Distinguishing withdrawal relief from absolute facilitation: commentary on Bell et al

A recent article in this journal by Bell and colleagues (Bell SL, Taylor RC, Singleton EG, Henningfield JE, Heishman SJ, Nicotine & Tobacco Research 1:45-52, 1999) studied the effects of smoking on cognitive performance using an overnight smoking abstention design. They interpreted their results for a two-letter search task (poorer performance following abstention that was improved by smoking) as indicating 'nicotine withdrawal-induced cognitive impairment' (p. 50). However, in this commentary, we point out that overnight-abstention experimental designs cannot distinguish withdrawal relief from absolute facilitation of performance (or a combination of the two). We suggest two approaches to resolving the issue of the nature of smoking/nicotine's effects on human cognitive performance.

Intraneural perineurioma involving the median nerve

Intraneural perineurioma is a rare clinical entity, which tends to affect major nerve trunks in the upper extremities. On light microscopy, numerous pseudo-onion-bulb structures having a central clear area are surrounded by concentric layers of eosinophilic elongate cells having spindled nuclei. Immunohistochemistry of concentric cells stains positive for epithelial membrane antigen but negative for S100 protein. Because of the small number of cases, no consensus has been made on proper treatment of this entity. Although none of the patients who have had excision of tumor with nerve grafting have had sensory nerve recovery, we believe each patient should be individualized until more data are available regarding this tumor.

Increasing students' cultural sensitivity. A step toward greater diversity in nursing

Increasing minority representation in nursing is essential to assure culturally competent care in the next century. Academic institutions need to recruit, encourage, and retain minority students and faculty. Students need minority mentors in their academic and clinical environments. Euro-American faculties teaching in predominantly white institutions need to explore effective ways to facilitate aggregate understanding and appreciation of cultural diversity within the profession. The author explains a teaching strategy to increase awareness and sensitivity of graduate nursing students to the role of minority nurses within the culture of nursing. Becoming culturally sensitive is a prerequisite to increasing diversity and culturally competent care.

A simplified device for protein identification by microcapillary gradient liquid chromatography-tandem mass spectrometry

A simplified device and procedure have been developed for microcapillary gradient liquid chromatography-tandem mass spectrometry (LC-MS/MS). This procedure has proved useful in identifying low level quantities of proteins from sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) gel bands. Microelectrospray needles are packed with reversed-phase resin and function both as a high performance liquid chromatography (HPLC) column and a nanospray mass spectrometer tip when interfaced between an HPLC and ion trap mass spectrometer. Variable submicroliter flow rates are generated by flow splitting between the microelectrospray capillary and an HPLC system. A manual injector is used to inject a protein digest mixture that binds to the column and is then washed at a high flow rate (2 microL/min post split). Gradient elution of bound peptides was initiated by the injection of a filled loop of 70% v/v methanol (5 microL) concomitant with a reduction of flow rate (0.1 microL/min post split). This forms a diffusion-dependent gradient of variable length (typically 15-30 min in length) depending upon the final flow rate. Chromatographic separations of a standard solution digest demonstrate that this diffusion-dependent gradient provides reasonable separations such that multiple peptide identifications by MS/MS can be obtained. Application of this methodology to the analysis of several in-gel-digested gel-separated proteins is presented to demonstrate its utility.

P300 and response selection: a new look using independent-components analysis

PURPOSE

The most prevalent current view of the functional role of the P300 component of the event-related potential (ERP) is that it indexes strategic processing related to context updating. Using independent-components analysis (ICA), the present study examined the role of P300 in the tactical process of response selection.

METHODS

In a task crossing manipulations of perceptual difficulty (PD) and response-selection difficulty (R-SD), ICA was employed to measure not only P300 latency, but its onset and duration as well.

RESULTS

Increased PD delayed P300 latency and onset in parallel, while increased R-SD lengthened P300 duration.

CONCLUSIONS

The latency and onset results suggest that the often-cited covariation of P300 latency with stimulus-evaluation time is secondary to effects on processing stages preceding P300. The results for duration indicate that P300 is involved in response selection, suggesting that it is not a unitary phenomenon. While P300's well-known relation to stimulus probability indicates a strategic role, our findings indicate a tactical role as well.

Stochastic acquisition of Qa1 receptors during the development of fetal NK cells in vitro accounts in part but not in whole for the ability of these cells to distinguish between class I-sufficient and class I-deficient targets

Fetal mouse NK cells are grossly deficient in the expression of Ly49 molecules yet show a limited ability to distinguish between wild-type and MHC class I-deficient target cells. In this paper we report that during their development in vitro from immature thymic progenitors, a proportion of C57BL/6 fetal NK cells acquires receptors for a soluble form of the nonclassical class I molecule Qa1b associated with the Qdm peptide, but not for soluble forms of the classical class I molecules Kb and Db. The acquisition of these Qa1 receptors occurs in a stochastic manner that is strictly controlled by cytokines, and in particular is strongly inhibited by IL-4. All fetal NK clones tested, including those that lack detectable Qa1 receptors, express mRNA for CD94 and for both inhibitory and noninhibitory members of the NKG2 family. Fetal NK cells lacking receptors for Qa1 (and also for classical class I molecules) cannot distinguish between wild-type and class I-deficient blasts but, surprisingly, distinguish efficiently between certain wild-type and class I-deficient tumor cells. A variant line that lacks several members of the NKG2 family kills both types of tumor cell equally well, suggesting the existence of NKG2-containing inhibitory receptors that recognize as yet undefined nonclassical class I molecules of restricted distribution.

The role of calcium homeostasis and flux during bacterial antigen processing in murine macrophages

We report that MHC class II (MHC-II)-restricted antigen processing of two CD4(+) T cell epitopes from the surface M protein of Streptococcus pyogenes in murine macrophages is dependent on intact calcium homeostasis and flux. We have previously shown that the CD4(+) T cell epitope 308-319 of the type 5 M protein is presented by newly synthesized MHC-II molecules via the classical pathway, while 17-31 is loaded on recycling MHC-II molecules via the recycling pathway. In this report we show that processing of viable bacteria for 308-319 presentation depended on the availability of intra- and extra cellular calcium, intact gadolinium-sensitive and/or T-type calcium channels, as well as on thapsigargin-sensitive homeostasis of intracellular calcium. In contrast, processing of 17-31 was independent of both intracellular calcium and gadolinium-sensitive calcium channels. The data suggest that alternative antigen processing pathways have different requirements for intracellular calcium homeostasis.

A double blind study of the effects of smoking on heart rate: is there tachyphylaxis?

RATIONALE

Smoking following overnight abstention reliably increases heart rate (HR), an effect due to nicotine absorption. The effect of subsequent cigarettes on HR is less than that associated with the first cigarette of the day, an indication of tachyphylaxis (acute tolerance). To date, smoking/HR studies have not been conducted double-blind. Instead, control conditions have included non-smoking or some type of "sham" smoking (puffing on an unlit cigarette or a straw).

OBJECTIVE

We investigated the HR response to smoking and its time course using double-blind methodology.

METHODS

HR was recorded in overnight-abstaining participants before and after smoking the first, second and third cigarette of the day (40 min between each cigarette) in two sessions. The experimental manipulation involved replacing the second cigarette of one session with a very low nicotine-yield cigarette (0.05 mg; FTC method) compared with the other five cigarettes (1.1-mg nicotine yield).

RESULTS

Smoking increased HR by 15, 8 and 7 beats/min (bpm) in the session where all three cigarettes had the higher yield. The comparable values for the session in which the second cigarette had the lower yield were 15, -1 and 11 bpm.

CONCLUSIONS

In the session where all three cigarettes had the higher yield, larger increase in HR after smoking the first than the second or third cigarettes indicates tachyphylaxis. The HR response in the other session was smaller for the third cigarette than the first cigarette, indicating that a period greater than 80 min would be needed before the HR response was fully restored.

Alcohol effects on mood, equilibrium, and simulated driving

BACKGROUND

The effects of alcohol on simple versus complex psychomotor performance were compared in 18 adults.

METHODS

Subjects received ethanol doses of 0.0, 0.5, and 0.8 g/kg in a randomized, double-blind, within-subject design. Forty minutes after finishing their drinking, the subjects completed a 60-min battery of tests that included: 1) a sensory organization posturography test (EquiTest); 2) latency to apply the brake after appearance of a barrier in a driving simulator (brake reaction time); 3) visual analog subjective-effects scales (VAS); 4) the Profile of Mood States (POMS); 5) critical flicker fusion (CFF); and 6) choice reaction time (CRT).

RESULTS

Alcohol dose dependently reduced composite equilibrium scores and increased brake reaction time. On the CRT task, total reaction time was significantly increased after the high dose but not the low dose. Alcohol dose dependently increased VAS "dizzy," "high," and "drug effect" ratings. The POMS and CFF were not significantly affected by alcohol.

CONCLUSIONS

These data suggest that an ethanol dose that neither influences certain mood states nor impairs simple psychomotor task performance nonetheless may impair equilibrium and complex psychomotor tasks (e.g., driving).

Little evidence that "denicotinized" menthol cigarettes have pharmacological effects: an EEG/heart-rate/sujective-response study

RATIONALE

A substantial portion of cigarette smokers prefer menthol-flavored cigarettes. To date, however, no studies have examined whether menthol in cigarettes has central pharmacological effects.

OBJECTIVE

We investigated psychophysiological and subjective effects of smoking menthol versus non-menthol cigarettes in both menthol and non-menthol smokers. To assess these effects independently of the immediate effects of nicotine, all cigarettes employed were "denicotinized" (FTC nicotine yield = 0.06 mg).

METHODS

The psychophysiological measures were EEG and heart rate (HR). The subjective measures assessed mental alertness, muscular relaxation, anxiety/nervousness, and how much a participant wanted to smoke one of his usual brand of cigarettes. Menthol and non-menthol smokers participated in a single session in which each participant smoked both a menthol and a non-menthol denicotinized cigarette (order balanced across participants). The psychophysiological and subjective measures were recorded before and after smoking each cigarette.

RESULTS

Out of 48 F-ratios spanning 22 analyses of variance involving the critical interaction between pre-/post-smoking and menthol/non-menthol cigarette, only one unambiguously fit a "pharmacological" pattern, a result indistinguishable from a type-I statistical error. We report evidence that menthol smokers may be chronically less aroused and more sensitive to the effects of nicotine than non-menthol smokers.

CONCLUSIONS

We found little evidence that menthol in cigarettes has central pharmacological effects.

Nitric oxide regulates Th1 cell development through the inhibition of IL-12 synthesis by macrophages

We have previously reported that mice lacking inducible nitric oxide synthase (NOS2) developed enhanced Th1 cell responses. We now investigated the mechanism by which NO modulates Th1 cells differentiation. Peritoneal macrophages from NOS2-deficient mice infected with Leishmania major in vivo or stimulated with IFN-gamma or lipopolysaccharide (LPS) in vitro produced significantly higher levels of IL-12 than those from heterozygous or wild-type mice. A macrophage cell line, J774, produced significant amounts of IL-12 following activation with LPS, or LPS plus IFN-gamma. This could be markedly enhanced by the NOS inhibitor L-NG monomethyl arginine (L-NMMA), but profoundly inhibited by the NO-generating compound S-nitroso-N-acetyl-penicillamine (SNAP). The effect of NO in this system is selective, since SNAP enhanced and L-NMMA decreased TNF-alpha synthesis by LPS-activated J774 cells. The differential effect of NO on IL-12 and TNF-alpha is at the transcriptional level and is activation dependent. Since IL-12 is a major inducer of Th1 cells which produce IFN-gamma that can activate macrophages to produce IL-12, our data demonstrate that NO can be an inhibitor of this feedback loop, preventing the excessive amplification of Th1 cells which are implicated in a range of immunopathologies.

Effects of marijuana on equilibrium, psychomotor performance, and simulated driving

Delta-9-tetrahydrocannabinol (THC) is frequently found in the blood of drivers involved in automobile accidents, and marijuana use has been associated with impaired field sobriety test performance. The present study used a within-subject design to compare the effects of marijuana (0, 1.77, or 3.95% THC) on equilibrium and simulated driving. Ten marijuana users (seven men, three women) smoked one marijuana cigarette at the beginning of each session. Then 2 min later, they began a 60-min test battery that included subjective effects scales, a computerized test of body sway, a rapid judgment task and brake latency measurement in a driving simulator, critical flicker fusion (CFF), and a choice reaction time task (CRT). Self-report ratings of 'high' and 'drug potency' increased comparably following both active doses. The high, but not the low, dose significantly increased body sway. The high dose also marginally increased brake latency by a mean of 55 ms (P < 0.10), which is comparable to an increase in stopping distance of nearly 5 feet at 60 mph Judgment, CFF, and CRT scores did not differ across dose conditions. The equilibrium and brake latency data with 3.95% THC are similar to prior results in our laboratory in participants with breath alcohol concentrations near 0.05%.

Selective expression and functions of interleukin 18 receptor on T helper (Th) type 1 but not Th2 cells

Interleukin (IL)-18 induces interferon (IFN)-gamma synthesis and synergizes with IL-12 in T helper type 1 (Th1) but not Th2 cell development. We report here that IL-18 receptor (IL-18R) is selectively expressed on murine Th1 but not Th2 cells. IL-18R mRNA was expressed constitutively and consistently in long-term cultured clones, as well as on newly polarized Th1 but not Th2 cells. IL-18 sustained the expression of IL-12Rbeta2 mRNA, indicating that IL-18R transmits signals that maintain Th1 development through the IL-12R complex. In turn, IL-12 upregulated IL-18R mRNA. Antibody against an IL-18R-derived peptide bound Th1 but not Th2 clones. It also labeled polarized Th1 but not Th2 cells derived from naive ovalbumin-T cell antigen receptor-alphabeta transgenic mice (D011.10). Anti-IL-18R antibody inhibited IL-18- induced IFN-gamma production by Th1 clones in vitro. In vivo, anti-IL-18R antibody reduced local inflammation and lipopolysaccharide-induced mortality in mice. This was accompanied by shifting the balance from Th1 to Th2 responses, manifest as decreased IFN-gamma and proinflammatory cytokine production and increased IL-4 and IL-5 synthesis. Therefore, these data provide a direct mechanism for the selective effect of IL-18 on Th1 but not Th2 cells. They also show that the synergistic effect of IL-12 and IL-18 on Th1 development may be due to the reciprocal upregulation of their receptors. Furthermore, IL-18R is a cell surface marker distinguishing Th1 from Th2 cells and may be a therapeutic target.

Identification of Asp95 as the site of succinimide formation in recombinant human glial cell line-derived neurotrophic factor

Human glial cell line-derived neurotrophic factor is a single polypeptide of 134 amino acids and functions as a disulfide-linked dimer. Incubation of the protein in pH 5.0 and at 37 degreesC for 1 week showed that 5% of the material was converted to a form that eluted after the major protein peak on a cation-exchange column. The modified component gave an average molecular mass of 30367.0 u (theoretical = 30384.8 u). Within measurement error, this 17.8-u decrease in mass indicated the loss of a water molecule. This observation, together with the protein's behavior on cation-exchange chromatography and the mode of incubation used to generate the modification, was consistent with cyclic imide (succinimide) formation at an aspartyl residue. Hence, only a monomer of the dimeric protein was modified. The modified monomer was purified and subjected to peptic degradation. By a combination of N-terminal analysis and mass spectrometry, the region containing Asp95-Lys96 was identified to be modified. This was further confirmed by carboxypeptidase Y digestion of the modified peptide where the modified region was found to be resistant to further enzymatic degradation. Furthermore, incubation of the modified monomer in pH 8. 5 for 2 h yielded two peaks, in agreement with the succinimide model where the cyclic imide was hydrolyzed into a mixture of isoaspartate and aspartate. Tryptic mapping of the isoaspartyl-containing protein showed that Asp95 was refractory to Edman degradation, confirming it was in the isoaspartate form. Hence, the modification observed was due to succinimide formation at Asp95. This is the first report of succinimide formation at an Asp-Lys linkage.

A further study of FTC yield and nicotine absorption in smokers

The relationship between nicotine yield as determined by the FTC method and nicotine absorption was examined in 72 smokers in a more rigorous repetition of a previous study of 33 smokers. For this study, 113 smokers evenly distributed across four FTC "tar" yield ranges were recruited, only 72 demonstrated reasonable compliance with the study criteria with regard to sample collections and cigarette brand style consistency. Subjects recorded the number of cigarettes smoked daily and collected a 24-h urine sample and a saliva sample on 3 consecutive days. Nicotine absorption was determined by monitoring urinary excretion of nicotine and its metabolites. In addition, saliva samples were monitored for cotinine using radioimmunoassay (RIA). The correlation of the relationship for nicotine absorbed per cigarette was positive and significant (r = 0.31, P = 0.008) but weaker than in the previous study. Only smokers in the highest yield range showed any statistical difference from smokers in the lower ranges. Our results suggest that FTC nicotine yield is weakly related to nicotine absorption and that smoker-controlled factors exert a great influence on the amount of nicotine absorbed by smokers. Compensation is substantial but incomplete for the minority (by market share) of smokers at the low end of the yield scale. It is uncertain how well any alternative set of machine parameters would predict nicotine absorption for the majority of smokers, even if it were more predictive for the small number of smokers at the lower yield part of the range.

Interleukin-12 is required for control of the growth of attenuated aromatic-compound-dependent salmonellae in BALB/c mice: role of gamma interferon and macrophage activation

The attenuated S. typhimurium SL3261 (aroA) strain causes mild infections in BALB/c mice. We were able to exacerbate the disease by administering anti-interleukin-12 (IL-12) antibodies, resulting in bacterial counts in the spleens and livers of anti-IL-12-treated mice that were 10- to 100-fold higher than the ones normally observed in premortem mice; yet the animals showed only mild signs of illness. Nevertheless, they eventually died of a slow, progressive disease. Mice infected with salmonellae become hypersusceptible to endotoxin. We found that IL-12 neutralization prevented the death of infected mice following subcutaneous injection of lipopolysaccharide. Granulomatous lesions developed in the spleens and livers of control animals, as opposed to a widespread infiltration of mononuclear cells seen in the organs of anti-IL-12-treated mice. In the latter (heavily infected), salmonellae were seen within mononuclear cells, indicating an impairment of the bactericidal or bacteriostatic ability of the phagocytes in the absence of biologically active IL-12. Gamma interferon (IFN-gamma) levels were reduced in the sera and tissue homogenates from anti-IL-12-treated mice compared to those in control animals. Furthermore, fluorescence-activated cell sorter analysis on spleen cells showed that IL-12 neutralization impaired the upregulation of I-Ad/I-Ed antigens on macrophages from infected mice. Inducible nitric oxide synthase and IFN-gamma mRNA production was down-regulated in anti-IL-12-treated mice, which also showed an increased production of IL-10 mRNA and a decrease in nitric oxide synthase activity in the tissues. Administration of recombinant IFN-gamma to anti-IL-12-treated mice was able to restore host resistance, granuloma formation, and expression of major histocompatibility complex class II antigens in F4/80(+) and CD11b+ spleen cells.

Delusional misidentification in association with parkinsonism

The delusional misidentification syndrome (DMS) has been associated with a range of neurological conditions. Three cases of DMS in patients with Parkinson's disease and dementia, treated with dopaminergic medications, are presented. It is postulated that DMS associated with parkinsonism results from a combination of dopaminergic psychosis and cognitive dysfunction involving the frontal lobe in particular. DMS in the setting of parkinsonism may be more frequent than commonly supposed.

Two T cell epitopes from the M5 protein of viable Streptococcus pyogenes engage different pathways of bacterial antigen processing in mouse macrophages

We studied the mechanisms of MHC class II-restricted bacterial Ag processing of the surface fibrillar M5 protein from viable Streptococcus pyogenes in murine macrophages. Two previously defined T cell epitopes were studied using T cell hybridomas specific for 308-319/Ad, associated with the cell wall on the surface of streptococci, and 17-31/Ed, located at the protruding amino terminus of M5. Studies with metabolic inhibitors showed that slow (1 h) processing of M5 308-319 occurred in late endosomes and was dependent on newly synthesized MHC class II molecules and microtubules and on communications between early and late endosomes, consistent with engagement of the classical MHC class II processing pathway. In contrast, fast (15 min) bacterial Ag processing of 17-31 occurred in early endosomes independently of newly synthesized MHC class II molecules and microtubules and of trafficking between early and late endosomes, consistent with the recycling MHC class II processing pathway. Finally, bacterial Ag processing of the epitopes exhibited differential sensitivity to blocking with anti-MHC class II Abs. Thus, two T cell epitopes of a single protective Ag from the surface of whole bacteria are routed to distinct MHC class II processing pathways.

Optimization of capillary chromatography ion trap-mass spectrometry for identification of gel-separated proteins

The current paradigm for protein identification using mass spectrometric derived peptide-mass and fragment-ion data employs computer algorithms which match uninterpreted or partially interpreted fragment-ion data to sequence databases, both protein and translated nucleotide sequence databases. Nucleotide sequence databases continue to grow at a rapid rate for some species, providing an unsurpassed resource for protein identification in those species. Ion-trap mass spectrometers with their ability to rapidly generate fragment-ion spectra in a data-dependent manner with high sensitivity and accuracy has led to their increased use for protein identification. We have investigated various parameters on a commercial ion trap-mass spectrometer to enhance our ability to identify peptides separated by capillary reversed phase-high performance liquid chromatography (RP-HPLC) coupled on-line to the mass spectrometer. By systematically evaluating the standard parameters (ion injection time and number of microscans) together with selection of multiple ions from the full mass range, improved tandem mass spectrometry (MS/MS) spectra were generated, facilitating identification of proteins at a low pmol level. Application of this technology to the identification of a standard protein and an unknown from an affinity-enriched mixture are shown.

Optimization of capillary chromatography ion trap-mass spectrometry for identification of gel-separated proteins

The current paradigm for protein identification using mass spectrometric derived peptide-mass and fragment-ion data employs computer algorithms which match uninterpreted or partially interpreted fragment-ion data to sequence databases, both protein and translated nucleotide sequence databases. Nucleotide sequence databases continue to grow at a rapid rate for some species, providing an unsurpassed resource for protein identification in those species. Ion-trap mass spectrometers with their ability to rapidly generate fragment-ion spectra in a data-dependent manner with high sensitivity and accuracy has led to their increased use for protein identification. We have investigated various parameters on a commercial ion trap-mass spectrometer to enhance our ability to identify peptides separated by capillary reversed phase-high performance liquid chromatography (RP-HPLC) coupled on-line to the mass spectrometer. By systematically evaluating the standard parameters (ion injection time and number of microscans) together with selection of multiple ions from the full mass range, improved tandem mass spectrometry (MS/MS) spectra were generated, facilitating identification of proteins at a low pmol level. Application of this technology to the identification of a standard protein and an unknown from an affinity-enriched mixture are shown.

Selective expression of a stable cell surface molecule on type 2 but not type 1 helper T cells

T helper cell type 1 (Th1) and 2 (Th2) are central to immune regulation. However, no stable cell surface marker capable of distinguishing and separating these two subsets of CD4(+) cells has yet been found. Using differential display PCR, we have identified a gene encoding a cell membrane bound molecule, originally designated ST2L, T1, DER4, or Fit, expressed constitutively and stably on the surface of murine Th2s, but not Th1s even after stimulation with a range of immunological stimuli. Antibody against a peptide derived from ST2L strongly and stably labeled the surface of cloned Th2s but not Th1s, and Th2s but not Th1s derived from naive T cells of ovalbumin T cell receptor-alpha/beta transgenic mice. Three-color single cell flow cytometric analysis shows that cell surface ST2L coexpressed with intracellular interleukin (IL)-4, but not with interferon (IFN)-gamma. The antibody selectively lysed Th2s in vitro in a complement-dependent manner. In vivo, it enhanced Th1 responses by increasing IFN-gamma production and decreasing IL-4 and IL-5 synthesis. It induced resistance to Leishmania major infection in BALB/c mice and exacerbated collagen-induced arthritis in DBA/1 mice. Thus, ST2L is a stable marker distinguishing Th2s from Th1s and is also associated with Th2 functions. Hence, it may be a target for therapeutic intervention.

Different endosomal proteolysis requirements for antigen processing of two T-cell epitopes of the M5 protein from viable Streptococcus pyogenes

We studied endosomal proteolysis of the surface fibrillar M5 protein from viable Streptococcus pyogenes as an essential step involved in major histocompatibility complex class II-restricted antigen processing of two immunodominant CD4(+) T-cell epitopes (17-31/Ed and 308-319/Ad). Intracellular proteolysis of viable streptococci for presentation of 17-31, bound by serine proteinase cleavage sites, was mediated by serine proteinases, whereas processing of soluble recombinant M5 protein required in addition cysteine proteinases. Furthermore, processing of 17-31 was resistant to ammonium chloride and thus was not dependent on endosome acidification. Cysteine and serine proteinase cleavage sites were located adjacent to 308-319, and its processing was dependent on serine, cysteine, and aspartic proteinases, as well as on endosomal acidification. The data suggest that antigen processing of two major T-cell epitopes on streptococcal M5 protein occurred in different endosomal compartments by different classes of intracellular proteinases.

A repeatable method for determination of carboxyhemoglobin levels in smokers

Fourteen male smokers participated in ten afternoon test sessions to determine the daily variation in expired breath carbon monoxide (CO), and whole blood percent carboxyhemoglobin (%COHb), hemoglobin and hematocrit levels. Each individual's test session was conducted at approximately the same time of day to estimate CO-related measures under relatively stable conditions. Subjects smoked ad libitum prior to testing. The 'usual brand' cigarette was smoked during the first measurement week (sessions 1-5 held on Monday through Friday) and a research cigarette prototype which primarily heats rather than burns tobacco (TOB-HT) was smoked by 12 of the 14 subjects for 3 weeks prior to and during the second measurement week (sessions 6-9 held on Tuesday through Friday). Following the last 'usual brand' measurement session, subjects completed 21 days of ad libitum smoking of the TOB-HT cigarette before starting sessions 6-9 to allow acclimation to the TOB-HT research cigarette. Following session 9, 11 of the 14 subjects continued to smoke the TOB-HT cigarette for an additional 3 weeks and then participated in an additional test session (session 10). The data indicate that daily measurements of afternoon %COHb and expired breath CO values for an individual are reproducible when using this protocol. Carboxyhemoglobin and expired breath CO levels were elevated by 24.4 and 30.6%, respectively, after switching to the TOB-HT cigarette. This increase was not due to an increase in the number of cigarettes consumed since the subjects smoked an average of 21 cigarettes prior to the measurement session when smoking either their 'usual brand' or the TOB-HT cigarette.

MHC class I expression protects target cells from lysis by Ly49-deficient fetal NK cells

Using appropriate conditions natural killer (NK) cells can be cultured from the liver and thymus of day 14 fetal mice. These fetal NK cells are phenotypically and functionally indistinguishable from adult NK cells with the exception that they lack measurable expression of all of the Ly49 molecules that can currently be detected with antibodies. Despite this, they preferentially kill tumor cells and blast cells deficient in the expression of major histocompatibility complex class I molecules, although the degree of discrimination is usually weaker than that shown by adult NK cells and varies depending on the particular combination of effector and target cells used. Polymerase chain reaction analysis revealed that although fetal NK cells are severely deficient in the expression of mRNA for Ly49A, B, C, D, G, H, and I they express high levels of Ly49E mRNA, raising the possibility that Ly49E may have an important and special function in the early development of the NK lineage.