Showing papers by "Heidelberg University published in 1987"

Sequence and functional expression of the GABA A receptor shows a ligand-gated receptor super-family

Abstract: Amino-acid sequences derived from complementary DMAs encoding the α- and β-subunits of the GAB A/ benzo diazepine receptor from bovine brain show homology with other ligand-gated receptor subunits, suggesting that there is a super-family of ion-channel-containing receptors. Co-expression of the in vitro-generated α-subunit and β-subunit RNAs in Xenopus oocytes produces a functional receptor and ion channel with the pharmacological properties characteristic of the GABAA receptor.

Exclusive non-leptonic decays ofD-,D s - andB-mesons

Abstract: Recent experimental results onD-,Ds- andB-decays are interpreted on the basis of the valence quark model. For nonleptonic decays generally good results are obtained using factorization with little direct annihilation. Final state interaction causes corrections, however: small bare amplitudes can be fed by stronger amplitudes through channel mixing. This effect can simulate or enhance weak annihilation processes in particular if high lying resonances contribute. A comparison of\(D^0 \to \bar K^0 \phi \) withDs→ϱπ decays will clarify this issue. The effective QCD coefficients obtained in the analysis are discussed and used to estimate the contribution of two-body decays to the total widths. The result reflects already the lifetime differences betweenD0 andD+ mesons. Predictions for numerousB-decay branching rations allow for further tests and for a determination of so far unknown decay constants. A first bound on |Vub| from nonleptonic decays is found from the experimental limit on\(\bar B^0 \to \pi ^ + \pi ^ - \).

The strychnine-binding subunit of the glycine receptor shows homology with nicotinic acetylcholine receptors.

Abstract: We have cloned and sequenced cDNAs of the strychnine-binding subunit of the rat glycine receptor, a neurotransmitter-gated chloride channel protein of the CNS. The deduced polypeptide shows significant structural and amino-acid sequence homology with nicotinic acetylcholine receptor proteins, indicating that there is a family of genes encoding neurotransmitter-gated ion channels.

Single-zircon evaporation combined with Pb+ emitter bedding for 207Pb/206Pb-age investigations using thermal ion mass spectrometry, and implications to zirconology

Abstract: The internal precision of Pb isotope analyses using single-zircon evaporation in a double-filament solid source mass spectrometer (Kober 1986) can be improved combining the evaporation of Pb directly from the single grain with a suitable Pb+ emitter-bedding technique. This is most easily done by step-wise evaporating the investigated grain at temperatures of 1700–1800 K generating on the ‘cold’ ionization filament a deposit of radiogenic Pb together with further elements and compounds derived directly from the crystal. The heating of the deposit on the ionization filament to 1400–1500 K results in long-lived and stable Pb+ ion beams. The ‘activating reagents’ in the deposit are HfO2 and SiO2. Their release from the zircon grain together with the radiogenic Pb, which presumably is sited in the crystalline zircon domains as Pb4+, is probably due to disintegration reactions of trace-element silicates hosted in the grain.

One-step and extrapolation methods for differential- algebraic systems

Abstract: The paper analyzes one-step methods for differential-algebraic equations (DAE) in terms of convergence order. In view of extrapolation methods, certain perturbed asymptotic expansions are shown to hold. For the special DAE extrapolation solver based on the semi-implicit Euler discretization, the perturbed order pattern of the extrapolation tableau is derived in detail. The theoretical results lead to modifications of the known code. The efficiency of the modifications is illustrated by numerical comparisons over critical examples mainly from chemical combustion.

Response Effects in Surveys

Abstract: Since the early 1940s, survey interviews have become the dominant method of data collection in empirical social research (Phillips, 1971; Kaase, Ott, & Scheuch, 1983). Despite the popularity of the survey interview, the processes underlying the responses to survey questions are not well understood, and a ”theory of asking questions” (Hyman, 1954) has never been developed. Thus, survey methodology today is characterised by rigorous knowledge about sampling procedures on the one hand, and a surprising lack of knowledge about the ”art” (sicl) of asking questions (e.g., Noelle-Neumann, 1963) on the other hand. Unfortunately, however, empirical research (e.g., Sudman & Bradburn, 1974) suggests that nonsampling error provides considerable limitations to the usefulness of survey data.

Detailed Modeling of PAH Profiles in a Sooting Low-Pressure Acetylene Flame

Abstract: A detailed modeling study of the formation of polycyclic aromatic hydrocarbons in a burner-stabilized low-pressure sooting 23.6 % C2 H2-21.4% 02-Ar flame of Bockhorn and co-workers is reported. The model predicts the correct orders of magnitude and relative appearances of the concentration peaks, but overstates the decline of the species concentrations in the post-flame zone. Imprecise knowledge of the thermochemical data and unknown details of the oxidation of hydrocarbon radicals are the reasons identifed for the latter. The main reaction pathways for cyclization and growth of polycyclic aromatics and the results of the sensitivity tests are in close agreement with those of the previous modeling study of acetylene oxidation under shock-tube conditions. An additional factor that is important in the. flame environment is the diffusion of hydrogen atoms from the main reaction zone into a cooler preflame region

8-Cyclopentyl-1,3-dipropylxanthine (DPCPX)--a selective high affinity antagonist radioligand for A1 adenosine receptors.

Abstract: The properties of 8-cyclopentyl-1,3-dipropylxanthine (DPCPX) as an antagonist ligand for A1 adenosine receptors were examined and compared with other radioligands for this receptor. DPCPX competitively antagonized both the inhibition of adenylate cyclase activity via A1 adenosine receptors and the stimulation via A2 adenosine receptors. The Ki-values of this antagonism were 0.45 nM at the A1 receptor of rat fat cells, and 330 nM at the A2 receptor of human platelets, giving a more than 700-fold A1-selectivity. A similar A1-selectivity was determined in radioligand binding studies. Even at high concentrations, DPCPX did not significantly inhibit the soluble cAMP-phosphodiesterase activity of human platelets. [3H]DPCPX (105 Ci/mmol) bound in a saturable manner with high affinity to A1 receptors in membranes of bovine brain and heart, and rat brain and fat cells (KD-values 50-190 pM). Its nonspecific binding was about 1% of total at KD, except in bovine myocardial membranes (about 10%). Binding studies with bovine myocardial membranes allowed the analysis of both the high and low agonist affinity states of this receptor in a tissue with low receptor density. The binding properties of [3H]DPCPX appear superior to those of other agonist and antagonist radioligands for the A1 receptor.

Contaminated food and uptake of heavy metals by fish: a review and a proposal for further research.

Abstract: 1. The uptake of heavy metals via the alimentary tract can be an important factor for the metal budget of fish. 2. Concepts such as biomagnification, bioaccumulation, biotransference, or concentration factors, convey little information about the real threat originating from heavy metals in an aquatic food chain. 3. In polluted aquatic ecosystems the transfer of metals through food chains can be high enough to bring about harmful concentrations in the tissues of fish. This relationship is called the food chain effect. 4. Two kinds of ecological factors influence the food chain effect: firstly, high levels of contamination of the food, and, secondly, the reduction of species diversity. When susceptible species are eliminated, metal-tolerant food organisms may become dominant. Their tolerance may be based either on their ability to accumulate excessive amounts of metals or to exclude heavy metals from the tissues. These two strategies represent feedback mechanisms which may enhance or weaken the food chain effect. 5. It is concluded that future investigations on transference of heavy metals to fish must take into more careful consideration the specific ecological situation of a given environment.

The current potential of plastination

Abstract: This review surveys the potential of plastination, a technique of tissue preservation introduced eight years ago. In this process, water and lipids in biological tissues are replaced by curable polymer which are subsequently hardened, resulting in dry, odorless and durable specimens. The procedure consists of the following steps-fixation, dehydration, forced impregnation in a vacuum, and hardening. The properties of the finished specimen are determined by the class of polymer used. Silicone yields flexible, resilient speciemens, allows the broadest range of application, and provides satisfactory results with minimum equipment. Specimens plastinated with an epoxy-silicone copolymer are rigid enough to be polished, but are not unbreakable. This resin is used for thick, opaque body slices and showcase specimens. Epoxy resins are used for thin (2.5 mm), transparent body or organ slices. They are cast between polyester foils or glass plates and can be used for histological investigations. Polyester resin is used for the production of opaque brain slices, which gives excellent differentiation between grey and white matter. The application of plastination in research and the production of teaching specimens is discussed with special regard to the equipment required, cost, and feasibility of the processing.

Soccer, rooms, and the quality of your life: Mood effects on judgments of satisfaction with life in general and with specific domains

Abstract: Two studies on the impact of temporary moods on judgments of satisfaction with life in general and with specific life-domains are reported. It was hypothesized that individuals simplify the complex task of evaluating their life in general by referring to their mood at the time of judgment, but evaluate specific life-domains on the basis of domain-specific information. In accordance with this hypothesis, both studies demonstrated strong mood effects on judgments of general life-satisfaction but only weak and non-significant effects on judgments of specific domain-satisfactions. The findings are interpreted as supporting the hypothesis that affective states serve informative functions.

Myelin-associated glycoprotein, a member of the L2/HNK-1 family of neural cell adhesion molecules, is involved in neuron-oligodendrocyte and oligodendrocyte-oligodendrocyte interaction.

Abstract: A monoclonal antibody to the myelin-associated glycoprotein (MAG) was prepared and characterized to probe for the involvement of MAG in cell surface interactions among neural cells in vitro. The antibody reacts specifically with oligodendrocyte cell surface and myelin-rich brain regions as expected from previous investigations. Not all O4 antigen-positive oligodendrocytes express MAG in vitro. Fab fragments of the antibody interfere with neuron to oligodendrocyte and oligodendrocyte to oligodendrocyte adhesion, but not with oligodendrocyte to astrocyte adhesion. MAG-containing liposomes bind to the cell surfaces of the appropriate target cells by a mechanism that is specifically inhibitable by Fab fragments of monoclonal MAG antibodies, demonstrating that MAG is a neural cell adhesion molecule.

Immunohistochemical study of the expression of a Mr 34,000 human epithelium-specific surface glycoprotein in normal and malignant tissues.

Abstract: Monoclonal antibody HEA125 was used to study the tissue distribution of an epithelial cell surface glycoprotein of Mr 34,000 (Egp34) A large panel of normal and neoplastic tissues was examined for immunoreactivity with HEA125 by means of a sensitive immunoperoxidase technique HEA125 labeled most epithelial cell types throughout the body but did not label any nonepithelial tissue Major exceptions were epidermal keratinocytes, gastric parietal cells, hepatocytes, thymic cortical epithelial, and myoepithelial cells Normal mesothelial cells were unreactive In normal glandular epithelia and tubular adenocarcinomas exclusively the basolateral cell membranes were stained HEA125 intensely reacted with all tested carcinoma specimens derived from colorectum, stomach, pancreas, liver, lung, mammary gland, ovary, thyroid, kidney, urinary bladder, and prostate including a number of anaplastic, diffusely infiltrating carcinomas Metastatic lesions of these tumors were consistently positive Generally, the staining of tumor cells was very homogeneous The majority of squamous cell carcinomas were less strongly labeled than adenocarcinomas; keratinizing areas of the tumor masses were negative Germ cell tumors and mesotheliomas of epithelioid type focally expressed the antigen Egp34 was found to be absent from sarcomas, lymphomas, melanomas, and neurogenic tumors Hence, HEA125 is a useful reagent for the distinction of carcinomas from nonepithelial neoplasms, even at very low degrees of histological differentiation Furthermore, HEA125 allows the immunohistochemical detection of micrometastases originating from carcinomas The antigen is detectable in formalin-fixed paraffin sections

The 180-kD component of the neural cell adhesion molecule N-CAM is involved in cell-cell contacts and cytoskeleton-membrane interactions.

Abstract: N-CAM180, the molecular form of the three neural cell adhesion molecules (N-CAM) with the largest cytoplasmic domain, is accumulated at sites of cell-cell contact (cell bodies, neurites, growth cones) in cultures of neuroblastoma and cerebellum. At these sites the cytoskeletonmembrane linker protein brain spectrin and actin are also accumulated. Brain spectrin copurifies with N-CAM180 by immunoaffinity chromatography and binds specifically to N-CAM180 but not to N-CAM140 or N-CAM120 in a solid-phase binding test. These observations indicate an association of N-CAM180 with the cytoskeleton in vivo. This association may underlie the reduced lateral mobility of N-CAM180 in the surface membrane compared to N-CAM140 (Pollerberg et al. 1986). Together with the fact that N-CAM180 is only expressed after termination of neuron migration in vivo (Persohn and Schachner, unpublished) these results suggest a role for N-CAM180 in stabilization of cell contacts.

Biochemical and functional characterization of a novel neuron-glia adhesion molecule that is involved in neuronal migration.

Abstract: Adhesion molecule on glia (AMOG) is a novel neural cell adhesion molecule that mediates neuron-astrocyte interaction in vitro. In situ AMOG is expressed in the cerebellum by glial cells at the critical developmental stages of granule neuron migration. Granule neuron migration that is guided by surface contacts between migrating neurons and astroglial processes is inhibited by monoclonal AMOG antibody, probably by disturbing neuron-glia adhesion. AMOG is an integral cell surface glycoprotein of 45-50-kD molecular weight with a carbohydrate content of at least 30%. It does not belong to the L2/HNK-1 family of neural cell adhesion molecules but expresses another carbohydrate epitope that is shared with the adhesion molecules L1 and myelin-associated glycoprotein, but is not present on N-CAM or J1.

Immunoelectron microscopic localization of the neural cell adhesion molecules L1 and N-CAM during postnatal development of the mouse cerebellum.

Abstract: The cellular and subcellular localization of the neural cell adhesion molecules L1 and N-CAM was studied by pre- and postembedding immunoelectron microscopic labeling procedures in the developing mouse cerebellar cortex. The salient features of the study are: L1 displays a previously unrecognized restricted expression by particular neuronal cell types (i.e., it is expressed by granule cells but not by stellate and basket cells) and by particular subcellular compartments (i.e., it is expressed on axons but not on dendrites or cell bodies of Purkinje cells). L1 is always expressed on fasciculating axons and on postmitotic, premigratory, and migrating granule cells at sites of neuron-neuron contact, but never at contact sites between neuron and glia, thus strengthening the view that L1 is not involved in granule cell migration as a neuron-glia adhesion molecule. While N-CAM antibodies reacting with the three major components of N-CAM (180, 140, and 120 kD) show a rather uniform labeling of all cell types, antibodies to the 180-kD component (N-CAM180) stain only the postmigratory granule cell bodies supporting the notion that N-CAM180, the N-CAM component with the longest cytoplasmic domain, is not expressed before stable cell contacts are formed. Furthermore, N-CAM180 is only transiently expressed on Purkinje cell dendrites. N-CAM is present in synapses on both pre- and post-synaptic membranes. L1 is expressed only preterminally and not in the subsynaptic membranes. These observations indicate an exquisite degree of fine tuning in adhesion molecule expression during neural development and suggest a rich combinatorial repertoire in the specification of cell surface contacts.

CD19 monoclonal antibody HD37 inhibits anti-immunoglobulin-induced B cell activation and proliferation.

Abstract: The 95 Kd CD19 antigen is the broadest lineage specific surface marker for B cells: it is present on the surface of virtually all B lymphocytes, including early B progenitor cells. In this study we have evaluated the function of the CD19 antigen by using the CD19 mAb HD37. Binding of HD37 mAb to B cells at low doses (0.5 microgram/ml) induced a strong inhibition of the proliferative response to anti-Ig. This inhibition was not mediated by the Fc portion of the antibody, since F(ab')2 fragments were as effective as the whole antibody. Both dose-response curve analysis and experiments in which a cross-linking second step anti-mouse antibody was added suggested that cross-linking of CD19 antigens was necessary for optimal inhibition. Early phases in B cell activation were affected by the HD37 mAb: it significantly reduced the number of cells that left G0 and entered the G1 phase of the cell cycle upon triggering with anti-mu. The increase in free intracellular ionized calcium [Ca2+]i that is induced by anti-mu was also consistently reduced by CD19 mAb. Cross-linking was also crucial for this effect, suggesting that a causal relationship may exist between the inhibition of anti-Ig-mediated [Ca2+]i fluxes and inhibition of proliferation. A variable but clear increase in [Ca2+]i levels followed cross-linking of CD19 antigens by specific mAb. This evidence suggests that CD19 molecules may function in the downregulation of B cell growth and proliferation.

Trypanothione reductase from Trypanosoma cruzi. Purification and characterization of the crystalline enzyme.

Abstract: The structural differences between trypanothione reductase of Trypanosoma cruzi and human glutathione reductase, an enzyme of known three-dimensional structure, offer an opportunity for rational drug design against Chagas' disease. As a first step in the analysis of the parasite enzyme we report its purification and characterization. 2.2 mg trypanothione reductase was extracted from 33 g wet weight of cultured epimastigotes or from 4 g lyophilized cells. The flavoenzyme was purified 2400-fold to homogeneity in three steps with an overall yield of 45%. The enzyme is a dimer with a subunit Mr of 50,000. Using NADPH (Km = 5 microM) and trypanothione disulfide (Km = 45 microM) as substrates, a turnover number of 14,200 min-1 was estimated. Trypanothione reductase, the parasite enzyme, and glutathione reductase, the host enzyme, exhibit mutually exclusive specificities for their respective disulfide substrates. When screening cell cultures or column eluates for the presence of trypanothione reductase, a microassay based on Ellman's reagent as indicator was used. A mixture of regioisomeric glutathionylspermidine disulfides isolated from Escherichia coli served as substrate in this microassay. Experimentally, the catalytic cycle of the enzyme can be subdivided into the half-reactions Eox + NADPH + H+----EH2 + NADP+, and EH2 + trypanothione disulfide----Eox + dihydrotrypanothione. This is also true for the crystallized enzyme in the presence of 2 M (NH4)2SO4. The spectral properties of trypanothione reductase both in the oxidized form (Eox) and in the two-electron-reduced form (EH2) closely resemble those of human glutathione reductase. Both proteins contain a flavin and a redox-active disulfide at the catalytic site. After reduction of Eox to EH2, trypanothione reductase can be inactivated by specifically alkylating one of the nascent active-site thiols.

The duck hepatitis B virus pre-C region encodes a signal sequence which is essential for synthesis and secretion of processed core proteins but not for virus formation.

Abstract: Analysis of the serum of duck hepatitis B virus (DHBV)-infected ducks has revealed the presence of C-terminally truncated viral core proteins (e antigens). These proteins are glycosylated and therefore were not released from infected cells by lysis but rather by active secretion, indicating that the DHBV core protein can be synthesized alternatively as a cytoplasmic or a secretory protein. Transient expression of cloned wild-type DHBV DNA and of a specifically designed viral mutant in a human hepatoma cell line (Hep-G2) showed that the DHBV core gene promoter is active in differentiated human liver cells and that synthesis and secretion of the processed core proteins are dependent on the expression of the pre-C region, a small open reading frame which precedes the core gene. In addition, these experiments showed that the mechanism of core protein processing and secretion is conserved between DHBV and the human hepatitis B virus and therefore might be important for the hepatitis B virus life cycle in general. In spite of this, intrahepatic injection of the pre-C mutant into uninfected ducks resulted in viremia without concomitant e-antigen synthesis, indicating that virus formation is independent of pre-C expression.

Regulation of neural cell adhesion molecule expression on cultured mouse Schwann cells by nerve growth factor

Abstract: Schwann cells from early postnatal mouse sciatic nerve were obtained as a homogenous population and shown by indirect immunofluorescence to express the neural cell adhesion molecules L1, N-CAM and J1 and their common carbohydrate epitope L2/HNK-1. L1 and N-CAM are synthesized in molecular forms that are slightly different from those expressed by small cerebellar neurons or astrocytes. As in astrocytes, the J1 antigen is expressed by Schwann cells in multiple forms generally ranging from 160 to 230 kd in the reduced state. J1 is secreted by Schwann cells in a 230-kd mol. wt form. Expression of L1 by Schwann cells can be regulated by nerve growth factor (NGF). L1 expression on the cell surface is increased 1.6-fold in the presence of NGF after 3 days of maintenance in vitro and 3-fold after 16 days. NGF does not change expression of N-CAM. The glia-derived neurite-promoting factor (GdNPF) increases L1 expression by a factor of 1.9 and decreases N-CAM expression by a factor of 0.4 after 3 days in vitro. J1 expression on Schwann cell surfaces remains unchanged in the presence of NGF or GdNPF. Antibodies to NGF abolish the influence of NGF on L1 expression. Addition of NGF antibodies to the Schwann cell cultures without exogenously added NGF decreases L1 expression, indicating that Schwann cells secrete NGF that may influence L1 expression by an autocrine mechanism. Our experiments show for the first time that cell adhesion molecule expression on a non-neuronal cell, the Schwann cell, can be directly regulated by the neurotrophic factor NGF. These observations indicate a considerable degree of 'plasticity' of peripheral glia in regulating cell adhesion molecule expression.

Three dimensional image correlation of CT, MR, and PET studies in radiotherapy treatment planning of brain tumors.

Abstract: A treatment planning system for stereotactic convergent beam irradiation of deeply localized brain tumors is reported. The treatment technique consists of several moving field irradiations in noncoplanar planes at a linear accelerator facility. Using collimated narrow beams, a high concentration of dose within small volumes with a dose gradient of 10-15%/mm was obtained. The dose calculation was based on geometrical information of multiplanar CT or magnetic resonance (MR) imaging data. The patient's head was fixed in a stereotactic localization system, which is usable at CT, MR, and positron emission tomography (PET) installations. Special computer programs for correction of the geometrical MR distortions allowed a precise correlation of the different imaging modalities. The therapist can use combinations of CT, MR, and PET data for defining target volume. For instance, the superior soft tissue contrast of MR coupled with the metabolic features of PET may be a useful addition in the radiation treatment planning process. Furthermore, other features such as calculated dose distribution to critical structures can also be transferred from one set of imaging data to another and can be displayed as three-dimensional shaded structures.

Afferent connections and spinal projections of the pressor region in the rostral ventrolateral medulla of the cat

Abstract: Following microinjection of wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP) into the pressor region of the rostral ventrolateral medulla of the cat, the medulla, pons and hypothalamus were examined for retrogradely labelled cell bodies, while the thoracolumbar segments of the spinal cord were examined for anterogradely labelled axons. Dense groups of labelled cells were found in the following areas: (1) the nucleus of the solitary tract, particularly the medial, ventrolateral and commissural subnuclei; (2) the ambiguus complex and immediately surrounding area; (3) the Kolliker-Fuse nucleus in the pons; (4) the paraventricular nucleus and lateral hypothalamic area. In the spinal cord, labelled axons formed a band extending throughout the dorsolateral and ventrolateral funiculi at thoracic segments, while terminal labelling was observed in the intermediolateral nucleus and to a lesser extent the central autonomic area, but not in other parts of the grey matter. The findings are discussed in relation to the role of the rostral ventrolateral medulla in cardiovascular regulation, particularly the baroreceptor reflex.

The use of local anaesthetic microinjections to identify central pathways: a quantitative evaluation of the time course and extent of the neuronal block.

Abstract: The time course and extent of local anaesthetic blocks within the spinal cord of cats were evaluated. A monopolar stimulation electrode with the tip lowered into the dorsal columns (DC) 1000 μm below cord surface was used to activate antidromically DC fibers at the T13 level and evoke cord dorsum potentials at the level of the lumbar spinal cord. The amplitude of the negative deflection, the N-wave, was determined for various stimulation intensities (stimulation-response-function, SRF). Lidocaine (1%) was microinjected in volumes of 0.5 or 1.0 μl into the DC from a glass micropipette 1 mm caudal to the stimulation site. Conduction block was characterized by a reversible shift of the SRFs to higher stimulation intensities. The diameter of the blocked area in the transverse plane was evaluated from threshold intensities and was found to be 0.9±0.1 mm 4 to 30 min after the injection of 0.5 μl lidocaine and 1.6±0.36 mm 10 to 45 min after the injection of 1.0 μl lidocaine. In the sagittal plane, the diameter of the blocked area following 1.0 μl lidocaine was found to be up to 2.8 mm. The DC-block was reversible within 92 min following injection of 1.0 μl and 69 min after the injection of 0.5 μl lidocaine. The application of the present findings for blocks in other CNS structures is discussed.

Vacuum Structure and Diffraction Scattering

Abstract: A simple model of the vacuum is developed in order to explain the properties of the pomeron observed in experiments. In the model, pomeron exchange corresponds to two-gluon exchange. We explain how it can be that when the pomeron couples to a hadron, the two gluons couple predominantly to the same quark in the hadron, and how together their coupling is similar to that of aC=1 isoscalar photon.

Demonstration of 1,25(OH)2 vitamin D3 receptors and actions in vascular smooth muscle cells in vitro.

Abstract: Binding of [3H] 1,25 (OH)2D3 and effects of 1,25 (OH)2D3 on cell ultrastructure were evaluated in vascular smooth muscle cells (VSMC) primary cultures (aortic media). Specific reversible binding of [3H] 1,25 (OH)2D3 by a 3.5 S macromolecule with DNA binding, KD 6.2×10−10M and Nmax 16 fmol/mg protein was demonstrated. Incubation of VSMC with 10−8 M 1,25 (OH)2D3, but not 25 (OH)D3, in the presence of 10% FCS for up to three weeks caused rapid reversible appearance in the cytoplasm of membrane-bounded electron-dense lysosomal particles which on electronspectroscopic imaging contained Ca and Pi. VSMC are targets for vitamin D.