Identification of higher brain centres that may encode the cardiorespiratory response to exercise in humans

1. Positron emission tomography (PET) was used to identify the neuroanatomical correlates underlying 'central command' during imagination of exercise under hypnosis, in order to uncouple central command from peripheral feedback. 2. Three cognitive conditions were used: condition I, imagination of freewheeling downhill on a bicycle (no change in heart rate, HR, or ventilation, V(I)): condition II, imagination of exercise, cycling uphill (increased HR by 12 % and V(I) by 30 % of the actual exercise response): condition III, volitionally driven hyperventilation to match that achieved in condition II (no change in HR). 3. Subtraction methodology created contrast A (II minus I) highlighting cerebral areas involved in the imagination of exercise and contrast B (III minus I) highlighting areas activated in the direct volitional control of breathing (n = 4 for both; 8 scans per subject). End-tidal P(CO(2)) (P(ET,CO(2))) was held constant throughout PET scanning. 4. In contrast A, significant activations were seen in the right dorso-lateral prefrontal cortex, supplementary motor areas (SMA), the right premotor area (PMA), superolateral sensorimotor areas, thalamus, and bilaterally in the cerebellum. In contrast B, significant activations were present in the SMA and in lateral sensorimotor cortical areas. The SMA/PMA, dorso-lateral prefrontal cortex and the cerebellum are concerned with volitional/motor control, including that of the respiratory muscles. 5. The neuroanatomical areas activated suggest that a significant component of the respiratory response to 'exercise', in the absence of both movement feedback and an increase in CO(2) production, can be generated by what appears to be a behavioural response.

Does Hypercapnia-Induced Cerebral Vasodilation Modulate the Hemodynamic Response to Neural Activation?

Increases in cerebral blood flow produced by vasoactive agents will increase blood oxygen level-dependent (BOLD) MRI signal intensity. The effects of such vasodilation on activation-related signal changes are incompletely characterized. The two signal changes may be simply additive or there may be more a complex interaction. To investigate this, BOLD MRI was performed in four normal male subjects using T2*-weighted echo planar imaging; brain volumes were acquired every 6.2 s, using a Siemens VISION scanner operating at 2 Tesla; each volume consisted of 64 sequential transverse slices (64 x 64 pixels per slice, 3 x 3 x 3 mm). Sixteen periods of visual stimulation were produced using a flickering checkerboard (8 Hz, 31 s On/31 s Off); this was coupled with five periods of hypercapnia (4% inspired CO(2), 62 s On/124 s Off). Data were analyzed using SPM96. Mean signal intensity, calculated globally for the whole brain, closely mirrored changes in the partial pressure of end-tidal CO(2) (PCO(2)), and hypercapnia was associated with widespread significant signal increases (P < 0.001), predominantly within grey matter. As expected, the visual stimulation produced significant signal changes within the occipital cortex (P < 0.001). Within the occipital cortex, no significant interactions (P > 0.001) between the effects of the visual stimulation and PCO(2) were present. The increases in PCO(2) imposed dynamically in the present study would increase cerebral blood flow by between 25 and 40%, an increase within the physiological range and comparable to that induced by neural activation. With this flow change the effects of vasodilation, on an activation-related signal change, are simply additive.

An evaluation of the mutagenicity, metabolism, and DNA adduct formation of 5-nitrobenzo[b]naphtho[2,1-d]thiophene

Thioarenes, sulfur-containing polycyclic aromatic compounds, are environmental contaminants suspected of posing human health risks. In this study, 5-nitrobenzo[b]naphtho[2,1-d]thiophene (5-nitro-BNT), a nitrated-thioarene, was examined for its mutagenicity, metabolism and subsequent formation of DNA adducts. 5-Nitro-BNT was weakly mutagenic in Salmonella typhimurium strains TA98 and TA100 without Aroclor-1254-induced rat liver S9 (S9), and its activity was increased in the presence of S9. Anaerobic metabolism of 5-nitro-BNT by S9 or xanthine oxidase (XO) produced one major metabolite, identified as 5-amino-BNT by NMR, MS, and UV spectroscopy and by comparison with an authentic standard. Aerobic S9 metabolism of 5-nitro-BNT produced a major metabolite, identified as trans-9,10-dihydroxy-9,10-dihydro-5-nitro-BNT (5-nitro-BNT-9,10-diol). Also present was a minor amount of 5-amino-BNT and trans-9,10-dihydroxy-9,10-dihydro-5-amino-BNT (5-amino-BNT-9,10-diol). DNA adduct analyses were performed using the (32)P-postlabeling assay and reversed-phase HPLC. Three major XO-derived calf thymus DNA adducts were detected. On the basis of their chromatographic mobilities, two adducts were identified as reaction products of 5-nitro-BNT with 2'-deoxyguanosine and one adduct with 2'-deoxyadenosine. Incorporation of allopurinol (a specific XO inhibitor) in the incubation mixture resulted in loss of all three adducts, confirming enzymatic mediation by XO. Aerobic S9 activation of 5-nitro-BNT with calf thymus DNA produced three adducts. On the basis of their chromatographic mobilities, two were identified as reaction products of 5-nitro-BNT with 2'-deoxyguanosine and one with 2'-deoxyadenosine. Incorporation of 1-aminobenzotriazole (a P450 inhibitor) in the incubation mixture resulted in a loss of these adducts, confirming enzymatic mediation by P450. Aerobic S9-catalyzed metabolism of 5-nitro-BNT-9,10-diol produced the same DNA adducts as observed with 5-nitro-BNT. Aerobic S9-catalyzed metabolism of 5-amino-BNT-9,10-diol produced the same deoxyadenosine-derived DNA adducts as observed with 5-nitro-BNT and 5-nitro-BNT-9,10-diol. These results provide additional information that both ring oxidation and nitroreduction are involved in the metabolism, DNA adduct formation and mutagenicity of 5-nitro-BNT.

Impact of age on breathing and resistive pressure in people with and without sleep apnea

We investigated the effect of age on breathing and total pulmonary resistance (RL) during sleep by studying elderly (>65 yr) and young (25-38 yr) people without sleep apnea (EN and YN, respectively) matched for body mass index (BMI). To determine the impact of sleep apnea on age-related changes in breathing, we studied elderly and young apneic patients (EA and YA, respectively) matched for apnea and BMI. In all groups (n = 11), breathing during periods of stable sleep was analyzed to evaluate the intrinsic variability of respiratory control mechanisms. In the absence of sleep apnea, the variability of the breathing was similar in the elderly and young [mean (+/- SD) coefficient of variation (CV) of tidal volume (VT); wake: EN 21.0 +/- 14.9%, YN 14.7 +/- 5.5%; sleep: EN 14.0 +/- 6.0%; YN 11.5 +/- 6.4%]. In patients with sleep apnea, breathing during stable sleep was more irregular, but there were no age-related differences (CV of VT; wake: EA 22.0 +/- 11.6%, YA 16.7 +/- 11.3%; sleep: EA 32.8 +/- 24.9%, YA 25.2 +/- 16.3%). In addition, EN tended to have a higher RL (n = 6, RL midinspiration, wake: EN 7.1 +/- 3.0; YN 9.1 +/- 6.4 cmH(2)O. l(-1). s, sleep: EN 17.5 +/- 11.7; YN 9.8 +/- 2.0 cmH(2)O. l(-1). s). We conclude that aging per se does not contribute to the intrinsic variability of respiratory control mechanisms, although there may be a lower probability of finding elderly people without respiratory instability.

Terminal sialylation is altered in airway cells with impaired CFTR-mediated chloride transport

Reduced terminal sialylation at the surface of airway epithelial cells from patients with cystic fibrosis may predispose them to bacterial infection. To determine whether a lack of chloride transport or misprocessing of mutant cystic fibrosis transmembrane conductance regulator (CFTR) is critical for the alterations in glycosylation, we studied a normal human tracheal epithelial cell line (9/HTEo(-)) transfected with the regulatory (R) domain of CFTR, which blocks CFTR-mediated chloride transport; DeltaF508 CFTR, which is misprocessed, wild-type CFTR; or empty vector. Reduced cAMP-stimulated chloride transport is seen in the R domain and DeltaF508 transfectants. These two cell lines had consistent, significantly reduced binding of elderberry bark lectin, which recognizes terminal sialic acid in the alpha-2,6 configuration. Binding of other lectins, including Maakia amurensis lectin, which recognizes sialic acid in the alpha-2,3 configuration, was comparable in all cell lines. Because the cell surface change occurred in R domain-transfected cells, which continue to express wild-type CFTR, it cannot be related entirely to misprocessed or overexpressed CFTR. It is associated most closely with reduced CFTR activity.

The shuttle walking test: a reproducible method for evaluating the impact of shortness of breath on functional capacity in patients with advanced cancer

BACKGROUND

Breathlessness leading to exercise limitation is common in patients with advanced cancer and is ineffectively treated. There are few research data to guide clinicians on best practice. The shuttle walking test has been validated for some conditions such as chronic obstructive pulmonary disease but not for advanced cancer. One of the well documented difficulties of doing clinical research in palliative care is the acceptability of assessment tests. This study examined the reproducibility of the shuttle walking test in patients with advanced cancer to help facilitate the systematic evaluation of interventions designed to improve breathlessness.

METHODS

Patients performed three shuttle walks on separate days with continuous monitoring of arterial oxygen saturation and heart rate; simple pulmonary function (FEV(1)) was also recorded. Data on quality of life, anxiety, and depression were collected throughout the study period using appropriate questionnaires. Breathlessness was measured before and after exercise using a visual analogue scale.

RESULTS

Data from 22 patients were compared between visits 2 and 3. There were no significant differences between the FEV(1) (1.89 v 1.90, p=0.73), distance walked on each test (245 m v 256 m, p=0.14), end-exercise levels of heart rate (107/min v 108/min, p=0.11), oxygen saturation (93.4% v 93.2%, p=0.38), or breathlessness scores (p=0.62) on the two occasions. Indices of quality of life, anxiety, and depression were also not different between the two tests. The investigation was very acceptable to patients, families, and staff.

CONCLUSIONS

The shuttle walking test is a reproducible test of functional capacity in ambulant patients with advanced cancer, WHO performance status 1 or 2. The data indicate that a practice session is needed. It is easy to carry out and acceptable for patients with advanced cancer.

Matching short break services for children with learning disabilities to family needs and preferences

Short breaks or respite care is a much-valued service by families and the demand for it is likely to exceed supply. It is all the more imperative that the services provided are matched to the needs and preferences of families. A census was undertaken within one Health and Social Services Board in Northern Ireland of families who received short break services for their child with disabilities during a 12-month period. Information was also collected on pertinent child and family characteristics. This enabled profiles to be drawn up of the recipients of six types of short-term breaks: (1) hospital-based overnight care; (2) overnight stays in a residential home; (3) domiciliary service in the family home; (4) breaks provided in another family home; (5) residential holidays; and (6) breaks provided through leisure schemes organized after-school or during holidays. A second study entailed interviews with families who were resident in one area served by a Health and Social Service Trust regarding their usage and preferences for each type of service noted above. This too identified variations in parental preferences and usage. This information gathered should assist commissioners in developing cost-beneficial short break services although further research is needed to validate the possible predictors for each service.

Acute partial paralysis alters perceptions of air hunger, work and effort at constant P(CO(2)) and V(E)

Breathing sensations of AIR HUNGER, WORK and EFFORT may depend on projections of central motor discharge (corollary discharge) to the forebrain. Source of motor drive (brainstem or cortex) may determine what is perceived. To test the effect of changing motor discharge at constant ventilation, we induced partial neuromuscular blockade during hypercapnic hyperpnea (31 + or - 9 L min(-1); PET(CO(2))=49 + or - 2 Torr) and during matched volitional hyperpnea (34 + or - 5 L min(-1); PET(CO(2))=41 + or - 1 Torr). Decline of vital capacity was similar between conditions (39%). Ventilation was unchanged with paralysis, indicating increased respiratory motor drive to maintain hyperpnea. Sensations were rated on a seven point ordinal scale. Median EFFORT and WORK increased 3-3.5 points with paralysis during both forms of hyperpnea (P<0.02, Wilcoxon signed rank). Median AIR HUNGER increased 2.5 points with paralysis during hypercapnic (P<0.02) but not during volitional hyperpnea. Data suggests that EFFORT and WORK arise from motor cortex activity (subjects reported engaging volitional control when paralyzed even during hypercapnia) and suggests that AIR HUNGER arises from medullary motor activity.

Breathlessness in humans activates insular cortex

Dyspnea (shortness of breath, breathlessness) is a major and disabling symptom of heart and lung disease. The representation of dyspnea in the cerebral cortex is unknown. In the first study designed to explore the central neural structures underlying perception of dyspnea, we evoked the perception of severe 'air hunger' in healthy subjects by restraining ventilation below spontaneous levels while holding arterial oxygen and carbon dioxide levels constant. PET revealed that air hunger activated the insular cortex. The insula is a limbic structure also activated by visceral stimuli, temperature, taste, nausea and pain. Like dyspnea, such perceptions underlie behaviors essential to homeostasis and survival.

The respiratory response to inspiratory resistive loading during rapid eye movement sleep in humans

We investigated the respiratory response to an added inspiratory resistive load (IRL) during rapid eye movement (REM) sleep in humans and compared this with those in non-REM (NREM) sleep and wakefulness. Results were obtained from 7 out of 15 healthy subjects (n = 7; 32 +/- 9 years, mean +/- s.d.). Linearised IRLs (4 and 12 cmH(2)O l(-1) s(-1)) were applied for five breaths during NREM sleep (4-10 trials per subject; total 101), REM sleep (2-5 trials; total 46) and wakefulness (2-3 trials; total 40). Respiratory variables were compared, between unloaded breathing (UL: mean of 5 breaths preceding IRL) and the 1st (B1) and 5th (B5) loaded breaths in each state. During wakefulness, 12 cmH(2)O l(-1) s(-1) IRL produced an immediate respiratory compensation with prolongation of inspiratory time (T(I); UL: 2.0 +/- 0.6; B1: 2.6 +/- 0.7 s) and an increase in tidal volume (V(T); UL: 0.49 +/- 0.12; B1: 0.52 +/- 0.12 l). During REM sleep, T(I) was prolonged (UL: 2.0 +/- 0.3; B1: 2.2 +/- 0.5 s), although V(T) fell (UL: 0.27 +/- 0.15; B1: 0.22 +/- 0.10 l). For both wakefulness and REM sleep the TI response was significantly greater than seen in NREM sleep (UL: 1.9 +/- 0.3; B1: 1.9 +/- 0.3 s.). For VT, only the wakefulness response was significantly different from NREM sleep (UL: 0.31 +/- 0.14; B1: 0.21 +/- 0.10 l). The B5 responses were not significantly different between states for any of the variables. REM sleep is associated with partial respiratory load compensation suggesting that exacerbation of sleep disordered breathing in REM (compared to NREM) sleep is unlikely to be secondary to an inability to overcome increases in upper airway resistance.

The effect of imaging guidelines on the number and quality of outpatient radiographic examinations

OBJECTIVE

A significant percentage of outpatient diagnostic radiology is performed by nonradiologists. Studies have shown nonradiologists have higher utilization and cost, as well as quality problems. We sought to determine if, in a managed care environment, a set of guidelines limiting imaging privileges of nonradiologist physicians could decrease imaging costs while ensuring that equipment and personnel providing imaging were of the highest quality.

MATERIALS AND METHODS

We determined the number and type of radiographic imaging studies performed the year after these guidelines were set in place (1997) and compared these findings with those of the year before the guidelines were established (1995) and with preguideline trends. We established quality criteria and, based thereon, inspected imaging offices.

RESULTS

The number of radiographic examinations per 1000 enrollees decreased 20-25% from the previous trend. Nonradiologists' share of the total fell from 39% to 15%. No deficiencies were found in the inspection of five radiologists' offices, whereas significant deficiencies of equipment, equipment maintenance, or documentation of the examinations performed were found in 78% of nonradiologists' offices. None of the quality indicators monitored by the health plan showed significant change.

CONCLUSION

Specific guidelines can effect change in the location and number of radiologic examinations performed, with an improvement in the quality of the studies and a decrease in radiation dose and cost. No decline in quality of care appears to result, despite claims by opponents to such changes that widespread serious quality impairment would occur.

Development of an endoscopic navigation system based on digital image processing

We developed a new system to couple the endoscope to an optical position measurement system (OPMS) so that the image frames from the endoscope camera can be labeled with the accurate endoscopic position. This OPMS is part of the EasyGuide Neuro navigation system, which is used for microsurgery and neuroendoscopy. Using standard camera calibration techniques and a newly developed system calibration, any 3-dimensional (3-D) world point can be mapped onto the view from the endoscope. In particular, we can display the coordinates of any anatomical landmark of the patient as it is viewed from the current position of the camera. This and other image-processing techniques are applied to the labeled frame sequence in order to offer the neurosurgeon a variety of control modules that increase the safety and flexibility of neuroendoscopic operations. Several modules, including a new motion alarm system and the "tracking" and "virtual map" modules, were tested in a human cadaveric model using the frontal and occipital approaches. A failure rate of 8.6% was experienced during testing of the first version of the software, but the second version was 100% successful. Thus, an endoscopic navigation system based on digital image processing has been developed that could be a revolutionary advance in image-guided surgery.

8,9-dihydroxy-8,9-dihydrodibenzo[a,l]pyrene is a potent morphological cell-transforming agent in C3H10T(1)/(2)Cl8 mouse embryo fibroblasts in the absence of detectable stable covalent DNA adducts

The comparative genotoxic effects of racemic trans-8,9-dihydroxy-8, 9-dihydrodibenzo[a,l]pyrene (trans-DB[a,l]P-8,9-diol), the metabolic K-region dihydrodiol of dibenzo[a,l] pyrene (DB[a,l]P) (dibenzo[def, p]chrysene) and DB[a,l]P in transformable mouse embryo C3H10T(1)/(2)Cl8 (C3H10T(1)/(2)) fibroblasts was investigated. The C3H10T(1)/(2) mouse embryo morphological cell-transforming activities of these polycyclic aromatic hydrocarbons (PAHs) were assayed using concentration-response studies. At concentrations of 33 nM and above both trans-DB[a,l]P-8,9-diol and DB[a,l]P produced significant (and similar) numbers of type II and III foci per dish and numbers of dishes with type II and II foci. Concomitant cytotoxicity studies revealed a reduction in colony survival of approximately 25% up to 198 nM for both PAHs. DNA adducts of trans-DB[a,l]P-8,9-diol and DB[a,l]P in C3H10T(1)/(2) cells were analyzed by a (32)P-post-labeling TLC/HPLC method. No adducts were observed in the DNA of C3H10T(1)/(2) cells treated with trans-DB[a, l]P-8,9-diol at concentrations that induced morphological cell transformation. Under the same exposure and chromatographic conditions, DNA adducts of deoxyadenosine and deoxyguanosine derived from the fjord region anti-DB[a,l]P-11,12-diol-13,14-epoxide and syn-DB[a,l]P-11,12-diol-13,14-epoxide were observed in the DNA of DB[a,l]P-treated cells. These results indicate that trans-DB[a,l]P-8, 9-diol has intrinsic genotoxic activity equal to that of DB[a,l]P, based on morphological cell transformation of mouse embryo fibroblasts. The activity of trans-DB[a,l]P-8,9-diol is apparently not associated with the formation of observable stable covalent DNA adducts. These results suggest that under appropriate conditions, trans-DB[a,l]P-8,9-diol may serve as an intermediate in the genotoxicity of DB[a,l]P.

Human, bovine, and rabbit retinal glutamate-induced [3H]D-aspartate release: role in excitotoxicity

The pharmacological basis of glutamate-induced [3H]D-aspartate release was investigated in isolated human, bovine and rabbit retinas. Isolated mammalian retinas were preloaded with [3H]D-aspartate and then prepared for studies of neurotransmitter release using the superfusion method. Release of [3H]D-aspartate was elicited by K+ (50 mM) or by L-glutamate. In bovine retinas, L-glutamate, but not D-glutamate induced an overflow of [3H]D-aspartate that was partially inhibited by low external calcium, omega-conotoxin (10 nM) or nitrendipine (1 microM). Metabotropic glutamate receptor (GLUR) agonists also evoked [3H]D-aspartate release in both bovine and human retinas whereas polyamines only enhanced the excitatory effects of L-glutamate on [3H]D-aspartate release. Antagonists of GLURs and the polyamine site inhibited L-glutamate evoked [3H]D-aspartate overflow with the following rank order of potency: MCPG >ifenprodil > AP-5 > arcaine> MK-801. In conclusion, L-glutamate-induces a stereoselective, calcium-dependent release of [3H]D-aspartate from isolated mammalian retinas that can be mimicked by GLUR agonists (and blocked by both receptor and polyamine site antagonists).

Unique issues of older medical students

PURPOSE

Many persons applying to medical school have had other careers or experiences prior to their application. Comprising an increasing proportion of our student population, these older medical students often have unique difficulties differing from those of their younger peers. We undertook a 2-part study to evaluate possible differences in attitudes and beliefs between younger and older medical students.

SUMMARY

We conducted the study in 2 parts. In the 1st part, a focus group of students who would be 30 years old or older at the completion of medical school ("older students") was assembled to ascertain potential themes. Themes articulated by this group were then constructed into a questionnaire that was administered to the entire 4th-year class. Results of the questionnaire were evaluated qualitatively by content and quantitatively when appropriate. Eight students participated in the focus group. The themes expressed by the group included increased home responsibilities relative to their peers, lack of perceived respect by attendings and residents, and different learning strategies. Eighty-eight students completed the questionnaire. More older than younger students agreed with the statements that their previous experiences made them better learners (p = .06) and that their personal responsibilities made it difficult to study (p = .0001). On open-ended questions, the responses from the older students were longer and contained stronger language.

CONCLUSION

Older medical students express unique concerns regarding the learning environment and the impact of medical school on their personal lives. This study provides preliminary information that our older students may have more special needs and concerns than traditional students.

Modulation of the corticospinal control of ventilation by changes in reflex respiratory drive

We have determined whether changes in PCO(2) above and below eucapnia modulate the precision of the voluntary control of breathing. Twelve trained subjects performed a compensatory tracking task in which they had to maintain the position of a cursor (perturbed by a variable triangular forcing function) on a fixed target by breathing in and out of a spirometer (ventilatory tracking; at 10 l/min). Before each task, subjects hyperventilated for 5 min, and the end-tidal PCO(2) (PET(CO(2))) was controlled; tracking was then performed separately at hypocapnia, eucapnia, and hypercapnia (PET(CO(2)) approximately 25, 37, and 43 Torr, respectively). Ventilatory tracking error was unchanged during hypocapnia (P > 0.05) but was significantly worse during hypercapnia (P < 0.003), compared with eucapnia; arm tracking error, performed as a control, was not significantly affected by PET(CO(2)) (P > 0. 05). In conclusion, ventilatory tracking performance is unaffected by the eucapnic PCO(2). From this, we suggest that resting breathing in awake humans may be independent of chemical drives and of the prevailing PCO(2).

Botanical medicines with gynecological anticancer activity: a literature review

This article reviews the existing scientific literature reporting effects of botanical substances on the prevention and treatment of gynecological cancers. Anticancer effects were reported for 14 of 27 herbal substances searched for, 8 of which had reported effects specifically in gynecological cancer models. Research reviewed included in vitro studies in gynecological cancer cell lines, animal studies, an ex vivo study, and an epidemiological study. No clinical trials on gynecological cancer prevention or treatment were found for any of the 8 identified agents. Despite the increasing use of botanical medicines in the prevention and treatment of cancer in general, there is a paucity of studies describing their efficacy or safety in gynecological cancer. Given the prevalent use of botanical medicine in complementary and alternative cancer therapy, the need for research to evaluate safety and efficacy using both in vitro and in vivo methods is pressing.

A quantitative comparison of dibenzo[a,l]pyrene-DNA adduct formation by recombinant human cytochrome P450 microsomes

Dibenzo[a,l]pyrene (DB[a,l]P), an extremely potent environmental carcinogen, is metabolically activated in mammalian cells and microsomes through the fjord-region dihydrodiol, trans-DB[a,l]P-11, 12-diol, to syn- and anti-DB[a,l]P-11,12-diol-13,14-epoxides (syn- and anti-DB[a,l]PDEs). The role of seven individual recombinant human cytochrome P450s (1A1, 1A2, 1B1, 2B6, 2C9, 2E1, and 3A4) in the metabolic activation of DB[a,l]P and formation of DNA adducts was examined by using (32)P postlabeling, thin-layer chromatography, and high-pressure liquid chromatography. We found that, in the presence of epoxide hydrolase, only P450 1A1 and P450 1B1 catalyzed the formation of DB[a,l]PDE-DNA adducts and several unidentified polar adducts. Human P450 1A1 catalyzed the formation of DB[a, l]PDE-DNA adducts and unidentified polar adducts at rates threefold and 17-fold greater than did human P450 1B1 (256 fmol/h/nmol P450 versus 90 fmol/h/nmol P450 and 132 fmol/h/nmol P450 versus 8 fmol/h/nmol P450, respectively). P450 1A1 DNA adducts were derived from both anti- and syn-DB[a,l]PDE at rates of 73 fmol/h/nmol P450 and 51 fmol/h/nmol P450, respectively. P450 1B1 produced adducts derived from anti-DB[a,l]PDE at a rate of 82 fmol/h/nmol, whereas only a small number of adducts were derived from syn-DB[a,l]PDE (0.4 fmol/h/nmol). These results demonstrated the potential of human P450 1A1 and P450 1B1 to contribute to the metabolic activation and carcinogenicity of DB[a,l]P and provided additional evidence that human P450 1A1 and 1B1 differ in their stereospecific activation of DB[a,l]P. Mol. Carcinog. 26:74-82, 1999. Published 1999 Wiley-Liss, Inc.

Sleep-related changes in the human 'neuromuscular' ventilatory response to hypoxia

The ventilatory responses to hypercapnia and hypoxia are reduced during sleep compared to wakefulness. However, sleep-related increases in upper airways' resistance could reduce these ventilatory responses independently of any change in the neural output to the respiratory pump muscles. It is therefore possible that respiratory chemosensitivity, per se, is unchanged by sleep. To investigate this, four healthy male subjects were mechanically ventilated to abolish spontaneous respiratory muscle activity. The response to transient isocapnic hypoxia was quantified from the magnitude of the electromyographic activity induced in the diaphragm and from the associated reduction in peak inspiratory pressure; these indicies of respiratory motor output will not be affected by any sleep-related changes in upper airways' resistance. In all individuals, the responses to hypoxia were markedly attenuated during sleep compared to wakefulness. These observations, assessing the 'neuromuscular' ventilatory response, are consistent with a sleep-related reduction in respiratory chemosensitivity that is independent of any changes that may be due to increases in upper airways' resistance.

The "Let's Get Alarmed!" initiative: a smoke alarm giveaway programme

OBJECTIVES

To reduce fires and fire related injuries by increasing the prevalence of functioning smoke alarms in high risk households.

SETTING

The programme was delivered in an inner London area with above average material deprivation and below average smoke alarm ownership. The target population included low income and rental households and households with elderly persons or young children.

METHODS

Forty wards, averaging 4000 households each, were randomised to intervention or control status. Free smoke alarms and fire safety information were distributed in intervention wards by community groups and workers as part of routine activities and by paid workers who visited target neighbourhoods. Recipients provided data on household age distribution and housing tenure. Programme costs were documented from a societal perspective. Data are being collected on smoke alarm ownership and function, and on fires and related injuries and their costs.

RESULTS

Community and paid workers distributed 20,050 smoke alarms, potentially sufficient to increase smoke alarm ownership by 50% in intervention wards. Compared with the total study population, recipients included greater proportions of low income and rental households and households including children under 5 years or adults aged 65 and older. Total programme costs were 145,087 Pounds.

CONCLUSIONS

It is possible to implement a large scale smoke alarm giveaway programme targeted to high risk households in a densely populated, multicultural, materially deprived community. The programme's effects on the prevalence of installed and functioning alarms and the incidence of fires and fire related injuries, and its cost effectiveness, are being evaluated as a randomized controlled trial.

Modulation of CCAAT/enhancer-binding protein-alpha gene expression by metabolic signals in rodent adipocytes

The transcription factor CCAAT/enhancer-binding protein-alpha (C/EBPalpha) is a positive modulator of transcription for several adipocyte-specific genes that play a role in energy metabolism. However, there is little information available regarding the regulation of its expression by metabolic signals. Exposure to insulin for 5-24 h attenuated C/EBPalpha expression when 3T3-L1 adipocytes were incubated in 24 mM glucose, but not in 5.7 mM glucose. Nuclear run-on transcription assays indicated a transcriptional repression of C/EBPalpha gene, but not that of C/EBPbeta. Glucosamine, a product of the hexosamine pathway, in the presence of low glucose mimicked high glucose's ability to reduce C/EBPalpha messenger RNA expression in insulin-treated cells. Similar results were obtained with xylitol, an activator of the pentose phosphate pathway. There was no correlation between the accumulation of hexosamine pathway metabolites (e.g. UDP-N-acetylhexosamines) and/or changes in intracellular protein glycosylation with the ability of high glucose, glucosamine, or xylitol to down-regulate C/EBPalpha gene expression. None of these treatments caused a reduction in intracellular ATP levels. Stable transfection of 3T3-L1 cells with the 5'-flanking 468-bp sequence of the mouse C/EBPalpha gene fused to luciferase demonstrated that promoter activity was also reduced by these nutrients. Of interest, treatment of rats with glucose or glucosamine led to a reduction in C/EBPalpha messenger RNA levels in epididymal, but not omental, fat. Taken together, these results suggest that metabolic signals serve to down-regulate C/EBPalpha expression both in vitro and in vivo.