Adenine auxotrophic heterozygosity in Candida krusei

Candida krusei CK 18 carries heterozygosity for a recessive adenine biosynthesis allele, as it can be induced by UV irradiation to form adenine mutants at high frequency. The resultant mutants were characterized with the phenotype of red colony and residual growth on minimal media. The majority of the descendant prototrophic segregates were capable of continuous segregation to adenine mutants, suggesting gene conversion as one possible mechanism for the occurrence of the adenine auxotroph in the isolate.

[Experimental study on antagonizing action of herba Epimedii on side effects induced by glucocorticoids]

The experimental result has shown that the water extract of Herba Epimedii (Epimedium sagittalum) works very well in preventing and curing the side effects induced by long-term use of glucocorticoids in rats, especially in antagonizing adrenocortical atrophy and osteoporosis.

A novel intact circular dsDNA supercoil

A novel intact circular dsDNA supercoil is proposed as an alternative to the conventional DNA supercoil, so that the two complementary strands of ssDNA circles are separable without any covalent bond breakage. This new structure can be visualized by using two tubings: one black and one clear. Twist the black tubing a number of times and connect its two ends. Do the same for the clear tubing. Then wrap the two tubings together. This forms the separable or novel supercoil. On the other hand, the conventional supercoil can be modeled by twisting the black and clear tubings together and then connect their respective ends, so that the two tubings are not separable unless one of them is cut. Experimentally, in the absence of any enzyme, many intact plasmid dsDNA circles give two bands on agarose gel electrophoresis under a certain given condition, while the same plasmid molecules after cutting once by a restriction enzyme give only one band under the same condition. In the case of intact pUC19 plasmids, these two bands can then be recovered and sequenced separately, using two primers in opposite directions. Each band gives mostly one sequence which is complementary to that of the other band. The combination of the above theoretical model and experimental results strongly suggests that there is an alternative structure of DNA which does not have the usual difficulty of unwinding, rewinding and requiring numerous covalent bond breakages and ligations during semiconservative.

[A study on plasma non-species specific antibody in employees working in a automobile engine testing workshop]

To investigate the existence of the non-species specific antibody in plasma of the employees working in an automobile engine testing workshop, and to use it as a scanning marker of various hazards, the heat-stress protein antigen method and western blot technique were used. This study showed that employees working in the automoblile engine testing workshop were affected by various hazards, such as noise, toxic chemicals (carbon monoxide, lead fume, benzene, and so on), and there existed non-species specific antibodies against protein 103,900 and 54,200 of rat liver in their plasma, which were postulated as the specific products produced by exposure to occupational hazards, such as noise, carbon monoxide, et al.

[Effects of gossypol acetic acid on human ejaculated sperm Ca2+ influx and rat vas deferens contraction action]

It has been reported that gossypol acetic acid (GAA) inhibits sperm motility and calcium plays an important role in regulating the function of the sperm flagella. In order to explore the mechanism by which GAA inhibits sperm motility, the effects of GAA on human ejaculated sperm Ca2+ influx and isolated rat vas deferens contraction action were studied. The results showed that GAA inhibited sperm Ca2+ influx in a dose-dependent manner, and breaked the dynamic equilibrium of sperm internal and external Ca2+ gradient concentrations. It may be one of important mechanism by which GAA inhibits sperm motility. But GAA exerts no effect on the high K+ induced contraction of smooth muscle of isolated rat vas deferens. It is likely that GAA has selective action on the sperm membrane of the rats.

Comparison of muscle force, muscle endurance, and electromyogram activity during an expedition at high altitude

Handgrip force (HF), maximal pinch force (MF), muscle endurance (ME), and the median power frequency (MdPF) of the activity shown in the electromyogram (EMG) were studied at various altitudes in eight normal healthy subjects. MF and ME were measured between the index finger and thumb, and all measurements were obtained at altitudes ranging from 610 to 4860 m during an expedition in the Qinghai Plateau in China. With the change in altitude HF, ME, and MF showed no significant change. Compared to the MdPF at 2260 m on ascent, the MdPF at other altitudes showed a significant decrease (P < 0.01). Thus, we conclude that muscle performance (HF, MF, and ME) was not affected by the environment at high altitude. However, MdPF was affected and the mean MdPF at 610 m after the expedition did not recover to initial values of MdPF. We suggest these results may have been affected by fatigue and chronic exposure to the hypobaric hypoxic environment, since the members of the expedition party expressed feelings of sluggishness and fatigue after the expedition.

Adenovirus type 5 early region 4 is responsible for E1A-induced p53-independent apoptosis

In the absence of E1B, the 289- and 243-residue E1A products of human adenovirus type 5 induce p53-dependent apoptosis. However, our group has shown recently that the 289-residue E1A protein is also able to induce apoptosis by a p53-independent mechanism (J. G. Teodoro, G. C. Shore, and P. E. Branton, Oncogene 11:467-474, 1995). Preliminary results suggested that p53-independent cell death required expression of one or more additional adenovirus early gene products. Here we show that both the E1B 19-kDa protein and cellular Bcl-2 inhibit or significantly delay p53-independent apoptosis. Neither early region E2 or E3 appeared to be necessary for such cell death. Analysis of a series of E1A mutants indicated that mutations in the transactivation domain and other regions of E1A correlated with E1A-mediated transactivation of E4 gene expression. Furthermore, p53-deficient human SAOS-2 cells infected with a mutant which expresses E1B but none of the E4 gene products remained viable for considerably longer times than those infected with wild-type adenovirus type 5. In addition, an adenovirus vector lacking both E1 and E4 was unable to induce DNA degradation and cell killing in E1A-expressing cell lines. These data showed that an E4 product is essential for E1A-induced p53-independent apoptosis.

Differential radioprotection of three mouse strains by basic or acidic fibroblast growth factor

Recently we found that human recombinant basic fibroblast growth factor (FGF2) radioprotected C3H/HeNCr mice after whole body irradiation (WBI). The purpose of the present study was to compare the in vivo radioprotective effects of human recombinant acidic fibroblast growth factor (FGF1) or FGF2 in three strains of mice (C3H/HeNCr, BALB/CAn, C57BL/6). In vivo administration of 6 micrograms/mouse of FGF1 or FGF2 pre- or post- WBI significantly protected only C3H and BALB/C mice. Dose modification factor was: C3H(FGF1/2) 1.09 +/- 0.02/1.14 +/- 0.04; BALB/C(FGF1/2) 1.13 +/- 0.02/1.15 +/- 0.01. Response was minimal or absent in C57 mice (FGF2 1.02 +/- 0.02). Increasing the FGF dose above 12 micrograms/mouse did not increase radioprotection in any strain. In single radiation dose studies, FGF2 was more potent than FGF1 in C3H mice; FGF1 and FGF2 were equipotent in BALB/C mice; and both had minimal effect in C57 mice. Significant radioprotection occurred in only two of the three strains of mice studied. We therefore suggest caution in applying mouse radioprotection data to other species.

The excitatory effect of cholecystokinin on rat neostriatal neurons: ionic and molecular mechanisms

Whole-cell patch-clamp recordings were performed to study ionic and molecular mechanisms by which cholecystokinin (CCK) peptides modulate the membrane excitability of acutely dissociated rat neostriatal neurons. Immunohistochemical staining studies indicated that about 95% of acutely isolated neostriatal neurons were GABA(gamma-aminobutyric acid)ergic medium-sized cells. During current-clamp recordings, sulfated cholecystokinin octapeptide (CCK-8) depolarized neostriatal neurons and evoked action potentials. During voltage-clamp recordings, CCK-8 induced inward currents at negative membrane potentials by increasing the voltage-insensitive and non-selective cationic conductance. Cholecystokinin tetrapeptide (CCK-4), a selective CCKB receptor agonist, also evoked cationic currents. The CCK-8-induced cation currents were antagonized by PD135,158 (4-{[2-[[3-(1H-indol-3yl)-2-mehtyl-1-oxo-2-[[[1.7.7.-trimeth yl-bicyclo [2.2.1]hept-2-yl)oxy]carbonyl]amino]propyl]amino]-1-phenylethyl]amino-4- oxo- [1S-1 alpha, 2 beta [S*(S*)]4 alpha]}-butanoate N-methyl-D-glucamine), a highly specific and potent CCKB receptor antagonist. The CCK-8-evoked inward currents were blocked by the internal perfusion of 1 mM GDP-beta-S. In neostriatal neurons dialyzed with 0.5 mM GTP-gamma-S, the cationic currents produced by CCK-8 became irreversible. Pretreating neostriatal neurons with 500 ng/ml pertussis toxin did not prevent CCK-8 from evoking cationic currents. Internal administration of heparin (2 mg/ml), an inositol 1,4,5-trisphosphate (IP3) receptor antagonist, and buffering of intracellular calcium with the Ca(2+)-chelator, BAPTA (1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid, 10 mM), suppressed CCK-8-evoked cationic currents. These findings suggest that, by activating CCKB receptors, CCK-8 excites rat neostriatal neurons through enhancing a non-selective cationic conductance and that pertussis toxin-insensitive G-proteins mediate CCK-8 enhancement of the cationic conductance. The coupling mechanism via G-proteins is likely to involve the production of IP3, and the subsequent IP3-evoked Ca2+ release leads to the opening of non-selective cation channels.

Characterization of terminal sialic acid linkages on human thymocytes. Correlation between lectin-binding phenotype and sialyltransferase expression

T cell surface sialylation changes during maturation in the thymus. We have previously demonstrated increased expression of mRNA encoding the Gal beta 1, 3GalNAc alpha 2,3-sialyltransferase in mature medullary human thymocytes, compared with immature cortical thymocytes. For this enzyme, increased expression of transferase mRNA correlated with increased sialylation of O-glycans. We have now examined the pattern of expression in the human thymus of two additional sialyltransferases, the Gal beta 1,4GlcNAc alpha 2,6-sialyltransferase (ST6N) and the Gal beta 1,3/4GlcNAc alpha 2,3-sialyltransferase (ST3N). The patterns of mRNA expression were compared with the pattern of binding of two sialic acid-specific plant lectins, Sambucus nigra agglutinin and Maackia amurensis agglutinin, which preferentially recognize alpha 2,6- and alpha 2,3-linked sialic acids, respectively, on N-glycans. By in situ hybridization, mRNA encoding ST3N was detected uniformly throughout the thymus. All thymocytes bound M. amurensis agglutinin, demonstrating a direct correlation between the level of ST3N mRNA expression and cell-surface glycosylation. In contrast, mRNA encoding ST6N was also expressed uniformly throughout the thymus; however, only mature (CD3hi) medullary thymocytes bound S. nigra agglutinin. On mature thymocytes, S. nigra agglutinin appeared to bind primarily to the cell-surface glycoprotein CD45; since only the mature thymocytes expressed the CD45RA isoform, while both mature and immature populations expressed the CD45R0 isoform, CD45RA may be a preferred substrate for ST6N. These results demonstrate that glycoprotein sialylation is tightly regulated during T cell development and that the developmentally regulated expression of specific oligosaccharide structures on the cell surface may be influenced by expression of both the relevant glycosyltransferase and specific acceptor substrates.

[Study on the subclinical infection of the recipients of measles vaccine]

Through observation to subclinical infection of the 71 children who had been inoculated against measles 12 years ago and then exposed to natural measles from three classes at a primary school, we have noticed: (1) Subclinical infection did exist among the crowd who were inoculation against measles; The rate of subclinical infection of the three classes was between 18.5%-75.0%, with an average of 45.1%. (2) The level of the HI Ab titer was between 1:2-1:16. The peak level was between 1:2 and/or 1:4. So the rate of subclinical infection who had been inoculation against measles but later exposed to natural measles would depend on the proportion of those whose titer of HI Ab was 1:2-1:4 in the crowd. (3) The epidemiological significance of subclinical measles infection lies in that it can actively keep and consolidate the level of immunity to certain extent in a crowd who had been inoculation against measles.

The Competence of Maize Shoot Meristems for Integrative Transformation and Inherited Expression of Transgenes

We have developed a novel and reproducible system for recovery of fertile transgenic maize (Zea mays L.) plants. The transformation was performed using microprojectile bombardment of cultured shoot apices of maize with a plasmid carrying two linked genes, the Streptomyces hygroscopicus phosphinothricin acetyltransferase gene (bar) and the potato proteinase inhibitor II gene, either alone or in combination with another plasmid containing the 5[prime] region of the rice actin 1 gene fused to the Escherichia coli [beta]-glucuronidase gene (gus). Bombarded shoot apices were subsequently multiplied and selected under 3 to 5 mg/L glufosinate ammonium. Co-transformation frequency was 100% (146/146) for linked genes and 80% (41/51) for unlinked genes. Co-expression frequency of the bar and gus genes was 57% (29/51). The co-integration, co-inheritance, and co-expression of bar, the potato proteinase inhibitor II gene, and gus in transgenic R0, R1, and R2 plants were confirmed. Localized expression of the actin 1-GUS protein in the R0 and R1 plants was extensively analyzed by histochemical and fluorometric assays.

[Study on the test and evaluation of the toxicity of the strains preparation of the different subspecies of Bacillus thuringiensis and on the research into its standardization]

In this paper using the preparation of Bacillus thuringiensis of USA standard sample-subsp. kurstaki HD-1-S-1980 (H3a3b) the toxicity to different subspecies preparations such as subsp. dendrolimus U strain(H4a4b), subsp. galleriae C88 strain (H5a5b) is tested and evaluated. And product's standardization is also researched. Comparing their toxicity to various test-insects between the standard sample prepared from U strain and USA, standard sample, the boilogical determined results are as follows: the toxicity of U strain standard sample is respectively 18666.6 IU/mg(test-insects: Dendrolimus punctatus, 2nd larva), 22956.5 IU/mg(test-insects: Plutella kylostella, 2nd larva). The above-mentioned toxicity evaluations are higher than that of 16000 IU/mg of USA standard sample. The comparison in susceptibility shows as follows: suscepticibility of plutella kylostella is stronger than that of Dendrolimus punctatus. The products from U strain and C88 strain are trial-produced in medium-scale. The product's toxicity to test-insect Dendrolimus punctatus is determined using USA standard sample. The results are obtained as follows the toxicity evaluation of U strain products is 36444.4 IU/mg; that of C88 strain products is 28521.7 IU/mg. The both are obviously higher than that of USA standard sample. This proves that different subspecies strain's toxicity to the same test-insect is with defference and it is an important way to raise product's toxicity by improving and optimizing process in production. The whole experiment shows it is feasible to rectify the evaluation of the toxicity of our country's present products using USA standard sample, Dendrolimus punctatus and Plutella kylostella as test-insets. And it is simple and convienient as well as save time and save effort to make statistical analysis in computer with Basic program. To do statistical and operational analysis using our designed basic programming by micro-computer is more accurate and repid than by caculator.

In-vitro proteinase production by oral Candida albicans isolates from individuals with and without HIV infection and its attenuation by antimycotic agents

In-vitro proteinase production by oral Candida albicans isolates from patients with and without HIV infection (18 isolates from each group) was assessed by image analysis of a plate assay, with bovine serum albumin (BSA) as a substrate. The effect of sub-minimal inhibitory concentrations (sub-MICs) of nystatin, amphotericin B, clotrimazole and miconazole on in-vitro proteinase production by these yeast isolates was also investigated. Proteinase production by C. albicans isolates from patients with HIV infection was significantly greater than production by those from individuals without infection. All 18 isolates from HIV-infected individuals produced proteinase, in comparison to 56% of isolates from uninfected individuals. Pre-exposure of C. albicans isolates (seven proteinase producers from each group) to 1/4 and 1/16 MICs of nystatin, amphotericin B, clotrimazole and miconazole resulted in decreased proteinase production in all isolates tested. However, after exposure to the four antimycotic agents, proteinase production was decreased to a significantly greater extent in isolates from uninfected individuals than in those with HIV disease. Furthermore, when the relative concentration effect of antimycotic agents on proteinase production was compared, C. albicans isolates from the HIV-free group demonstrated a salient dose-response relationship compared with the HIV-infected group. These results indicate that C. albicans from patients with HIV infection are significantly more proteolytic than those from individuals without the infection, and that polyenes and imidazoles curtail the proteolytic activity of all C. albicans isolates, albeit to a lesser extent in those from HIV-infected patients. It appears that HIV disease favours oral colonisation by more proteolytic C. albicans isolates, with resilient proteolytic activity.

G alpha q/11 mediates cholecystokinin activation of the cationic conductance in rat substantia nigra dopaminergic neurons

Using acutely isolated rat substantia nigra neurons, our previous studies indicated that sulfated cholecystokinin octapeptide (CCK-8) excites substantia nigra dopaminergic neurons by increasing the cationic conductance and that pertussis toxin-insensitive G proteins mediate CCK-8 induction of cationic currents. G alpha q and G alpha 11 are expressed in various tissues, including the brain, and likely to mediate pertussis toxin-insensitive neural signal transductions. In the present study, two different experiments were performed to test the hypothesis that G alpha q/11 mediates CCK-8 enhancement of the cationic conductance. First, we investigated the expression of G alpha q and G alpha 11 mRNAs in CCK-8-responsive substantia nigra dopaminergic neurons by combining whole-cell patch-clamp recordings with a single-cell reverse transcriptase-polymerase chain reaction assay. After CCK-8-evoked cationic currents were recorded, cellular RNA was harvested from single neurons and used as a template for the subsequent reverse transcriptase-polymerase chain reaction analysis. G alpha q and G alpha 11 mRNAs were present in all substantia nigra dopaminergic neurons that responded to CCK-8. Substantia nigra dopaminergic neurons were also internally perfused with the antibody raised against the common C-terminus of G alpha q and G alpha 11 during whole-cell recordings. CCK-8 failed to induce cationic currents after dopaminergic neurons were dialyzed with the anti-G alpha q/11 antibody. Our studies suggest that CCK-8 activation of the cationic conductance in substantia nigra dopaminergic neurons is transduced by G alpha q and/or G alpha 11.

Tumor necrosis factor-alpha induces the 85-kDa cytosolic phospholipase A2 gene expression in human bronchial epithelial cells

Phospholipase A2 (PLA2) activity has been suggested to mediate some of the tumor necrosis factor (TNF) induced cellular responses including cytotoxicity. We evaluated the induction of both the 85-kDa cytosolic phospholipase A2 (cPLA2) and non-pancreatic group II PLA2 gene expression by TNF-alpha in a human bronchial epithelial cell line (BEAS 2B cell). TNF-alpha (20 ng/ml) induced a significantly increased release of prelabeled [3H]arachidonic acid (AA) following 4-24 h incubation. Calcium ionophore A23187 (10(-5) M) further increased the [3H]AA release from the TNF-alpha-treated cells. In vitro activity assay revealed that TNF-alpha increased the dithiothreitol (DTT)-resistant PLA2 activity which was blocked by the cPLA2 inhibitor AACOCF3. Treatment with TNF-alpha for 4-24 h increased the cPLA2 protein and mRNA levels which were blocked by the broad inhibitor of protein kinases staurosporine, the protein kinase C (PKC) inhibitor calphostin C, and to a lesser extent the calcium/calmodulin-dependent protein kinase inhibitor W-7. Reverse transcription and polymerase chain reaction amplification of the group II PLA2 mRNA showed that it is expressed in human lung but not in the bronchial epithelial cell line. TNF-alpha failed to induce the expression of group II PLA2 in the BEAS 2B cells. These results demonstrate that the cPLA2 gene expression is up-regulated by TNF-alpha and this effect may contribute to the TNF-alpha stimulated AA release in airway epithelial cells.

G alpha q/11 mediates neurotensin excitation of substantia nigra dopaminergic neurons

Using acutely dissociated substantia nigra pars compacta (SNC) dopaminergic (DA) neurons, our previous studies indicated that neurotensin (NT) excites SNC DA neurons by increasing the cationic conductance and reducing the inwardly rectifying K+ conductance. Further investigation also revealed that pertussis toxin (PTX)- insensitive G-proteins mediate neurotensin modulation of cation and potassium channels. G alpha q and G alpha 11 are widely distributed in various tissues including the brain and likely to mediate PTX-insensitive signal transductions in the nervous system. In this study, two different experiments were conducted to test the hypothesis that G alpha q/11 mediates neurotensin regulation of the cationic and K+ conductances. First, we investigated the expression of G alpha q and G alpha 11 mRNAs in NT-responsive SNC DA neurons by combining whole-cell patch-clamp recordings with single-cell reverse transcriptase-polymerase chain reaction (RT-PCR) assay. After recording NT-evoked membrane currents, the cellular content was harvested from single neurons and used as the template for the subsequent RT-PCR analysis. Both G alpha q and G alpha 11 mRNAs were present in all SNC DA neurons that responded to neurotensin. SNC DA neurons were also internally dialyzed with an antibody directed against the common C-terminus of G alpha q and G alpha 11 during whole-cell recordings. In DA neurons perfused with the anti-G alpha q/11 antiserum, neurotensin failed to evoke inward currents resulting from the opening of cation channels and the closure of inward rectifier K+ channels. It is concluded that NT modulation of cation and inward rectifier K+ channels in SNC DA neurons is transduced by G alpha q and/or G alpha 11.

Recovery patterns of motor and somatosensory evoked potentials following treatment of vitamin B12 deficiency

Motor and somatosensory pathway functions were studied using motor evoked potentials (MEPs), somatosensory evoked potentials (SEPs) and F-wave responses in a woman with vitamin B12 deficiency. Initial evaluation before treatment revealed: 1) prolongation of central motor conduction to both the upper and lower limbs, and prolongation of peripheral conduction to the lower limbs; 2) prolongation of central conduction time to median nerve stimulation and absence of cortical SEPs to tibial nerve stimulation; and 3) prolongation of F-wave responses to tibial and peroneal nerve stimulation. After 11 months of treatment with hydroxocobalamin, follow-up studies disclosed: 1) normalization of central motor conduction to the upper limbs, peripheral motor conduction to the lower limbs and improvement of central motor conduction to the lower limbs; 2) normalization of central conduction time to median nerve stimulation but persistent absence of cortical SEPs to tibial nerve stimulation; and 3) normalization of F-wave responses. These data suggest that both central and peripheral conductions of motor and somatosensory pathways may respond to hydroxocobalamin therapy, and that MEPs are useful in the early detection of central and peripheral motor pathway function recovery following treatment with vitamin B12 deficiency.

[Experimental study on zhuanggu shengbao in preventing hormone-induced osteoporosis of rats]

Twenty four male Sprague-Dawley rats at 3 months of age were divided randomly into 3 groups. Prednisone acetate was given to the group B twice per weeks, Zhuanggu Shengbao (ZGSB) was added to the group C besides prednisone, the group A was control. The histomorphometric parameters of bone slides of proximal tibia were measured and calculated with image pattern analyser after 3 months of medication. Results showed that in comparing with group A, in group B the area and number of trabecula decreased, the intertrabecular space increased due to the bone resorption exceeded the bone formation, and the symptoms of osteoporosis revealed obviously. However, in group C, the bone resorption rate was markedly inhibited, and the formation of new bone accelerated so that the bone mass increased significantly. These results indicated the ZGSB could prevent the osteoporosis induced by prednisone acetate.

Fluctuating hemiparesis caused by a quadrigeminal arachnoid cyst: case report

A 42-year-old woman presented with intermittent hemiparesis mimicking a reversible ischemic neurologic deficit. Magnetic resonance imaging (MRI) demonstrated a compression of the left side of the midbrain by a quadrigeminal arachnoid cyst without hydrocephalus. After the cystic wall was widely excised under operating microscope, the patient made a good recovery and remained well at a follow-up of 18 months. The absence of hydrocephalus in a symptomatic patient with a quadrigeminal cyst was exceptional, which might result from the early diagnosis with MRI. The use of microsurgical technique made it possible to excise the cystic wall widely and omit a shunting procedure.

Hypoxia-induced paracrine regulation of vascular endothelial growth factor receptor expression

Vascular endothelial growth factor (VEGF)/vascular permeability factor (VPF), an endothelial cell (EC)-specific mitogen, stimulates angiogenesis in vivo, particularly in ischemic regions. VEGF/VPF expression by cells of hypoxic tissues coincides with expression of its two receptors, KDR and flt-1, by ECs in the same tissues. We investigated whether hypoxia or hypoxia-dependent conditions operate in coordinating this phenomenon. Human umbilical vein and microvascular ECs were exposed to direct hypoxia or to medium conditioned (CM) by myoblasts maintained in hypoxia for 4 d. Control ECs were maintained in normoxia or normoxia-CM. Binding of 125I-VEGF to ECs was then evaluated. Hypoxic treatment of ECs had no effect on 125I-VEGF binding. However, treatment of ECs with hypoxia-CM produced a threefold increase in 125I-VEGF binding, with peak at 24 h (P < 0.001, ANOVA). Scatchard analysis disclosed that increased binding was due to a 13-fold increase in KDR receptors/cell, with no change in KDR affinity (Kd = 260 +/- 51 pM, normoxia-CM versus Kd = 281 +/- 94 pM, hypoxia-CM) and no change in EC number (35.6 +/- 5.9 x 10(3) ECs/cm2, normoxia-CM versus 33.5 +/- 5.5 x 10(3) ECs/cm2, hypoxia-CM). Similar results were obtained using CM from hypoxic smooth muscle cells. KDR upregulation was not prevented by addition to the hypoxia-CM of neutralizing antibodies against VEGF, tumor necrosis factor-alpha, transforming growth factor beta 1 or basic fibroblast growth factor. Similarly, addition of VEGF or lactic acid to the normoxia-CM had no effect on VEGF binding. We conclude that mechanism(s) initiated by hypoxia can induce KDR receptor upregulation in ECs. Hypoxic cells, normal or neoplastic, not only can produce VEGF/VPF, but can also modulate its effects via paracrine induction of VEGF/VPF receptors in ECs.