Dissociation of nicotine tolerance from tobacco dependence in humans

Chronic functional tolerance to nicotine generally is believed to be associated with processes responsible for tobacco dependence. The dose-related effects of nicotine (0-20 microg/kg by nasal spray) on subjective, cardiovascular, and performance responses were compared among four groups varying in current or past dependence: dependent smokers (21 cigarettes per day for 20 years; n = 45), nondependent smokers (three cigarettes per day for 14 years; n = 12), former dependent smokers (mean of 7 years quit after smoking 25 cigarettes per day for 19 years; n = 17), and life-long nonsmokers (n = 19). Chronic tolerance was determined by a shift to the right, or flattening, of the dose-response curve relative to the curve for nonsmokers. Responses were corrected for plasma nicotine concentration to rule out dispositional tolerance. Chronic tolerance was observed for most subjective responses, but little or none for cardiovascular and performance effects. Tolerance was substantial and virtually identical between dependent and nondependent smokers, whereas tolerance of former smokers was intermediate between nonsmokers and dependent smokers. Identical chronic tolerance between dependent and nondependent smokers indicates that tolerance is not a linear function of smoking exposure and does not require presence of dependence. Thus, the wide variability in daily smoking rate among smokers cannot be attributed to differences in tolerance and must involve other processes of adaptation to nicotine. The modest reversal of tolerance in long-time former smokers suggests that such tolerance reversal is either limited or extremely slow after extended abstinence, despite loss of dependence. These results suggest there is no close link between nicotine tolerance and dependence and question the utility of tolerance as one of the criteria for defining dependence.

Greater sensitivity to subjective effects of nicotine in nonsmokers high in sensation seeking

The personality characteristic of sensation seeking is associated with risk of smoking, perhaps because of greater initial sensitivity to nicotine. Young healthy nonsmokers (N = 37) were administered 0, 10, and 20 microg/kg nicotine by nasal spray in 3 separate sessions, and subjective responses were assessed. Sensation-Seeking Scale (SSS) scores were then correlated with these responses. A comparison group of smokers (N = 55) was included to determine whether sensation seeking was associated specifically with initial sensitivity to nicotine or with general sensitivity regardless of past nicotine exposure. SSS subscales, particularly Experience Seeking and Disinhibition, were correlated with subjective responses to nicotine in nonsmokers but generally not in smokers. These findings indicate that sensation seeking is associated with greater initial sensitivity to nicotine's subjective effects and may provide directions for further study of individual-differences characteristics that predispose people to the risk of becoming smokers.

The discriminative stimulus and reinforcing effects of nicotine in humans following nicotine pretreatment

Smokers often report that the first cigarette of the day is the most rewarding, and subsequent smoking is less rewarding. Reduction in smoking enjoyment later in the day may be related to acute tolerance to the discriminative stimulus effects of nicotine. We examined changes in nicotine discrimination behaviour in humans as a function of acute nicotine pretreatment. Male and female dependent smokers (n = 15) were initially trained to discriminate 20 microg/kg nicotine by nasal spray from placebo (0 microg/kg) without nicotine pretreatment. They then were tested on generalization of discrimination across a range of spray doses from 0-20 microg/kg following pretreatment with placebo, moderate dose (14-21 mg) or high dose (28-42 mg) transdermal nicotine. Generalization testing involved both two- and three-response ('novel' option) quantitative procedures. Subjects also engaged in a self-administration phase at the end of each session, involving choices between nicotine (20 microg/kg) and placebo spray. Nicotine pretreatment significantly attenuated nicotine-appropriate responding at higher nicotine spray doses, suggesting acute tolerance, but only in women. Similar results were seen for subjective 'head rush', suggesting this effect may be related to discrimination behaviour in women. However, nicotine pretreatment also increased novel-appropriate responding, especially in men, following intermediate generalization doses, suggesting qualitatively different stimulus effects. Although differences were not significant, nicotine self-administration tended to be inversely associated with nicotine pretreatment dose in men but not in women. These results only modestly support the notion of acute tolerance to the discriminative stimulus effects of nicotine, and even then only in women and not in men.

Subjective responses to nicotine in smokers may be associated with responses to caffeine and to alcohol

Sensitivity in responses to one drug may relate to sensitivity to other drugs, suggesting broad individual differences in characteristic responsivity across drugs. Data from two separate studies of smokers were reanalyzed to examine associations between acute subjective and cardiovascular effects of nicotine vs. caffeine and between nicotine vs. alcohol. Typical intakes of cigarettes, alcohol, and caffeine were included as covariates when they were correlated with the responses of interest. Significant associations between nicotine and caffeine were seen for most of the subjective measures and for blood pressure responses. Fewer significant associations were observed between nicotine and alcohol. Responses associated between nicotine and both of the other drugs tended to reflect psychomotor stimulation. These results suggest that smokers who are more responsive to some of nicotine's subjective and blood pressure effects are also more sensitive to the same effects of caffeine and, to a lesser extent, of alcohol.

Biased V beta usage in immature thymocytes is independent of DJ beta proximity and pT alpha pairing

During thymus development, the TCR beta locus rearranges before the TCR alpha locus. Pairing of productively rearranged TCR beta-chains with an invariant pT alpha chain leads to the formation of a pre-TCR and subsequent expansion of immature pre-T cells. Essentially nothing is known about the TCR V beta repertoire in pre-T cells before or after the expression of a pre-TCR. Using intracellular staining, we show here that the TCR V beta repertoire is significantly biased at the earliest developmental stage in which VDJ beta rearrangement has occurred. Moreover (and in contrast to the V(H) repertoire in immature B cells), V beta repertoire biases in immature T cells do not reflect proximity of V beta gene segments to the DJ beta cluster, nor do they depend upon preferential V beta pairing with the pT alpha chain. We conclude that V gene repertoires in developing T and B cells are controlled by partially distinct mechanisms.

Anti-smoking advice from general practitioners: is a population-based approach to advice-giving feasible?

General practitioners' (GPs') advice against smoking has a small, beneficial effect on patients' smoking. Consequently, GPs have been urged to adopt a population-based approach to advice-giving that involves discussing smoking repeatedly with the maximum possible number of smokers. This discussion paper assesses how far GPs' current clinical practice is from a population-based approach to advice-giving and finds that GPs prefer a problem-orientated approach to advising those who present with smoking-related problems. Discussion focuses on the feasibility of suggesting that GPs adopt a population-based approach instead.

Results of two national surveys of leadership personnel needs in deaf education

Seventy university teacher preparation programs and 100 instructional programs serving at least 120 deaf and hard of hearing students were surveyed separately to (a) determine the demand for additional doctoral-level leadership personnel in deaf education, (b) obtain guidance for university leadership preparation programs in deaf education for the purpose of recruiting leadership personnel, and (c) identify experiences that would be relevant to the positions for which prospective leadership personnel are preparing. Data representing 54% of teacher preparation programs and 65% of instructional programs serving deaf and hard of hearing students in the United States evince the need for additional doctoral-level personnel for faculty positions in university teacher preparation programs in deaf education, as well as the need for leadership positions in instructional programs serving deaf and hard of hearing children. Data also provide direction for leadership preparation programs in addressing the leadership personnel needs of the field.

Cutting edge: an essential role for Notch-1 in the development of both thymus-independent and -dependent T cells in the gut

Whereas most T cells arise in the thymus, a distinct lineage of extrathymically derived T cells is present in the gut mucosa. The developmental origin of extrathymic T cells is poorly understood. We show here that Notch-1, a transmembrane receptor involved in T cell fate specification of bipotential T/B precursors in the thymus, is absolutely required for the development of extrathymic (as well as thymus-derived) mature T cells in the intestinal epithelium. In the absence of Notch-1, CD117(+) T cell precursors are relatively more abundant in the gut than the thymus, whereas immature B cells accumulate in the thymus but not the gut. Collectively, these data demonstrate that Notch-1 is essential for both thymic and extrathymic T cell fate specification and further suggest that bipotential T/B precursors that do not receive a Notch-1 signal adopt a B cell fate in the thymus but become developmentally arrested in the gut.

The 1999 annual report of the Regional Infant and Child Mortality Review Committee

The 1999 Annual Report of the Regional Infant and Child Mortality Review Committee (RICMRC) is presented. Our Regional (Minnehaha, Lincoln, and Turner Counties) incidence for Sudden Infant Death (SIDS) continues to significantly exceed the national rate. In this study, SIDS is strongly associated with prone sleeping and sleeping on soft surfaces or bedding. The Back-to-Sleep campaign that has been an important part of lowering the national SIDS rate appears to have been less successful in our region. The Regional Infant Child Mortality Review Committee therefore has elected to serve not only as a data collection committee, but has also actively engaged in community education programs directed towards providing a safer environment for our children.

Using content analysis of video-recorded consultations to identify smokers' "readiness" and "resistance" towards stopping smoking

Although physicians' brief advice against smoking is effective in helping smokers to stop, very little is known about the process of counseling smokers. We describe the development of a coding system for describing smokers' motivation to stop smoking as judged by their behaviour when discussing smoking with their family physician. We analysed video-recordings of consultations between 47 self-reported smokers and 29 family physicians where smoking was discussed. By a process of observing recordings, reading transcripts and discussion, we developed a coding system for describing smokers' levels of motivation to stop smoking. This consists of four behaviours thought to indicate "readiness" (higher motivation to stop) and four "resistance" (lower motivation to stop). Interobserver reliability between two observers was good (Kappa = 0.71 for readiness, 0.73 for resistance behaviours). We discuss the relevance of our descriptions for clinicians and the possibility of developing this work further to enable systematic research into doctor-patient interactions where smokers are counseled to stop.

Frequent loss of BRCA1 mRNA and protein expression in sporadic ovarian cancers

Germline mutations in the BRCA1 gene cause inherited susceptibility to breast and ovarian cancers. However, somatic mutations of BRCA1 are rare in sporadic breast and ovarian tumours. To establish whether BRCA1 is altered during the development of sporadic ovarian cancer by mechanisms other than somatic mutation, we have analysed 57 sporadic epithelial ovarian tumours for BRCA1 protein and RNA expression. Reduced or absent protein expression was observed in 90% of tumours. Decreased protein expression was significantly associated with a reduction in the levels of RNA expression. Somatic mutations of BRCA1 and LOH at the BRCA1 locus were detected in 3.5% and 44% of informative tumours, respectively; there was no significant correlation between the levels of protein and RNA expression and the DNA mutation and/or LOH status. Together, these data suggest that expression of BRCA1 is down-regulated at the level of transcription during the development of sporadic ovarian cancers.