Effect on rates of breast feeding of training for the baby friendly hospital initiative

PROBLEM

Breastfeeding rates and related hospital practices need improvement in Italy and elsewhere. Training of staff is necessary, but its effectiveness needs assessment.

CONTEXT

Eight hospitals in different regions of Italy.

DESIGN

Controlled, non-randomised study. Data collected in three phases. Training after the first phase in group 1 hospitals and after the second phase in group 2.

STRATEGIES FOR CHANGE

Training of trainers and subsequent training of health workers with a slightly adapted version of the 18 hour Unicef course on breastfeeding management and promotion.

KEY MEASURES FOR IMPROVEMENT

Hospital practices, knowledge of 571 health workers, and breastfeeding rates at discharge, three, and six months in 2669 mother and baby pairs.

EFFECTS OF CHANGE

After training hospitals improved their compliance with the "ten steps to successful breast feeding," from an average of 2.4 steps at phase one to 7.7 at phase three. Knowledge scores of health professionals increased from 0.41 to 0.72 in group 1 (training after phase one) and from 0.53 to 0.75 in group 2 (after phase two). The rate of exclusive breast feeding at discharge increased significantly after training: 41% to 77% in group 1 and 23% to 73% in group 2, as did the rates of full (exclusive plus predominant) breast feeding at three months (37% to 50% in group 1 v 40% to 59% in group 2) and any breast feeding at six months (43% to 62% in group 1 v 41% to 64% in group 2).

LESSONS LEARNT

Training for at least three days with a course including practical sessions and counselling skills is effective in changing hospital practices, knowledge of health workers, and breastfeeding rates.

Breastfeeding by objectives

BACKGROUND

In many countries, the rates of breastfeeding fall far short of those recommended. National plans to promote breastfeeding are badly needed. We describe the results of a breastfeeding promotion programme planned by objectives and financial penalties in a small region of Italy.

METHODS

This observational study was conducted in all the maternity hospitals and immunisation clinics of the six local health authorities of Friuli Venezia Giulia, in the northeast of Italy. The regional health authority included breastfeeding in its annual plans for 1998 and 1999, and asked local health authorities to develop local workplans and targets. A financial penalty was contemplated for local health authorities not achieving objectives and targets. The rates of exclusive, predominant and complementary breastfeeding were measured at birth and at 16-19 weeks of age. Data were collected, using standard definitions and methods, at discharge from hospitals and at the time of the second mandatory immunisation.

RESULTS

All local health authorities and hospitals set up a breastfeeding reporting system in 1998 and defined breastfeeding promotion activities for 1999. The rate of exclusive breastfeeding at discharge and at 16-19 weeks increased significantly between 1998 and 1999, with a corresponding reduction of complementary breastfeeding.

CONCLUSION

Financial penalties may contribute to the promotion of exclusive breastfeeding.

Role of native-state topology in the stabilization of intracellular antibodies

The role played by the geometric position of each amino acid in the folding process of the immunoglobulin (Ig) variable domain is identified and measured through molecular dynamics simulations of models based on the topology of its native state. This measure allows identifying the parts of the protein that, for geometrical reasons, when mutated, would result in relevant protein stability changes. Simulations were performed without considering the covalent disulfide bond present in most of the Ig domains. The results are in good agreement with site-directed mutagenesis experiments on the folding of intracellular antibodies in which the disulfide bond does not form. We also found agreement with data on amino acid conservation in the Ig variable domain sequences. This indicates a new way for a rational approach to the design of intracellular antibodies more resistant to the suppression of the disulfide bond that occurs in the cytoplasm.

Purification, crystallization and preliminary X-ray analysis of the Fab fragment from MNAC13, a novel antagonistic anti-tyrosine kinase A receptor monoclonal antibody

The monoclonal antibody MNAC13 is a potent antagonist that prevents the binding of nerve-growth factor (NGF) to its tyrosine kinase A receptor (TrkA) in a variety of systems. Structural studies of the FabMNAC13 fragment were performed to gain insights into the mechanism of action of this potentially therapeutic monoclonal antibody. The optimal conditions for crystallization of FabMNAC13 were determined. Crystals appeared as prismatic bundles, displayed P2(1)2(1)2(1) space-group symmetry and diffracted to a resolution of 1.8 A. The unit-cell parameters were determined to be a = 52.73, b = 67.55, c = 111.43 A. The data set was 99.5% complete. Molecular replacement was performed, resulting in a correlation coefficient of 0.55 and an R value of 0.40. The structure refinement is now in progress.

Use of sedative and analgesic drugs in the first week of ICU stay. A pharmaco-epidemiological perspective

AIM

To assess the current practice of pharmacological sedation and analgesia in patients admitted in Italian intensive care units.

METHODS

DESIGN

observational, prospective, cohort study, involving all patients admitted during a one-month period to participating Centers in 1994. All patients were followed-up for vital status until discharge and evaluated for pharmacological sedation and analgesia for the first week of ICU stay.

SETTING

128 Italian, adult, general, intensive care units, approximately representing 1/3 of all Italian Units.

PATIENTS

2932 patients were analyzed. They generated 22612 patient-days of intensive care unit stay, 11221 of which were evaluated.

RESULTS

A total of 31 different sedative drugs were used in 1751 patients. On 64% of sedated days only one drug was utilized, whereas two or more drugs were administered in the remaining days. Propofol was the most widely prescribed drug, followed by fentanyl and diazepam, while morphine accounted for 14.8% of sedated days. The analysis of the pattern of sedation over time revealed a trend to linearly reduce the use of this practice.

CONCLUSIONS

Our results depict a relatively low prevalence of sedation in Italy, with the use of large number of different agents. We also observed a larger than expected use of some drugs, like propofol and fentanyl, that could be due to the unavailability of new sedative and analgesic drugs in Italy on 1994. In conclusion, Italian intensivists seem to be very conservative about the practice of pharmacological sedation in critically ill patients.

Mismatch between BDNF mRNA and protein expression in the developing visual cortex: the role of visual experience

Brain-derived neurotrophic factor (BDNF) messenger RNA (mRNA) expression in the rat visual cortex of young and postnatal day 90 (P90) animals is developmentally regulated and influenced by visual experience. In the present paper we compared the expression of BDNF mRNA to the actual changes of BDNF protein occurring during postnatal development and verified whether BDNF protein distribution is controlled by visual activity. To achieve this aim we analysed BDNF mRNA and/or BDNF protein cellular distribution in the rat visual cortex at different postnatal ages by using immunohistochemistry and highly sensitive in situ hybridization. We found that before eye opening (P13), in all cortical layers a large number of visual cortical neurons contain BDNF mRNA with no detectable amount of BDNF protein. At later ages (P23 and P90), the number of BDNF-immunostained cells increases; most neurons are double labelled for BDNF mRNA and protein, and a small group of neurons is labelled only for BDNF protein. The cellular increase of BDNF immunolabelling is blocked in animals deprived of visual experience from birth (dark rearing), with a large population of neurons containing BDNF mRNA but not BDNF protein. This is similar to what is observed before eye opening. Exposure of dark-reared rats to a brief period (2 h) of light restores a good match between BDNF mRNA and BDNF protein cellular expression. We propose that visual experience controls the neuronal content of BDNF mRNA and BDNF protein in developing visual cortex.

Homicide in children and adolescents: a case-control study in Recife, Brazil

OBJECTIVE

The homicide rate for children and adolescents in Recife, Brazil, mostly caused by firearms, is one of the highest that has been reported. The present case-control study was designed to identify factors that were potentially modifiable through preventive interventions.

METHODS

Cases were 255 homicide victims under 20 years of age, who had died in 1997 and been identified at the Institute of Forensic Medicine, Police Department, Recife, and whose relatives were interviewed by two community health workers when they claimed the corpse. The 255 controls were neighbours of the cases, paired by age and sex to them, and identified within one week of identification of each case, and whose relatives were interviewed by a third community health worker.

FINDINGS

The overall homicide rate in Recife for under-20-year-olds in 1997 was 49 per 100,000; among males aged 15-19 years it was 324 per 100,000. Firearms were responsible for 97% of deaths. After multivariate logistic regression, history of personal police records (odds ratio (OR) = 18.65; 95% confidence interval (CI) = 1.91-182.50), use of illicit drugs (OR = 7.48; 95% CI = 1.86-30.17), tap water at home (OR = 7.30; 95% CI = 1.80-29.59), and maternal age at birth over 26 years (OR = 3.98; 95% CI = 1.79-8.84) were identified as risk factors, while higher education (OR = 0.22; 95% CI = 0.11-0.43), religious practice (OR = 0.25; 95% CI = 0.10-0.65), and presence of the father in the household (OR = 0.28; 95% CI = 0.09-0.81) were protective factors.

CONCLUSION

Public health authorities should plan preventive interventions based on the findings of this study and should control the acquisition, possession and carrying of firearms.

Comparison of two training strategies for essential newborn care in Brazil

OBJECTIVE

To compare the effectiveness of two training strategies for improving essential newborn care in the state of Pernambuco, Brazil.

METHODS

Eight hospitals were selected, divided into two groups of four, and paired by geographical, structural, and functional characteristics. Doctors and nurses working at hospitals in Group 1 were given a conventional 5-day training course. Those in Group 2 were given the same manual used by Group 1 but the training course was organized as self-directed learning, with the participants having 5 weeks to complete the course. Participants' knowledge was tested at baseline, immediately after the course, and 3-6 months later. Participants' practices were observed before training and 3-6 months after training during 20 births and by interviewing 20 mothers before discharge at each hospital.

FINDINGS

Not all participants completed all of the tests. The scores on the tests of knowledge improved more among those in Group 2 than those in Group 1 when the answers were classified as right or wrong, but there was no difference between groups when a scoring method was used that classified answers as correct, partially correct, incorrect, or missing. Practices related to thermal control after birth improved among those in Group 2 after training but practices related to thermal control on the ward worsened. The promotion of breastfeeding improved in both groups.

CONCLUSION

There was no difference between the two training strategies, although self-directed learning was cheaper than conventional training. Neither strategy brought about the expected improvements in the quality of care. Other interventions in addition to training may be needed to improve care.

The solution structure of the C-terminal segment of tau protein

Pathological changes in the microtubule associated protein tau, leading to tau-containing filamentous lesions, are a major hallmark common to many types of human neurodegenerative diseases, including Alzheimer's disease (AD). No structural data are available which could rationalize the extensive conformational changes that occur when tau protein is converted to Alzheimer's paired helical filaments (PHF). The C-terminal portion of tau plays a crucial role in the aggregation of tau into PHF and in the truncation process that generates cytotoxic segments of tau. Therefore, we investigated the solution structure of the hydrophobic C-terminal segment 423-441 of tau protein (PQLATLADEVSASLAKQGL) by 1H 2D NMR spectroscopy. The peptide displays the typical NMR evidence consistent with a alpha-helix geometry with a stabilizing C-capping motif. The reported data represent the first piece of structural information on an important portion of the molecule and can have implications towards the understanding of its pathophysiology.

Kangaroo mother care with limited resources

Kangaroo mother care (KMC) for low birthweight infants (LBWI) was introduced in a Mozambican hospital with limited resources and without facilities for intensive care. Six months were needed to change policies, organize the ward, train staff and overcome constraints. Facilitating factors were a KMC national policy, the commitment of health authorities, technical assistance and availability of some funds, and the perception of improved quality of care and survival. The obstacles and constraints were resistance to change by the staff, cultural problems, and managerial difficulties. Out of 32 LBWI (< or = 1.800 g) admitted in 3 months, survival was 73 per cent in 22 KMC and 20 per cent in 10 non-KMC infants (p < 0.01). KMC is a feasible and appropriate technology in hospitals with very limited resources.

Differential somato-dendritic localization of TrkA, TrkB, TrkC and p75 mRNAs in vivo

TrkB mRNA was shown to be localized in the somatodendritic compartment in vitro but no data are currently available on the subcellular distribution of the neurotrophin receptors mRNAs in vivo. Here we describe the subcellular distribution of TrkA, TrkB, TrkC and p75 mRNAs in the adult rat basal forebrain. We find that TrkA, TrkC and p75 mRNAs are restricted to the cell soma but in addition, p75 mRNA labelling extends in average for 8 microm within the proximal dendrites of 34% of the labelled neurons. TrkB mRNA has a somatodendritic distribution in 95% of the labelled neurons reaching variable distances in different neurons (23-84.5 microm) and forebrain regions (mean: 40, 51 and 55 microm for diagonal band, septum and ventral pallidum).

The neuronal microtubule-associated protein tau is a substrate for caspase-3 and an effector of apoptosis

We have identified a class of tau fragments inducing apoptosis in different cellular contexts, including a human teratocarcinoma-derived cell line (NT2 cells) representing committed human neuronal precursors. We have found a transition point inside the tau molecule beyond which the fragments lose their ability to induce apoptosis. This transition point is located around one of the putative caspase-3 cleavage sites. This is the only site that can be effectively used by caspase-3 in vitro, releasing the C-terminal 19 amino acids of tau. These results establish tau as a substrate for an apoptotic protease that turns tau itself into an effector of apoptosis. Accordingly, tau may be involved in a self-propagating process like what has been predicted for the pathogenesis of different neurodegenerative disorders.

Alzheimer-like neurodegeneration in aged antinerve growth factor transgenic mice

Neurotrophin nerve growth factor (NGF) has been suggested to be involved in age-related neurodegenerative diseases, but no transgenic model is currently available to study this concept. We have obtained transgenic mice expressing a neutralizing anti-NGF recombinant antibody, in which the levels of antibodies are three orders of magnitude higher in adult than in newborn mice [F.R., S. C. , A.C., E. Di Daniel, J. Franzot, S. Gonfloni, G. Rossi, N. B. & A. C. (2000) J. Neurosci., 20, 2589-2601]. In this paper, we analyze the phenotype of aged anti-NGF transgenic mice and demonstrate that these mice acquire an age-dependent neurodegenerative pathology including amyloid plaques, insoluble and hyperphosphorylated tau, and neurofibrillary tangles in cortical and hippocampal neurons. Aged anti-NGF mice also display extensive neuronal loss throughout the cortex, cholinergic deficit in the basal forebrain, and behavioral deficits. The overall picture is strikingly reminiscent of human Alzheimer's disease. Aged anti-NGF mice represent, to our knowledge, the most comprehensive animal model for this severe neurodegenerative disease. Also, these results demonstrate that, in mice, a deficit in the signaling and/or transport of NGF leads to neurodegeneration.

Brain-derived neurotrophic factor (BDNF) induces dendritic targeting of BDNF and tyrosine kinase B mRNAs in hippocampal neurons through a phosphatidylinositol-3 kinase-dependent pathway

This study aims to understand the mechanisms of dendritic targeting of brain-derived neurotrophic factor (BDNF) and tyrosine kinase B (TrkB) mRNAs. We show that brief depolarizations are sufficient to induce accumulation of BDNF and TrkB mRNAs in dendrites of hippocampal neurons. Endogenous BDNF, secreted during the KCl stimulation, contributes significantly to the dendritic accumulation of BDNF-TrkB mRNAs. In the absence of depolarization, 1 min pulses of exogenous BDNF are sufficient to induce dendritic accumulation of BDNF-TrkB mRNAs. After binding to TrkB, BDNF exerts this action by activating a PI-3 kinase-dependent pathway. The accumulation of dendritic mRNA by BDNF is not mediated by BDNF-induced neurotransmitter release. Because most hippocampal neurons coexpress BDNF and TrkB receptors, these results show that the subcellular distribution of BDNF-TrkB mRNAs is under the control of an autocrine-paracrine BDNF-TrkB-dependent loop.

Trk B signalling controls LTP but not LTD expression in the developing rat visual cortex

Neurotrophins have been suggested to act as liaison molecules between activity-dependent synaptic plasticity and the establishment of patterns of synaptic connectivity during postnatal developmental in different brain areas, including the visual cortex. In particular, recent studies have shown that Trk B ligands are involved in the formation of the ocular dominance columns during postnatal development. Here, we examined the contribution of endogenous Trk B activation to the regulation of different forms of synaptic plasticity including long-term potentiation (LTP), long-term depression (LTD) and LTP after LTD in the developing visual cortex. Rat cortical slices were incubated with a soluble form of Trk B receptor (TrkB IgG) preventing Trk B activation by endogenous ligands. LTP expression was also studied at P23 (postnatal), when the expression of brain-derived neurotrophic factor (BDNF) reaches a peak and the LTP expression is normally downregulated. The present results demonstrate that Trk B activation is required for the long-term maintenance, > 30 min, of both LTP and LTP after LTD at P17. At P23, a higher concentration of TrkB IgG was necessary to impair LTP. In contrast, neither amplitude nor duration of LTD were affected by Trk B ligands blockade. Taken together, these results indicate that endogenous Trk B ligands are necessary for the expression of LTP but not LTD at a critical time during postnatal cortical development.

Phenotypic knockout of nerve growth factor in adult transgenic mice reveals severe deficits in basal forebrain cholinergic neurons, cell death in the spleen, and skeletal muscle dystrophy

The disruption of the nerve growth factor (NGF) gene in transgenic mice leads to a lethal phenotype (Crowley et al., 1994) and hinders the study of NGF functions in the adult. In this study the phenotypic knockout of NGF in adult mice was achieved by expressing transgenic anti-NGF antibodies, under the control of the human cytomegalovirus promoter. In adult mice, antibody levels are 2000-fold higher than in newborns. Classical NGF targets, including sympathetic and sensory neurons, are severely affected. In the CNS, basal forebrain and hippocampal cholinergic neurons are not affected in the early postnatal period, whereas they are greatly reduced in the adult (55 and 62% reduction, respectively). Adult mice show a reduced ability in spatial learning behavioral tasks. Adult, but not neonatal, transgenic mice further show a new phenotype at the level of peripheral tissues, such as apoptosis in the spleen and dystrophy of skeletal muscles. The analysis of this novel comprehensive transgenic model settles the controversial issue regarding the NGF dependence of cholinergic neurons in adult animals and reveals new NGF functions in adult non-neuronal tissues. The results demonstrate that the decreased availability of NGF in the adult causes phenotypic effects via processes that are at least partially distinct from early developmental effects of NGF deprivation.

Feasibility, acceptability and cost of kangaroo mother care in Recife, Brazil

This descriptive study on kangaroo mother care (KMC) of low-birthweight infants (LBWIs) was carried out in a tertiary care hospital in Recife, Brazil. Of 244 LBWIs weighing less than 1750 g admitted over 14 months, 112 (46%) died before inclusion, 18 (7%) were excluded, and 114 (47%), after stabilization, were cared for by KMC 24 hours a day until discharge. No deaths were recorded in hospital; two twins died of severe pneumonia after discharge and before the age of 3 months. There were no episodes of moderate or severe hypothermia but mild hypothermia (36-36.4 degrees C axillary temperature) occurred at a rate of 30 episodes per 100 infant days, mainly related to occasional separation from the mother. One hundred infants (88%) were discharged on exclusive breastfeeding, eight (7%) were still taking expressed breast-milk from a cup and six (5%) were being fed breast-milk plus formula. The mean daily weight gain during KMC was 15 g. At follow-up, 87% were still exclusively breastfed at 1 month and 63% at 3 months. KMC was acceptable to mothers and staff. An important advantage of KMC over previous conventional care is cost--US$20 vs US$66 per bed/day. This study confirms that KMC for stabilized LBWIs in hospital is feasible, acceptable and cheap and in hospitals with limited resources is an appropriate alternative to conventional incubator care.

Muscular dystrophy in adult and aged anti-NGF transgenic mice resembles an inclusion body myopathy

The role of nerve growth factor (NGF) and its receptors in the physiology of skeletal muscles has not been extensively studied in animal models. We describe the production of transgenic lines of mice expressing a neutralizing antibody against NGF (alphaD11) and the morphological and histochemical analysis of skeletal muscles from adult and aged anti-NGF mice. This study reveals that the chronic deprivation of NGF results in a decreased size of myofibers of dorsal and hindlimb muscles in adult but not in postnatal day (P)2 mice. In myofibers from adult anti-NGF mice, the presence of central nuclei, vacuolization of the cytoplasm, and inflammatory cell infiltration was observed. The immunohistochemical analysis of these muscular fibers revealed an upregulation of p75 expression, a decrease in adenosine triphosphatase (ATP)ase activity, and a subsarcolemmal Congo Red-positive staining. Immunostaining with an antibody against amyloid precursor protein showed an increased labeling of the cytoplasm of myofibers from adult and aged anti-NGF mice. These features are reminiscent of human myopathies, such as inclusion body myositis. We conclude that NGF deficits might be relevant for a class of human myopathies.

Diverting a protein from its cellular location by intracellular antibodies. The case of p21Ras

We describe the use of phage libraries to derive new antibodies against p21Ras to be used for intracellular expression in mammalian cells. A panel of single-chain antibody fragments, binding to Ras, were analyzed and characterized for their capacity to interfere in vitro with (a) the intrinsic GTPase activity of Ras and (b) the binding of Ras to its effector Raf, and were found not to neutralize its function, according to these biochemical criteria. When expressed intracellularly in mouse 3T3 K-Ras transformed cells all the anti-Ras single-chain variable fragments (scFv) tested inhibited cell proliferation, as assessed by bromodeoxyuridine incorporation. Double immunofluorescence analysis of transfected cells using confocal microscopy confirmed that anti-Ras antibody fragments colocalize with endogenous Ras, at subcellular locations where the protein Ras is not normally found. These data suggest that the ability of phage-derived anti-Ras scFv fragments to inhibit the function of Ras in vivo is a rather general and frequent property and that the range of antibodies that can be successfully used for intracellular inhibition studies is much greater than anticipated, exploiting the mode of action of diverting protein traffic.

Are data on the prevalence and duration of breastfeeding reliable? The case of Italy

Many countries produce data on the prevalence and duration of breastfeeding, but are they reliable? We reviewed 16 studies on breastfeeding in Italy published after 1990. They report a prevalence of breastfeeding at and around birth ranging from 66% to 91%, decreasing to 17-52% at 4 mo and 28-36% at 6 mo. Most studies refer to a non-representative sample of the Italian population. Two studies used standard definitions of breastfeeding, but their results are difficult to interpret or cannot be generalized. Five other studies used non-standard definitions that undermine the interpretation of results. The remaining nine studies used no definition at all. All studies used a recall period different from 24 h, or from the whole hospital stay for breastfeeding at discharge, making the interpretation of results even more difficult. We conclude that the published information gives an inaccurate picture of the prevalence and duration of breastfeeding in Italy, leading to unjustified optimism and inaction. The actual figures may be lower, as shown by preliminary data from a small Italian region: using standard definitions and methods during a 9-mo monitoring period, exclusive breastfeeding averaged 35% at discharge and 23% at about 4 mo of age.

Blocking the NGF-TrkA interaction rescues the developmental loss of LTP in the rat visual cortex: role of the cholinergic system

Although nerve growth factor (NGF) is a crucial factor in the activity-dependent development and plasticity of visual cortex, its role in synaptic efficacy changes is largely undefined. We demonstrate that the maintenance phase of long-term potentiation (LTP) is blocked by local application of exogenous NGF in rat visual cortex at an early stage of postnatal development. Long-term depression (LTD) and bidirectional plasticity are unaffected. At later postnatal ages, blockade of either endogenous NGF by immunoadhesin (TrkA-IgG) or TrkA receptors by monoclonal antibody rescues LTP. Muscarinic receptor activation/inhibition suggests that LTP dependence on NGF is mediated by the cholinergic system. These results indicate that NGF regulates synaptic strength in well-characterized cortical circuitries.

Functional blockade of tyrosine kinase A in the rat basal forebrain by a novel antagonistic anti-receptor monoclonal antibody

We have exploited a new monoclonal antibody against the tyrosine kinase A (TrkA) nerve growth factor (NGF) receptor to block the NGF-TrkA interaction in the rat basal forebrain. The monoclonal antibody MNAC13 is a potent antagonist that prevents the binding of NGF to TrkA in a variety of systems. This antibody was used to study the maintenance of the cholinergic phenotype in the rat basal forebrain in vivo, by the implant of antibody-secreting cells. Basal forebrain cholinergic neurons (BFCNs) are greatly affected by the antibody treatment, both in terms of cell number and of cell soma size. When antibody-secreting cells are implanted at postnatal day 2 (P2), the effects observed at P8 are as severe as those obtained with anti-NGF antibodies and, interestingly, are observed also if anti-TrkA cells are implanted at P8, when anti-NGF antibodies, delivered by the same route, are no longer effective (). The effects induced by anti-TrkA, as those induced by anti-NGF, are reversible, but the time required for recovery and the critical period in the sensitivity of BFCNs to the functional inactivation of TrkA is twice as long than that observed when NGF is intercepted. These results demonstrate that BFCNs are more sensitive to the block of TrkA activation than they are to the block of NGF. The cloning of MNAC13 variable regions and their assembly into a functional polypeptide of reduced size (single chain Fv fragment) will allow its use in gene transfer applications.

Selection of antibodies for intracellular function using a two-hybrid in vivo system

Expression of antibodies inside cells has been used successfully to ablate protein function. This finding suggests that the technology should have an impact on disease treatment and in functional genomics where proteins of unknown function are predicted from genomic sequences. A major hindrance is the paucity of antibodies that function in eukaryotic cells, presumably because the antibodies fold incorrectly in the cytoplasm. To overcome this problem, we have developed an in vivo assay for functional intracellular antibodies using a two-hybrid approach. In this assay, antibody, as single-chain Fv (scFv) linked to a transcriptional transactivation domain, can interact with a target antigen, linked to a LexA-DNA binding domain, and thereby activate a reporter gene. We find that several characterized antibodies can bind their target antigen in eukaryotic cells in this two-hybrid format, and we have been able to isolate intracellular binders from among sets of scFv that can bind antigen in vitro. Furthermore, we show a model selection in which a single scFv was isolated from a mixture of half a million clones, indicating that this is a robust procedure that should facilitate capture of antibody specificities from complex mixtures. The approach can provide the basis for de novo selection of intracellular scFv from libraries, such as those made from spleen RNA after immunization with antigen, for intracellular analysis of protein function based only on genomic or cDNA sequences.

Differential regulation of brain-derived neurotrophic factor messenger RNA cellular expression in the adult rat visual cortex

In this study, we report a comparative analysis of the distribution of brain-derived neurotrophic factor messenger RNA in the binocular primary visual cortex of rats analysed at the end of the critical period for monocular deprivation (postnatal day 35) and during adulthood (postnatal day 90). High-resolution non-isotopic in situ hybridization coupled with Nissl staining allowed to determine the relative number of neurons expressing brain-derived neurotrophic factor messenger RNA. In postnatal day 90 rats, the relative number of neurons positive for brain-derived neurotrophic factor messenger RNA significantly decreases in layer II/III with respect to postnatal day 35 animals, being constant in all the other cortical layers. Moreover, we demonstrate that dark rearing for 22 days, starting from postnatal day 90, determines: (i) a decrease of the overall level of brain-derived neurotrophic factor messenger RNA with a consequent reduction of labelling intensity in all cells throughout cortical layers II-VI; (ii) an increase of cell numbers expressing brain-derived neurotrophic factor messenger RNA in layers IV and V; and (iii) a decreased intensity of staining for brain-derived neurotrophic factor messenger RNA in dendrites after dark rearing. A re-exposure to light for 2 h after the period of darkness almost restores the number of brain-derived neurotrophic factor RNA-positive neurons. We conclude that the maturation of brain-derived neurotrophic factor messenger RNA in neurons of layer II/III goes beyond postnatal days 35-40, which can be considered the end of the critical period [Fagiolini M. et al. (1994) Vis. Res., 34, 709-720]. Moreover, we show that the cellular expression of brain-derived neurotrophic factor messenger RNA is regulated by light in adult rats as well as during development.