Biomedical subjects

A Baur

Publications and source records attributed to A Baur.

At least 37 records · Page 2Linked to original sources

PubMed2000

Dynamic contrast-enhanced MR angiography from the distal aorta to the ankle joint with a step-by-step technique.

OBJECTIVE: The aim of this study was to visualize the arteries from the distal aorta to the ankle joint and to determine the accuracy of MR angiography for detecting stenoses and occlusions. SUBJECTS AND METHODS: Twenty-four patients with peripheral arterial occlusive disease underwent digital subtraction angiography and were examined on a 1.5-T MR scanner. The transit time for contrast material was determined with a test bolus injection. A T1-weighted three-dimensional gradient-echo sequence with short TR and TE was used for a dynamic measurement at the level of the iliac arteries, the upper leg, and the lower leg arteries. For each level a single dose of gadolinium was injected into an antecubital vein with an MR power injector. Maximal-intensity-projection reconstructions were calculated after subtraction of the first measurement at each level. Two experienced MR radiologists who were unaware of the digital subtraction angiography results interactively evaluated both the MIP reconstructions and the single slices on a workstation, first independently and then in a consensus interpretation. RESULTS: With digital subtraction angiography, 80 hemodynamically significant stenoses and 39 occlusions were detected. For the stenoses and occlusions, a sensitivity of 100% was found for MR angiography. The specificity for the assessment of stenoses and occlusions was 98% and 94%, respectively, for the iliac arteries; 98% and 94%, respectively, for the upper leg arteries; and 94% and 95%, respectively, for the lower leg arteries. Most false-positive findings of occlusion were due to metal stents present in the iliac (n = 3) and upper leg (n = 4) arteries. CONCLUSION: The MR imaging technique that we used revealed the arteries from the distal aorta to the ankle and proved to be reliable at showing arterial stenoses and occlusions.

Aged↗

PubMed1999

[MRI-controlled regional hyperthermia].

PURPOSE: Regional hyperthermia in combination with chemotherapy or/and radiotherapy is a promising treatment concept for locally advanced, deep-seated tumors. The purpose of the project is the optimization of the therapy using non-invasive, three-dimensional imaging of tissue changes or of the temperature distribution during regional hyperthermia. METHODS: MRI offers methods suitable in principle for tissue characterization and MR thermometry. A new MRI-hyperthermia hybrid system has been developed based on an innovative hyperthermia applicator and an open MRI system. RESULTS: After successful testing of the new MRI-hyperthermia hybrid system simultaneous MRI and regional hyperthermia in patients could be accomplished for the first time. At present the T1 relaxation time seems to be a promising parameter for MR thermometry. CONCLUSION: The first clinical application of the MRI-hyperthermia hybrid system can be regarded as an important step towards the development of regional hyperthermia. This new hybrid system and the MR thermometry methods have to be investigated prospectively in clinical studies.

Equipment Design↗

PubMed1999

Cloning of the mistletoe lectin gene and characterization of the recombinant A-chain.

Mistletoe lectin I (MLI) is the major active constituent of mistletoe extracts, which are widely used for adjuvant tumour therapy. The 66-kDa heterodimeric disulphide-linked glycoprotein is classified as type II ribosome-inactivating protein (RIP) due to the rRNA-cleaving enzyme activity of the A-subunit, also referred to as toxic entity. MLI and the close relative ricin both belong to the family of the two-chain plant type II RIP proteins. Isolation of the glycosylated proteins from plant material yield inhomogeneous material probably due to post-translational modifications. The aim of this study was to prepare pure and homogeneous protein as a prerequisite for structural and mechanistic studies in order to gain insight into the mode of action of this cytotoxic plant protein on tumour and immune cells. Of particular interest was to explain whether the differences in toxicity of ML and ricin are the result of variations of their enzymatic activities. By investigating the sequence homologies between the active sites of different RIPs we were able to deduce a set of primers which were suitable for specific amplification of the mistletoe lectin gene. Applying this PCR strategy the full-length 1923 nucleotide DNA sequence coding for the prepro-protein was obtained showing the existence of a single intron-free gene. In order to elucidate the molecular basis for the observed differences in cytotoxicity within the family of RIP the enzymatic A-subunit was expressed in a heterologous system. Expression of the A-chain in E. coli BL21/pT7 resulted in production of insoluble inclusion bodies constituting 20-30% of total protein. Refolding led to a pure and homogeneous protein species with an apparent molecular mass of 27 kDa and a pI value of 6.4. The ribosome-inactivating activity of the unglycosylated recombinant A-chain (IC50 20.5 pM) protein was in the same range as that of the glycosylated plant-derived ML A-chain (IC50 3.7 pM), which was very similar to that of ricin A-chain (IC50 4.9 pM). Thus, the higher cytotoxicity of ricin cannot be accountable for differences in the enzymatic activities of the type II RIP A-chains.

Amino Acid Sequence↗

PubMed1999

Phenol as an adjuvant for local control in the treatment of giant cell tumour of the bone.

AIMS: Intralesional treatment of giant cell tumour (GCT) of the bone may result in a high rate of local recurrence. The introduction of local adjuvant therapy, such as cementation or phenolization, has lead to a significant reduction in recurrence rates. Due to the combined use of phenol and cementation in most studies, the effect of phenol alone is described in this study. METHODS: Twenty primary and nine recurrent surgical procedures in 26 patients with GCT of the bone with a median follow-up of 61 months were reviewed retrospectively. The mean age was 33.5 years (range 13.5-76.5 years). Eighteen curettages and 11 resections were performed. For the curettages, a large bone window was cut followed by high speed burring and bone graft reconstruction. In 11 of 18 curettages and three of 12 resections, phenol was additionally applied. RESULTS: Four patients showed pulmonary metastasis. Three of these four cases also experienced local recurrences. Three patients died due to metastatic disease. In total, five patients developed local recurrence (17.2%); three in the first 2 years and one after 4 years. Four of 18 curettages recurred (22.2%), compared to one of 11 resections (9.1%). Only one of 11 patients (9.1%) treated with curettage and adjuvant phenol recurred, whereas three of seven patients (42.9%) treated with curettage alone recurred. CONCLUSION: Phenolization is an effective and safe local adjuvant therapy for GCT. We did not observe any significant differences in recurrence rates for curettage, phenolization and bone grafting compared to most published results using cryosurgery or cementation alone. We recommend adjuvant phenolization in the treatment of GCT of the bone after careful curettage in applicable cases, regardless of whether additional cementation is used.

Adolescent↗

PubMed1999

Type 1 deiodinase is stimulated by iodothyronines and involved in thyroid hormone metabolism in human somatomammotroph GX cells.

BACKGROUND: Local 5'-deiOdination of l-thyroxine (T4) to the active thyroid hormone, 3,3',5-tri-iodothyronine (T3) via two deiodinase isoenzymes (D1 and D2) has an important role for various T3-dependent functions in the anterior pituitary. However, no evidence has been presented yet for thyroid hormone inactivation via the 5-deiodinase (D3) in anterior pituitary models. METHODS: Using the human somatomammotroph cell line, GX, we analysed effects of T3 and its 5'-deiodination product, 3,5-di-iodothyronine (3,5-T2), on deiodinase activities, measuring release of iodide-125 (125I-) from phenolic-ring- or tyrosyl-ring-labelled substrates respectively. RESULTS: T3 and 3,5-T2 rapidly stimulated D1 activity in GX cells in the presence of serum in the culture medium, whereas D2 activity was not detectable under these conditions. However, when the cells were kept under serum-free conditions, specific activity of D2 reached levels similar to those of D1. With tyrosyl-ring labelled 3, 5-[125I]-,3'-T3 as substrate, a significant release of 125I- was observed in GX cell homogenates. This is comparable to the D1 activity of liver membranes, which preferentially catalyses 5'-deiodination, but to some extent also 5-deiodination, at the tyrosyl ring. CONCLUSIONS: D1 activity of human GX cells is increased by T3 and 3,5-T2. Inactivation of T3 in the anterior pituitary might occur by deiodination at the tyrosyl ring via D1, thus terminating the stimulatory thyroid hormone signal in human somatomammotroph cells.

Animals↗

PubMed1999

Surgical treatment of osseous metastases in patients with renal cell carcinoma.

Forty-five patients who underwent surgical treatment for osseous metastases secondary to renal cell carcinoma between 1980 and 1998 were reviewed. The diagnosis was confirmed histologically in all patients. The mean age of the 34 men was 61.5 +/- 9 years and of the 11 women 55.2 +/- 17.6 years. The most common locations of the metastases were the spine (15 patients), the pelvis (eight patients), and the femur (11 patients). In 21 patients, the renal cell carcinoma was diagnosed when the osseous metastasis was detected. The time from diagnosis of the primary tumor to metastasis in the remaining patients ranged from 0 to 23 years (mean, 3 +/- 5 years). At presentation, 19 patients had a singular lesion. Nine patients had multiple osseous metastases and 17 patients had additional visceral involvement. In seven patients, a wide or radical resection was done; in 35 patients, a palliative procedure was done; and in three patients, only a diagnostic procedure was done. For the whole group, the survival was 49% after 1 year, 39% after 2 years, and 15% after 5 years. Only the extent of the disease and the latency period between primary tumor diagnosis and first detection of osseous metastasis could be identified as independent factors of survival. Nine patients with solitary metastasis to the bone more than 12 months after resection of the primary tumor showed a 5-year survival of 54%.

Adult↗

PubMed1998

Selenoproteins are expressed in fetal human osteoblast-like cells.

Selenoproteins are involved in mechanisms of cell differentiation and defense. We investigated the expression of glutathione peroxidases, as well as other selenoproteins, in fetal human osteoblasts (hFOB-cells). Using 75-selenium metabolic labelling of viable hFOB-cells, we identified several selenoproteins in cell lysates of about 45-80 kDa and in the migration range of 14 kDa to 24 kDa. Cells expressed low mRNA levels of both cellular glutathione peroxidase and plasma glutathione peroxidase mRNA as analysed by Southern analysis of RT-PCR products. Basal cellular glutathione peroxidase enzyme activity in hFOB-cells (19.7 nmol NADPH oxidised per min and microg protein) was further increased 2.5-fold by the addition of 100 nM sodium selenite to the culture medium for 3 days. Furthermore, expression of selenoprotein P mRNA was demonstrated by RT-PCR. hFOB-cells did not show activities of the selenoproteins type I or type II 5'-deiodinase. In summary, we identified cellular glutathione peroxidase, plasma glutathione peroxidase and selenoprotein P among of a panel of several 75-selenium labelled proteins in human fetal osteoblasts. The expression of selenoproteins like glutathione peroxidases in hFOB-cells represents a new system of osteoblast antioxidative defense that may be relevant for the protection against hydrogen peroxide produced by osteoclasts during bone remodelling.

Antioxidants↗

PubMed1998

Sperm allocation in the simultaneously hermaphroditic land snail Arianta arbustorum.

To test the idea that individuals of the simultaneously hermaphroditic land snail Arianta arbustorum can control the number of spermatozoa in their spermatophores, we investigated whether they differentially release sperm to virgin or nonvirgin partners with respect to the potential risk of sperm competition in a given mating. The number of sperm transferred ranged from 802 620 to 3 968 800 (X= 2 185 100; N=91), but was related neither to the mating history of the partner nor to copulation duration. This indicates that individuals of A. arbustorum are not able to adjust sperm expenditure to the mating history of the partner. Furthermore, the number of sperm transferred was correlated neither with the size of the donor nor with the size of the recipient. It has been proposed that the sexual conflict between the two genders in simultaneous hermaphrodites could be resolved by gamete trading. Theory predicts that sperm trading should occur in hermaphrodites in which the female role controls fertilization, for example in gastropods with a gametolytic gland and/or sperm storage such as A. arbustorum. To see whether sperm trading occurs, we also examined whether individuals of A. arbustorum adjust the number of sperm they release to the number they receive from their mating partner. There was a high degree of reciprocity in spermatophore transfer: in 45 of the 46 mating pairs investigated both partners delivered a spermatophore that contained spermatozoa. The numbers of sperm transferred by the two mating partners were not correlated, however. This indicates that sperm trading does not occur in this simultaneously hermaphroditic land snail. Copyright 1998 The Association for the Study of Animal Behaviour.

Journal Article↗

PubMed1998

Light chain deposition disease in multiple myeloma: MR imaging features correlated with histopathological findings.

The clinical, histopathological, and imaging findings on MRI of a 56-year-old woman with light chain deposition disease occurring in multiple myeloma are presented. Light chain deposition disease is a variant of multiple myeloma with distinct clinical and histological characteristics. MRI of this patient also revealed an infiltration pattern in the bone marrow distinct from that of typical multiple myeloma. Multiple small foci of low signal intensity were present on T1- and T2-weighted spin echo and STIR images, corresponding to conglomerates of light chains in bone marrow biopsy. Contrast-enhanced T1-weighted spin echo images show diffuse enhancement of 51% over all vertebral bodies, with a minor enhancement of the focal conglomerates of light chains. Light chain deposition disease in multiple myeloma should be added to the list of those few entities with normal radiographs and discrete low-signal marrow lesions on T1- and T2-weighted spin echo pulse sequences.

Bone Marrow↗

PubMed1998

[Magnetic resonance tomography in plasmacytoma: ranking of various sequences in diffuse and focal infiltration patterns].

PURPOSE: The aim of this study was to compare various pulse-sequences employing the spine array coil while considering the different infiltration patterns in multiple myeloma, in order to develop a fast and cost effective screening method. MATERIALS AND METHODS: In a prospective study, 50 patients with histologically proven multiple myeloma were examined with the following standardised sequences: T1-weighted SE, T2-weighted FSE, opposed phase GRE, FSE STIR, T1-weighted SE post gadopentate dimeglumine without and with fat saturation. The images were evaluated in a ROC analysis by three radiologists in consensus with a 5-grade scale separatively for diffuse and focal involvement. The gold standard was bone marrow histology in cases of diffuse infiltration and the combination of all sequences with the staging system according to Durie and Salmon. RESULTS: For focal bone marrow involvement the area under curve was greatest for FSE STIR sequences, in cases of diffuse infiltration the area under curve was superior for unenhanced T1-w SE-Sequenz images. The sensitivity can be increased by contrast material application and signal intensity measurements. A combined focal and diffuse infiltration and a "salt and pepper" pattern can be diagnosed with the combination of T1-w SE-Sequenz and FSE STIR sequences. CONCLUSION: With T1-weighted SE-Sequenz sequences pre- and post-contrast and FSE STIR all therapeutical relevant infiltration patterns of plasmocytoma can be identified and bone marrow screening of the spine can be carried out with an acquisition time of 5.58 minutes.

Adult↗

PubMed1998

[Differential diagnosis of erosive osteochondrosis and bacterial spondylitis: magnetic resonance tomography (MRT)].

PURPOSE: To evaluate retrospectively criteria in the differential diagnosis of erosive osteochondrosis (EO) and infectious spondylitis (IS) on the basis of MRI. METHODS: T1-weighted sagittal images before and after Gd-DTPA application, T2-weighted TSE or T-STIR images of 23 patients with proven 15 and 41 patients with EO were evaluated. Criteria for this evaluation were morphology and extension of bone marrow edema, visibility of the low-intensity vertebral endplate, contrast enhancement and signal intensity in the disc space on T2-weighted and T-STIR images. RESULTS: Bone marrow edema was more extensive in IS than in EO. The mean rated value for bone marrow edema on a four-level scale (0-3) was for IS 2.91 (+/- 0.29), for EO 1.32 (+/- 0.76, p < 0.001). In 37/41 cases of EO and in 22/23 cases of IS Gd-DTPA enhancement was found in the disc space (n.s.). In EO the low intensity endplate was visible in all parts in 36/41 cases (87.8%) on T1-weighted images, in IS not in a single case (0%). On T2-weighted or STIR images signal intensity of the discs was decreased in 82.1% of EO, 82.6% of segments in IS had water-equivalent signal intensity (p < 0.001). CONCLUSION: If all the criteria are taken into consideration differential diagnosis of EO and IS on the basis of MRI findings is possible.

Adult↗

PubMed1998

[Penetrating aortic ulceration: an unusual form of aortic dissection].

PURPOSE: The aim was to present clinical findings and imaging criteria for patients with aortic ulcers of the thoracic aorta. METHODS: From 1993 to 1996 computed tomography of patients suffering from acute thoracic pain and suspected pathologies of the aorta were reviewed for penetrating aortic ulcers. Pathoanatomical correlation was done by autopsy in three cases and with intraoperative inspection in two cases. MRI was available in three patients and angiography in 5 patients. RESULTS: 9 patients with aortic ulcers could be identified. The imaging criteria in CT were: 1. Hyperdense wall thickening on unenhanced CT scans (medial haematoma). 2. Displaced intimal calcifications outlining the lumen. 3. Small contrast-filled ulcer. 4. Absence of a contrast-filled false lumen. In 4 of the 9 cases the aorta ascendens was affected. The clinical presentation is that of an elderly patient with acute onset of thoracic pain and generalised atherosclerosis due to hypertension and nicotine abuse. DISCUSSION: Penetrating ulcers with haematoma of the media are a special case of aortic dissection, with different features on unenhanced and enhanced CT scans.

Aged↗

PubMed1998

Diffusion-weighted MR imaging of bone marrow: differentiation of benign versus pathologic compression fractures.

PURPOSE: To evaluate the usefulness of diffusion-weighted magnetic resonance (MR) imaging of bone marrow for differentiating between benign and pathologic vertebral compression fractures. MATERIALS AND METHODS: Thirty patients with 39 vertebral compression fractures were examined with MR imaging. Diffusion-weighted MR imaging was performed with a steady-state free precession sequence in 22 acute benign osteoporotic and/or traumatic fractures and 17 pathologic compression fractures. Biplanar radiographs, T1-weighted spin-echo (SE) MR images, and short inversion time inversion-recovery (STIR) MR images were available for all patients. The signal intensity characteristics were analyzed qualitatively and quantitatively (bone marrow contrast ratios and signal-to-noise ratios) for all sequences. RESULTS: At diffusion-weighted MR imaging, all benign vertebral compression fractures were hypo- to isointense to adjacent normal vertebral bodies. Pathologic compression fractures were hyperintense to normal vertebral bodies. Benign vertebral fractures had negative bone marrow contrast ratios at diffusion-weighted imaging, whereas pathologic vertebral fractures had positive values (P < .001). The difference in bone marrow contrast ratios for benign and pathologic compression fractures at T1-weighted SE and STIR imaging was not significant (P > .01). CONCLUSION: Diffusion-weighted MR imaging provided excellent distinction between pathologic and benign vertebral compression fractures.

Adult↗

PubMed1997

MRI gadolinium enhancement of bone marrow: age-related changes in normals and in diffuse neoplastic infiltration.

OBJECTIVE: To quantify gadolinium-related enhancement in the bone marrow of the spine in normals and in patients with homogeneous diffuse malignant bone marrow infiltration. DESIGN AND PATIENTS: The patients consisted of two groups: group 1 comprised 94 healthy adults (18-86 years) without bone marrow disease and group 2 comprised 30 patients with homogeneous diffuse malignant bone marrow infiltration due to myeloma (n = 20) or breast carcinoma (n = 10). All patients received intravenous gadopentetate dimeglumine (Gd-DTPA), 0.1 mmol/kg body weight. Pre- and postcontrast signal intensity (SI) on T1-weighted spin-echo (SE) images (TR/TE: 572 ms/15 ms) was measured over a region of interest (ROI) and the percentage SI increase was calculated. The results were confirmed by bone marrow biopsy (n = 20) and clinical parameters (n = 10). Dynamic contrast-enhanced studies using a spoiled gradient-recalled-echo (GRE) sequence (TR/TE/alpha: 68 ms/6 ms 75 degrees) were performed in 10 controls with normal bone marrow. RESULTS AND CONCLUSION: Contrast material enhancement in healthy persons can vary greatly (range 3-59%, mean 21%, SD 11%). With increasing age there is a significant decrease in contrast enhancement (Pearson's correlation, P < 0.01). The percentage SI increase in patients with intermediate-grade (biopsy 20-50 vol%) and high-grade (biopsy > 50 vol%) diffuse malignant bone marrow infiltration was significantly higher than in normals (mean 67%, SD 34%, P < 0.001). Low-grade (biopsy < 20 vol%) diffuse malignant bone marrow infiltration can not be assessed by non-enhanced T1-weighted SE images or Gd-DTPA application. In conclusion, contrast material enhancement in healthy persons can vary greatly and is dependent on age, while intermediate-grade and high-grade diffuse malignant bone marrow infiltration can be objectively assessed with SI measurements.

Adolescent↗

PubMed1997

Imaging findings in patients with ventral dural defects and herniation of neural tissue.

The aim of this paper is to describe clinical and imaging findings in three patients with ventral dural defects and herniation of the spinal cord or cauda equina. The literature is reviewed and the clinical, radiological and operative findings are compared. Three patients with ventral dural defects of different etiologies are presented. One patient gave a longstanding history of ankylosing spondylitis, the second patient presents 37 years after spinal trauma, and the third patient presents with spontaneous spinal cord herniation. All patients had typically slowly progressive neurological symptoms with multiple hospitalizations until diagnosis was made. Characteristic findings in postmyelographic CT included a ventral or ventrolateral displacement with deformation of the spinal cord or the cauda equina. Sagittal MRI showed this abrupt and localized anterior deviation of the spinal cord or the cauda equina to the posterior portions of a vertebral body with or without a bony vertebral defect optimally. Additionally, due to the ventral displacement of the spinal cord, the dorsal subarachnoid space was relatively enlarged without evidence of an arachnoid cyst, in all patients. Magnetic resonance imaging and postmyelographic CT can diagnose ventral dural defects with spinal cord herniation or nerve root entrapment. Dural defects must be considered in the presence of neurological symptoms in cases of longstanding ankylosing spondylitis, late sequelae of fractures of vertebral bodies, and without history of spinal trauma or surgery.

Aged↗

PubMed1997

3,5-diiodo-L-thyronine stimulates type 1 5'deiodinase activity in rat anterior pituitaries in vivo and in reaggregate cultures and GH3 cells in vitro.

Local deiodination of L-thyroxine (T4) to the active thyroid hormone T3 via two 5'deiodinase isoenzymes (5'DI and 5'DII) plays an important role for various T3-dependent functions of the anterior pituitary (AP). Recently, it was reported that 3,5-T2, the 5'deiodination product of T3, acts as a specific agonist in the feedback mechanism on TSH secretion at the pituitary level. We now examined the effects of 3,5-T2 on pituitary 5'deiodinase activities in vivo in male, adult rats and in vitro using rat AP reaggregate cultures and the somatomammotroph cell line GH3. 5'DI activity in the AP was transiently increased after a single injection of 3,5-T2. Serum TSH levels declined, and 24 h after 3,5-T2 application, betaTSH steady-state mRNA levels in the APs were markedly lower. In reaggregate cultures of the AP, 3,5-T2 stimulated 5'DI activity 24 h after application, dose-dependently. Compared with 5'DI activities, those of 5'DII were an order of magnitude lower, in vivo as well as in vitro, and were rapidly and transiently decreased by the higher dose of 3,5-T2. GH3 cells responded to 3,5-T2 and T3 by an 1.7-fold stimulation of 5'DI activity. Stimulation of DNA-binding was demonstrated in electrophoretic mobility shift assays for a specific RXR-containing protein complex with a DR+4 thyroid hormone response element of the human type 1 5'DI promoter using nuclear extracts from GH3 cells treated with 3,5-T2. In summary, 3,5-T2 and T3 exert direct thyromimetic effects on 5'DI activity and TSHbeta expression at the pituitary level. 5'DI is regulated by its substrate(s) and/or products and may serve an important function within the modulation of thyroid hormone-dependent gene expression in the AP.

Analysis of Variance↗

PubMed1996

Complete nucleotide sequence of Saccharomyces cerevisiae chromosome X.

The complete nucleotide sequence of Saccharomyces cerevisiae chromosome X (745 442 bp) reveals a total of 379 open reading frames (ORFs), the coding region covering approximately 75% of the entire sequence. One hundred and eighteen ORFs (31%) correspond to genes previously identified in S. cerevisiae. All other ORFs represent novel putative yeast genes, whose function will have to be determined experimentally. However, 57 of the latter subset (another 15% of the total) encode proteins that show significant analogy to proteins of known function from yeast or other organisms. The remaining ORFs, exhibiting no significant similarity to any known sequence, amount to 54% of the total. General features of chromosome X are also reported, with emphasis on the nucleotide frequency distribution in the environment of the ATG and stop codons, the possible coding capacity of at least some of the small ORFs (<100 codons) and the significance of 46 non-canonical or unpaired nucleotides in the stems of some of the 24 tRNA genes recognized on this chromosome.

Amino Acid Sequence↗

PubMed1996

Transforming growth factor-beta 1 induces alpha-smooth muscle-actin expression in cultured human and monkey trabecular meshwork.

Transforming growth factor-beta 1 (TGF-beta 1) induces alpha-smooth muscle (sm)-actin expression and a contractile myofibroblast-like phenotype in a considerable number of different cell types. Since alpha-sm-actin is expressed in some of the resident human trabecular meshwork (TM) cells in situ, and TGF-beta 1 is synthesized by TM in vitro, alpha-sm-actin expression in TM might also be under the influence of TGF-beta 1. To assess this question, TM cultures were initiated from the eyes of three human donors and three cynomolgus monkeys. Various doses of TGF-beta 1 (0.5-5 ng ml-1) were added to confluent cultures from third to fourth passages. Experiments were performed in the presence of fetal calf serum or under chemically defined serum-free conditions. Four days after treatment, cells were stained immunocytochemically for alpha-sm-actin, and the number of positively labelled cells was quantitatively evaluated. In addition, reverse transcription polymerase chain reaction (PCR) was performed using oligonucleotide primers specific for alpha-sm-actin. In control cultures supplemented with serum, 19.0 +/- 9.4% of human meshwork cells, and 10.2 +/- 4.5% of monkey meshwork cells expressed immunoreactivity for alpha-sm-actin. In human cultures, this number was significantly higher in serum-free conditions (34.1 +/- 7.7%). Treatment with TGF-beta 1 induced alpha-sm-actin expression in a dose-dependent manner. At 5 ng ml-1 TGF-beta 1, 75.5 +/- 7.1% of human meshwork cells expressed distinct stress fibers that stained positively for alpha-sm-actin (P < or = 0.01). A similar albeit smaller increase in alpha-sm-actin positive cells was observed in monkey cultures following treatment with TGF-beta 1. These effects were seen with and without serum, but not when TGF-beta 1 was supplemented in the presence of neutralizing antibodies. In PCR experiments, a distinct product was amplified with cDNA derived from cells treated with 0.1 ng and 1 ng ml-1 TGF-beta 1, but not in control cultures. We conclude that TGF-beta 1 may play a role in differentiating TM cells towards a myofibroblast-like cell type by modulating the expression of alpha-sm-actin.

Actins↗