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Biomedical subjects

D L Evans

Publications and source records attributed to D L Evans.

At least 127 records · Page 7Linked to original sources
PubMed1994

Target-cell sensitivity to natural killer-cell lysis is determined by the expression of a novel antigen in conjunction with major histocompatibility complex class-I molecules.

Recently, a panel of monoclonal antibodies (MoAbs) was developed that identified a novel tumour-cell antigen conserved across species (mouse, rat and man). Fluorescence-activated cell sorter (FACS) analysis demonstrated that this antigen was expressed at highest levels on human tumour cell lines sensitive to natural killer (NK)-cell lysis. These MoAbs inhibited NK cell lysis of K562 target cells (by up to 90%), as well as a variety of other NK-sensitive target cells. Biochemical analyses revealed that the MoAbs reacted with a polypeptide of 42 kDaltons, distinct from other known cell surface antigens. Now the expression of this antigen has been analysed further with a panel of 24 tumour cell lines to determine its role in NK cell function. The expression of target cell major histocompatibility complex (MHC) molecules in conjunction with sensitivity to NK cell lysis was examined also. For each of the 24 cell lines it was found that the level of expression of the novel target cell antigen determined the sensitivity of the cell line to NK cell lysis. However, the level of MHC antigen expression could modulate target cell sensitivity to NK cell lysis, in that high levels of MHC class-I molecule expression resulted in a target cell that was insensitive to NK cell lysis regardless of the level of expression of the novel antigen. Thus, for most transformed cell lines, sensitivity to NK cell lysis appeared to be determined by the expression and levels of the novel antigen in association with MHC class-I molecules.

Adolescent↗
PubMed1994

Evolutionary conservation of a human function-associated molecule on murine natural killer cells: expression and function.

Using a novel anti-natural killer (NK) cell monoclonal antibody (MoAb), we have recently identified an evolutionary conserved function-associated molecule (FAM) present on fish, rat and human NK cells. This molecule is involved in NK cell function as anti-FAM MoAbs inhibit cytotoxicity, stimulate lymphokine secretion and inhibit conjugate formation between effector cells and target cells. We now have examined murine NK cells for the presence of this structure. It was observed by two-colour flow cytometric analysis that the anti-FAM MoAb 5C6 specifically bound to a subpopulation of nylon wool non-adherent splenic lymphocytes (19-20%). The expression of the FAM molecule was restricted to NK cells that expressed the NK1.1 antigen. Neither T cells, B cells, nor macrophages reacted with the anti-FAM MoAb. Analysis of FAM expression in various lymphoid tissues revealed that splenocytes expressed the greatest numbers of MoAb(+) cells. Generation of lymphokine-activated killer (LAK) cells and adherent lymphokine-activated killer (ALAK) cells resulted in higher levels of FAM expression. The anti-FAM MoAb 5C6 also detected the presence of FAM on fresh SCID NK cells. It was demonstrated that the anti-FAM MoAb 5C6 inhibited the lysis of target cells by endogenous NK cells, activated NK cells, 5d LAK cells, ALAK cells and SCID NK cells. Moreover, conjugate assays demonstrated involvement of this molecule in recognition between NK cells and target cells.

Animals↗
PubMed1994

Partial amino acid sequence of a novel protozoan parasite antigen that inhibits non-specific cytotoxic cell activity.

Monoclonal antibody (MoAb) 18C2, prepared against a human EBV transformed lymphoblastic cell line (NC-37) is specific for a target cell ligand recognized by fish NCC and by mammalian NK cells. MoAb 18C2 inhibits the lysis of a variety of transformed murine and human cells (e.g. NC-37, YAC-1, K562, etc.). This MoAb also recognizes a determinant on the fish protozoan parasite Tetrahymena pyriformis. In the present study, we used MoAb 18C2 to identify a target antigen in detergent lysates of T. pyriformis. MoAb 18C2 recognized a 46-50 kDa target antigen (NKTag) by Western blot analysis of both crude and ammonium sulphate (AS) fractionated (25-40% saturation) T. pyriformis lysates. AS fractionated or purified soluble NKTag inhibited NCC mediated lysis of IM-9 target cells in a dose dependent fashion. AS fractionated NKTag also inhibited NCC lysis of a variety of human and murine transformed targets (e.g. HL-60, MOLT-4, DAUDI, NC-37, U-937, YAC-1, EL-4). Inhibition was specific for NCC and inhibition could be removed by adsorption of AS fractionated NKTag with MoAb 18C2 hybridoma cells. NKTag was prepared for amino acid sequencing by preparative SDS PAGE of whole cell detergent (CHAPS) lysate followed by Western transfer to nitrocellulose. The MoAb 18C2 recognized NKTag was excised and submitted for microsequence analysis. Direct N-terminal analysis yielded a 12 residue sequence. Additional sequences, obtained from in situ trypsin digests of the NKTag on nitrocellulose yielded four additional peptides of 10, 13, 16 and 21 residues. None of the sequences examined had significant homology to known sequences (Swiss-Prot protein sequence database). These data indicate that MoAb 18C2 recognized a novel protein on T. pyriformis which may be involved in target cell recognition/lysis by NCC. Further, these data extend our previous observation that a common target determinant exists between higher and lower eukaryotic cells, and its expression may provide an explanation for the susceptibility of both protozoan parasites and transformed tumour cells to NK/NCC lysis.

Amino Acid Sequence↗
PubMed1994

Relationships between electrocardiographic findings, racing performance and training in standardbred horses.

The presence of abnormal T waves in three or more electrocardiographic leads has been used to diagnose the cause of poor race performance in horses. This study investigated the relationship between previous racing performance in Standardbred horses and T waves, and the effect of training on the T wave. Thirty-two horses were electrocardiographed in two Sydney racing stables. Sixteen horses (50%) had ECGs with three or more leads with abnormal T waves, and these horses had won more races, had a greater ratio of wins per start and a greater number of dollars earned per start than horses with less than three abnormal T waves (P < 0.05). Horses with abnormal T waves also had significantly faster racing times (P < 0.01). There were significant (P < 0.01) correlations between the number of abnormal T waves and both number of wins (R = 0.47) and dollars earned per start (R = 0.45). Fastest winning mile rate was also negatively correlated with number of leads with abnormal T waves (R = -0.52, P < 0.01). Twenty two horses were also electrocardiographed within seven days of good racing performance. The mean number of abnormal T waves was 2.7 +/- 0.41, and the mean T wave amplitude in the four chest leads (CV, CR, CL, CF) was 0.9 +/- 0.15 mV. Thirteen horses (59%) had abnormal T waves in three or more leads. The effect of training on the T wave was also investigated in nine previously untrained and unraced Standardbred racehorses.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMed1994

Significance for exercise capacity of some electrocardiographic findings in racehorses.

Various cardiorespiratory and metabolic indices were assessed during treadmill exercise in Thoroughbred and Standardbred racehorses with T wave changes in 4 or more leads on the electrocardiogram or second-degree atrio-ventricular (AV) block, and in horses that had no abnormalities on clinical examination, resting electrocardiography or upper respiratory tract endoscopy. No significant differences in heart rate, plasma lactate concentration, arterial blood gases, oxygen uptake, run time, peak velocity, or blood and red cell volumes were found between normal horses and horses with T wave changes or second-degree AV block. These results indicate that some electrocardiographic findings that are considered by some clinicians to indicate cardiac dysfunction, may have little effect on exercise capacity.

Animals↗
PubMed1994

Cardiorespiratory and metabolic responses to exercise in horses with various abnormalities of the upper respiratory tract.

A standardised incremental exercise test was performed by 9 racehorses with idiopathic laryngeal hemiplegia (ILH), 1 horse with maxillary sinus cysts, 1 horse with epiglottic entrapment, 1 horse with a lesion on the vocal folds, and 1 horse with pharyngitis. Two of the horses with ILH were retested after laryngoplasty and ventriculectomy. The findings were compared with those from 20 normal racehorses. Heart rate, plasma lactate concentration, arterial blood gases, stride frequency, oxygen uptake (VO2) and carbon dioxide production were assessed during treadmill exercise on a +10% slope. The group of horses with ILH had significantly (P < 0.01) lower peak VO2 values (136 +/- 5 ml/kg/min) than did the normal group (154 +/- 3 ml/klg/min). These values represent mean +/- sem. Horses with ILH also had significantly higher (P < 0.05) arterial carbon dioxide tensions (PaCO2) at 10 m/s and lower speeds at a heart rate of 200 bpm (V200) than the normal group. The horse with maxillary sinus cysts had higher PaCO2 tension at 10 m/s than normal, and abnormal values for several cardiorespiratory and metabolic indices. Horses with vocal fold lesions, aryepiglottic entrapment and pharyngitis had arterial blood gas and cardiorespiratory indices that were similar to those of normal horses. One horse which underwent corrective surgery for ILH showed improvements in arterial blood gases and cardiorespiratory indices during exercise, while the other horse had values which were the same as, or worse than, values before surgery. We conclude that the measurement of arterial blood gases and cardiorespiratory indices during treadmill exercise is useful in determining the effect on exercise capacity of various upper airway abnormalities in racehorses.

Animals↗
PubMed1994

Mood disorders in HIV infection: prevalence and risk factors in a nonepicenter of the AIDS epidemic.

OBJECTIVE: The authors studied the lifetime, initial cross-sectional, and 6-month follow-up prevalence of mood disorders in asymptomatic HIV-infected and uninfected homosexual men who lived in an area with a low prevalence of HIV. They also determined the relationship between current major depression and potential depression risk factors. METHOD: Subjects included 98 asymptomatic HIV-infected and 71 uninfected homosexual men. Subjects underwent extensive clinical, psychiatric, neuropsychological, and laboratory evaluations. RESULTS: Similar proportions of HIV-infected and uninfected subjects reported a lifetime (29% and 45%, respectively), an initial current (8% and 3%), and a 6-month follow-up (9% and 11%) history of major depressive disorder. Anxiety disorders were less common, with similar proportions of HIV-infected and uninfected subjects reporting a lifetime (7% and 13%, respectively), an initial current (3% and 7%), and a 6-month follow-up (2% and 5%) history of anxiety disorders. There were no differences in the severity of mood symptoms between HIV-infected and uninfected subjects. Current major depression at initial visit was significantly associated with lifetime history of major depression but not with neuropsychological function or vitamin B12 level. CONCLUSIONS: These findings are in agreement with previous studies of areas with a high prevalence of HIV. However, the proportion of subjects with mood disorders is high compared with general population studies. Both HIV-infected and uninfected homosexual men may be at high risk for major depression, especially if they have a past history of depression. Moreover, in the asymptomatic stage of HIV infection, major depression does not appear to be secondary to HIV central nervous system effects or low vitamin B12 levels.

Acquired Immunodeficiency Syndrome↗
PubMed1993

Dopamine D4 versus D2 receptor selectivity of dopamine receptor antagonists: possible therapeutic implications.

The dopamine D4 receptor, which is considered a close variant of the dopamine D2 receptor, has recently been cloned. Receptor binding studies demonstrated that clozapine, which is an effective antipsychotic agent but atypical in that it lacks the usual side effects of other antipsychotic agents, has high selectivity for the dopamine D4 receptor versus the dopamine D2 receptor. Comparative binding affinity studies have been carried out for a number of interesting dopaminergic agents using membranes prepared from cloned dopamine D2 and D4 receptor containing cells. It was found that clozapine is selective for the dopamine D4 vs. the D2 receptor by a factor of 2.8. Other compounds with dopamine D4 receptor selectivity were (+)-apomorphine (8.7), (+)-N-propyl-norapomorphine (NPA) (2.4) and melperone (1.3). Compounds with considerable selectivity for the dopamine D2 receptor were haloperidol (0.31), chlorpromazine (0.084), trifluoperazine (0.034) and raclopride (0.001). Overall, the results with the antipsychotic agents tested, support the concept that dopamine D4 receptor selectivity may confer clozapine-like antipsychotic efficacy and furthermore that dopamine D2 receptor selectivity may confer side effect liability (extrapyramidal side effects and tardive dyskinesia).

Animals↗
PubMed1993

Effects of cisplatin on the induction of apoptosis in proliferating hepatoma cells and nonproliferating immature thymocytes.

A 2-h exposure of JB1 rat hepatoma cells in late log phase of growth to 50 microM cis-diamminedichloroplatinum (II) (cisplatin) resulted in the asynchronous detachment of cells from the monolayer over 4 days. Detached but not monolayer cells exhibited condensed chromatin and DNA fragmentation, which is indicative of endonuclease activation, the hallmarks of apoptosis in epithelial cells. The number of cisplatin-treated cells identified as apoptotic at any one time was never > 1% of the total cell number present on addition of drug. Two days after drug addition there was a decrease from 85% to 29% cells in G1 phase of the cell cycle, cells in S phase increased from 9% to 18%, and cells in G2/M phase increased from 6% to 51% with respect to untreated cells. Previous studies by Eastman and colleagues demonstrated that cisplatin-induced apoptosis of Chinese hamster ovary cells occurred in the G2 phase of the cell cycle [A. Eastman, Cancer Cells (Cold Spring Harbor), 2: 275-280, 1990]. Continuous exposure of JB1 cells to cycloheximide (1 microM) during and after exposure to cisplatin prevented both drug-induced changes in cell cycle distribution and the engagement of apoptosis. Freshly isolated immature rat thymocytes are known to be exquisitely sensitive to the induction of apoptosis by multiple stimuli including dexamethasone, etoposide, and irradiation. However, no significant increase in the amount of apoptosis above control levels was observed up to 36 h after a 2-h exposure to 50 microM cisplatin. JB1 cells have a doubling time of 24 h, whereas > 90% of immature rat thymocytes are noncycling. The data presented here provide indirect evidence that initiation of cisplatin-induced apoptosis may need to be coupled to a cell cycle-mediated event.

Animals↗
PubMed1993

Nonspecific cytotoxic cells in fish: antigenic cross-reactivity of a function associated molecule with the intermediate filament vimentin.

Nonspecific cytotoxic cells (NCC) in fish may lyse tumor cells and protozoan parasites in a similar fashion as their mammalian NK counterparts. Previous studies have shown that recognition and binding by NCC may be mediated by a receptor. In the present study the putative receptor or function-associated molecule (FAM) on NCC was shown to contain antigenic cross-reactivity with the mammalian intermediate filament vimentin. This was accomplished by comparing the specificity of anti-FAM monoclonal antibody 5C6 with commercially available anti-vimentin mabs V9 and 13.2 and with a polyclonal anti-vimentin antiserum. Tissue distribution studies indicated that the anti-vimentin antibodies bound to significantly fewer (< 50%) anterior kidney, spleen, kidney, and brain cells than mab 5C6. These mabs, however, produced inhibition of NCC lysis of IM-9 target cells. Conditions of mab incubation (with NCC) which were previously shown to modulate NCC cytotoxicity by 5C6 also produced large increases in NCC lysis of IM-9 targets in the presence of mabs V9 and 13.2. The determinant(s) recognized by these antibodies is present on the cell membrane. Microscopic examination of nonpermeabilized or acetone-treated and antibody-stained cells demonstrated that acetone permeabilization produced a 28-32% increase in staining (due to intracellular binding) compared to the staining of viable cells. Biochemical analysis of the cross-reactive antigens was done using analytical 2D SDS-PAGE and Western blot experiments. Mab 5C6 detected a 32- to 35-kDa protein (pI 6.3-6.5) in NCC extracts. Anti-vimentin mab 13.2 recognized a 57-kDa vimentin protein which had a relatively broad pI range (pH 6.3-6.7). Mab 13.2 also cross-reacted (in the same Western blot) with the NCC receptor protein (pI = pH 6.3-6.5). These data indicate that the FAM on NCC/NK cells contain vimentin-like antigenic determinants which may function in target cell binding.

Animals↗
PubMed1993

Effect of the Z mutation on the physical and inhibitory properties of alpha 1-antitrypsin.

A major feature of the structure of alpha 1-antitrypsin is a five-stranded A-sheet into which the reactive center loop inserts after cleavage. We describe here the effect of the Z mutation (342Glu to Lys) at the head of the fifth strand of the A-sheet on the mobility of the reactive center loop and hence on the physical properties of the antitrypsin molecule. The mutant Z but not the normal M antitrypsin spontaneously polymerizes at 37 degrees C by a mechanism involving the insertion of the reactive center loop of one molecule into the A-sheet of a second. It is demonstrated that Z antitrypsin polymerized after incubation with 1.0 M guanidinium chloride at 37 degrees C at the same rate as M antitrypsin. Reducing the temperature to 4 degrees C favored the formation of the L-state in M antitrypsin in which the loop is stably incorporated into the A-sheet, but resulted in loop-sheet polymerization in Z antitrypsin. Z, like M antitrypsin, undergoes the S to R transition, but we show that the accompanying change in thermal stability results from loop-sheet polymerization (S) which can be prevented by the insertion of the cleaved strand of the reactive center loop into the A-sheet (R). Z antitrypsin has a reduced association rate constant with neutrophil elastase [(5.3 +/- 0.06) x 10(7) and (1.2 +/- 0.02) x 10(7) M-1 s-1 for M and Z, respectively], but both M and Z antitrypsin had Ki values of less than 5 pM.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1993

Inhibition of plasmin, urokinase, tissue plasminogen activator, and C1S by a myxoma virus serine proteinase inhibitor.

The myxoma and malignant rabbit fibroma poxviruses are lethal tumorigenic viruses of rabbits whose virulence is modulated by the production of a virus-encoded secreted serine proteinase inhibitor, SERP-1. This viral protein was detected in medium harvested from myxoma and malignant rabbit fibroma virus-infected cells, and its inhibitory profile has been characterized by gel and kinetic analysis. SERP-1 forms complexes with and inhibits the human fibrinolytic enzymes plasmin, urokinase, and two-chain tissue-type plasminogen activator (association rate constants 3.4 x 10(4), 4.3 x 10(4), and 3.6 x 10(4) M-1 s-1 respectively). It is also able to inhibit C1S, the first enzyme in the complement cascade with an association rate constant which was unaffected by the addition of heparin (1.3 x 10(3) M-1 s-1). SERP-1 acts as a substrate for and is cleaved by thrombin, porcine trypsin, human neutrophil elastase, porcine pancreatic elastase, thermolysin, subtilisin, bovine alpha-chymotrypsin, and factor Xa. Incubation with kallikrein and cathepsin G had no effect. The structure of SERP-1 has been modeled on other members of the serpin family which revealed the characteristic serpin architecture apart from the absence of the D-helix. Structural analysis and kinetic assays demonstrate that the absence of this region does not prevent inhibitory activity and furthermore allow the identification of cysteine residues involved in internal and intermolecular disulfide bonding.

Amino Acid Sequence↗