Gene structure of the rat kainate receptor subunit KA2 and characterization of an intronic negative regulatory region

We have isolated and analyzed the structure of the gene grik5 (glutamate receptor ionotropic kainate 5), encoding the rat kainate receptor subunit KA2. Six overlapping DNA fragments containing the entire grik5 gene were identified in a rat genomic library. grik5 is a unique gene composed of 20 exons that together span over 54 kilobases (kb). Reporter gene analysis demonstrated that 2 kb of grik5 5'-flanking sequence confers tissue-specific expression on a chloramphenicol acetyltransferase gene in vitro. We show that (i) the first intron of grik5 (3.4 kb) inhibited transcription of the chloramphenicol acetyltransferase gene driven by the 2-kb grik5 5'-flanking region; (ii) the negative regulatory element was located within 500 bp of the 3'-end of intron 1, and this 500-bp fragment selectively bound nuclear proteins isolated from neural and nonneural cells; (iii) the effect of the negative regulatory element on grik5 transcription was orientation- and distance-independent; and (iv) a 24-nucleotide sequence (CTTTCTGTGGCCTCTGACCTTTCC) was identified as the binding site for nuclear proteins within the 500-bp fragment, as determined by footprinting and gel shift assays. We conclude that an intronic element that displays features of a silencer modulates grik5 transcription.

Inhibition of Toosendanin on the delayed rectifier potassium current in neuroblastoma x glioma NG108-15 cells

The effect of Toosendanin (TSN), a presynaptic transmission blocker, on the outward delayed rectifier potassium current (IKD) of NG108-15 cells was studied by using the whole-cell voltage-clamp technique. It was observed that externally applying TSN not only reduced IKD amplitude in a dose-dependent and partial reversible manner but also accelerated its inactivation. The effect of internally applying TSN was also examined by including TSN in the electrode, and it was the same as that of externally applying TSN. Further, comparison observations with TEA, 4-AP, verapamil, nifedipine, and (+/-)-Bay K 8644 were also made, and the results were as follows. The time courses of TSN's inhibition effect as well as its recovery after washing were much slower than those of TEA and 4-AP. Externally applying TEA or 4-AP reduced IKD amplitude but did not accelerate its inactivation. Externally applying verapamil, nifedipine, or (+/-)-Bay K 8644, however, similarly to the effect of TSN, not only reduced IKD amplitude but also accelerated its inactivation. Thus, from the obtained results it is suggested that TSN might diffuse into the cell interior and act intracellularly, and the underlying mechanism might be different from that of TEA and 4-AP but similar to that of verapamil, nifedipine, and (+/-)-Bay K 8644 to some extent.

Membrane permeabilization induced by cytolytic delta-endotoxin CytA from Bacillus thuringiensis var. israelensis

CytA is a member of a functionally defined family of insecticidal delta-endotoxins occurring in parasporal crystals of Bacillus thuringiensis var. israelensis. We investigated the ability of CytA to permeabilize the membrane and release fluorescence marker molecules from unilamellar lipid vesicles. Both protoxin (27 kDa) and proteolytically activated toxin (24 kDa) were very effective in permeabilization of unilamellar lipid vesicles: concentrations as low as several nanomolar produced a significant effect. The toxin was about 2-3 times more effective than the protoxin. The concentration of CytA required for the same extent of calcein release in large unilamellar vesicles (LUV) was 5-10 times lower than that in small unilamellar vesicles (SUV). Both small (calcein) and large (fluorescein-dextrans, MW 3000 and 10 000) molecules were released from the vesicles by CytA with comparable single-exponential kinetics. The release was an all-or-none event, i.e., each vesicle either released all of its contents or remained completely intact. Binding of CytA to lipid membranes did not show appreciable cooperativity, the apparent binding constant (Kapp) being on the order of 10(5) M-1. The plots of kinetics of release vs bound protein/ lipid ratio and the differential effects of CytA on LUV vs SUV indicate that at least 140 toxin molecules or 311 protoxin molecules must bind to an LUV before the latter starts losing its integrity. The necessity of adsorption of this relatively large number of toxin molecules to trigger permeabilization, together with the lack of discrimination in the size of the released marker molecules, suggests that the effect of CytA is a general, detergent-like, perturbation of the membrane rather than creation of small, well-defined, proteinaceous channels.

Searching eye movement, smooth pursuit eye movement and schizophrenia

OBJECTIVE

To detect whether the smooth pursuit eye movement (SPEM) and searching eye movement (SEM) could be considered as a biological marker of schizophrenia, and used as a tool in helping diagnosis of schizophrenia.

METHODS

88 schizophrenics, 77 patients with mood disorders, 32 with "neurosis", and 74 normal healthy controls were examined for SPEM and SEM individually. The authors verified the results in all the first-visit 150 outpatients in March 1993 by comparing the examination results with the clinical diagnoses after a 6-month follow-up.

RESULTS

Significant differences were found in the number of eye fixation (NEF) and total eye scanning length (TESL) of SEM between schizophrenics and normal controls or patients with other disorders. Less NEF and shorter TESL could be helpful in differential diagnosis, and the agreement rate, Kappa coefficient was 0.62. No significant differences were found in SPEM in this investigation between non-medicated schizophrenics and normal controls.

CONCLUSION

Searching eye movement (SEM) might be considered as a biological marker of schizophrenia and might be used as a supplementary tool in its diagnosis.

Assessment of chromatographic peak purity by means of artificial neural networks

An improved chemometric approach is proposed for assessing chromatographic peak purity by means of artificial neural networks. A non-linear transformation function with a back-propagation algorithm was used to describe and predict the chromatographic data. The Mann-Whitney U-test was used for the concluding the purity of the chromatographic peak. Simulation data and practical analytical data for both pure and mixture samples were analysed with satisfactory results. A prior knowledge of the impurity and the related compound is unnecessary when a slight difference between their chromatogram and spectrum exists. The performance on simulated data sets by this approach was compared with the results from principal component analysis.

Interaction of nitric oxide synthase with the postsynaptic density protein PSD-95 and alpha1-syntrophin mediated by PDZ domains

Neuronal nitric oxide synthase (nNOS) is concentrated at synaptic junctions in brain and motor endplates in skeletal muscle. Here, we show that the N-terminus of nNOS, which contains a PDZ protein motif, interacts with similar motifs in postsynaptic density-95 protein (PSD-95) and a related novel protein, PSD-93.nNOS and PSD-95 are coexpressed in numerous neuronal populations, and a PSD-95/nNOS complex occurs in cerebellum. PDZ domain interactions also mediate binding of nNOS to skeletal muscle syntrophin, a dystrophin-associated protein. nNOS isoforms lacking a PDZ domain, identified in nNOSdelta/delta mutant mice, do not associate with PSD-95 in brain or with skeletal muscle sarcolemma. Interaction of PDZ-containing domains therefore mediates synaptic association of nNOS and may play a more general role in formation of macromolecular signaling complexes.

A patient-derived cytotoxic T-lymphocyte clone and two peptide-dependent monoclonal antibodies recognize HLA-B27-peptide complexes with low stringency for peptide sequences

HLA-B27 molecules expressed on the T2 mutant cell line do not have peptides. Such empty HLA-B27 molecules were not recognized by an HLA-B27-restricted cytotoxic T-lymphocyte (CTL) clone (auto-1) derived from synovial fluid. To test for peptide dependency of the clone, B27-T2 cells were incubated with a panel of 48 different peptides. This lack of stringency was compared with that of a peptide-dependent monoclonal antibody, B27.M2. Positive B27.M2 reactivity resulted when the B27-T2 cells were incubated with two peptides: RRKAMFEDI and RRMGPPVGHR, derived from Chlamydia HSP60 and human ribonucleoprotein, respectively. Because of the limited availability of CTL versus monoclonal antibody, the specificity of B27.M2 was studied in greater detail. The importance of the HLA-B27 heavy chain in antibody recognition of class I-peptide complexes was demonstrated by site-directed mutagenesis. The stringency of the peptide residues was tested by making analogs of each of the nine residues in RRKAMFEDI, creating a panel of 180 analogs. Although stringency was highest for the sixth position, as many as six different amino acids provided positive reactivity. These results indicate that immune recognition of HLA-B27-peptide complexes might have rather low stringency for the peptide sequences. In theory, then, pathogen-derived peptides which induce autoimmunity by generating autoreactive CTL might not share much sequence similarity with the responsible self peptides.

Transforming growth factor beta 1 (TGF beta 1) is an autocrine positive regulator of colon carcinoma U9 cells in vivo as shown by transfection of a TGF beta 1 antisense expression plasmid

A transforming growth factor beta1 (TGF beta1) antisense expression plasmid under constitutive control of the Rous sarcoma virus promoter was introduced into the highly tumorigenic and invasive colon carcinoma U9A cell line, which uses its autocrine TGF beta1 as a growth-stimulating factor. Stable transfectants were infrequent, and only the K6 transfectant exhibited 39 and 33%, respectively, of the levels of TGF beta1 mRNA and active, secreted TGF beta1 protein of the parental line. K6 exhibited no change in TGF beta2 expression, and TGF beta3 expression was not detected in either parental or transfectant cells. Compared to the parental line, the K6 antisense transfectant exhibited a 3-fold increase in lag time in anchorage-dependent colony formation. The parental line was 44 times as invasive through a collagen l-coated polycarbonate membrane in vitro as K6 cells and, after s.c. injection at low-cell inocula, U9A cells induced tumors 75 times as large in vivo as did the K6 antisense transfectant. The decreases in in vitro invasion and anchorage-dependent colony formation seen in K6 cells were largely reversed by the addition of TGF beta1. Tumors that did arise from the K6 antisense transfectant cells had lost antisense TGF beta1 expression and expressed the same TGF beta1 mRNA levels as controls. U9A cells were more metastatic to the liver after intrasplenic injection than K6 cells. These findings demonstrate a role for autocrine TGE beta1 in colon cancer tumorigenicity and invasion. They also show that a relatively small decrease in TGF beta1 levels was enough to markedly decrease colon carcinoma cell aggressiveness. This is not unprecedented, as we had found in an earlier study that a small, 2-4-fold increase in TGF beta1 protein levels in human colon cancers correlated with disease progression to metastases (E. Friedman et al., Cancer Epidemiol, Biomarkers & Prev., 4:549-554, 1995).

Boron-containing oligodeoxyribonucleotide 14mer duplexes: enzymatic synthesis and melting studies

A set of three 14mer oligodeoxyribonucleotides of sequence d(5'-CTATGGCCTCAG*CT-3'/3'-GATACCGGAGTCGA-5') containing G* variants either as 2'-deoxyguanosine phosphate (unmodified), N7-cyanoborane 2'-deoxyguanosine phosphate (base-modified) or 2'-deoxyguanosine boranophosphate (backbone-modified) were synthesized by template-directed primer extension. Both the N7-cyanoborane 2'-deoxyguanosine triphosphate and 2'-deoxyguanosine alpha-boranotriphosphate nucleotides are good substrates for Sequenase. We infer that a single Sp boranophosphate linkage (which has a stereochemistry equivalent to the corresponding Rp thiophosphate analog) is formed in the backbone-modified 14mer. Thermally induced helix-coil transitions were monitored for the hybridized duplexes using UV and circular dichroism (CD) spectroscopy. The CD spectra of the two types of boron-modified hybrids closely resemble the unmodified parent duplex, forming B-type helices in 150 mM NaCl, 1 mM EDTA, 10 mM phosphate, pH 7.4, buffer. UV melting results indicate that both hybrids have stabilities comparable with the parent duplex as measured by Tm or delta G degree 25. These studies indicate that singly modified base- or backbone-boronated DNA are good analogs of normal DNA.

Platelet-derived growth factor-B increases colon cancer cell growth in vivo by a paracrine effect

PDGF-B released from colon tumor cells regulated tumor growth in athymic mice in a paracrine manner by inducing blood vessel formation. A positive correlation was found between expression of PDGF B-chain in cells grown in vitro and the number of factor VIII-positive blood vessels in tumors induced by three classes of colon carcinoma cell lines. Elevated expression of PDGF-B was also correlated with tumor size. Each cell line had the same mutations in the colon cancer genes APC, DCC, and p53 and had wild type c-K-ras genes (Huang et al. [1994] Oncogene, 9:3701-3706.) eliminating the possibility that any differences in tumor blood vessel formation were due to mutations and/or deletions in these genes. Colon carcinoma cells released biologically active PDGF capable of stimulating the growth of NIH3T3 cells, which was inhibited by neutralizing antisera to PDGF-AB chains. An inverse correlation was found between induction of factor VIII-positive blood vessels and expression of vascular endothelial growth factor (VEGF), while no correlation was seen with expression of either TGF alpha or k-FGF. Basic fibroblast growth factor (FGF) expression was not detected in these tumor cells. TGF beta 1 was capable of inducing PDGF-B expression in the undifferentiated U9 colon carcinoma cell line, but this sensitivity was not seen in differentiated cells. In contrast, TGF beta 1 inhibited VEGF expression in both undifferentiated cells and differentiated colon cancer cells. Thus, TGF beta 1 has two roles in the growth of undifferentiated U9 colon carcinoma cells in vivo: direct stimulation of cell proliferation as we have showed in earlier studies, and an increase in angiogenesis by inducing PDGF-B.

[Detection of estrogen receptor messenger ribonucleic acid in normal and ovariectomized rat bone]

Using ovariectomized female SD rats (OVX) as animal osteoporosis models, RNA samples were extracted directly from rat bone. Reverse transcriptase-polymerase chain reaction (RT-PCR) was used to examine the estrogen receptor (ER) messenger RNA (mRNA) level of expression in normal and OVX rat bone tissue. Results demonstrated that the rat ER gene is expressed in normal rat bone. DNA sequencing showed 300 bases sequence. We found that the OVX rats showed a sharp decrease in ER mRNA level when estrogen was reduced after ovariectomy and the expression of bone ER mRNA increased during estradiol therapy, suggesting that the expression of bone ER mRNA relies upon the level of estrogen. In addition, ER plays a very important role in the pathogenesis by means of its gene regulatory functions.

N7-cyanoborane-2'-deoxyguanosine 5'-triphosphate is a good substrate for DNA polymerase

The 5'-triphosphate of the boronated nucleoside analog N7-cyanoborane-2'-deoxyguanosine (7bdGTP) was synthesized, and a series of experiments was initiated to assess the potential of the compound to serve as a substrate for DNA polymerases. We show here that 7bdGTP can be incorporated into DNA by Sequenase. The resulting hemiboronated extension products are resistant to cleavage by treatment with either DMS and heat or a number of restriction enzymes. Further, in the polymerase chain reaction, 7bdGTP can be utilized as a substrate for Taq polymerase. Finally, by kinetic analysis, we have found that 7bdGTP is a more efficient substrate for exonuclease-free Klenow than normal dGTP. Thus, the introduction of a cyanoborane moiety to the N7 position of dGTP results in a nucleotide that is accepted in lieu of normal dGTP by a number of DNA polymerases.

Colon carcinoma cells with inactive nm23 show increased motility and response to motility factors

nm23H1 has properties of a metastasis suppressor gene. Although its mechanism of action is unknown, nm23 has been implicated in transforming growth factor beta 1 (TGF beta 1) signal transduction. In an earlier study we decreased nm23 mRNA levels 2- to 8-fold by antisense phosphorothiolated oligonucleotides in two HT29 colon carcinoma sublines at different stages in tumor progression with different responses to TGF beta 1: the HD3 subline, which shows TGF beta 1-induced growth arrest and differentiation; and the more tumorigenic U9 subline, whose growth and invasion are stimulated by TGF beta 1. Only TGF beta 1-mediated responses in HD3 cells were inhibited by nm23 antisense oligos, suggesting that nm23 functions in only one TGF beta 1 signaling pathway. In the current report we have extended this study to cell motility. HD3 motility was increased by nm23 phosphorothiolated antisense oligos which decrease nm23 mRNA levels, while HD3 cell motility was conversely decreased by TGF beta 1 which increases nm23 mRNA levels. HD3 motility was not increased by basic FGF, TGF beta 1 or TGF alpha, while the 13-fold higher basal motility of U9 cells was stimulated 3-fold by basic FGF, 4-fold by TGF beta 1 and 5-fold by TGF alpha, but not by scatter factor. Differences in motility and response to motility factors could not be ascribed to differences in either basal levels of proteases or modulation of their levels by TGF beta 1. Both HD3 and U9 cells displayed equal levels of urokinase activity and mRNA, equal expression of the metalloproteinase inhibitor TIMP-1, and no detectable collagenases by zymography. No differential response to TGF beta 1 was seen in any of these assays. Thus limited cell motility and lack of response to motility factors in HD3 colon cancer cells could be correlated with expression of nm23 active in signal transduction.

Colon absorptive epithelial cells lose proliferative response to TGF alpha as they differentiate

As colon epithelial cells migrate up the cylindrical colonic crypt, they terminally differentiate and lose their ability to divide. Elevated levels of the epithelial cell mitogen TGF alpha have been found at the top of the crypt by other investigators, causing us to speculate that colon epithelial cells lose mitogenic response to TGF alpha as they differentiate. We tested this hypothesis by using the HT29 colon carcinoma sublines U4 and U4H as models of one colonocyte lineage, fluid-transporting enterocytes. TGF alpha was mitogenic for the U4 cells, but inhibited the growth of the more differentiated U4H cells. However, p44 MAP kinase was activated by TGF alpha in both U4 and U4H cells, as well as in two control undifferentiated HT29 sublines which showed no change in proliferation in response to TGF alpha. In addition, TGF alpha activated the EGF receptor in each line by increasing its tyrosine phosphorylation. No relationship was found in these four lines between response to TGF alpha and level of expression of either the EGF receptor or two EGF receptor ligands, TGF alpha and amphiregulin. Activated EGF receptors initiate both growth-inhibitory and mitogenic signals in these cells since blocking some of the EGF receptors on TGF alpha-growth-inhibited U4H cells and TGF alpha-unresponsive U9 cells overrode the inhibitory signals and made both U9 and U4H cells sensitive to mitogenesis by added TGF alpha. These data imply that upon reaching stages of greater maturation, colon enterocytes lose proliferative response to TGF alpha because of changes in signaling by their EGF receptors.

Time of symptom onset of eight common medical emergencies

Specific time periods of the day may be associated with different frequencies of symptom onset in different diseases. The purpose of the current study was to examine times of symptom onset in eight commonly encountered emergent conditions--cerebral infarction, cerebral hemorrhage, transient ischemic attacks, cardiac dysrhythmias, angina pectoris, acute myocardial infarction, gastrointestinal bleeding, and acute asthma. Data from 4554 cases were retrospectively reviewed. Symptom onset frequency curve diagrams were derived, illustrating peak hours of symptom presentation for each of the eight emergent conditions. Hormonal and metabolic factors that may be related to diurnal variations in symptom onset of the eight diseases are briefly discussed.

Colon goblet cells lose proliferative response to TGF alpha as they differentiate

Two cell line models for colon goblet cells expressed 6- to 14-fold elevated levels of the EGF receptor, 3- to 5-fold levels of TGF alpha and 11- to 15-fold levels of amphiregulin compared with 2 cell lines which model colon enterocytic differentiation, suggesting a role for the EGF receptor and its ligands in goblet cell growth control. Two HT29 colon carcinoma sublines were used to model normal goblet cells at different stages of maturation. TGF alpha induced a 2-fold increase in growth of the HD8 subline but inhibited the growth of the more differentiated HD6 subline by 40%. EGF receptors were activated in each line by ligand, but signal transduction varied sharply. Both MAP kinase isoforms, p44 and p42, were markedly activated in HD8 cells for at least 20 min, while only a marginal activation was seen in HD6 cells. In contrast, the more differentiated HD6 cells showed an increase in 105 kDa MBP kinase activity with EGF treatment, while HD8 cells displayed constitutively elevated levels of this kinase. Thus, activated EGF receptors initiated different signalling pathways in model cell lines for colon goblet cells at different stages of maturation. TGF alpha protein levels have been shown by other investigators to be restricted to the top of the cylinder-like colonic crypt, where cells terminally differentiate and cease division, an unexpected location for an epithelial cell mitogen. Our data with model cell lines imply that normal colon goblet cells lose proliferative response to TGF alpha as they differentiate and the elevated levels of TGF alpha at the top of the colonic crypt in vivo serve to inhibit goblet cell growth.

An extensive subfrontal approach to the lesions involving the skull base

A modification of the transbasal approach of Dorome called extensive subfrontal approach and the surgical results with this approach in 22 cases are presented. Bilateral frontal craniotomies incorporated with the removal of orbital ridges and part of the orbital roofs were fashioned en bloc. It may give rise to good exposure of the midline lesions of the anterior, middle and posterior skull base, minimizing the need for the retraction of frontal lobes. There was no surgical mortality in this series of cases. Of the 20 cases with tumors, total resections were achieved in 11 cases, subtotal or large resections in 4 cases and partial resection in one case. Two patients with spontaneous rhinorrhea were successively treated surgically. 21 patients had a follow-up with a time ranging from 1-11 years (a mean of 3 years). 15 patients resumed their jobs with no evidence of recurrence of the original disease, and 5 patients able to live self-care. One patient with an olfactory neuroblastoma died 3 years after the operation owing to relapse of the tumor.

The effect of multiple blood conservation techniques on donor blood exposure in adult coronary and valve surgery performed with a membrane oxygenator: a multivariate analysis on 1310 patients

The object of the study was to retrospectively evaluate protective and risk factors for receiving donor blood products and red cell transfusions after coronary and valve surgery performed with a hollow-fiber oxygenator and with multiple blood-saving techniques. During the period of January 1991 to June 1993, 1310 patients underwent primary coronary and valve surgery using a hollow-fiber oxygenator at our institution; the mean age of this population was 61 +/- 10 years; 977 patients were men (74.6%). Of these patients, 73.5% (963/1310) underwent coronary, 21.5% (281/1310) valve, and 5% (66/1310) combined surgery. Two hundred seventy-six (21.1%) needed donor blood product transfusions, while 153 (11.7%) patients underwent red cell transfusions. Significant risk factors for homologous blood product exposure after multivariate logistic regression analysis were, in order of importance: (1) postoperative blood loss (O.R. = 1.0009 per mL, p = 0.0000); (2) cardiopulmonary bypass (CPB) time (O.R. = 1.008 per min, p = 0.0001); (3) age at intervention (O.R. = 1.031 per calendar year, p = 0.0026); and (4) reoperation for bleeding (O.R. = 1.71, p = 0.0078). Protective factors were: (1) male gender (O.R. = 0.56, p = 0.0000); (2) preoperative withdrawal of autologous blood (O.R. = 0.66, p = 0.0018); and (3) a preoperative hematocrit greater than 34% (O.R. = 0.76, p = 0.0005).(ABSTRACT TRUNCATED AT 250 WORDS)

Composite valve graft replacement of the ascending aorta and the aortic valve by a modified button technique: the influence of aortic pathology on early mortality and late survival

The risk factors for in-hospital mortality and mid-term survival in patients undergoing composite graft replacement of the aortic root with reimplant or coronary arteries by a modified button technique were evaluated with special emphasis on the underlying aortic pathology. Between 1985 and 1993 74 patients underwent replacement of the ascending aorta and the aortic valve following a modified button technique. The patients were divided into three groups according to aortic pathology: annuloaortic ectasia (43.58%), type A dissection (18.24%), and miscellaneous (13.18%). In-hospital mortality rates were 4.7%, 33.3% and 23.1%, respectively (P = 0.011). Univariate analysis showed that aortic pathology, NYHA class, emergency operation, redo operation, acute aortic dissection, preoperative cardiogenic shock, preoperative cardiac tamponade, longer cardiopulmonary bypass (CPB) and aortic cross-clamp times, and the need of femoral vein or femoral artery cannulation at intervention had univariate influence on in-hospital mortality. Multivariable stepwise logistic regression analysis identified CPB time odds ratio (OR) = 1.021/min, P = 0.007), the need of femoral vein cannulation at intervention (OR= 4.85, P = 0.008) and preoperative cardiac tamponade (OR = 3.11, P = 0.07) as independent predictors of in-hospital death. Follow-up ranged from 1 to 98 months (mean 39 +/- 30 months) with an actuarial survival rate of 75 +/- 9%, 52 +/- 13% and 67 +/- 14% at 5 years in annuloaortic ectasia, type A dissection, and miscellaneous patients, respectively (P = 0.18); when survival was evaluated in hospital survivors only, Kaplan-Meier survival rates were 77 +/- 9%, 79 +/- 14% and 89 +/- 10% at 5 years (P = 0.87). Comparing survival of annuloaortic ectasia patients (5-year survival 75 +/- 9%) versus survival of all other patients pooled together (5-year survival 55 +/- 11%), there was a statistically significant difference (P < 0.05); such a difference was no longer significant when comparing hospital survivors alone (5-year survival rate 77 +/- 9% annuloaortic ectasia patients vs 79 +/- 12% all other patients P = 0.61). Although aortic root replacement carries higher in-hospital mortality in some high-risk subgroups of patients, mid-term survival seems to be less affected by aortic pathology; high-risk patients are expected to have an out-hospital outcome comparable to the low-risk ones.

The capacity for growth stimulation by TGF beta 1 seen only in advanced colon cancers cannot be ascribed to mutations in APC, DCC, p53 or ras

Human colon cancer development is associated with the accumulation of mutations and deletions in the suppressor genes DCC, APC and p53 and mutations in the dominant oncogene K-ras, with loss of wild type alleles. In earlier studies we had observed that about half of the resected human colon cancers placed into primary culture were growth stimulated by TGF beta 1. This group included the more advanced cancers which were either poorly differentiated primary-site cancers or metastases. In contract, the more differentiated colon cancers were inhibited or unaffected by TGF beta 1, indicating that a switch in response to TGF beta 1 occurs during colon cancer progression. Different sublines of the HT29 colon carcinoma cell line model the resected cancers, responding to TGF beta 1 by proliferation, inhibition or no growth modulation. The current study shows that while the poorly differentiated, TGF beta 1-stimulated sublines are most tumorigenic, all the sublines have the same spectrum of mutations: truncating mutations in both APC (adenomatous polyposis coli) alleles, no activated ras genes, mutated and thus overexpressed p53, and very low expression of DCC compared to normal colon cells. Genes other than the four already implicated in colon carcinoma evolution are responsible for the mitogenic response to TGF beta 1 found in the more advanced cancers.

The effect of mutant beta 2-microglobulins on the conformation of HLA-B27 detected by antibody and by CTL

The arthritis-predisposing HLA-B27 consists of a heavy chain, a small peptide, and the monomorphic beta 2-microglobulin (beta 2-m). CTLs and a mAb, Ye-2, which recognize the complex with specificities both for the heavy chain and for the peptide, are available. The beta 2-m is in noncovalent association with the heavy chain at multiple points and is exchangeable with free beta 2-m outside of the complex. The purpose of our experiments was to test whether mutant beta 2-m capable of modulating HLA-B27 activity could be created. Eighteen recombinant mutants of the human beta 2-m were experimentally generated. In 14 of these, mutations were at or near residues that are either contact residues or interface residues with the heavy chain. Relative to the parent beta 2-m, two-thirds of the mutants showed reduced ability to exchange into HLA-B27 complexes. However, at least four of them induced more than 80% decrease in Ye-2 Ab reactivity. Two mutants were able to induce a minor decrease in susceptibility to lysis by four CTL clones. One of the CTL clones was autoreactive. Two of the CTL clones were specific for HLA-B27 cells experimentally infected with arthritis-causing Yersinia enterocolitica. These results indicate that certain beta 2-m residues play an indirect role in peptide presentation, although they are not directly associated with the peptide residues.

The effect of mutant beta 2-microglobulins on the conformation of HLA-B27 detected by antibody and by CTL

The arthritis-predisposing HLA-B27 consists of a heavy chain, a small peptide, and the monomorphic beta 2-microglobulin (beta 2-m). CTLs and a mAb, Ye-2, which recognize the complex with specificities both for the heavy chain and for the peptide, are available. The beta 2-m is in noncovalent association with the heavy chain at multiple points and is exchangeable with free beta 2-m outside of the complex. The purpose of our experiments was to test whether mutant beta 2-m capable of modulating HLA-B27 activity could be created. Eighteen recombinant mutants of the human beta 2-m were experimentally generated. In 14 of these, mutations were at or near residues that are either contact residues or interface residues with the heavy chain. Relative to the parent beta 2-m, two-thirds of the mutants showed reduced ability to exchange into HLA-B27 complexes. However, at least four of them induced more than 80% decrease in Ye-2 Ab reactivity. Two mutants were able to induce a minor decrease in susceptibility to lysis by four CTL clones. One of the CTL clones was autoreactive. Two of the CTL clones were specific for HLA-B27 cells experimentally infected with arthritis-causing Yersinia enterocolitica. These results indicate that certain beta 2-m residues play an indirect role in peptide presentation, although they are not directly associated with the peptide residues.

The role of nm23 in transforming growth factor beta 1-mediated adherence and growth arrest

nm23 has properties of a metastasis suppressor gene and also has been implicated in the control of response to transforming growth factor beta 1 (TGF beta 1) by studies in melanoma cells. In this report, we have examined the role of nm23 in two HT29 colon carcinoma sublines at different stages in tumor progression with different responses to TGF beta 1: the HD3 subline, which shows TGF beta 1-induced growth arrest and differentiation; and the more invasive and tumorigenic U9 subline, which induces tumors 7-fold as large as those induced by HD3 cells with one-half the latency. Analysis by semiquantitative reverse transcription-polymerase chain reaction showed that antisense phosphorothiolated oligonucleotides to the nm23 initiation site (nm23 AS oligos) decreased nm23 mRNA levels 2-8-fold in HD3 and U9 cells when normalized to beta-actin mRNA levels. However, a role for nm23 in TGF beta 1-mediated responses could only be found in HD3 cells. nm23 AS oligos inhibited the differentiation property of cell adherence over 90% in HD3 cells, and this loss of adherence could be partially blocked by concurrent treatment with TGF beta 1. In contrast, U9 cell adherence was not detectably altered by nm23 AS oligos, whether added in the presence or absence of TGF beta 1. The TGF beta 1-induced inhibition of HD3 cell proliferation was blocked by nm23 AS oligos, whereas the TGF beta 1-induced proliferation of U9 cells was unaffected by nm23 AS oligos.(ABSTRACT TRUNCATED AT 250 WORDS)

Colon carcinoma cells switch their response to transforming growth factor beta 1 with tumor progression

Transforming growth factor beta 1 (TGF-beta 1) switches from an inhibitor of tumor cell growth to a stimulator of growth and invasion during human colon carcinoma progression. We originally observed that metastatic colon carcinoma cells in primary culture responded to TGF-beta 1 by proliferation, whereas moderate to well-differentiated primary site colon carcinomas were growth inhibited by TGF-beta 1 (P. Schroy et al., Cancer Res., 50: 261-265, 1990). We then cloned several colon carcinoma cell lines which modeled these responses to TGF-beta 1 and expressed TGF-beta 1 (M. M. Hafez et al., Cell Growth & Differ., 1: 617-626, 1990; 3: 753-762, 1992). Two of these colon carcinoma cell lines, U9 and HD3, which activate approximately equal amounts of TGF-beta 1 and express equal amounts of TGF-beta receptors, are now used to compare the effects of TGF-beta 1 in modulating invasive behavior. The U9 cell line exhibits autocrine-positive growth regulation in vitro by TGF-beta 1, whereas the HD3 cell line shows the opposite response, autocrine-negative regulation. Blocking endogenous TGF-beta 1 with isotype-specific antibody inhibited U9 cell growth because autocrine TGF-beta 1 acts as a mitogen for U9 cells. In contrast, antibody to TGF-beta 1 stimulated HD3 cell proliferation because autocrine TGF-beta 1 inhibits growth of these cells. U9 cells were 13-fold more invasive in vitro through a collagen I layer than HD3 cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Position-reading and the emergence of sense organ precursors in Drosophila

Genetic analysis of development in Drosophila melanogaster has advanced our understanding of "position reading", where the expression of particular genes informs a cell of its position in the developing animal. The first step in localization of fly sense organs is the local expression of a gene conferring neural competence on epidermal cells. The four genes of the achaete-scute (AS-C) complex play crucial roles in the localization of sense organs. The resolution of local expression of AS-C genes along one dimension is about 10%; accuracy is improved by the balancing local expression of AS-C antagonist genes such as extramacrochaete. Position reading seems to depend primarily on such patterns of gene expression, and not upon the compartmental identity of the cells. No evidence has been found for differing roles of the four AS-C genes in the generation of sense organ progenitor cells or in the specification of neuronal properties of innervating neurons. The formation of each sense organ may be a unique case where the different proneural and neurogenic gene products have varying importance, and fortuitous local effects acting on this complex combination of factors have come to be important. The fly may be evolving from a flexible regular pattern to an inflexible irregular pattern strongly dependent on local factors, turning the fly into a crystallized system. (Written by R. Wayne Davies.).

Testing the importance of each residue in a HLA-B27-binding peptide using monoclonal antibodies

When a peptide derived from histone 3.3 was incubated with mouse L cells transfected with HLA-B27, the cells became highly reactive with Ye-2, an anti-HLA-B27 mAb. The critical residues were analyzed by testing analogues in which each of the nine residues in the peptide was consecutively substituted by 19 other amino acids. The conclusions were separately verified using a different HLA-B27-positive cell line. The ability of some of these peptides to bind to HLA-B27 was also assayed by their ability to stabilize HLA-B27 in a mutant cell line which required HLA-B27-binding peptides to express HLA-B27 at 37 degrees C. These experiments showed that in P4, P5, P6, P7, P8, and P9, all 20 different amino acids could be substituted without eliminating the ability of the analogues to bind to HLA-B27. The residues which were responsible for the HLA-B27-peptide complex reacting with the Ye-2 antibody were P8 and P9. The latter might mediate its effect by altering either the surface conformation of the closely associated HLA-B27 heavy chain or the conformation of the peptide itself.

Testing the importance of each residue in a HLA-B27-binding peptide using monoclonal antibodies

When a peptide derived from histone 3.3 was incubated with mouse L cells transfected with HLA-B27, the cells became highly reactive with Ye-2, an anti-HLA-B27 mAb. The critical residues were analyzed by testing analogues in which each of the nine residues in the peptide was consecutively substituted by 19 other amino acids. The conclusions were separately verified using a different HLA-B27-positive cell line. The ability of some of these peptides to bind to HLA-B27 was also assayed by their ability to stabilize HLA-B27 in a mutant cell line which required HLA-B27-binding peptides to express HLA-B27 at 37 degrees C. These experiments showed that in P4, P5, P6, P7, P8, and P9, all 20 different amino acids could be substituted without eliminating the ability of the analogues to bind to HLA-B27. The residues which were responsible for the HLA-B27-peptide complex reacting with the Ye-2 antibody were P8 and P9. The latter might mediate its effect by altering either the surface conformation of the closely associated HLA-B27 heavy chain or the conformation of the peptide itself.

NURSETALK: the latest addition to the information highway

NURSETALK is an electronic bulletin board system (BBS) developed to provide information and meet the communication needs of three different nursing organizations in North Carolina. It was designed and conceptualized from a user perspective to promote functionality and acceptance.

Molecular cloning and structure of the human (GABATHG) GABA transporter gene

A cDNA molecule encoding the human GABA transporter was synthesized by means of polymerase chain reaction (PCR) technique and used as probe for selecting a human genomic DNA fragment encoding GABA transporter. A positive clone harboring the whole gene was obtained from a human lymphocyte genomic library through utilizing the genomic 'walking' technique. The clone, designated as pHGAT, harbours a DNA fragment of about 39 kb in length inserted into the BamHI site in cosmid pWE15. The gene covers about 25 kb in length and is constituted by four EcoRI restricted fragments which are 13.7 kb, 3.1 kb, 4.2 kb and 7.2 kb long, respectively. The genomic clone contains 15 introns, including two introns prior to the initiator methionine (i.e., the translation start site is in exon 3). Eleven exons encode the twelve transmembrane regions in the transporter protein. Thus as in the case for a number of other membrane proteins, there appears to be a strong tendency for the putative transmembrane domains to be encoded by separate exons. It is noted that the structure of the human GABA transporter gene reported here differs from the mouse gene which is contains 12 introns.

Can the stability of protein mutants be predicted by free energy calculations?

The use of free energy simulation techniques in the study of protein stability is critically evaluated. Results from two simulations of the thermostability mutation Asn218 to Ser218 in Subtilisin are presented. It is shown that components of the free energy change can be highly sensitive to the computational details of the simulation leading to the conclusion that free energy calculations cannot currently be used to reliably predict protein stability. The different factors that undermine the reliability are discussed.

Recombinant human G-CSF and retinoic acid in synergistically inducing granulocyte differentiation of human promyelocytic leukemic cells

The effects of recombinant human G-CSF (rhG-CSF) and retinoic acid (RA) were studied on the proliferation and differentiation of HL-60 cells and human acute myeloid leukemic cells. Synergistic effect on granulocyte differentiation was observed when HL-60 cells and primary acute promyelocytic leukemic cells were cocultured with RA plus rhG-CSF. rhG-CSF combined with RA increased more significantly the percentage of mature cells than RA alone and greatly increased NBT reduction activity (P < 0.001). These results suggested that proliferated effect of rhG-CSF on leukemic cells may be important for inducing differentiation of myeloid leukemic cells. But this effect might expose the patients to the risk of acute myeloblastic leukemia if G-CSF was used alone. However, RA could not only rule out the latter situation but retain former merit as well. The authors suggest that the combined use of G-CSF with RA is probably a new approach to the treatment of leukemia.

Effect of glycolipids on the phase behavior and dynamic properties of phospholipid liposomes

The glycolipids of Acholeplasma laidlawii AIH089 membranes were identified and purified. The effect of monoglucosyldiacylglycerol (MGDG) and diglucosyldiacylglycerol (DGDG) on the thermotropic behavior of multilamellar vesicles of dipalmitoylphosphatidylcholine (DPPC), dipalmitoylphosphatidylglycerol (DPPG) has been investigated by high sensitivity differential scanning calorimetry. The main transition peaks were broadened, the enthalpies were decreased. DGDG caused the decrease in the transition temperatures of DPPC, DPPG liposomes by 3.08 degrees C, 4.18 degrees C, respectively. MGDG did not cause the alteration of the transition temperature of DPPC liposomes but caused the decrease of the transition temperatures of DPPG liposomes by 2.20 degrees C. ESR experiments indicate that MGDG decreased the rotational correlation time of DPPC and DPPG liposomes.

Multiple transcripts encoded by the ilvGMEDA gene cluster of Escherichia coli K-12

We report here that, using Northern (RNA) blots, we identified two relatively stable transcripts of 4.6 and 1.1 kb that correspond to the products of the ilvEDA and ilvE genes and two relatively unstable transcripts of 6.7 and 3.6 kb that correspond to the products of the ilvGMEDA and ilvDA genes. The transcripts were identified by the use of eight probes derived from segments of the ilvGMEDA cluster. In addition, we used two strains with deletions of ilvG or ilvDA and observed the expected decrease in transcript size in Northern blots. Primer extension with reverse transcriptase generated a 169-nucleotide product corresponding to a 5' end within the ilvED intercistronic region, 37 nucleotides from the AUG codon of the ilvD gene. This primer extension product presumably indicates the 5' end of the ilvDA transcript that we detected in Northern blots. The stability of the transcripts was monitored, and RNase E was found to play a major role in ilv transcript degradation. Transcript levels varied in response to growth in the presence of the end product amino acids and in response to the presence of the polar frameshift site in ilvG. Although there have been speculations about the identities and numbers of transcripts derived from the ilvGMEDA cluster on the basis of the identification of some of the sites of transcription initiation and termination, this is the first report of the use of Northern blots to determine the actual sizes and distribution of mRNAs present in vivo.

[Role of enteric Klebsiella pneumonia infection and HLA-B27 in ankylosing spondylitis]

Klebsiella pneumonia (KP) infection and HLA-B 27 have been shown to be strongly associated with ankylosing spondylitis (AS). In the present study, faecal cultures were performed and showed faecal carriage rate of KP was much higher in patients with AS (10/30) and hospital volunteers (2/10) than in the non-hospital volunteers (0/20). An octadecapeptide encompassing the shared hexamer between HLA-B 27 and KP nitrogenase residue was synthesized and autoantibodies against this short peptide were detected in sera of patients with AS and Reiter's syndrome (RS) and other related disease and normal controls. The results showed that such autoantibodies were detected in 42.2% of AS and 30% of RS patients yielding positive rate much higher than those found in other control groups. It is concluded that enteric KP infection were strongly implicated in the pathogenesis of AS probably by the mechanism of molecular mimicry with HLA-B 27.

[Granulocyte differentiation of human promyelocytic leukemic cells induced by coordinate action of granulocyte colony stimulating factor and retinoic acid]

We analysed the effects of recombinant human G-CSF (rhG-CSF) and retinoic acid (RA) on proliferation and differentiation of HL-60 cells and human acute myeloid leukemic (AML) cells. A synergistic effect on granulocyte differentiation was observed when HL-60 cells and primary cultured acute promyelocyte leukemic cells were cocultured with 10(-8)mol/L RA plus 1:2000 or 1:1000 rhG-CSF. The rhG-CSF plus RA treated cells demonstrated significant increase in the percentage of mature cells. Morphological changes and nitroblue tetrazolium (NBT) reduction activity evidenced more increase than RA treatment alone (P less than 0.001). The results suggest that RA not only inhibits the proliferative action of G-CSF, but also retains and enhances the action of G-CSF to induce differentiation. Therefore, we believe that the combined use of G-CSF with RA may improve the treatment of leukemia.

The emergence of sense organs in the wing disc of Drosophila

We have examined the origin of a set of precisely located sense organs in the notum and wing of Drosophila, in transformant flies where lacZ is expressed in the progenitor cells of the sense organs (the sensory mother cells) and in their progeny. Here we describe the temporal pattern of appearance and divisions of the sensory mother cells that will form the eleven macrochaetes and the two trichoid sensilla of the notum, and five campaniform sensilla on the wing blade. The complete pattern of sensory mother cells develops in a strict sequence that extends over most of the third larval instar and the first 10 h after puparium formation. The delay between the onset of lacZ expression and the first differentiative division ranges from 30 h, in the case of the earliest mother cells, to 2 h for the latest mother cells. The first division shows a preferential orientation which is also specific for each sensory mother cell. Up to this stage, there is no marked difference between the three types of mechanosensory organs.

Antioxidant action of certain simple phenolic compounds derived from Chinese herbs

H2O2 and hydroxyl free radical active oxygen generation systems were utilized to define the antioxidant activities of simple phenolic compounds derived from Chinese herbs. Although the antioxidant activities of compounds differed when assessed in the two systems, all compounds tested were found to be effective at preventing red blood cell membrane lipid peroxidation, with the propyl and butyl esters of gallic acid being especially potent. No compound was able to prevent hemoglobin oxidation. All compounds but salicylic acid were found to interact dose-dependently with H2O2 and hydroxyl free radical as determined by a chemiluminescence method.

Sequence and transcriptional activity of the Escherichia coli K-12 chromosome region between rrnC and ilvGMEDA

We previously identified a protein related to the expression of the ilvGMEDA cluster of Escherichia coli K-12. It was observed that this ilv-related protein was produced at higher levels in UV irradiated cells infected with lambda dilvGMEDA phage with specific ilvG mutations (ValR), compared to phage carrying the wild-type(ValS) ilvG allele. The gene encoding this protein was further localized to a region between rrnC and ilvGMEDA by analyzing restriction fragment subsets in maxicells. We have now determined the nucleotide (nt) sequence of the 3.5-kb segment between rrnC and ilvGMEDA, and two open reading frames (ORFs) are present in the region expected to contain the ilv-related gene. These ORFs predicts Mrs of 18,751 (ORFI) and 20,085 (ORFII) Da, and both ORFs have a strong probability to encode proteins based on codon frequency analysis. Maxicell analysis revealed that a 1319-bp HindIII-SmaI fragment containing ORFI encodes the ilv-related peptide. We deleted a ClaI fragment that removed a portion of ORFI encoding the C-terminal region of the peptide, and maxicell analysis revealed a decrease in the size of the protein produced in accord with the prediction. RNA slot blots and Northern blots were used to characterize transcripts encoding ORFI. A transcript initiated 112 nt from the ilvGp2 promoter, but proceeding in the opposite direction, may encode the ORFI peptide.

Correction factor for strongly reflecting U-path RACs

An equation from the literature describing multiple reflections in a U-path surface-acoustic-wave (SAW) reflective array compressor (RAC) is simplified for RACs with a large time-bandwidth product, yielding a very convenient expression consisting of the relation for weakly reflecting RACs plus phase and amplitude correction factors. The quantitative effect of multiple reflections is immediately apparent, so that the designer has a better understanding of how various parameters affect the final performance. A down-chirp, which is more common in practical devices, is described. Empirical extensions to higher-order and variable weighing are deduced and verified numerically, while the possibility of variable chirp is discussed.

Medium-loss SAW filters with synthesized characteristics

Medium-loss surface acoustic wave (SAW) filters based on the in-line dot array structure are reported. This configuration is very amenable to device synthesis, potentially to specifications comparable to conventional high-loss designs. The design procedure fully allows for multiple reflections within the reflecting arrays and can handle chirps. The devices have achieved up to 0.2-dB RMS passband ripple and 32-dB rejection after direct coupling and multistrip coupler (MSC) reflection are removed. Passband loss (6-8 dB) could be reduced if transducer and MSC loss (3 dB) can be improved. The devices also have sharp cutoffs, and fairly uniform input and output impedances in the pass and transition bands. The reflectors chosen for the reflecting arrays are thin metal dots. The results of computation and experimental verification of dot reflectivity and velocity change for the particular size of dots and dot pattern used are given. The device design, and the measured results are discussed.

The power reflected in a SAW RAC

Considerations relating to the design of surface-acoustic-wave (SAW) reflective array pulse compressors (RACS), including the effect of array width on power reflected, the transmitted beam profile and the effect of randomized arrays, are discussed. Only a first-order analysis is used. Potential misunderstandings of these issues that could arise from the existing literature are clarified.