A machine learning tool for re-planning and adaptive RT: A multicenter cohort investigation.

PURPOSE: To predict patients who would benefit from adaptive radiotherapy (ART) and re-planning intervention based on machine learning from anatomical and dosimetric variations in a retrospective dataset. MATERIALS AND METHODS: 90 patients (pts) treated for head-neck cancer (H&N) formed a multicenter data-set. 41 H&N pts (45.6%) were considered for learning; 49 pts (54.4%) were used to test the tool. A homemade machine-learning classifier was developed to analyze volume and dose variations of parotid glands (PG). Using deformable image registration (DIR) and GPU, patients' conditions were analyzed automatically. Support Vector Machines (SVM) was used for time-series evaluation. "Inadequate" class identified patients that might benefit from replanning. Double-blind evaluation by two radiation oncologists (ROs) was carried out to validate day/week selected for re-planning by the classifier. RESULTS: The cohort was affected by PG mean reduction of 23.7±8.8%. During the first 3weeks, 86.7% cases show PG deformation aligned with predefined tolerance, thus not requiring re-planning. From 4th week, an increased number of pts would potentially benefit from re-planning: a mean of 58% of cases, with an inter-center variability of 8.3%, showed "inadequate" conditions. 11% of cases showed "bias" due to DIR and script failure; 6% showed "warning" output due to potential positioning issues. Comparing re-planning suggested by tool with recommended by ROs, the 4th week seems the most favorable time in 70% cases. CONCLUSIONS: SVM and decision-making tool was applied to overcome ART challenges. Pts would benefit from ART and ideal time for re-planning intervention was identified in this retrospective analysis.

Comparative study of permanent interstitial prostate brachytherapy post-implant evaluation among seven Italian institutes.

BACKGROUND AND PURPOSE: The purposes of this multicentric study are (a) the evaluation of four different commercially available treatment planning systems (TPSs) and (b) to verify whether the dosimetric results are comparable, also when considering the inter-observer variabilities and the different scanning protocols used. This work is to be considered a first step to test the value of multicentric studies based on dosimetric evaluation of the quality of the implants. PATIENTS AND METHODS: Four different TPSs were used and the following tests were performed:Comparison of the parameters and mathematical algorithms used; comparison of the dose distributions generated by three different geometries of sources based on 32 dose-points on each source geometry. An octagonal geometric phantom was used to compare volume algorithms and dose-volume histogram (DVH) calculations (V150(Gy), V100(Gy), V50(Gy) and V25(Gy)). Comparison of the post-plan source distribution performed on a prostate-phantom implanted with (125)I seeds. A CT scan of the phantom was obtained at each participating center. Both the geometrical coordinates (with respect to the most caudal one), and the spread of the geometrical distribution, were calculated. The volumes included within different isodoses were also collected. Comparison of the post-plan source distribution performed on an actual patient. Post-plan V100% and D90(Gy) derived from seed distributions obtained by different operators were calculated, using the same target delineation. RESULTS: All the considered TPSs satisfied the AAPM dosimetric parameter recommendations. Point-dose examinations revealed differences smaller than 5%, except for one of the systems. Although the volume algorithm was not the same for all systems, no statistically significant difference was found in the volume measurements. The DVHs also presented differences smaller than 5%, except for one TPS. The distances between the seeds, based on the same CT images, showed a mean SD of 0.13 mm. The mean maximum difference of the position of each seed was 0.36 mm. The most significant errors were made in the cranio-caudal direction (mean maximal difference: 0.44 mm); here the size of the step between slices played an important role. The algorithm of source positioning of the different TPSs may also help explain this difference. The compiled DVHs showed differences smaller than 5%. Post-plans derived from different seed distributions showed a mild dependence upon operators. We obtained a mean value of 97.8 and 152.7 with a percentage of SD of 0.43 and 1.7, respectively, for V100% and D90(Gy). CONCLUSIONS: Three-dimensional (3D) geometric reconstructions of seed distributions are slightly dependent upon the operators and the scanning protocols have little effect on the dosimetric evaluation. Some relevant discrepancies were found between one of the TPSs and the other three if few sources were used; increasing the number of seeds those differences became less pronounced. Multicentric studies on the quality of prostate implants based on post-implant dosimetry are feasible, provided an accurate step-wise evaluation of the procedure be performed.

Evaluation with MR, perfusion MR and cerebral flowSPECT in NPSLE patients.

PURPOSE: To compare the performance of MR, cerebral flow SPECT and perfusion MRI (PWI) in NPSLE patients by using image co-registration. MATERIALS AND METHODS: 20 SLE patients underwent MR (T2-weighted FLAIR), perfusion and diffusion MR, and SPECT (after ( 99m)Tc-HMPAO intravenous injection). Two experienced operators analysed the images both independently and jointly after multi-modal volumetric co-registration ("Statistical Parametric Mapping" software, based on the Maximization of mutual information method). RESULTS: The FLAIR examination depicted 82 small lesions in 11/20 patients. Perfusion SPECT showed 43 hypoperfused areas in 17/20 patients. PWI showed 13 hypoperfused areas in 10/20 patients. After co-registration of images, anatomical agreement between SPECT and PWI was found in 10 hypoperfused areas (8 patients). Co-registration with FLAIR showed some false positives, more frequent in SPECT (9/43 areas) than in PWI (2/13 areas). DISCUSSION AND CONCLUSIONS: The FLAIR examination confirmed its high sensitivity in detecting lesions. Perfusion SPECT confirmed high sensitivity for the detection of hypoperfused cerebral areas. PWI showed fewer areas of cerebral hypoperfusion than did SPECT. The disagreement between SPECT and PWI may be related to the different modalities for disease detection. The anatomical agreement of hypoperfused areas between SPECT and PWI, assessed after co-registration, can suggest the prognostic hypothesis of delayed appearance of permanent parenchymal lesions. Co-registration modality, being able to show some false positives, seems to be a valid support for the interpretation of SPECT and PWI findings; the joint analysis of SPECT and PWI highlighted the capability of PWI for the interpretation of uncertain cases.

Center for Synchrotron Biosciences' U2B beamline: an international resource for biological infrared spectroscopy.

A synchrotron infrared (IR) beamline, U2B, dedicated to the biomedical and biological sciences has been constructed and is in operation at the National Synchrotron Light Source (NSLS) of Brookhaven National Laboratory. The facility is operated by the Center for Synchrotron Biosciences of the Albert Einstein College of Medicine in cooperation with the NSLS. Owing to the broadband nature of the synchrotron beam with brightness 1000 times that of conventional sources, Fourier transform IR spectroscopy experiments are feasible on diffraction-limited sample areas at high signal-to-noise ratios and with relatively short data-acquisition times. A number of synchrotron IR microscopy experiments that have been performed in the mid-IR spectral range (500-5000 cm(-1)) are summarized, including time-resolved protein-folding studies in the microsecond time regime, IR imaging of neurons, bone and other biological tissues, as well as imaging of samples of interest in the chemical and environmental sciences. Owing to the high flux output of this beamline in the far-IR region (50-500 cm(-1)), investigations of hydrogen bonding and dynamic molecular motions of biomolecules have been carried out from 10 to 300 K using a custom-made cryostat and an evacuated box. This facility is intended as an international resource for biological IR spectroscopy fully available to outside users based on competitive proposal.

Can intracellular signalling pathways predict developmental abnormalities?

Abstract Sensitivity of the adenylyl cyclase/c-fos protooncogene cascade to ß-adrenergic agonists and glucocorticoids in foetal rat We examined whether measurements of adenylyl cyclase and its control of c-fos protooncogene mRNA expression in mid-gestation foetal rat could be used to detect developmental effects of apparently unrelated compounds: terbutaline, a ß-adrenergic receptor stimulant, and dexamethasone, a glucocorticoid hormone. On gestational day 14, acute administration of terbutaline to pregnant rats resulted in sixfold induction of c-fos mRNA within 1 h; the same increase was obtained when a membrane-permeable analogue of cAMP was given. Treatment with dexamethasone on gestational days 11,12 and 13 produced the same increase in c-fos mRNA on gestational day 14 as had been seen with acute terbutaline or CAMP; no further increase could be obtained with acute CAMP treatment in the dexamethasone-pretreated animals. Adenylyl cyclase activity was evaluated on gestational day 14. Animals treated with dexamethasone showed a 50% enhancement of basal enzyme activity that reflected a parallel increase in total catalytic activity as measured with forskolin-Mn(2+). Dexamethasone also increased adenylyl cyclase activity in the presence of a ß-agonist but to a lesser extent than the increase in total catalytic activity. These results indicate that cell signalling pathways mediating the expression of the genes that control cell differentiation are a likely target for structurally and mechanistically unrelated drugs and chemicals and may therefore be useful as early biomarkers of abnormal development.

Beta-adrenergic control of c-fos expression in fetal and neonatal rat tissues: relationship to cell differentiation and teratogenesis.

beta-Adrenergic receptors appear in noradrenergic target tissues well before the arrival of nerve terminals, and are thought to play a role in the control of cell differentiation. We examined the ability of beta-agonists to stimulate expression of the nuclear transcription factor, c-fos, in developing rat liver and heart. This factor has been shown to associated with trophic activation of genes involved in both cell differentiation and cell growth. In response to terbutaline, a beta 2-selective agonist, marked stimulation of c-fos was demonstrated in the liver, which contains beta 2-receptors, on Gestational Day 20, as well as on Postnatal Days 1 and 8. In the heart, which contains predominantly beta 1-receptors, isoproterenol (a non-subtype-selective beta-agonist) was more effective that terbutaline, indicating that either receptor subtype can elicit stimulation of c-fos. In both tissues, the response magnitude increased with age, rather than following changes in receptor number, which increase in the heart but decrease in the liver; the same pattern has been seen for the ability of beta-agonists to promote cell differentiation at the expense of replication; the implication is that ontogenetic changes in post-receptor coupling are much more important than is the number of receptors in determining neurotrophic influences on gene expression and cell development. In keeping with the view that fetal/neonatal beta-adrenergic stimulation of c-fos is related to cell differentiation rather than simply to growth, repeated administration of isoproterenol to neonatal rats did not elicit cardiac hypertrophy, whereas the same treatment did produce hypertrophy in adult rats. The intracellular signaling cascade from beta-receptor to c-fos expression may thus provide one of the basic cellular mechanisms for trophic control of differentiation by biogenic amines, and for the teratologies associated with beta-adrenergic agonist therapy.

Role of presynaptic input in the ontogeny of adrenergic cell signaling in rat brain: beta receptors, adenylate cyclase and c-fos protooncogene expression.

Neurotransmitters act as trophic factors during brain development, regulating expression of genes that control cellular differentiation. One example of this trophism is the beta adrenergic signaling cascade: activation of beta receptors leads sequentially to increased cyclic AMP (cAMP), augmented expression of the nuclear transcription factor, c-fos, and induction of ornithine decarboxylase (ODC), an enzyme obligatory for neuronal development. After neonatal lesioning of noradrenergic nerves with 6-hydroxydopamine (6-OHDA), beta receptors become uncoupled from ODC induction in the cerebellum, a region that undergoes its peak of cell replication/differentiation postnatally. The present study investigates the mechanism for uncoupling of beta receptors from response elements. In the cerebellum, 6-OHDA had minor effects on beta receptor binding capabilities and caused slight supersensitivity of the beta adrenergic response of adenylate cyclase; the latter reflected increased expression of cyclase catalytic subunits, rather than a specific effect on beta receptor coupling. In contrast, the linkage of cAMP to cerebellar c-fos expression showed marked deficiencies in lesioned animals and a corresponding loss of the ability of beta receptors to induce c-fos; accordingly, this is a likely point at which beta adrenergic control of ODC is programmed by neuronal input. A critical period exists for neurotrophic influence: the alterations persisted past the point at which cerebellar norepinephrine levels recovered, and comparable effects did not occur in earlier-developing regions. In the forebrain, for example, neonatal lesions produced receptor upregulation and supersensitivity of c-fos to cAMP stimulation. These results suggest that presynaptic input is vital in programming beta adrenergic responsiveness during a critical period of development, and that interruption of transsynaptic events occurring at this time can lead to lasting alterations in neuronal differentiation and responsiveness.

The treatment of acute low back pain--bed rest, exercises, or ordinary activity?

BACKGROUND: Bed rest and back-extension exercises are often prescribed for patients with acute low back pain, but the effectiveness of these two competing treatments remains controversial. METHODS: We conducted a controlled trial among employees of the city of Helsinki, Finland, who presented to an occupational health care center with acute, nonspecific low back pain. The patients were randomly assigned to one of three treatments: bed rest for two days (67 patients), back-mobilizing exercises (52 patients), or the continuation of ordinary activities as tolerated (the control group; 67 patients). Outcomes and costs were assessed after 3 and 12 weeks. RESULTS: After 3 and 12 weeks, the patients in the control group had better recovery than those prescribed either bed rest or exercises. There were statistically significant differences favoring the control group in the duration of pain, pain intensity, lumbar flexion, ability to work as measured subjectively, the Oswestry back-disability index, and number of days absent from work. Recovery was slowest among the patients assigned to bed rest. The overall costs of care did not differ significantly among the three groups. CONCLUSIONS: Among patients with acute low back pain, continuing ordinary activities within the limits permitted by the pain leads to more rapid recovery than either bed rest or back-mobilizing exercises.

Loss of neonatal hypoxia tolerance after prenatal nicotine exposure: implications for sudden infant death syndrome.

Maternal cigarette smoking has a high correlation with sudden Infant Death Syndrome, a condition in which cardiorespiratory failure occurs during an hypoxic episode, as in sleep apnea. Pregnant rats were given nicotine infusions of 2 or 6 mg/kg/day throughout gestation, regimens that produce plasma nicotine levels spanning the range in smokers. The day after birth, animals in the high dose group displayed excessive mortality during hypoxic challenge. These animals were found to be deficient in an essential response component, namely adrenomedullary catecholamine release that is required to maintain neonatal cardiac rhythm during hypoxia; the defect was in adrenal cell function rather than in altered innervation or nicotinic receptor desensitization. We also examined brainstem and forebrain noradrenergic mechanisms that are involved in neonatal respiratory control. The nicotine group showed suppressed spontaneous neuronal activity, but were hyperresponsive to hypoxia. As these projections are inhibitory for respiration, the nicotine-induced sensitization would be expected to contribute to respiratory arrest during hypoxia. Prenatal nicotine exposure may thus provide a useful animal model with which to study the physiological mechanisms that underlie Sudden Infant Death Syndrome, while at the same time providing a biological explanation for the association of the syndrome with smoking.

In search of a mechanism for receptor-mediated neurobehavioral teratogenesis by nicotine: catecholamine release by nicotine in immature rat brain regions.

Nicotine disrupts central nervous system development through interactions with nicotinic cholinergic receptors found in immature brain, leading to discoordination of target cell replication and differentiation. However, it is unclear whether the net result is achieved by nicotine's actions on its specific target cells, or indirectly through receptor-mediated release of other neurotransmitters, such as catecholamines, that possess neurotrophic properties. In the current study, developing rats (1, 7, 14 and 21 days old) were challenged acutely with nicotine (0.3 mg/kg) and the release of catecholamines was evaluated in vivo (AMPT method) in three brain regions that differ in nicotinic receptor concentrations. Nicotine did not stimulate catecholamine release at birth, but developed the capacity to do so in parallel with the ontogeny of nicotinic cholinergic receptors in the midbrain+brainstem and in the forebrain. In the cerebellum, which remains poor in nicotinic receptors, no response was obtained at any age. Superimposed on this general pattern, changes in sensitivity to nicotine were also seen that corresponded to ontogenetic changes in endogenous cholinergic tone, suggesting that receptor desensitization occurs normally during developmental stages in which neuronal activity is high. The absence of a catecholamine response to nicotine at birth in the rat indicates that neurobehavioral teratology associated with fetal nicotine exposure does not reflect secondary actions mediated through catecholamines. However, because brain development in the neonatal rat corresponds to fetal stages in man, the onset of these mechanisms may be relevant to human fetal exposure.

Role of thyroid status in the ontogeny of adrenergic cell signaling in rat brain: beta receptors, adenylate cyclase, ornithine decarboxylase and c-fos protooncogene expression.

In adulthood, thyroid hormone regulates beta adrenergic responsiveness. We addressed whether similar processes operate in the developing brain, thus playing a role in neurotransmitter control of target cell differentiation. Rats were made hyperthyroid [triiodothyronine (T3)] or hypothyroid [propylthiouracil (PTU)] during the immediate perinatal period, and the development of beta adrenergic signal transduction was evaluated in three brain regions. PTU treatment resulted in an ubiquitous deficit in the number of beta receptor binding sites. Although beta adrenergic stimulation of adenylate cyclase activity was also obtunded by PTU, the effects were much less prominent and were restricted to one region (forebrain); comparison with basal adenylate cyclase and with total enzymatic activity (forskolin stimulation) indicated that the differences in isoproterenol response were at the level of adenylate cyclase expression, rather than in specific receptor coupling. PTU also reduced responsiveness of ornithine decarboxylase (ODC), a key enzyme that couples receptors to differentiation, again, changes in receptor-mediated responsiveness reflected alterations in total enzyme activity, rather than effects on receptor coupling. In contrast, measurements of c-fos, a protooncogene that couples cyclic AMP to induction of ODC, showed increased responses to beta adrenergic or cyclic AMP stimulation in PTU-treated animals. The effect of PTU on c-fos responsiveness occurred in the absence of alterations in basal c-fos expression, a situation different from that seen with adenylate cyclase or ODC. T3 administration had only small effects on any of these variables. The role of thyroid hormones thus involves targeting of beta receptors and receptor-mediated stimulation of nuclear transcription factors (c-fos), as well as basal expression of transduction components in the signalling cascade (adenylate cyclase, ODC). The effects of PTU, contrasted with the failure of T3 to enhance development of beta receptors or their transduction components, suggest that thyroid hormone is obligatory for normal development of this pathway, but that endogenous hormone levels are already optimally permissive.

Glucocorticoids enhance intracellular signaling via adenylate cyclase at three distinct loci in the fetus: a mechanism for heterologous teratogenic sensitization?

Although high doses of glucocorticoids are teratogenic, endogenous hormones are necessary for development. Because of the central role of cAMP to control cell differentiation, we examined the dose dependence, tissue selectivity, and critical periods involved in glucocorticoid regulation of fetal intracellular signaling mediated by adenylate cyclase. Pregnant rats were given dexamethasone at doses spanning the threshold for therapeutic effects (0.05, 0.2, and 0.8 mg/kg) on either Gestational Days 11, 12, and 13 or Days 17, 18, and 19. Development of adenylate cyclase was evaluated in cell membrane preparations using basal activity in the absence or presence of GTP, maximal G-protein activation by fluoride, and maximal catalytic subunit stimulation by forskolin-Mn2+. Even at the lowest dose, dexamethasone on gestational days 11 through 13 enhanced fetal adenylate cyclase activity by accelerating development of both the G-protein component and the catalytic subunit. As a result, supersensitivity of the response to beta-adrenergic receptor stimulation by isoproterenol was also produced, even though development of beta-adrenergic receptors was unaffected. Treatment with dexamethasone later in gestation similarly fostered development of both G-protein and catalytic subunit components, with selectivity for liver and heart as opposed to brain. Again, heterologous sensitization to isoproterenol stimulation was demonstrable; in addition, late gestational treatment elevated yet a third signal transduction locus, the beta-adrenergic receptor binding site. These effects are likely contributors to glucocorticoid teratogenesis (high doses) or to more subtle disruption of cell development (low doses); because adenylate cyclase is at the convergence of multiple neuronal, hormonal, and environmental inputs, glucocorticoids may sensitize the cell to heterologous stimuli, lowering the threshold for teratogenesis by other agents.

Impact of fetal nicotine exposure on development of rat brain regions: critical sensitive periods or effects of withdrawal?

Fetal nicotine exposure evokes alterations in central nervous system structural, neurochemical, and behavioral development. In the current study, the relative importance of critical developmental exposure periods and withdrawal were examined by infusing nicotine to pregnant rats using osmotic minipumps beginning on the fourth day of gestation. Infusions were confined to either the first 8 days (withdrawal on gestational day 13), to nearly all of gestation (withdrawal on gestational day 21), or throughout gestation and continued into the first 2 postnatal weeks. Maternal weight gain was retarded by nicotine, with a hierarchy corresponding to the duration of nicotine exposure. Similarly, fetal and neonatal body weights were unaffected in the group receiving the shortest duration of nicotine exposure, and were less affected by the intermediate infusion regimen than by the longest regimen; brain region weights were reduced significantly only with the longest regimen. Using ODC activity, a sensitive marker for altered brain cell development, we found little change in animals exposed to nicotine in early gestation and undergoing withdrawal on day 13. However, in the groups receiving nicotine through the end of gestation or through gestation and into the postnatal period, ODC activity was significantly elevated. These results indicate that withdrawal from nicotine contributes little, if any, effect either to the growth deficits or to abnormalities of brain cell development. Instead, the most important factor appears to be exposure within the developmental period corresponding to the proliferation of nicotinic receptors and the timing of receptor control of cell replication and differentiation.

Differential development of cholinergic nerve terminal markers in rat brain regions: implications for nerve terminal density, impulse activity and specific gene expression.

During critical developmental periods, cholinergic activity plays a key role in programming the development of target cells. In the current study, ontogeny of cholinergic terminals and their activity were contrasted in 4 brain regions of the fetal and neonatal rat using choline acetyltransferase activity, which is unresponsive to changes in impulse flow, and [3H]hemicholinium-3 binding, which labels the high-affinity choline transporter that upregulates in response to increased neuronal stimulation. In all 4 regions (cerebral cortex, midbrain + brainstem, striatum, hippocampus) choline acetyltransferase activity increased markedly from late gestation through young adulthood, but generally did so in parallel with the expansion of total membrane protein, reflective of axonal outgrowth and synaptic proliferation. In contrast, [3H]hemicholinium-3 binding was extremely high in late gestation and immediately after birth, declined in the first postnatal week and then rose again into young adulthood. The ontogenetic changes reflected alterations primarily in the number of binding sites (Bmax) and not in binding affinity. Only the latter phase of development of [3H]hemicholinium-3 binding corresponded to the ontogenetic changes in choline acetyltransferase activity; in the hippocampus, there were disparities even in young adulthood, where [3H]hemicholinium-3 binding showed a spike of activity centered around the 5th to 6th postnatal week, whereas choline acetyltransferase did not. Correction of binding for membrane protein development did not eliminate any of the major differences in developmental patterns between the two markers. These results suggest that development of the choline transporter binding site is regulated independently of the outgrowth of the bulk of cholinergic nerve terminals.(ABSTRACT TRUNCATED AT 250 WORDS)

Deficits in development of central cholinergic pathways caused by fetal nicotine exposure: differential effects on choline acetyltransferase activity and [3H]hemicholinium-3 binding.

Nicotine has been hypothesized to induce neurobehavioral teratology by mimicking prematurely the natural developmental signals ordinarily communicated by the ontogeny of cholinergic synaptic transmission. In the current study, the effects of fetal nicotine exposure (2 mg/kg/day or 6 mg/kg/day) on development of central cholinergic pathways were examined in striatum and hippocampus of animals exposed from gestational days 4 through 20, using maternal infusions with osmotic minipumps. Brain region weights and choline acetyltransferase activity, an enzymatic marker for development of cholinergic nerve terminals, were within normal limits in the nicotine-exposed animals. However, development of [3H]hemicholinium-3 binding which labels the presynaptic high affinity cholinergic transporter, was deficient in both striatum and hippocampus. Abnormalities occurred during two distinct phases; in the early neonatal period, when [3H]hemicholinium-3 binding sites are transiently overexpressed, and during or after the period of rapid synaptogenesis, when binding in controls is rising consequent to the increase in nerve impulse activity. These data thus indicate that fetal nicotine exposure, even at doses that do not cause overt signs of maternal/fetal/neonatal toxicity or growth impairment, influences both specific gene expression of cholinergic nerve terminal markers, as well as indices of neuronal function. Comparison of regional selectivity at the two dose levels indicated greater sensitivity of the striatum, a region with a prenatal peak of neuronal mitosis, as compared to hippocampus, where mitosis peaks postnatally; the regional differences are consistent with vulnerability to nicotine during a critical phase of cell development.

Fetal nicotine exposure ablates the ability of postnatal nicotine challenge to release norepinephrine from rat brain regions.

Exposure of the fetus to nicotine is known to affect the function of noradrenergic pathways in the central nervous system. In the current study, synaptic mechanisms underlying the functional defects were evaluated in the offspring of pregnant rats given nicotine infusions of 2 mg/kg/day throughout gestation, administered by osmotic minipumps. At 30 days postpartum, norepinephrine levels in brain regions of the offspring were significantly reduced. More importantly, acute challenge with either 0.1 mg/kg or 0.3 mg/kg of nicotine evoked significant norepinephrine release from brain regions of control animals, but failed to do so in the fetal nicotine cohort. These results suggest that prenatal exposure to nicotine produces a deficit in subsequent noradrenergic responsiveness, deficits which may participate in behavioral and neuroendocrine abnormalities.

Altered development of basal and forskolin-stimulated adenylate cyclase activity in brain regions of rats exposed to nicotine prenatally.

Exposure of the fetus to nicotine is known to affect cellular development, synaptogenesis and synaptic activity of a wide variety of neurotransmitter pathways in the central nervous system. In the current study, pregnant rats received nicotine infusions of 6 mg/kg/day throughout gestation, administered by osmotic minipumps. After birth, offspring of the nicotine infused dams displayed marked alterations in membrane-associated adenylate cyclase activity; the regional selectivity correlated both with nicotinic cholinergic receptor concentration and the maturational timetable of each region. In the midbrain and brainstem, which display relatively high receptor concentrations and earliest cell development, basal adenylate cyclase activity in the nicotine group was elevated in the immediate period postpartum, returned to normal by the end of the first month, but then became subnormal in young adulthood. The initial promotion of basal activity was mirrored by forskolin-stimulated activity, suggesting that in this phase, the alterations were occurring at the level of the adenylate cyclase catalytic unit itself. The lack of effect on forskolin stimulation in the later phase, where basal activity was subnormal in the nicotine group, suggests that some alterations in regulatory subunits are responsible for the maturational switch in nicotine's effects on adenylate cyclase. In the cerebellum, where cell replication occurs primarily after birth and receptor concentrations are low, basal adenylate cyclase showed only a deficit in the nicotine group; again, although forskolin stimulation was significantly affected, the actions on basal activity were much more prominent, suggesting defects at the level of G-proteins.(ABSTRACT TRUNCATED AT 250 WORDS)

Immune response to inactivated influenza virus vaccine: antibody reactivity with epidemic influenza B viruses of two highly distinct evolutionary lineages.

Vaccination of adults (healthy female employees potentially capable of transmitting influenza to high-risk persons; n = 104) in autumn 1990 with a trivalent influenza virus vaccine containing B/Yamagata/16/88 induced a low antibody response to B/Finland/150/90, a recent variant of B/Victoria/2/87-like viruses, as compared with the antibody response to B/Finland/172/91, a current variant in the lineage of B/Yamagata/16/88-like viruses. Up to the end of the epidemic season, the antibody status declined but was still significantly better than before the vaccination. The results suggest that the vaccine strain was appropriate for the outbreak of 1990 to 1991 in Finland, but may provide unsatisfactory protection against B/Victoria/2/87-like viruses. Evidence is given that use of Madin-Darby canine kidney (MDCK)-grown virus as an antigen in the haemagglutination inhibition test (HI) may provide more reliable information about the protective antibodies than use of untreated or ether-treated egg-grown viruses. Significantly higher postvaccination and postepidemic antibody titres were recorded among subjects who exhibited the antibody before vaccination than among seronegative subjects. A significantly higher response rate among initially seronegative people than among seropositive people was recorded for antibody to B/Finland/150/90, but no clear evidence was obtained that the pre-existing antibody could have had a negative effect on the antibody production.

Glucocorticoids and the development of neuronal function: effects of prenatal dexamethasone exposure on central noradrenergic activity.

Although glucocorticoids slow the development of most cell types, they have been hypothesized to promote the differentiation of catecholaminergic cells. In the current study, pregnant rats were given dexamethasone on gestational days 17, 18 and 19, and the functional state of noradrenergic synaptic activity was assessed throughout postnatal development by measurements of transmitter levels and turnover, and receptor binding capabilities. Despite growth inhibition caused by dexamethasone, the steroid treatment had little or no effect on transmitter levels or receptor binding and accelerated the maturation of norepinephrine turnover in a regionally selective manner. Effects were most notable in the midbrain and brainstem, where turnover rose to maximum levels 1-2 weeks in advance of controls. Turnover also leveled off prematurely in the dexamethasone group, leading to deficits in the postweaning period and into young adulthood. Although similar patterns were obtained in other, later-developing regions, the effects were less consistent and robust; the smaller effects also extended to dopamine turnover. These results suggest that glucocorticoids have a specific promotional effect on the development of central catecholaminergic activity and that administration of exogenous steroids during critical periods of development can lead to lasting functional abnormalities.

Dose-dependent glucocorticoid effects on noradrenergic synaptogenesis in rat brain: ontogeny of [3H]desmethylimipramine binding sites after fetal exposure to dexamethasone.

Glucocorticoid administration slows the development of many types of cells, but may selectively accelerate differentiation of catecholaminergic cells. In the current study, pregnant rats were given dexamethasone on gestational days 17, 18 and 19 and noradrenergic synaptogenesis assessed in the offspring by measurements of binding capabilities for [3H]desmethylimipramine (DMI), a radioligand probe for noradrenergic presynaptic terminals. After treatment with 0.05 mg/kg of dexamethasone, a dose that did not suppress body or brain region growth, [3H]DMI was initially enhanced in midbrain + brainstem and in cerebellum; the former region also displayed a secondary phase of augmented [3H]DMI binding during the ontogenetic peak occurring in the second to third postnatal week. At a higher dose (0.2 mg/kg) that elicited moderate growth impairment, fetal dexamethasone exposure produced biphasic effects on [3H]DMI binding: initial enhancement was still apparent in cerebral cortex and cerebellum, but there were subsequent deficits in binding and the peak in midbrain + brainstem was shifted to later stages. At the highest dose (0.8 mg/kg), profound growth impairment was evident and only the cerebellum showed unequivocal evidence of enhanced [3H]DMI binding. All changes were associated with alterations in the maximum [3H]DMI binding capacity (Bmax) not in the binding affinity (Kd). These results suggest that low doses of dexamethasone that do not suppress general growth, enhance noradrenergic synaptogenesis in a regionally-selective and age-selective manner; at higher, growth-suppressing doses, this effect is intermixed with general delays in maturation, likely contributing to the variable effects of glucocorticoids on neurobehavioral development.