Stereoselective interaction of uncharged esters at four muscarinic receptor subtypes

We investigated the binding and pharmacological properties of the esters of 3,3-dimethylbutan-1-ol (the carbon analogue of choline) with either diphenylglycolic acid, (R)-phenylcyclohexylglycolic acid, or (S)-phenylcyclohexylglycolic acid [BS-6181, (R)-BS-7826 and (S)-BS-7826, respectively] at muscarinic M1, M2, M3 (Hm3) and M4 receptors. The three uncharged compounds were muscarinic receptor antagonists, with pA2 or pKi values between 7.9 and 5.6. The achiral ester BS-6181 displayed highest affinity for M1, M3 (Hm3) and M4 receptors (pA2 or pKi = 7.2-7.6) and lower affinity for M2 receptors (pA2 or pKi = 6.7 and 6.8). The four muscarinic receptor subtypes were able to distinguish between the two enantiomers of the cyclohexyl derivative of BS-6181 [(R)- and (S)-BS-7826], with a preference for the (R)-isomer (up to 79-fold). Interestingly, the (S)-enantiomer of BS-7826, being the distomer, was found to be M4 selective (pKi/M4 = 6.9; pA2 or pKi/M1-M3 (Hm3) = 5.6-6.2). These results indicate that uncharged compounds may (stereo)selectively bind to muscarinic receptors via hydrophobic interactions. Thus, an ionic bond between muscarinic ligands and an anionic site of the receptor is not absolutely necessary for recognition of muscarinic receptors.

Molecular characterization of the di-leucine-based internalization motif of the T cell receptor

Several cell surface receptors including the T cell receptor (TCR) are phosphorylated and down-regulated following activation of protein kinases. We have recently shown that both phosphorylation of Ser-126 and the presence of the di-leucine sequence Leu-131 and Leu-132 in CD3 gamma are required for protein kinase C (PKC)-mediated TCR down-regulation. To identify additional residues required for PKC-mediated phosphorylation of CD3 gamma and for TCR down-regulation, an alanine scanning of CD3 gamma was done. Mutations of Arg-124, Ser-126, Lys-128, and Gln-129 inhibited both phosphorylation and TCR down-regulation, whereas mutation of Asp-127 only inhibited down-regulation. Further analyses demonstrated a discrepancy between the ability to be phosphorylated on CD3 gamma and to down-regulate the TCR in several transfectants. Phosphorylation was not as strictly dependent on the nature and position of the phosphoacceptor group and basic residues as were the subsequent steps involved in TCR down-regulation. Our results suggest that PKC-mediated TCR down-regulation may be regarded as a two-step process. 1) Recognition and phosphorylation of CD3 gamma by PKC. In this process Arg-124, Ser-126, Lys-128, and Gln-129 are important. 2) Recognition of phosphorylated CD3 gamma by molecules involved in receptor internalization. In this process Ser(P)-126, Asp-127, Leu-131, and Leu-132 are important.

Dual vasoactive effects of tolazoline on rabbit pulmonary arteries

OBJECTIVES

To determine the vasoactive effects of tolazoline on isolated rabbit pulmonary arteries.

DESIGN

Prospective, in vitro, randomized, controlled trial.

SETTING

Experimental laboratory in a university-affiliated hospital.

PARTICIPANTS

New Zealand White Rabbits.

INTERVENTIONS

The pulmonary artery rings were obtained via thoracotomy. Their vasoactive responses were assessed in the presence and absence of intact endothelium and with or without precontraction by norepinephrine (NE, 3 x 10(-6) M) or potassium chloride (KCl, 3 x 10(-2) M). Using a tissue bath preparation, cumulative concentration response curves of tolazoline were obtained at different concentrations (10(-9) to 10(-4) M) after a period of stabilization.

MEASUREMENTS AND MAIN RESULTS

Tolazoline caused vasoconstriction of isolated pulmonary arteries without any pretreatment. The magnitude of the constriction was dose related and reached 300 g/g wet tissue at a concentration of 10(-4) M. On KCl-precontracted pulmonary arteries, tolazoline caused significant dose-related vasoconstriction. On the NE-precontracted vessel rings, it elicited significant dose-dependent vasodilation up to 60% relaxation at 10(-5) M. All the above effects were endothelium independent.

CONCLUSIONS

Tolazoline has dual endothelium-independent vasoactive effects, causing vasoconstriction on isolated rabbit pulmonary arteries, either untreated or precontracted with KCl, and vasodilation on those precontracted with NE. Tolazoline may act as a competitive alpha-adrenoceptor blocking agent.

Influence of monovalent cations on the binding of a charged and an uncharged ('carbo'-)muscarinic antagonist to muscarinic receptors

1. The effect of the buffer concentration on binding of [3H]-N-methylscopolamine to muscarinic receptors M2 was tested in rat heart. Tracer binding was of low affinity in a 20 mM imidazole buffer (pKD 8.3), inhibited by an increase from 10 to 100 mM of the sodium phosphate buffer concentration (pKD 9.92 to 9.22), slightly inhibited by an increase of the Tris/HC1 buffer concentration from 20 to 100 mM (pKD 9.70 to 9.47) and unaffected by an increase of the histidine/HC1 buffer concentration from 20 to 100 mM (pKD 9.90 to 9.82). We chose the last buffer to analyse the effect of ions on antagonists binding to cardiac M2 receptors and to transiently expressed wild-type and (Y533-->F) mutant m3 muscarinic receptors in COS-7 cells. 2. Equilibrium [3H]-N-methylscopolamine binding to cardiac M2 receptors was inhibited, apparently competitively, by monovalent salts (LiCl > or = NaCl > or = KCl). In contrast, binding of the uncharged 3,3-dimethylbutan-1-ol ester of diphenylglycolic acid (BS-6181) was facilitated by addition of monovalent salts (LiCl > or = NaCl > or = KCl) to the binding buffer. This cation binding pattern is consistent with interaction with a large, negative field strength binding site, such as, for instance, a carboxylic acid. 3. In the presence of 100 mM NaCl, [3H]-N-methylscopolamine had a similar affinity for the wild-type m3 receptor (pKD 9.85) and for a (Y533-->F) mutant m3 receptor (pKD 9.68). However, in the absence of added salts, the tracer had a significantly lower affinity for the mutated (pKD 10.19) as compared to the wild-type (pKD 10.70) m3 receptor. BS-6181 had a significantly lower affinity for the (Y533-->F) mutant m3 muscarinic receptor, as compared to the wild-type m3 receptor, both in the absence (pKD 6.19-6.72) in the presence (pKD 6.48-7.40) of 100 mM NaCl. The effects of NaCl on binding of the uncharged ester and of [3H]-N-methylscopolamine to the m3 receptor were decreased by the mutation. 4. Taken together, these results support the hypothesis that monovalent cations from the buffer may interact with the cation binding site of the receptors (an aspartate residue in the third transmembrane helix of muscarinic receptors). Buffer cations may inhibit competitively the binding of (charged) muscarinic ligands having a tertiary amine or ammonium group, while facilitating the receptor recognition by uncharged, isosteric 'carbo-analogues'. Mutation of the (Y533-->F) of the m3 receptor decreased the affinity of the receptor for positive charges, including the sodium ion.

A mouse kidney- and liver-expressed cDNA having homology with a prokaryotic parathion hydrolase (phosphotriesterase)-encoding gene: abnormal expression in injured and polycystic kidneys

To investigate abnormalities in gene expression associated with cyst formation in polycystic kidney disease, differential cDNA library screening was carried out using RNA from normal and cystic kidneys of the C57BL/6J-cpk mouse. Among a number of genes found to be abnormally expressed was one (cDNA clone 56-1) that was significantly underexpressed in cystic kidneys. Hybridization analyses revealed that the 56-1 mRNA is expressed primarily in kidney and liver, and that the kidney expression begins postnatally and continues in the adult. Expression of this mRNA was found to be significantly decreased upon acute renal injury induced by a single intraperitoneal injection of folic acid, and to return to normal levels upon recovery of kidney function. Analysis of the cDNA sequence predicted a protein of 349 amino acids (aa), which was confirmed by in vitro translation of a sense-strand transcript, producing a protein of approx. 39 kDa. The aa sequence shows similarity to Flavobacterium sp. and Pseudomonas diminuta parathion hydrolase (phosphotriesterase or PTE), an enzyme that hydrolyzes toxic organophosphates and other phosphotriesters, and to the predicted product of an Escherichia coli open reading frame of unknown function (phosphotriesterase homology protein or PHP). Use of optimal alignment programs demonstrated a significant overall homology between the bacterial and mouse sequences, with greater than 50% aa sequence similarity. This cDNA represents the first eukaryotic sequence showing similarity to these prokaryotic genes. Based on this apparent homology, it has been named mpr56-1 (for mouse phosphotriesterase-related 56-1).

Role of CD3 gamma in T cell receptor assembly

The T cell receptor (TCR) consists of the Ti alpha beta heterodimer and the associated CD3 gamma delta epsilon and zeta 2 chains. The structural relationships between the subunits of the TCR complex are still not fully known. In this study we examined the role of the extracellular (EC), transmembrane (TM), and cytoplasmic (CY) domain of CD3 gamma in assembly and cell surface expression of the complete TCR in human T cells. A computer model indicated that the EC domain of CD3 gamma folds as an Ig domain. Based on this model and on alignment studies, two potential interaction sites were predicted in the EC domain of CD3 gamma. Site-directed mutagenesis demonstrated that these sites play a crucial role in TCR assembly probably by binding to CD3 epsilon. Mutagenesis of N-linked glycosylation sites showed that glycosylation of CD3 gamma is not required for TCR assembly and expression. In contrast, treatment of T cells with tunicamycin suggested that N-linked glycosylation of CD3 delta is required for TCR assembly. Site-directed mutagenesis of the acidic amino acid in the TM domain of CD3 gamma demonstrated that this residue is involved in TCR assembly probably by binding to Ti beta. Deletion of the entire CY domain of CD3 gamma did not prevent assembly and expression of the TCR. In conclusion, this study demonstrated that specific TCR interaction sites exist in both the EC and TM domain of CD3 gamma. Furthermore, the study indicated that, in contrast to CD3 gamma, glycosylation of CD3 delta is required for TCR assembly and expression.

Effect of exposure to novelty on brain monoamines in C57BL/6 and DBA/2 mice

Male and female mice from two inbred strains, C57BL/6 (B6) and DBA/2 (D2), were exposed to a novel environment (vs. undisturbed control) for 10 min. Immediately after this treatment, the animals were sacrificed by cervical dislocation, and the brains were removed and dissected into ventral midbrain (VMB), caudate-putamen (CP), nucleus accumbens (NA), and medial prefrontal cortex (FC). Analyses of dopamine (DA) and its metabolites, dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA) and serotonin (5-HT) and its metabolite, 5-hydroxyindole-3-acetic acid (5-HIAA) were made by high-performance liquid chromatography. Utilization of the parent amines was estimated by the ratios, DOPAC/DA, HVA/DA, and 5-HIAA/5-HT. Novelty increased DOPAC levels in NA of both strains of mice and in CP of D2 males; however, it did not induce significant changes in DA, or 5-HT levels or utilization of the latter. The results did, however, reveal large strain differences in DA and its metabolites. The data suggest that genetically based neurophysiological and neurochemical differences exist in dopaminergic and serotonergic systems in mice, and that the DA systems in NA may be more sensitive to novelty than other DA systems.

Duration of inhibition of local microvascular ACE in spontaneously hypertensive rats

OBJECTIVE

To investigate in vivo the duration of inhibition of local angiotensin converting enzyme (ACE) in the microcirculation after a 2-week oral treatment by three different ACE inhibitors.

DESIGN

The local renin-angiotensin system was studied in the microcirculation of cremaster muscle in spontaneously hypertensive rats treated by gavage with equihypotensive doses of trandolapril (0.6 mg/kg per day), enalapril (10 mg/kg per day) and perindopril (2 mg/kg per day) for 2 weeks. Intravital microscopy was used in an original preparation of cremaster isolated from its normal blood supply and externally perfused with physiological solution, allowing exclusion of the circulating converting enzyme. Local ACE activity was estimated by measuring vasoconstriction in response to 0.01 and 0.1 nmol/ml angiotensin I in the arterioles studied and classified as being of second, third and fourth order (mean diameters 58 +/- 6, 30 +/- 4 and 15 +/- 1 mu m for the three orders, respectively).

RESULTS

No difference among the ACE inhibitors was found 3 h after the last dose. Conversely at 7, 24 and 48 h after the last dose, a significant difference was found among the ACE inhibitors, with ACE inhibitors being higher in rats treated with trandolapril than in the other two groups. In addition, a comparison with untreated spontaneously hypertensive rats showed that significant inhibition persisted 48 h after the last dose for trandolapril- and perindopril- but not enalapril-treated rats.

CONCLUSION

Large differences exist between the duration of inhibition of the microvascular ACE in vivo. At that level of the vascular system, trandolapril appeared to provide the greatest duration of inhibition among the three ACE inhibitors tested.

[Correlation between roentgenogram and CT scans with the changes of cells in bronchoalveolar lavage fluid in sarcoidosis]

Considering protean and variability of chest findings of sarcoidosis, the correlation between finding on roentgenogram and CT scans with changes of total, differential cell count and subsets of lymphocytes of BALF in 25 cases with sarcoidosis was studied. The results showed that CT could detect more groups of enlarged lymph nodes in the mediastinum and more minimal lesions in lung parenchyma in those patients who showed stage 0 and I on chest roentgenogram. The parenchymal changes were distributed mainly among the bronchovascular sheath. Good correlation was found between findings on CT scan and total cell count in BALF. Fibrotic changes on CT scan were usually associated with an increase in neutrophils of BALF. It indicated that CT could more precisely assess the lesions in the mediastinum and lung parenchyma and be served as an important supplementary diagnostic measure to roentgenogram for patients with sarcoidosis.

The (S)-(+)-enantiomer of dimethindene: a novel M2-selective muscarinic receptor antagonist

The present study was designed to determine to determine the in vitro affinity profile of (R)-(-)-dimethindene and (S)-(+)-dimethindene at muscarinic receptor subtypes using both functional and binding assays. In addition, the racemate was investigated in functional studies. The functional muscarinic receptors studied were putative M1 receptors in rabbit vas deferens and rat duodenum, M2 receptors in guinea-pig left atria and rabbit vas deferens, as well as M3 receptors in guinea-pig ileum and trachea. Furthermore, the histamine H1 antagonism by (R)-(-)- and (S)-(+)-dimethindene has been examined in guinea-pig ileum. Muscarinic binding selectivity was assessed in homogenates from human neuroblastoma NB-OF 1 cells (M1), rat heart (M2), pancreas (3) and striatum (M4). The results demonstrate that (S)-(+)-dimethindene is a potent M2-selective muscarinic receptor antagonist (pA2 = 7.86/7.74; pKi = 7.78) with lower affinities for the muscarinic M1 (pA2 = 6.83/6.36; pKi = 7.08), the M3 (pA2 = 6.92/6.96; pKi = 6.70) and the M4 receptors (pKi = 7.00), respectively. The (S)-(+)-enantiomer was more potent (up to 41-fold) than the (R)-(-)-enantiomer in all muscarinic assays. In contrast, the stereoselectivity was inverse at histamine H1 receptors, the (R)-(-)-enantiomer being the eutomer (pA2 = 9.42; pA2/(S)-isomer = 7.48). In conclusion, (S)-(+)-dimethindene is a useful tool to investigate muscarinic receptor heterogeneity. In addition, this lipophilic compound might become the starting point for the development of M2-selective muscarinic receptor antagonists useful as diagnostic tools for quantifying muscarinic M2 receptors in the central nervous system with positron emission tomography imaging, and to test the hypothesis that muscarinic M2 receptor antagonists show beneficial effects in the treatment of cognitive disorders.

Comparative vasoactive effects of amrinone on systemic and pulmonary arteries in rabbits

Amrinone has been increasingly used in management of low cardiac output syndrome during anesthesia, particularly when associated with right heart failure and pulmonary hypertension. This in vitro study was performed to determine and compare the direct vasoactive effects of amrinone on isolated rabbit systemic and pulmonary arteries. Responses of aortic and pulmonary artery rings from New Zealand white rabbits were assessed in the presence and absence of intact endothelium and with or without precontraction by norepinephrine (NE, 3 x 10(-6)M) or potassium chloride (KCl, 3 x 10(-2)M). Using a tissue bath preparation, cumulative concentration response curves of amrinone were obtained at different concentrations after a period of stabilization. Amrinone caused a dose-related vasodilation of NE-precontracted aortic and pulmonary arteries. It elicited about 65% and 90% relaxation, respectively, at a concentration of 300 mumol/L. Amrinone also induced a dose-related vasodilation of KCl-precontracted aortic and pulmonary arteries but to a lesser degree. All these effects were endothelium independent. By comparison, amrinone caused more relaxation in both NE- and KCl-precontracted pulmonary artery than aortic rings. In conclusion, amrinone has significant endothelium-independent, direct vasodilatory effects on isolated rabbit systemic and pulmonary arteries, more pronounced in the latter, particularly NE-precontracted vessels. Amrinone may have some calcium channel-blocking effect.

S-100 beta immunoreactivity in neurones of the rat peripheral sensory ganglia

S-100 beta, which is capable of exerting neurotrophic effects on cultured neurones and promoting the survival of motor neurones in vivo, has recently been found in distinct neurones of the rat hindbrain. Here we report that S-100 beta, as well as being present in satellite and Schwann cells, is also present in neurones of sensory ganglia (dorsal root ganglion, trigeminal, petrosal, jugular and nodose ganglia) but absent from neurones of the superior cervical ganglion. In the sensory ganglia, many neurones were immunoreactive, while the staining intensity varied among the neurones. Neuronal S-100 beta appeared in developing rats as early as postnatal day 1. No immunoreactive neurones were observed in the superior cervical ganglion during development. The results are suggestive of selective neurotrophic effects of S-100 beta.

WT1 suppresses synthesis of the epidermal growth factor receptor and induces apoptosis

The Wilms tumor suppressor gene WT1 encodes a developmentally regulated transcription factor that is mutated in a subset of embryonal tumors. To test its functional properties, we developed osteosarcoma cell lines expressing WT1 under an inducible tetracycline-regulated promoter. Induction of WT1 resulted in programmed cell death. This effect, which was differentially mediated by the alternative splicing variants of WT1, was independent of p53. WT1-mediated apoptosis was associated with reduced synthesis of the epidermal growth factor receptor (EGFR), but not of other postulated WT1-target genes, and it was abrogated by constitutive expression of EGFR. WT1 repressed transcription from the EGFR promoter, binding to two TC-rich repeat sequences. In the developing kidney, EGFR expression in renal precursor cells declined with the onset of WT1 expression. Repression of EGFR and induction of apoptosis by mechanism that may contribute to its critical role in normal kidney development and to the immortalization of tumor cells with inactivated WT1 alleles.

[Changes of proteoglycans in lumbar intervertebral disc of bipedal rats with aging]

Using a computer based image analysis system and histological sections stained with Safranin O, we investigated systematically the variation of proteoglycans (PG) contents in the low lumbar discs of bipedal rats. Topographically, the PG concentration increased from the outer annulus to the inner nucleus pulposus region, which possesses the highest PG concentration. The PG content decreased with age, and a significant loss of PG was observed in the lumbar discs of bipedal rats as compared with controls, especially in the nucleus pulposus. These observations support the view that the higher abnormal mechanical stress accelerates disc degeneration.

Vasoactive effects of ketamine on isolated rabbit pulmonary arteries

Ketamine has been used in patients with congenital heart disease and pulmonary hypertension with hypothetical controversy. Its direct effect on pulmonary arteries has not yet been clearly characterized. This in vitro study was performed to determine the direct vasoactive effects of ketamine on isolated rabbit pulmonary arteries. Responses of pulmonary artery rings from New Zealand white rabbits were assessed in the presence and absence of intact endothelium and with or without precontraction by norepinephrine (NE, 3 x 10(-6)M) or potassium chloride (KCl, 3 x 10(-2)M). Using a preparatory tissue bath, cumulative concentration response curves of ketamine were obtained at different concentrations (0.03, 0.1, 0.3, 1, 3 mM) after a period of stabilization. Ketamine caused a dose-related vasodilation on KCl-precontracted pulmonary arteries. It elicited almost 100% relaxation at a concentration of 3 mM. Ketamine also induced a dose-related vasodilation on NE-precontracted pulmonary arteries at a lesser degree. All of the effects were endothelium independent. In conclusion, ketamine has strong endothelium-independent, direct vasodilatory effects on isolated rabbit pulmonary arteries. Ketamine may act through Ca++ channel-blocking effect as well as inhibition of Ca++ release from sarcoplasmic reticulum.

Distinct domains of the CD3-gamma chain are involved in surface expression and function of the T cell antigen receptor

The T cell antigen receptor (TcR) is a multisubunit complex that consists of at least six different polypeptides. We have recently demonstrated that the CD3-delta subunit cannot substitute for the CD3-gamma subunit in TcR cell surface expression, in spite of significant amino acid homology between these two subunits. To identify CD3-gamma-specific domains that are required for assembly of the complete TcR and for surface expression and function of the TcR, chimeric CD3-gamma/CD3-delta molecules were constructed and expressed in T cells devoid of endogenous CD3-gamma. Substitution of the extracellular domain of CD3-gamma with that of CD3-delta did not allow cell surface expression of the TcR. In contrast, substitution of the transmembrane and/or the intracellular domains of CD3-gamma with those of CD3-delta did allow TcR cell surface expression. These results conclusively demonstrate that the extracellular domain of CD3-gamma plays a unique role in TcR assembly. Functional analyses of the transfectants demonstrated that the intracellular domain of CD3-gamma is required for protein kinase C-mediated down-regulation of TcR but is dispensable for the pattern of tyrosine phosphorylation observed following activation through TcR.

Monoclonal antibody induced hearing loss

Monoclonal antibodies KHRI-3 and KHRI-5 identify antigens expressed on inner ear supporting cells and auditory hair cells respectively. To determine if these antibodies affect inner ear function groups of syngeneic Balb/c mice were inoculated with hybridomas KHRI-3, KHRI-5 and other Ig-secreting hybridomas. Hybridomas UM-A9, UM-7F11, the non-secreting SP2/0 myeloma and mice with no hybridoma were used as controls. Animals were tested for auditory brainstem responses (ABR) for frequencies of 4, 8, 16 and 24 kHz, before the inoculation of the hybridomas and at intervals of 6 to 10 days thereafter or daily once tumors became palpable. In normal mice there were no changes in ABR thresholds over the course of the experiment. Other control animals showed little change in ABR even when the growth of the hybridoma or myeloma tumors were far advanced. Of the KHRI-5 hybridoma bearing animals only one of seven animals exhibited threshold shifts greater than 15 dB. In contrast, most mice bearing the KHRI-3 hybridoma exhibited high frequency threshold shifts of 40-50 dB that coincided temporally with the growth of the hybridoma, the presence of circulating KHRI-3 antibody, and greatly increased immunoglobulin titers. Ears from KHRI-3-bearing mice that developed high frequency hearing loss also had a novel type of lesion in the basal turn of the cochlea that was characterized by loss of outer hair cells and absence of typical supporting cell scars. Such changes were not found in control hybridoma-bearing mice. These findings suggest that KHRI-3 antibody has an effect on hearing that is secondary to damage to the organ of Corti and loss of outer hair cells. Our results have important implications for antibody-mediated mechanisms of hearing loss and provide an animal model in which to study this phenomenon.

[An experimental study on the relationship between disc nutrition and disc degeneration]

Micro-angiography, scanning electron microscopy and hydrogen washout technique were used to investigate the disc nutrition condition and the nutritional pathway of endplate in bipedal rats with agting. Compared with the controls, the nutrition condition of bipedal rats underwent deterioration and the number of vascular distribution under the endplate decreased significantly, but no increase in thickness of endplate caused by microfractures of subchondral bone and callus formed during the healing process was observed. The abnormal stress may bring about vertebral body intra-osseous circulation disorder and then consequent decrease of vascular channels which related to the disturbance of disc nutrition. This strongly suggested that nutrition conditions of nucleus pulposus were not deteriorated by impaired diffusion capacity, but by decrease of vasculature that contacts with endplate.

Dual effect of clonidine on isolated rabbit pulmonary arteries

Clonidine, a partially selective agonist for alpha 2-adrenoceptors, has been increasingly used in anesthesia. Its direct effect on pulmonary arteries has not yet been clearly characterized. This in vitro study was performed to determine the vasoactive effects of clonidine on isolated rabbit pulmonary arteries. Responses of pulmonary artery rings from New Zealand white rabbits were assessed in the presence and absence of intact endothelium and with or without precontraction by norepinephrine (NE, 3 x 10(-6) M) or potassium chloride (KCl, 3 x 10(-2) M). Using tissue bath preparation, cumulative concentration response curves of clonidine were obtained at different concentrations (10(-8), 10(-7), 10(-6), 10(-5), 10(-4) M) after a period of stabilization. Clonidine caused vasoconstriction of isolated pulmonary arteries without any pretreatment. The magnitude of the constriction was dose related at lower concentrations and reached maximum of 300 g/g wet tissue when above 10(-6) M. On KCl-precontracted pulmonary arteries, clonidine caused significant dose-related vasoconstriction. On the NE-precontracted vessel rings, it elicited significant dose-dependent vasodilation up to 80% relaxation at 10(-4) M. All the above effects were endothelium independent. In conclusion, clonidine has dual endothelium-independent vasoactive effects, causing vasoconstriction on isolated rabbit pulmonary arteries, either untreated or precontracted with KCl, and vasodilation on those precontracted with NE. Clonidine may act as a competitive alpha-adrenoceptor blocking agent.

Leukocyte adherence in an ischemic muscle perfused by a collateral circulation

Leukocyte adherence was studied in an original experiment that allowed study of the microcirculation in an ischemic muscle perfused by a collateral circulation. In this model, the artery feeding the cremaster muscle was ligated. Then the muscle homolateral to the ligation and its contralateral muscle were both studied by intra-vital-microscopy at 4 h, 1, 3, 7, and 21 days after the ligation. Rats were treated or not with 20 mg/kg/day pentoxifylline (PTX) i.m. In untreated rats, we found that both short-lasting and long-lasting leukocyte adherence was largely increased in the postcapillary venules of the ischemic muscle but not in its contralateral control. This dramatic increase was not limited to the hours immediately after the arterial ligation but was also found up to 3 weeks after the ligation when blood flow was almost restored to normal. This suggested that when muscle blood flow was chronically reduced, some changes promoting leukocyte adherence may occur in the endothelium. In rats treated with PTX, we found very effective inhibition of leukocyte adherence.

Structural requirements for the occupancy of rat brain PACAP receptors and adenylate cyclase activation

N-terminally shortened analogues of PACAP(1-27) and PACAP(1-38), and analogues modified in position 1,2 or 3 were compared for their ability to interact with PACAP receptors and to activate or inhibit adenylate cyclase in rat brain hippocampus membranes. In the PACAP(1-27) series, deletion of the first two amino acids decreased the potency 3000-fold. PACAP fragments (3-27) to (9-27) were inactive on the enzyme. N-terminally shortened PACAP(1-38) analogues showed a similar profile but were 70 to 300-fold more potent than their PACAP(1-27) equivalents. PACAP(6-27) and PACAP(6-38) were competitive inhibitors of the PACAP(1-27) stimulated enzyme. The Kd values of PACAP(6-27) and PACAP(6-38) were of 1000 and 2 nM respectively. Surprisingly, the Kd values of PACAP(6-31) and (6-35), that were also unable to stimulate adenylate cyclase activity, were of 3 and 300 nM respectively. Replacement of His1 by Phe1 in PACAP(1-27) reduced the potency 600-fold. Replacement of Ser2 by Ala2 in PACAP(1-27) and PACAP(1-38) was of little consequence. Substitution of Ser2 by Phe2, DPhe2, Arg2 or DArg2 reduced 60 to 1000-fold the PACAP(1-27) potency but only 7 to 30-fold the PACAP(1-38) potency. Phe2 derivatives were inactive on the enzyme. Replacement of Asp3 by Asn reduced 4000-fold the PACAP(1-27) potency.(ABSTRACT TRUNCATED AT 250 WORDS)

Induction of epidermal growth factor receptor gene transcription by transforming growth factor beta 1: association with loss of protein binding to a negative regulatory element

Transforming growth factor beta (TGF-beta) is a potent modulator of cell growth in many systems. In normal rat kidney fibroblasts, TGF-beta 1 increases epidermal growth factor (EGF) receptor gene transcription and synergizes with EGF to stimulate growth in soft agar, a characteristic of the transformed phenotype. In order to identify the target of TGF-beta 1 action, we have used a series of 5' deletion mutants of the EGF receptor promoter linked to a chloramphenicol acetyltransferase reporter gene (ERCAT). The TGF-beta response element(s) was localized to a cis-regulatory region which resides between positions -919 and -860 relative to the ATG translation initiation codon of the EGF receptor promoter. This 60-base pair region contains a repressor of the EGF receptor promoter and a TGF-beta inhibitory element that mediates TGF-beta 1 suppression of transin/stromelysin gene transcription through binding of a Fos-containing protein complex. Cotransfection of c-fos, c-jun, or both expression vectors with the intact or 5'-deleted ERCAT constructs identified several Fos-responsive inhibitory regions within the EGF receptor promoter, but these did not localize to the -919 to -860 promoter region. Mobility shift assays showed binding of the 60-base pair DNA fragment to proteins in extracts from untreated normal rat kidney cells; the binding was specifically competed by oligonucleotides containing a CAGATG sequence but not by oligonucleotides containing the EGF receptor repressor or the TGF-beta inhibitory element. TGF-beta 1 treatment but not anti-Fos antibody caused a decrease in specific 60-base pair DNA-protein complex formation.(ABSTRACT TRUNCATED AT 250 WORDS)

Nitric oxide-independent response to acetylcholine by terminal arterioles in rat cremaster muscle

The aim of the present study was to establish whether, in terminal arterioles from the rat cremaster, acetylcholine (ACh) elicits nitric oxide (NO)-independent dilation corresponding to the transient ACh-induced endothelium-dependent hyperpolarization described in arteries. For this purpose, the responses of terminal arterioles [mean diam 15.0 +/- 0.4 (SE) microns] were studied by intravital microscopy in rat cremaster muscle. During 15 min of superfusion by 10(-5) M ACh, the response was characterized by an initial maximal dilation (peak time < 3 min) followed by a more sustained dilation that slightly decreased with time. Inhibition of NO synthesis by 2 x 10(-4) M N omega-nitro-L-arginine (L-NNA) significantly reduced, but did not eliminate, both the peak and sustained responses. Simultaneous administration of 2 x 10(-4) M L-NNA and 2 x 10(-5) M mefenamic acid, an inhibitor of prostaglandin synthesis, did not induce a significantly different response from that observed with L-NNA alone. Procaine (10(-3) M), which is known to inhibit completely ACh-induced hyperpolarization in carotid artery, drastically reduced the initial part of the ACh-induced dilation but not the sustained response. Simultaneous administration of procaine and L-NNA almost completely inhibited the peak response to ACh. Similar results were obtained when L-NNA was combined with a superfusion bath containing 20 mM KCl, a concentration known to reduce hyperpolarization in arteries.(ABSTRACT TRUNCATED AT 250 WORDS)

Local renin-angiotensin system in the microcirculation of spontaneously hypertensive rats

We studied the local renin-angiotensin system in the microcirculation of cremaster muscle in spontaneously hypertensive rats (SHR) and their normotensive Wistar-Kyoto (WKY) controls. We used intravital microscopy in an original preparation of cremaster isolated from its normal blood supply and externally perfused with physiological solution, thus allowing the exclusion of circulating converting enzyme, circulating renin, and circulating angiotensinogen. We classified arterioles studied as second-, third-, and fourth-order, with mean diameters, respectively, of 67 +/- 6, 35 +/- 2, and 17 +/- 1 microns in WKY controls and 61 +/- 5, 34 +/- 2, and 16 +/- 1 microns in SHR. No difference between WKY controls and SHR was found for arteriolar vasoconstrictions in response to topical administration of 0.01 to 1 nmol/mL angiotensin II. Conversely, in response to 0.01 to 1 nmol/mL angiotensin I, significantly more arteriolar vasoconstriction was found in SHR cremaster muscle. In both strains, responses to angiotensin I were significantly inhibited by 10 nmol/mL of the angiotensin-converting enzyme inhibitor lisinopril. When angiotensinogen-rich, renin-free plasma containing 2.3 nmol/mL angiotensinogen was administered, almost no vasoconstriction was found in WKY controls, but significant constrictions were observed in SHR (23 +/- 4%, 30 +/- 5%, and 41 +/- 4% for second-, third-, and fourth-order arterioles, respectively). In SHR, vasoconstriction in response to angiotensinogen-rich, renin-free plasma was dose dependent, was inhibited by lisinopril, and was not found 24 hours after bilateral nephrectomy. Topical administration of 1.2 micrograms/mL renin did not induce arteriolar vasoconstriction in either WKY or SHR cremaster muscle.(ABSTRACT TRUNCATED AT 250 WORDS)

Functionally important amino acids in the TCR revealed by immunoselection of membrane TCR-negative T cells

A spontaneous TCR cell surface variant (3P11) of the Jurkat T cell line is described and characterized. 3P11 was selected by incubation of Jurkat cells with anti-TCR mAb followed by passage through Ig anti-Ig columns and cloning. 3P11 contained mRNA for both Ti alpha and Ti beta and CD3 gamma, delta, epsilon and zeta. Biochemical analyses demonstrated that all of the TCR components were produced in 3P11 cells. The Ti alpha beta/CD3 gamma delta epsilon zeta complex was assembled in the endoplasmic reticulum but the zeta did not associate with this complex. Epitopes recognized by the Ti beta chain specific mAb beta F1 and JOVI as well as anti-V beta 8 were affected in the 3P11 Ti beta chain indicating that the 3P11 Ti beta chain was mutated. Transfection of a wild-type Ti beta cDNA into 3P11 cells reconstituted TCR expression. Sequence analyses of the 3P11 Ti beta chain demonstrated a guanine to adenine change in the second nucleotide of the triplet coding for cysteine191 resulting in a cysteine to tyrosine exchange. Cysteine191 is the C-terminal cysteine involved in the intrachain disulfide bond in the C domain of the Ti beta chain; thus, the 3P11 Ti beta chain did not contain this disulfide bond. Transfection of a site-directed Ti beta chain containing the 3P11 mutation into a Ti beta negative variant of the Jurkat cell line resulted in a TCR phenotype identical with 3P11 demonstrating that the mutation identified in the 3P11 Ti beta chain was the sole cause for the 3P11 defect.

Functionally important amino acids in the TCR revealed by immunoselection of membrane TCR-negative T cells

A spontaneous TCR cell surface variant (3P11) of the Jurkat T cell line is described and characterized. 3P11 was selected by incubation of Jurkat cells with anti-TCR mAb followed by passage through Ig anti-Ig columns and cloning. 3P11 contained mRNA for both Ti alpha and Ti beta and CD3 gamma, delta, epsilon and zeta. Biochemical analyses demonstrated that all of the TCR components were produced in 3P11 cells. The Ti alpha beta/CD3 gamma delta epsilon zeta complex was assembled in the endoplasmic reticulum but the zeta did not associate with this complex. Epitopes recognized by the Ti beta chain specific mAb beta F1 and JOVI as well as anti-V beta 8 were affected in the 3P11 Ti beta chain indicating that the 3P11 Ti beta chain was mutated. Transfection of a wild-type Ti beta cDNA into 3P11 cells reconstituted TCR expression. Sequence analyses of the 3P11 Ti beta chain demonstrated a guanine to adenine change in the second nucleotide of the triplet coding for cysteine191 resulting in a cysteine to tyrosine exchange. Cysteine191 is the C-terminal cysteine involved in the intrachain disulfide bond in the C domain of the Ti beta chain; thus, the 3P11 Ti beta chain did not contain this disulfide bond. Transfection of a site-directed Ti beta chain containing the 3P11 mutation into a Ti beta negative variant of the Jurkat cell line resulted in a TCR phenotype identical with 3P11 demonstrating that the mutation identified in the 3P11 Ti beta chain was the sole cause for the 3P11 defect.

CD3 gamma contains a phosphoserine-dependent di-leucine motif involved in down-regulation of the T cell receptor

Several cell surface receptors including the T cell receptor (TCR) are phosphorylated and down-regulated following activation of protein kinase C (PKC). Among other substrates the activated PKC in T cells phosphorylates the CD3 gamma subunit of the TCR. To investigate the role of CD3 gamma phosphorylation in PKC-mediated TCR down-regulation, point mutated CD3 gamma cDNA was transfected into the CD3 gamma-negative T cell line JGN and CD3 gamma transfectants were analysed. Phosphorylation at S126 but not S123 in the cytoplasmic tail of CD3 gamma was required for PKC-mediated down-regulation of the TCR. Furthermore, analysis of a series of CD3 gamma truncation mutants indicated that in addition to S126 phosphorylation a motif C-terminal of S126 was required for TCR down-regulation. Point mutation analyses confirmed this observation and demonstrated that a membrane-proximal di-leucine motif (L131 and L132) in the cytoplasmic tail of CD3 gamma was required for PKC-mediated TCR down-regulation in addition to phosphorylation at S126. Incubation of T cells in hypertonic medium known to disrupt normal clathrin lattices severely inhibited PKC-mediated TCR down-regulation in non-mutated T cells, indicating that the TCR was down-regulated by endocytosis via clathrin coated pits. Based on the present results and previously published observations on intracellular receptor sorting, a general model for intracellular sorting of receptors containing di-leucine- or tyrosine-based motifs is proposed.

Structure of the T cell receptor in a Ti alpha V beta 2, alpha V beta 8-positive T cell line

The T cell receptor (TcR) is composed of at least six different polypeptide chains consisting of the clonotypic Ti heterodimer (Ti alpha beta or Ti gamma delta) and the noncovalently associated CD3 chains (CD3 gamma delta epsilon zeta). The exact number of subunits constituting the TcR is still not known; however, it has been suggested that each TcR contains two Ti dimers. To gain insight into the structure of the TcR we constructed a Ti alpha V beta 2, alpha V beta 8-positive T cell line which expressed the endogenous human TiV beta 8 and the transfected mouse TiV beta 2 both in association with the endogenous Ti alpha and CD3 chains at the cell surface. Preclearing experiments with radioiodinated cell lysate prepared with digitonin lysis buffer demonstrated that depleting the lysate of Ti alpha V beta 8 by immunoprecipitation with anti V beta 8 monoclonal antibody (mAb) did not reduce the amount of Ti alpha V beta 2 in the lysate, and likewise, depleting the lysate of Ti alpha V beta with anti-V beta 2 mAb did not reduce the amount of Ti alpha V beta 8. Comodulation experiments showed that V beta 8 and V beta 2 did not comodulate with each other. Furthermore, functional tests demonstrated that TcR containing V beta 8 and TcR containing V beta 2 mediated transmembrane activation signals independently of each other. These data demonstrate that mouse V beta 2 and human V beta 8 were not expressed in the same TcR in agreement with a TcR model where each TcR contains only one Ti dimer.

Identification of an epidermal growth factor receptor transcriptional repressor

Identification of the factors controlling transcription of the epidermal growth factor (EGF) receptor gene is essential for understanding regulation of the EGF receptor and its overexpression in human carcinomas. In this study, we have identified a 60-base pair (bp) region (-919 to -860) relative to the AUG translation initiation codon in the EGF receptor 5' promoter that functions as a cis-acting EGF receptor transcriptional repressor (ETR). This fragment also acted as a repressor when linked to the thymidine kinase promoter. Gel mobility shift assays demonstrated that trans-acting factors bind to 60- and 19-bp fragments. Competition and chloramphenicol acetyltransferase assays with oligonucleotides containing mutations and deletions in this region indicate that the TTCGAGGG sequence (-877 to -870) is required for binding as well as repressor activity. While the ETR-protected region contains consensus sequences for the E2F binding site, no competition was observed with an E2F binding fragment. However, DNA-protein blot analysis indicates that both the 60- and 19-bp fragments specifically bind a 128-kDa polypeptide in extracts from HeLa or A431 human epidermoid carcinoma cells. These results suggest that a novel transcription factor(s) negatively regulates EGF receptor gene expression through binding to the ETR element.

Utility of quantitative enzyme immunoassay reactivity for predicting human immunodeficiency virus seropositivity in low- and high-prevalence populations

To assess the utility of quantitative enzyme immunoassay (EIA) reactivity for predicting human immunodeficiency virus seropositivity, we evaluated 22,823 serum samples from homo- and bisexual men, heterosexual intravenous drug users, and other heterosexuals with initial screening by EIA, retesting of reactive samples in duplicate, and confirmatory Western blot (immunoblot) testing. Quantitative EIA reactivity was determined by a mean of the optical density ratio of the three assays performed for each reactive specimen. A total of 1,773 samples (7.8%) were repeatedly reactive, and 1,747 (7.7%) were confirmed Western blot positive. All 26 EIA-reactive-Western blot-negative samples had low-level EIA reactivity (ratio < 2.2), while most (86%) of the Western blot-positive samples had high-level reactivity (ratio, > 3.0). The positive predictive value for samples with moderate-to-high-level EIA reactivity (ratio, > 2.2) was 100% for all risk groups. These results support the value of quantitative EIA reactivity in predicting human immunodeficiency virus seropositivity and suggest that confirmatory testing of specimens with high-level reactivity is not necessary in all situations.

Expression of pituitary adenylate cyclase activating polypeptide (PACAP) receptors in human glial cell tumors

Twenty-three human gliomas were analyzed: 13 astroglial neoplasms including three grade II, four grade III, and six grade IV tumors; seven ependymomas; and three oligodendrogliomas. A crude membrane fraction was prepared within 30 min after surgical removal of the tumors and was immediately tested for the presence of pituitary adenylate cyclase activating polypeptide (PACAP) receptors. PACAP stimulated adenylate cyclase activity in 23 tumors, but a specific binding of [125I-acetyl-His1]PACAP-27 was detected in only 16 tumors. In all cases, PACAP-27 and -38 were equipotent (Kd or Kact of 1-3 nM) and were 100- to 1000-fold more potent than VIP. PACAP stimulated threefold the adenylate cyclase activity in the presence of GTP. The results were compatible with an interaction of PACAP with a highly selective type I PACAP receptor and not with a high-affinity VIP/PACAP type II receptor. The presence of PACAP receptors on glial neoplasic opens the possibility of a control of the tumor growth by this family of peptides.

Red blood cell aggregation and microcirculation in rat cremaster muscle

Using intravital microscopy of the rat cremaster muscle, we studied the effects of changing red blood cell (RBC) aggregation on RBC arteriolar velocity and perfused capillary density (PCD). To modify RBC aggregation, 2 and/or 10% dextran (molecular weights 40,000, 70,000 or 480,000) or fresh rat plasma was infused into adult male rats via a normovolemic hemodilution procedure. The high-molecular-weight dextrans (70,000 and 480,000) both induced RBC hyperaggregation associated with similar dose-dependent decreases in RBC arteriolar velocity (30 and 40% for dextran concentrations of 2 and 10%, respectively) and in PCD (35 and 37%, respectively, for the two concentrations). Conversely, with 40,000 molecular weight dextran or plasma, we observed a 30% increase in RBC arteriolar velocity, but no change in PCD or hyperaggregation. Intravenous injection of the antiaggregating drug troxerutin (10(-3) M), either before or after 2% dextran 70,000, significantly inhibited the effects of this dextran on RBC arteriolar velocity and on PCD. We conclude that RBC hyperaggregation can lead to changes in both arteriolar velocity and PCD and may, therefore, impair tissue oxygenation.

Arteriolar constriction and local renin-angiotensin system in rat microcirculation

Intravital microscopy was used in a preparation of rat cremaster muscle that was isolated from its normal blood supply and externally perfused with a physiological solution, thus allowing exclusion of circulating converting enzyme, renin, and angiotensinogen. The arterioles studied were classified as second-, third-, and fourth-order arterioles with mean diameters of 60.5, 29.9, and 14.8 microns, respectively. Topical administration of 1 nmol/mL angiotensin I or 1 nmol/mL tetradecapeptide renin substrate induced marked vasoconstrictions (i.e., 38.5%, 61.5%, and 90.1% and 25%, 34%, and 88% for second-, third-, and fourth-order arterioles with angiotensin I and tetradecapeptide renin substrate, respectively). The angiotensin converting enzyme inhibitor quinapril significantly inhibited the vasoconstrictions caused by either angiotensin I or tetradecapeptide renin substrate. Almost no vasoconstriction was found when angiotensinogen-rich renin-free plasma containing either 2.45 nmol/mL of angiotensinogen or 1.2 micrograms/mL renin was administered. Conversely, these two compounds induced significant constrictions in cremaster muscle preparations in which normal blood perfusion (and thus circulating renin and angiotensinogen) was left in place. We concluded that, in skeletal muscle, 1) the microvascular network is a very effective site of local angiotensin converting enzyme activity and consequently an important target site of angiotensin converting enzyme inhibitors; 2) the effects of tetradecapeptide renin substrate are very different from those of angiotensinogen from plasma and suggest that a large part of the effect of tetradecapeptide renin substrate was due to its nonspecific hydrolysis; and 3) at the microvascular level, circulating renin and angiotensinogen are more effective in inducing arteriolar constriction, in the presence of their substrate or associated enzyme, than local renin and angiotensinogen.

Antagonistic properties are shifted back to agonistic properties by further N-terminal shortening of pituitary adenylate-cyclase-activating peptides in human neuroblastoma NB-OK-1 cell membranes

N-terminally shortened analogs of the 27-amino-acid and 38-amino-acid forms of the pituitary-adenylate-cyclase-activating neuropeptide, PACAP(1-27) and PACAP(1-38), were synthesized by a solid-phase method. Systematic deletion of the first 13 amino acids of both PACAP was tested by evaluating their ability to occupy the specific and selective PACAP receptor of human neuroblastoma NB-OK-1 cell membranes and to stimulate adenylate cyclase or, when inactive per se, to inhibit PACAP-stimulated adenylate cyclase activity. For each peptide, the Kact (concentration required for half-maximal adenylate cyclase activation) or Ki [concentration required to shift the dose/response curve of PACAP(1-27) twofold to the right] was in good agreement with the corresponding IC50 [concentration inhibiting 50% of 125I-[AcHis1]PACAP(1-27) binding to membranes], suggesting interaction with the same homogeneous class of adenylate cyclase-coupled receptors. The deletion of the two first amino acids (His1 and Ser2) sufficed to decrease the affinity for receptors and to suppress the capacity to activate adenylate cyclase. The shorter fragments 3-27 and 3-38, 4-27 and 4-38, 5-27 and 5-38, 6-27 and 6-38, 7-27 and 7-38, 8-27 and 8-38, and 9-27 and 9-38 were all competitive antagonists of PACAP(1-27)-stimulated activity with the N-terminally shortened PACAP(1-38) derivatives being 4-30-fold more potent than the equivalent PACAP(1-27) derivatives. In this group PACAP(6-38) was the most potent antagonist (Ki 1.5 nM). Surprisingly, the N-terminally shorter fragments 10-27 and 10-38, 11-27 and 11-38, 12-27 and 12-38, 13-27 and 13-38, and 14-27 and 14-38 were again able to stimulate adenylate cyclase, the smallest fragments, PACAP(14-27) and PACAP(14-38), being the most potent and efficient (Kact 2 microM and 0.1 microM, respectively). In this group of agonists, PACAP(1-38) derivatives deleted at the N-terminus were also more potent than the equivalent PACAP(1-27) derivatives.

[Acute herpes simplex encephalitis treated with acyclovir. Report of 5 cases]

5 cases of acute herpes simplex encephalitis were verified by specific IgG antibodies in cerebrospinal fluid and serum among 31 cases with 'sporadic encephalitis' within one year. All were treated with acyclovir, 4 with remarkable response--2 cured and 2 significantly recovered, except one died due to delayed specific treatment. The dosage of acyclovir used by the author was 5mg/kg/12-24 hours.

Structural mutations of C-domains in members of the Ig superfamily. Consequences for the interactions between the T cell antigen receptor and the zeta 2 homodimer

Several molecules belonging to the Ig superfamily are expressed together with noncovalently associated subunits. This applies for membrane-bound IgM and IgD, some of the FcR, and the Ti dimers of the TCR. The interactions between members of the Ig superfamily and their associated subunits are still not fully understood. We locate critical amino acid residues for TCR assembly in the Ti-alpha and -beta extracellular C-domains. A point mutation (phenylalanine195----valine) in a highly conserved residue in the Ti-alpha chain of the Jurkat variant J79 was identified by DNA sequencing. This mutation did not prevent cytoplasmic association of Ti alpha beta and CD3 gamma delta epsilon, but abolished binding of the zeta 2 homodimer to the rest of the TCR. The consequences of this mutation for TCR assembly were confirmed by transfection of a site-directed mutagenized Ti-alpha chain into a Ti-alpha-deficient Jurkat variant. Computer model analysis showed that the Ti-alpha phenylalanine195 directly contributed to the beta-sheet facing away from the Ti-beta chain, indicating that it could be directly involved in the interactions between one or more of the CD3 chains or the zeta 2 dimer. Site-directed mutagenesis of the corresponding residue in the Ti-beta chain demonstrated that a phenylalanine216----valine substitution had similar effects on TCR assembly as the Ti-alpha mutation, whereas a phenylalanine216----histidine substitution allowed TCR assembly and expression. Whether the consequences for TCR assembly of the Ti-alpha and -beta mutations were due to any direct effects on the interaction between zeta and the Ti alpha beta dimer or to indirect effects are discussed.

Structural mutations of C-domains in members of the Ig superfamily. Consequences for the interactions between the T cell antigen receptor and the zeta 2 homodimer

Several molecules belonging to the Ig superfamily are expressed together with noncovalently associated subunits. This applies for membrane-bound IgM and IgD, some of the FcR, and the Ti dimers of the TCR. The interactions between members of the Ig superfamily and their associated subunits are still not fully understood. We locate critical amino acid residues for TCR assembly in the Ti-alpha and -beta extracellular C-domains. A point mutation (phenylalanine195----valine) in a highly conserved residue in the Ti-alpha chain of the Jurkat variant J79 was identified by DNA sequencing. This mutation did not prevent cytoplasmic association of Ti alpha beta and CD3 gamma delta epsilon, but abolished binding of the zeta 2 homodimer to the rest of the TCR. The consequences of this mutation for TCR assembly were confirmed by transfection of a site-directed mutagenized Ti-alpha chain into a Ti-alpha-deficient Jurkat variant. Computer model analysis showed that the Ti-alpha phenylalanine195 directly contributed to the beta-sheet facing away from the Ti-beta chain, indicating that it could be directly involved in the interactions between one or more of the CD3 chains or the zeta 2 dimer. Site-directed mutagenesis of the corresponding residue in the Ti-beta chain demonstrated that a phenylalanine216----valine substitution had similar effects on TCR assembly as the Ti-alpha mutation, whereas a phenylalanine216----histidine substitution allowed TCR assembly and expression. Whether the consequences for TCR assembly of the Ti-alpha and -beta mutations were due to any direct effects on the interaction between zeta and the Ti alpha beta dimer or to indirect effects are discussed.

[Diagnostic value of cytological examination of the cerebrospinal fluid with the millipore membrane filter technique]

With the millipore membrane filter (MP) technic 280 samples of CSF from 203 cases with different diseases involving the central nervous system were studied. 76 of these samples were examined with the slide centrifuge technic simultaneously for comparison. In accordance with the pathological cell components (transformed lymphocytes, plasmocytes, different phagocytes, granular neurocytes and tumor cells) as well as the clinical data, the diagnostic results could be divided into three groups. The diagnoses were definitely established in 19.6% of the cases with the cytological examination of the CSF. The diagnoses were suggestive in 50.7% and not established with the cytological examination of the CSF in 29.6%. With intracranial infection, demyelinating disease, cerebrovascular accidents and brain tumors an overall higher positive diagnostic rate of 76.8% was obtained and with other neurological disorders it was only 19.2% (P less than 0.001). The advantages and disadvantages of the MP technic were compared with those of the slide centrifuge and sedimentation chamber technics. The limitation of the staining method for the MP slides remained to be further studied. More than two technics for concentrating CSF cells were recommended to be in use for the time being.

Acute effects of tumor necrosis factor on the microcirculation in rat cremaster muscle

The acute effects of TNF on the microcirculation were studied by in vivo microscopy in rat cremaster muscle. The changes in arteriolar diameter after topical administration of recombinant TNF (rTNF; 10(-4)-10(4) ng/ml) were studied in second-, third-, and fourth-order arterioles (A2-A4) whose mean diameters under control conditions were 64.3, 30.7, and 14.8 microns respectively. rTNF induced a concentration-dependent vasodilation whose amplitude was largest for the smallest arterioles. At the highest concentration tested, arteriolar diameter increased by 21, 29, and 41% of control diameter for the A2, A3, and A4 arterioles, respectively. Indomethacin or mefenamic acid, two structurally different prostaglandin synthesis inhibitors, markedly inhibited the degree of vasodilation induced by rTNF in the three arteriolar orders. As regards the effect of rTNF on vasoconstriction in response to norepinephrine, vasoconstriction was greatest for the smallest arterioles, and did not change 10 min after rTNF administration for any of the three arteriolar orders. We conclude that (a) rTNF has a direct vasodilatory effect which is greatest in the smallest arterioles, (b) this vasodilation is at least partly mediated by prostaglandins, and (c) administration of rTNF in itself does not acutely alter the response of the arterioles to vasopressive drugs.

Microvascular effects of cocaine; interaction with nitrendipine and enalaprilat

Cocaine abuse can cause cardiovascular damage leading to hypertension, myocardial ischaemia and infarction. This might be partly due to the effects of cocaine on the microcirculation about which little is known, although its effects on the macrovessels are well documented. Accordingly, we used in vivo videomicroscopy to study the vasoconstrictive effect of cocaine on arterioles of different diameter. They were classified into three orders (A2, A3, A4) according to their position in the microvascular network and their diameter. Since calcium antagonists have been reported to exert a protective effect against the cardiovascular disorders induced by cocaine, we tested the hypothesis that this protective action occurs in the microcirculation. We found that intra-arterial administration of the calcium antagonist Nitrendipine greatly inhibited the vasoconstriction induced by cocaine in all three arteriole orders. The degree of inhibition ranged from 44 to 56%. Combined administration of benzodiazepine and an angiotensin converting enzyme inhibitor has also been reported to protect rats against cocaine-induced hypertension and to increase survival rates after a toxic dose of cocaine. Since the mechanisms of this protection are not yet clear, we also studied the effect of the angiotensin converting enzyme inhibitor Enalaprilat on cocaine-induced vasoconstriction. Intra-arterial administration of Enalaprilat inhibited this vasoconstriction slightly but significantly in arteriole orders 2 and 3 by 27 and 24% respectively, but not in order 4. We concluded that Nitrendipine is a powerful inhibitor of cocaine-induced vasoconstriction in the microcirculation. The small but significant inhibition found with Enalaprilat for the larger arterioles suggests that the local angiotensin II level may affect the response to cocaine. However, since the Enalaprilat-induced inhibition was very limited, we conclude that mechanisms other than those occurring in the peripheral microcirculation account for the protection afforded by Enalaprilat against the harmful effects of cocaine.

Changes of blood humoral substances in experimental cirrhosis and their effects on portal hemodynamics

The changes of humoral substances in the blood of cirrhotic rats were studied together with their effects on portal hemodynamics at different stages during the development of cirrhosis. The profiles of humoral substances and hemodynamics in two different cirrhotic rat models were also investigated. During the development of cirrhosis, glucagon increased markedly in all stages, histamine and vasoactive intestinal polypeptide (VIP) increased in the early stage, serotonin (5-HT) and somatostatin (SS) increased in the middle and late stages. There were different patterns of humoral substances in different cirrhotic models. Glucagon was the main humoral substance elevated in CCL4 induced cirrhosis, but histamine and 5-HT were mainly elevated in the blood in thioacetamide (TAA) induced cirrhosis. The hemodynamics altered differently in different stages during the development of cirrhosis and differently in the two cirrhotic rat models. Exchange transfusions between normal and cirrhotic rats resulted in an elevation of portal flow in normal rats, but no such changes were found after exchange pressure and an increase of portal blood transfusions between normal rats. The relationship between the humoral substances and portal hemodynamics is discussed. The results of this study strongly support the hypothesis of "humoral mechanism" in the pathogenesis of portal hypertension due to cirrhosis.

Kashin-Beck disease: a cross-sectional study in seven villages in the People's Republic of China

Kashin-Beck disease (KBD) is an endemic disease that occurs in certain parts of the People's Republic of China and in Russia. The etiology of the disease is unknown. Selenium deficiency, mycotoxins, and chelating agents such as humic acid and decaying plant material from walnut tree forests have been suggested as causal agents. The primary lesion of this disease is the selective coagulative necrosis of the hypertrophic chondrocytes at the base of the articular and growth plate cartilages. A cross-sectional study was performed in the People's Republic of China in 7 villages, to focus on information about life styles, food consumption, and environmental factors from the village population where the disease is endemic. A total of 425 children were examined, of which 71 children had KBD. Results of detailed food consumption data analyses showed that certain combinations of food substances high in protein had a protective effect. It was also found that the disease was twice as prevalent in onset in boys as in girls, in the 12-yr-old age group. The overall onset of illness in this group of children ranged from 4 to 13 yr. Either the joints of the fingers or one ankle was affected first. Many of these children also had discolored teeth. However, this finding was unrelated to KBD.

Independent role of arterial O2 tension in local control of coronary blood flow

The aim of this study of a blood-perfused isolated rabbit heart preparation was to differentiate the effects on coronary resistance of large changes in arterial O2 tension (arterial PO2 = 45-400 Torr) from the effects of variations in arterial O2 content or myocardial O2 delivery. Standard stored human blood was resuspended in Krebs-Henseleit buffer and was oxygenated to obtain normal PO2, high PO2, and low PO2. Hemoglobin concentrations were adjusted to obtain the same arterial O2 content (CaO2) for the three PO2s. In a first set of experiments, in which coronary blood flow (CBF) was free and adapted to a constant perfusion pressure, switching from control [138 +/- 17 (SE) Torr] to high PO2 blood (380 +/- 27 Torr) induced a significant decrease in CBF and myocardial O2 consumption (MVO2). Switching from control (125 +/- 3 Torr) to low PO2 blood (49 +/- 5 Torr) induced a significant increase in CBF and MVO2. In a second set of experiments, the switch from control (159 +/- 5 Torr) to high PO2 (389 +/- 32 Torr) was performed in a preparation in which CBF and consequently O2 delivery were constant. Under these conditions, the increase in perfusion pressure demonstrated that PO2 affected coronary resistance, even though the O2 delivery was constant. No significant change in myocardial performance was observed in any of these experimental procedures. These results show that arterial PO2 may affect coronary blood flow regulation independently of any mediation by the autonomic nervous system and of any associated changes in O2 content or O2 delivery.

Epidermal growth factor and its receptors in human pancreatic carcinoma

The role of epidermal growth factor (EGF) in oncogenesis and progression of malignant tumors is a subject of vast interest. In this study, radioimmunoassay and radioreceptor assay of EGF were established. EGF contents in malignant and benign pancreatic tumors, in normal pancreas tissue, and in culture media of a human pancreatic carcinoma cell line were determined. EGF receptor binding studies were performed. It was shown that EGF contents in pancreatic carcinomas were significantly higher than those in normal pancreas or benign pancreatic tumors. EGF was also detected in the culture medium of a pancreatic carcinoma cell line. The binding of 125I-EGF to the pancreatic carcinoma cells was time and temperature dependent, reversible, competitive, and specific. Scatchard analysis showed that the dissociation constant of EGF receptor was 2.1 X 10(-9) M, number of binding sites was 1.3 X 10(5) cell. These results indicate that there is an over-expression of EGF/EGF receptors in pancreatic carcinomas, and that an autocrine regulatory mechanism may exist in the growth-promoting effect of EGF on tumor cells.

Arteriolar vasoconstriction and tachyphylaxis with intraarterial angiotensin II

Several aspects of the differences between the responses of the second- to fifth-order arterioles (A2 to A5) to intraarterial administration of angiotensin II (AII) were studied by intravital microscopy on an original preparation of rat cremaster muscle. Dose-response curves displayed a leftward shift when the arteriolar order increased. Doses inducing 50% vasoconstriction were 15.1, 0.51, and 0.08 micrograms for A3, A4, and A5, respectively. For A2, very small vasoconstriction was found even at the highest dose of angiotensin II. The dynamics of the response were also dependent on the arteriolar order. The duration of the peak of vasoconstriction increased from A3 to A5, and the interval between the contact of vascular wall with drug and the response was smaller in A4 and A5 than in A3. To understand the effect of diameter as a determinant of heterogeneity in the degree of arteriolar vasoconstriction, norepinephrine was administered under the same conditions as angiotensin II, and responses were measured on arterioles with the same morphological characteristics as those examined after angiotensin II. When comparing the regression curves for the percentage of vasoconstriction vs diameter, we found that this relationship was drug dependent. The significantly steeper slope for angiotensin II than for norepinephrine excluded the possibility that heterogeneity of the degree of vasoconstriction is solely due to differences between the morphological characteristics of the arterioles. Since tachyphylaxis to AII is considered to be a reflection of the drug-receptor interaction, we also studied the magnitude of this phenomenon from proximal to distal parts of the arteriolar network. We showed that the degree of partial tachyphylaxis after 1 microgram AII was dependent on the arteriolar order and a decreasing tachyphylaxis gradient was evidenced from A3 to A5 arterioles.