP2 were activated with ongoing dedifferentiation, whereas the gene for LTBP3 was constantly expressed, and negative results were obtained for the gene for LTBP4. The genes for LTBP1 and LTBP2 were activated with ongoing dedifferentiation. During chondrogenic differentiation, the MSCs constantly expressed TGFbeta1, beta2, beta3 and beta4. LTBP1, LTBP2 and TGFbeta-R3 were downregulated. In conclusion, TGFbeta3, TGFbeta4, TGFbetai, LTBP1 and LTBP2 may assist the process of dedifferentiation, while TGFbeta1 and beta2 might not be involved in this process. Of the TGFbeta-receptors, only type 3 might be involved in dedifferentiation.

Cell Differentiation↗

PubMed2005

Human chondrocytes differentially express matrix modulators during in vitro expansion for tissue engineering.

Cartilage tissue engineering plays an important role in the generation of grafts for reconstructive surgery. In cultured chondrocytes, the dedifferentiation of cells seems unavoidable for multiplication. Dedifferentiated cells produce matrix of less quality, and the molecular basis is still not well understood. Therefore, the aim of our study was to investigate the expression of matrix modulators in human chondrocytes during expansion. Human chondrocytes were isolated from septal cartilage (n=32) and held in primary cell culture. Cells were harvested after 1, 6 and 21 days. The differentiation of cells using light microscopy, the expression patterns of various proteins (MMPs, BMPs, and TIMPs) using immunohistochemistry, and the expression of distinct genes using microarray technique, were investigated. The chondrocytes showed strong in vitro proliferation. After 6 and 21 days, BMP-5 and -8 were up-regulated, BMP-2 was down-regulated and BMP-6 was inactivated. Other BMPs were not expressed. The expression of MMP-2, -3 and -13 was up-regulated from day 1 to 21, and MMP-12 and -20 were down-regulated. Other MMPs were not expressed. TIMP-1 was up-regulated and TIMP-3 was down-regulated during expansion. Differential expression of matrix modulators might influence the matrix composition of engineered cartilage. Improving the basic knowledge in this area may ultimately help clinicians to identify and proactively intervene in an attempt to prevent bioartificial cartilage from losing stability.

Bone Morphogenetic Protein 2↗

PubMed2005

Dual FISH analysis of benign and malignant tumors of the salivary glands and paranasal sinuses.

To date, the underlying genomic changes in benign and malignant tumors of salivary-gland and paranasal-sinus origin are poorly understood. This is due in part to the low incidence of these tumors and the enormous histological variety of tumors within this head and neck region. We examined 58 of these tumors (14 adenoid cystic carcinomas, 9 adenocarcinomas, 5 cylindrical carcinomas, 11 pleomorphic adenomas, and 19 inverted papillomas) by dual fluorescence in situ hybridization (FISH) with centromere-specific probes on six chromosomes (3, 7, 9, 11, 17, and 18) for numerical changes. In adenoid cystic carcinomas, monosomy of chromosome 17 and polysomy of chromosomes 3, 9 and 11 were most frequently encountered. In adenocarcinomas, monosomy of chromosome 17 and polysomy of chromosomes 7 and 11 were most frequent. In cylindrical cell carcinomas, polysomy of chromosomes 7, 9, 11 and 17 was present in the majority of tumors. Disomy is rare, even in benign tumors. Polysomy is more frequent in malignant tumors than in benign. Tetrasomy is found almost only in malignant tumors. In summary, the occurrence of polysomy might reflect a step towards malignancy in tumors of the salivary glands and paranasal mucosa. Polysomy of chromosome 11 could be defined as typical for all investigated histological types of malignant tumor in this region of the head and neck.

Adenocarcinoma↗

PubMed2004

Co-expression of different angiogenic factors in external auditory canal cholesteatoma.

OBJECTIVE: Although external auditory canal cholesteatoma (EACC) was first described in 1850, its cause remains surprisingly unclear. Angiogenesis, the formation of new blood vessels, is essential to normal development and wound healing in adults. Abnormal regulation of angiogenesis has been implicated in the pathogenesis of several disorders. The aim of this study was to analyse angiogenesis regulator expression in EACC. MATERIALS AND METHODS: Cryostat sections of 13 investigated EACC tissue samples and normal control tissue were immunostained for angiogenic hepatocyte growth factor (HGF)/scatter factor (SF), its c-Met receptor and vascular endothelial growth factor (VEGF) using a standard streptavidin-biotin complex procedure. Staining against von Willebrand factor (vWF) served as an endothelial marker. Statistical analysis was performed semiquantitatively. RESULTS: The assayed angiogenic factors were all present in the EACC tissue, and partly overexpressed. vWF was detected in the apical layers of the matrix epithelium. Positive immunoreactivity for c-Met and VEGF was detectable in all layers of the EACC epithelium; however, adjacent tissue did not express c-Met and VEGE. HGF/SF was predominantly expressed in the adjacent perimatrix tissue and fibroblasts in particular were stained positive. CONCLUSIONS: The presence of vWF in the apical part of the matrix depicted the attempt at angiogenesis in this part of the EACC. The detection of VEGF and c-Met in the epithelial part of the EACC implied that their origin may be epithelial, while HGF/SF may be secreted or stored in the adjacent mesenchymal EACC tissue. The angiogenic factors investigated seem to play an important role in establishing that EACC occurs by modulation of angiogenesis.

Adult↗

PubMed2004

Intratumoral genomic heterogeneity in primary head and neck cancer and corresponding metastases detected by dual-FISH.

Intratumoral genomic heterogeneity, which can be defined as both intersample and intrasample heterogeneity, is still a poorly understood phenomenon in head and neck squamous cell carcinoma (HNSCC) with presumed implications on tumor behavior and even prognosis. We analyzed 89 tumor specimen from 37 HNSCC patients by fluorescence in situ hybridization (dual-FISH) using specific DNA probes binding to centromeric sites of 6 chromosomes to investigate intratumoral heterogeneity. A derivation from disomy in at least 1/6 chromosomes was detected in 88/89 (99%) specimen. In 33% of these samples, a change in ploidy could be suspected. Intrasample heterogeneity was detected in 68/89 (76%). Intrasample heterogeneity was more pronounced in primary tumors than in metastatic tumors. Analysis of the intersample heterogeneity revealed notable differences between the 6 chromosomes with the highest discordance detected for chromosome 3 (46%) and the lowest for chromosome 11 (27%). Following our results, it seems important to us to underline that intratumoral heterogeneity exists as intra- and sample heterogeneity in HNSCC. Altogether, trisomic cells were significantly more frequent in primary tumors than in metastases (p=0.01) while, in turn, monosomic cells were significantly more frequent in metastases (p=0.029). In individual cases the extent of discordance between corresponding samples made a common clonal precursor unlikely. In these cases, the synchronous development of a primary tumor and a carcinoma of unknown primary ('CUP syndrome'), otherwise undetected, should be considered.

Aged↗

PubMed2004

Expression of IL-18 in patients with head and neck squamous cell carcinoma.

Interleukin-18 (IL-18), a recently described cytokine secreted mainly by macrophages, stimulates interferon-gamma (IFN-gamma) production by natural killer cells and T cells. The purpose of this study was to determine tissue expression and serum levels of IL-18 in head and neck squamous cell carcinoma (HNSCC) and to evaluate ethanol and endotoxin-driven cytokine secretion. In 24 patients with primary HNSCC and 28 healthy controls, PBMC were isolated and incubated with 50 mM ethanol, LPS (doses 25 ng/ml, 250 ng/ml, 2500 ng/ml) and both agents for 24 h. Levels of IL-18 in serum, and cell supernatants were analysed by capture ELISA, IL-18 tissue level by immunoblotting. Serum levels of IL-8, IL-10 and IL-12, IFN-gamma, and endotoxin plasma levels were also determined. Statistical analysis involved Welch t-test and Page's test for trend. The majority of patients with HNSCC had high concentrations of serum IL-18. The level of IL-18 in the sera of these patients had a mean level of 271.7 pg/ml, while the mean IL-18 serum level in healthy controls was 174,0 pg/ml (p<0.001). Levels of IL-10 and IL-12, IFN-gamma were not increased in patients. Endotoxin was not detectable in either group. LPS stimulated dose-dependently IL-18 secretion from PBMC of patients and controls in vitro (p<0.05). Incubation with ethanol alone did not affect basal IL-18 secretion, but ethanol reduced LPS-stimulated IL-18 secretion compared to LPS stimulation alone. The mRNA expression of IL-18 in unstimulated PBMC and the response of PBMC to ethanol and LPS was similar in patients and controls. Our data on elevated serum levels of IL-18 in the majority of HNSCC cancer patients, irrespective of its biological activity, suggest that serum IL-18 might be a candidate for a new marker for HNSCC. The pathways for IL-18 production and its mechanisms of action in patients with HNSCC remain to be determined. Understanding of the immunological pathways might offer new therapeutic options in head and neck cancer in the future.

Carcinoma, Squamous Cell↗

PubMed2004

Tissue engineering with chondrocytes and function of the extracellular matrix (Review).

Tissue engineering represents a promising method for the construction of autologous chondrogenic grafts for reconstructive surgery. The destruction or malformation of organs such as nasal cartilage, pinna and trachea in otorhinology-head and neck surgery can be caused by both: primary disease or treatment modalities. A large part of modern medical practice is aimed to repair, replace, maintain or enhance the function of damaged or diseased tissues and organs. Replacement or repair is by either artificial implants or transplantation of tissues. Such interventions are hindered by factors such as rejection by the immune system, limited blood supply or morbidity of the donor site. Reconstruction of an injured face using plastic surgery is a prime example of when the limitations of materials, science and reconstructive techniques become apparent. This review aims to briefly outline the use of chondrocytes for tissue engineering with special regard to the function of the extracellular matrix for the signalling between the chondrocytes.

Animals↗

PubMed2004

Targeting TGF-beta in human keratinocytes and its potential role in wound healing.

The pathology of chronic dermal ulcers is characterized by excessive proteolytic activity which degrades extracellular matrix (required for cell migration) and growth factors and their receptors. The transforming growth factor-beta (TGF-beta) has been identified as an important component of wound healing. Recent developments in molecular therapy offer exciting prospects for the modulation of wound healing, specifically those targeting TGF-beta. We investigated expression of angiogenic bFGF and VEGF, and collagenases MMP-2 and MMP-9 in tissue samples from chronic dermal wounds by immunohistochemistry. The effect of TGF-beta targeting using antisense oligonucleotides on the expression of these factors was analysed by ELISA in human keratinocytes. Immunohistochemical investigation demonstrated a decreased expression of bFGF and VEGF protein, and an increased expression of MMP-2 and MMP-9 in tissue samples from chronic dermal wounds compared to normal human skin. Antisense TGF-beta oligonucleotide treatment down-regulated collagenase secretion activity and up-regulated VEGF secretion in vitro. Therefore, TGF-beta antisense oligonucleotide technology may be a potential therapeutic option for the inhibition of proteolytic tissue destruction, and stimulation of angiogenesis in chronic wounds. Improving basic knowledge and pharmaceutical intervention in this area ultimately may help clinicians to identify and proactively intervene in an effort to prevent normal wounds from becoming chronic.

Cell Line↗

PubMed2004

Expression of collagen and fiber-associated proteins in human septal cartilage during in vitro dedifferentiation.

Chondrocytes surrounded by extracellular matrix are responsible for the maintenance of the cartilage as a functional entity. It is well accepted that chondrocytes cultivated for tissue engineering dedifferentiate in cell culture. We characterized the expression of different collagens and collagen related proteins in differentiated (primary) and cultured nasal chondrocytes by using microarray gene expression analysis and immunohistochemical staining. The genes for collagen subunits 1alpha1 (Col1alpha1) and 1alpha2 (Col1alpha2) were activated during a cell culture period of 5 and 20 days whereas Col2alpha1 could be detected both in differentiated and dedifferentiated chondrocytes. The long-term cell culture revealed a late activation of the Col3alpha1, Col4alpha1 and Col11alpha1 genes as well as biglycan, fibromodulin and lumican. In addition, short- and long-term cell culture resulted in down-regulation of Col9alpha1, Col9alpha2, Col9alpha3, Col10alpha1, Col18alpha1, ColQ and chondroadherin. The decorin gene showed up-regulation in short-term cell culture, but down-regulation in long-term culture. Immunohistochemical staining of the different cell populations confirmed the mRNA data for collagen type 1, 2, 3, 4, 9alpha2, 9alpha3, 18 and decorin. Because of their up-regulation in cultured chrondrocytes the collagen types 1, 3, 4 and 11 as well as biglycan, fibromodulin and lumican may be markers for dedifferentiation. The collagen types 9, 18 and Q as well as decorin and chondro-adherin revealed down-regulation and, presumably, represent markers for the differentiation of chondrocytes.

Biglycan↗

PubMed2003

Expression of beta-catenin in external auditory canal cholesteatoma (EACC).

External auditory canal cholesteatoma (EACC) is a chronic inflammation of the external auditory canal and is composed of hyperproliferative epithelium. The upward migration of the epithelial cells requires permanent breakdown and reformation of intercellular connection. This is established by the modulation of the adherent junctions consisting of an E-Cadherin-beta-catenin complex. Dissociated beta-catenin intranuclearly enables persistent activation of downstream transcription and growth factors and decreases the integrity of tissue. In our study we examined EACC and normal meatal auditory skin taken from 16 patients between 23 and 74 years of age. Immunostaining for beta-catenin was used for semiquantitative description of the specimens after assessing hematoxylin-eosin-stained slides. beta-catenin was expressed in all layers of AMS-epithelium, whereas in EACC only basal layer of the matrix epithelium showed positive immunostaining for beta-catenin. In the suprabasal layer of the epithelium only faint reactivity was detectable. The immunostaining was restricted to the membrane of the cells. We assumed that either the content of membranous beta-catenin was decreased or beta-catenin was changed due to molecular modification. It is known that stimulation of endothelial cells by certain growth factors, beta-catenin is maximally phosphorylated. In regard to the increased loss of immunoreactivity for beta-catenin in the suprabasal layers of the hyperplastic EACC-matrix, we assumed bio-molecular modification or loss of beta-catenin decreasing the cell-cell-integrity. Furthermore, this might result in desquamation of keratinocytes and accumulation of dead keratin debrids. In sum, this study should be understood as a descriptive analysis of beta-catenin expression in EACC.

Adult↗

PubMed2003

Chronic interstitial lung disease with lung fibrosis in a girl: uncommon sequelae of Epstein-Barr virus infection.

A 12-month-old immunocompetent girl presented with tachypnea, inspiratory crackles, mild hypoxemia, and failure to thrive after an acute Epstein-Barr virus (EBV) infection. The course of acute EBV infection was demonstrated by viral load measurement in plasma and peripheral blood mononuclear cells (PBMC) by using real-time polymerase chain reaction (PCR). EBV DNA was further detected by PCR in bronchoalveolar lavage (BAL) fluid and from a lung-tissue specimen obtained by open-lung biopsy, which indicates the pulmonary involvement of active EBV infection. Histology revealed an uncharacteristic interstitial infiltration and fibrosis. Following topic and systemic treatment with corticosteroids, the child became asymptomatic and showed normal weight gain as well as mental and physical development. Pulmonary parenchymal involvement during the course of primary EBV infection may result in interstitial lung disease and fibrosis not only in immunodeficient, but in immunocompetent children as well. Treatment with combined inhaled and oral steroids seems to be a treatment option in these patients.

Antibodies, Viral↗

PubMed2003

Establishment of age-dependent reference values for IgA subclasses.

BACKGROUND: Recently, subclass-specific antisera have been introduced for application in a nephelometric assay. The aim of this study was to establish age-dependent reference values for serum concentrations of the two IgA subclasses in children and adults. METHODS: Serum levels of IgA1 and IgA2 were measured by automated immunonephelometry in samples from 235 clinically healthy children between 6 months and 18 years of age and 36 healthy adults. RESULTS: Both IgA1 and IgA2 were detectable in all samples, and both IgA1 and IgA2 increased with increasing age. In adults, the mean value for IgA1 is 1.46 g/l for IgA2 0.21 g/l and for total IgA 1.94 g/l. Individual IgA2 values correlate significantly (p < 0.0001) with IgA1 values (r(2) = 0.5433). In addition, there was a highly significant (p < 0.0001) correlation (r(2) = 0.9530) between the measured total IgA and the sum of the two IgA subclasses indicating that immunonephelometry using highly specific polyclonal antisera might be superior to other methods. CONCLUSIONS: These results and the availability of age-dependent reference values make it worthwhile to reassess the role of IgA subclasses in immunodeficiency and autoimmune diseases where conventional methods have led to conflicting results.

Adult↗

PubMed2003

Relationships and origin of endemic Lake Baikal gastropods (Caenogastropoda: Rissooidea) based on mitochondrial DNA sequences.

The phylogenetic relationships and the origin of two groups of rissooid freshwater snails endemic to Lake Baikal were investigated using partial mitochondrial COI, 12S rDNA, and 16S rDNA sequences. The Baikalian Benedictiinae proved to be closely related to the Lithoglyphinae. According to a molecular clock estimate the two groups diverged in the Paleogene. The Benedictiinae might have evolved autochthonously in precursors of Lake Baikal. The Baikalian Baicaliidae are probably most closely related to the Amnicolidae and the Bithyniidae. These groups diverged at the latest during the Cretaceous. Thus the origin of the Baicaliidae predates the origin of the Baikal rift zone. The Baicaliidae evolved probably in other Central Asian freshwater reservoirs. However, the radiation of the extant Baicaliidae only started in the Neogene and might have occurred autochthonously in Lake Baikal. The conchological similarity of the Baicaliidae and the Pyrgulidae is due to convergence. The Pyrgulidae diverged from the common stem lineage of the other hydrobiid families at the latest in the Jurassic. The Bithyniidae is derived from hydrobiids and is related to the Amnicolidae.

Animals↗