Category-based attention facilitates memory search

We often need to decide whether the object we look at is also the object we look for. When we look for one specific object, this process can be facilitated by feature-based attention. However, when we look for many objects at the same time (e.g., the products on our shopping list) such a strategy may no longer be possible, as research has shown that we can actively prepare to detect only one or two objects at a time. Therefore, looking for multiple objects additionally requires long-term memory search, slowing down decision making. Interestingly, however, previous research has shown that distractor objects can be efficiently rejected during memory search when they are from a different category than the items in the memory set. Here, using EEG, we show that this efficiency is supported by top-down attention at the category level. In Experiment 1, human participants (both sexes) performed a memory search task on individually presented objects from different categories, most of which were distractors. We observed category-level attentional modulation of distractor processing from ∼150 ms after stimulus onset, expressed both as an evoked response modulation and as an increase in decoding accuracy of same-category distractors. In Experiment 2, memory search was performed on two concurrently presented objects. When both objects were distractors, spatial attention (indexed by the N2pc component) was directed to the object that was of the same category as the objects in the memory set. Together, these results demonstrate how top-down attention can facilitate memory search.Significance statement When we are in the supermarket, we repeatedly decide whether a product we look at (e.g., a banana) is on our memorized shopping list (e.g., apples, oranges, kiwis). This requires searching our memory, which takes time. However, when the product is of an entirely different category (e.g., dairy instead of fruit), the decision can be made quickly. Here, we used EEG to show that this between-category advantage in memory search tasks is supported by top-down attentional modulation of visual processing: The visual response evoked by distractor objects was modulated by category membership, and spatial attention was quickly directed to the location of within-category (vs. between-category) distractors. These results demonstrate a close link between attention and memory.

Temporal profiles of cortical oscillations in novice performers for goal-directed aiming in a shooting task

Goal-directed aiming relies on the ability to control attention and visuomotor movements while preparing for motor execution. Research in precision sports has investigated cortical oscillations for supporting expert performance. However, the results may be influenced by adaptive and strategic behaviors after intensive training. Whether and at what time points distinctive oscillations support goal-directed aiming without such training remains elusive. In this electroencephalographic (EEG) study, we investigated how the theta, alpha and beta oscillations change to support accurate aiming before novices took an action. We first conducted a model-based analysis to examine the correlation of cortical oscillations with accurate shooting on a trial-by-trial basis in a within-individual manner. The results showed that alpha and beta oscillations at different time points during the aiming period were better predictors of aiming accuracy. We then compared the oscillatory power for good versus poor performance. The results showed decreases in the alpha and beta power across distributed cortical areas and an increase in the frontal theta power successively before shot release. Moreover, greater intertrial phase coherence was observed for good performance than for poor performance in posterior alpha activity and anterior beta activity during the aiming period. In conclusion, these results advance our understanding of the temporal dynamics of theta, alpha and beta oscillations in orchestrating goal setting, motor preparation and focused attention to monitoring both external and internal states for accurate aiming. Among the three, alpha and beta oscillations are critical for predicting aiming performance and theta oscillations reflect effortful cognitive control.

The time course of categorical and perceptual similarity effects in visual search

During visual search for objects (e.g., an apple), the surrounding distractor objects may share perceptual (tennis ball), categorical (banana), or both (peach) properties with the target. Previous studies showed that the perceptual similarity between target and distractor objects influences visual search. Here, we tested whether categorical target-distractor similarity also influences visual search, and how this influence depends on perceptual similarity. By orthogonally manipulating categorical and perceptual target-distractor similarity, we could investigate how and when the two similarities interactively affect search performance and neural correlates of spatial attention (N2pc) using electroencephalography (EEG). Behavioral results showed that categorical target-distractor similarity interacted with perceptual target-distractor similarity, such that the effect of categorical similarity was strongest when target and distractor objects were perceptually similar. EEG results showed that perceptual similarity influenced the early part of the N2pc (200-250 ms after stimulus onset), while categorical similarity influenced the later part (250-300 ms). Mirroring the behavioral results, categorical similarity interacted with perceptual similarity during this later time window, with categorical effects only observed for perceptually similar target-distractor pairs. Together, these results provide evidence for hierarchical processing in visual search: categorical properties influence spatial attention only when perceptual properties are insufficient to guide attention to the target. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Spatially Specific Attention Mechanisms Are Sensitive to Competition during Visual Search

Extensive studies have focused on selection mechanisms during visual search. One important influence on these mechanisms is the perceptual characteristics of the stimuli. We investigated the impact of perceptual similarity between targets and nontargets (T-N similarity) in a visual search task using EEG. Participants searched for a predefined target letter among five nontargets. The T-N similarity was manipulated with three levels: high, middle, and low. We tested for the influences of T-N similarity on an ERP (e.g., N2pc) and alpha oscillations. We observed a significant N2pc effect across all levels of similarity. The N2pc amplitude was reduced and occurred later for high similarity relative to low and middle similarities. We also showed that the N2pc amplitude was inversely correlated with the RTs across all similarities. Importantly, we found a significant alpha phase adjustment about the same time as the N2pc for high similarity; by contrast, no such effect was observed for middle and low similarities. Finally, we showed a positive correlation between the phase-locking value and the N2pc—the stronger the alpha phase-locking value, the larger the N2pc, when the T-N similarity was high. In conclusion, our results provide novel evidence for multiple competitive mechanisms during visual search.

Regulation of expression of plasminogen activator inhibitor-1 in cultured rat osteoblastic cells by osteogenic protein-1 (BMP-7)

Osteogenic Protein-1 (OP-1), a member of the bone morphogenetic protein (BMP) family that belongs to the TGF-beta superfamily, induces bone formation in vivo and stimulates the synthesis of biochemical markers characteristic of osteoblast phenotypes in vitro. In the present study, effects of OP-1 on the expression of the plasminogen activator inhibitor-1 (PAI-1) in fetal rat calvaria (FRC) cells were examined. The PAI-1 protein levels in conditioned media of FRC cells treated with OP-1 or solvent control were determined by quantitative 2-dimensional polyacrylamide gel electrophoresis. The identity of PAI-1 was confirmed by mass spectroscopy. OP-1 increased the PAI-1 protein level by about 5-fold after 48 h. Northern blot analysis showed that the PAI-1 mRNA level was elevated by OP-1 by about 25% compared to the control. The observed increase in the PAI-1 mRNA and protein level was regulated post-transcriptionally as supported by the following observations: (a) OP-1 did not stimulate the cloned PAI-1 promoter-reporter gene activity in transient transfection studies, (b) inhibition of transcription by actinomycin D did not change the PAI-1 mRNA level in the OP-1-treated FRC cells, and (c) the stability of the PAI-1 mRNA in FRC cells treated with OP-1 was increased by about 28% compared to that in the control cells. Hence, the present study shows that primary cultures of rat osteoblastic cells synthesize and secrete PAI-1 protein and that OP-1 elevates the PAI-1 protein level. At least, one of the regulatory mechanism is by stabilizing the PAI-1 mRNA. J. Cell. Biochem. Suppl. 36: 46-54, 2001.

Differential regulation of IGF-binding protein gene expression by cAMP in rat C6 glioma cells

We previously reported that cAMP inhibits autocrine IGF-I gene expression in rat C6 glioma cells. In this study we examined the influence of cAMP on IGF-binding protein gene expression in C6 cells. cAMP potently inhibited IGF-binding protein-3 mRNA and, to a lesser extent, IGF-binding protein-4 mRNA and transiently stimulated IGF-binding protein-5 mRNA. The changes in secreted IGF-binding proteins whose molecular weights were consistent with IGF-binding protein-3 and -5 correlated with those of mRNA levels. cAMP decreased the IGF-binding protein-3 mRNA half-life, but did not alter IGF-binding protein-4 and -5 mRNA half-lives. An IGF-binding protein-5 promoter/luciferase fusion construct containing 888 bp of 5'-flanking sequence and the first 114 bp of exon 1 sequence was stimulated by cAMP after 24 h by approximately 2-fold in transient transfection assays. 5'- or 3'-deletion to -33 or +10 (the transcription start site was designated as +1), respectively, did not alter the increase caused by cAMP. Site-directed mutagenesis of the region from -14 to -5 led to a loss of the ability of the IGF-binding protein-5 promoter to respond to cAMP. H89, a cell-permeable protein kinase A inhibitor, did not alter the regulation of IGF-binding protein mRNAs in response to cAMP.

Production of a biopolymer flocculant from Bacillus licheniformis and its flocculation properties

Bacillus licheniformis CCRC 12826 produced extracellularly an excellent biopolymer flocculant in a large amount when it was grown aerobically in a culture medium containing citric acid, glutamic acid and glycerol as carbon sources. The biopolymer flocculant was an extremely viscous material with a molecular weight over 2 x 10(6) by gel permeation chromatography. It could be easily purified from the culture medium by ethanol precipitation. It was shown to be a homopolymer of glutamic acid by amino acid analysis and thin layer chromatography and presumed to be poly-glutamic acid (PGA). This bioflocculant efficiently flocculated various organic and inorganic suspensions. It flocculated a suspended kaolin suspension without cations, although its flocculating activity was synergistically stimulated by the addition of bivalent or trivalent cations Ca2+, Fe3+ and Al3+. However, the synergistic effects of metal cations were most effective at neutral pH ranges. The comparison of the flocculating activity between the present biopolymer and a commercial lower molecular weight product showed that the biopolymer of the present study had much higher activity. The high productivity and versatile applications of PGA make its development as a new biodegradable, harmless, biopolymer flocculant economical and advantageous.

Osteogenic protein-1 differentially regulates the mRNA expression of bone morphogenetic proteins and their receptors in primary cultures of osteoblasts

The mRNA expression patterns of several bone morphogenetic proteins (BMPs) and their receptors (BMPRs) in long-term primary cultures of fetal rat calvaria (FRC) cells were examined by Northern analysis. Their temporal orders of expression were correlated with those of several biochemical markers characteristic of osteoblastic cell differentiation. Distinct temporal patterns of expression of BMPs and BMPRs during osteoblastic cell differentiation were observed. BMP-2 and BMP-7 mRNA levels did not change significantly. BMP-4 mRNA expression increased and reached a peak prior to matrix formation. BMP-5 mRNA expression increased during the mineralization phase and BMP-6 mRNA expression increased throughout all phases of cell differentiation. Effects of BMP-7 (Osteogenic Protein-1; OP-1) on the expression patterns of several other members of the BMP family and the receptors were also studied. OP-1 downregulated the BMP-4, -5, and -6 mRNA levels by a maximal of 2-fold, 1.5-fold, and 6-fold, respectively. OP-1 did not change significantly the OP-1 and BMP-2 mRNA expression. Of the three type I BMPR examined, OP-1 upregulated ActR-I and BMPR-IA mRNA expression slightly but with statistical significance. OP-1 downregulated BMPR-IB mRNA expression slightly. OP-1 upregulated BMPR-II mRNA expression by a maximum of 2-fold. Our findings demonstrate that OP-1 differentially regulates the mRNA expression of several related members of the BMP family and their receptors in osteoblasts. The observations suggest that OP-1 action on osteoblastic cells involves a complex regulation of gene expression of related members of the BMP family and their receptors in a cell differentiation stage dependent manner.

Identification of an osteogenic protein-1 (bone morphogenetic protein-7)-responsive element in the promoter of the rat insulin-like growth factor-binding protein-5 gene

Osteogenic protein-1 (OP-1), a member of the bone morphogenetic protein subfamily of the transforming growth factor-beta superfamily, induces new bone formation in vivo and regulates the expression of numerous growth factors. We previously showed that OP-1 down-regulates the transcription of the insulin-like growth factor-binding protein-5 (IGFBP-5) in primary cultures of fetal rat calvaria (FRC) cells. In the present study we identified, within the IGFBP-5 promoter, a 21-bp region that confers OP-1 responsiveness in FRC cells. Within this region lie three putative cis-acting regulatory elements, viz. a CAAT-like sequence, a CCAAT/enhancer-binding protein (C/EBPalpha)-like element, and a c-Myb or E-box-like motif. Mutations in the CAAT-like sequence reduced the promoter activity in both control and OP-1-treated cells, but did not abrogate the OP-1-induced down-regulation. Mutations in the C/EBPalpha-like element reduced the promoter activity in both control and OP-1-treated cells without significantly affecting the extent of down-regulation. Mutations in the putative c-Myb or E-box-like motif reduced the promoter activity in both the OP-1-treated and control cells and completely abolished the inhibitory effect of OP-1 on the IGFBP-5 promoter activity. Gel mobility shift analyses further showed specific interaction between nuclear protein(s) in FRC cells and the 21-bp region. OP-1 down-regulates the nuclear regulatory protein interaction with the 21-bp region by reducing either the cellular concentration of the regulatory protein(s) or the affinity of the regulatory protein(s) for the OP-1 responsive element. In conclusion, we identified an OP-1 response region in the rat IGFBP-5 promoter and further showed that OP-1 down-regulates the nuclear protein interaction with the response element(s).

A second-site mutation at glutamate-257 that restores the function of the mutant yeast ribosomal protein L5 containing lysine-270,271-->arginine

A genetic approach was used to identify interacting regions of yeast ribosomal protein L5 (also known as L1, L1a, or YL3). Previous studies from our laboratory showed that residues K270 and K271 in protein L5 are essential for its function. The mutant L5 protein in which both residues were replaced by arginine residues (K270,271R) exhibited about 80% RNA binding capability compared to the wild-type and the mutant protein was assembled into the 60S ribosomal subunits in vivo. The yeast strain expressing this mutant protein in a homozygous form was lethal (Biochim. Biophys. Acta 1308 (1996) 133-141). In the present study, this non-functional mutant was used to select intragenic suppressors. A spontaneous, intragenic suppressor which contained an E257K substitution (in addition to the primary mutations) was identified. The suppressor protein bound about 60% of yeast 5S rRNA in vitro compared to the wild-type. To gain more insight into the nature of the intragenic suppressor, additional mutant proteins in which E257 was substituted by a variety of amino acids were produced by site-directed mutagenesis. The ability of each mutant protein to bind yeast 5S rRNA in vitro and to suppress the lethal effect of the double K270,271 mutation in vivo were examined. Results suggest communication between two non-contiguous domains on protein L5 and that several factors, such as electrostatic interaction and hydrogen bonding are likely to play a role in this global communication. Mutation studies on E257 alone also reveal that substitutions of this residue in L5 protein could affect cell growth under specified conditions, but a variety of changes could be tolerated without serious deleterious effects. We propose a working model in which E257 is located in a loop and the dynamic as well as the flexibility of this loop is important for L5 function.

In vitro assembly of yeast 5S rRNA and a fusion protein containing ribosomal protein L5 and maltose binding protein

Binding of yeast ribosomal protein L5 with 5S rRNA has long been considered a promising model for studying molecular mechanisms of protein-RNA interactions. However, in vitro assembly of a ribonucleoprotein (RNP) complex from purified yeast ribosomal protein L5 (also known as L1, L1a, or YL3) and 5S rRNA proved to be difficult, thus limiting the utility of this model. In the present report, we present data on the successful in vitro assembly of a RNP complex using a fusion (MBP-L5) protein consisting of the yeast ribosomal protein L5 fused to the carboxyl terminus of the E. coli maltose-binding protein (MBP). We demonstrated that: 1) the MBP-L5 protein binds yeast 5S rRNA but not 5.8S rRNA in vitro; 2) the MBP protein itself does not bind yeast 5S rRNA; 3) formation of the RNP complex is proportional to the concentration of MBP-L5 protein and 5S rRNA; and 4) the MBP moiety of the fusion protein in the RNP complex can be removed with factor Xa. The electrophoretic mobility of the resultant RNP complex is indistinguishable from that of L5-5S rRNA complex isolated from the ribosome. Using this new experimental approach, we further showed that the RNA binding capability of a mutant L5 protein is decreased by 60% compared to the wild-type protein. Additionally, the mutant RNP complex migrates slower than the wild-type RNP complex suggesting that the mutant RNP complex has a less compact conformation. The finding provides a probable explanation for an earlier observation that the 60S ribosomal subunit containing the mutant protein is unstable.

Osteogenic protein-1 increases gene expression of vascular endothelial growth factor in primary cultures of fetal rat calvaria cells

Osteogenic protein-1 (OP-1 or BMP-7) stimulates new bone formation in vivo and induces cell proliferation and differentiation of osteoblasts in vitro. In the present study, we examined effects of OP-1 on the expression of vascular endothelial growth factor (VEGF) in primary cultures of fetal rat calvaria (FRC) cells. OP-1 increased the steady-state level of VEGF mRNA by about 3-fold in an OP-1 concentration- and time-dependent manner. The increase in VEGF mRNA level depended on transcription and was sensitive to cell replication. The VEGF mRNA stability was unaffected. The mRNA levels for both types of VEGF receptors, Flk-1 and Flt-1 were low but detectable in FRC cells by RT-PCR and were not changed by OP-1. Inhibition of VEGF synthesis and function by antisense oligonucleotide and by suramin, respectively arrested the OP-1-induced alkaline phosphatase activity and mineralized bone nodule formation. Together with published studies of VEGF on vascular endothelial cells which are usually found in close proximity to osteoblastic cells in vivo, these results suggest that VEGF participates in the OP-1-induced osteogenesis by taking part in bone cell differentiation and by promoting angiogenesis at the site of bone formation.

Inhibition of BMP receptor synthesis by antisense oligonucleotides attenuates OP-1 action in primary cultures of fetal rat calvaria cells

Osteogenic protein-1 (OP-1 or bone morphogenetic protein-7 [BMP-7]) stimulates osteoblast differentiation in vitro and induces bone formation in vivo. BMPs exert their effects through complex formation with a heterodimeric receptor composed of a type I and a type II polypeptide. In the present study, mRNAs for three BMP subtype I receptors (ActR-I, BMPR-IA, and BMPR-IB) and one BMPR-II receptor were detected by Northern analysis in two human osteosarcoma cell lines (SaOS-2 and TE85) and in the primary cultures of fetal rat calvaria (FRC) cells. OP-1 affected the steady-state mRNA levels of these receptors differently among these cell types. To study the role of each receptor type in OP-1 action in FRC cells, receptor synthesis was inhibited by antisense oligonucleotides. Inhibition of receptor synthesis was confirmed by immunoprecipitation of radiolabeled cellular proteins with specific antibodies. The osteogenic action of OP-1 was measured by alkaline phosphatase (ALP) activity and mineralized bone nodule formation in FRC cells. Results showed that inhibition of synthesis of a single subtype I receptor alone did not affect significantly the OP-1-stimulated ALP activity. Inhibition of BMPR-II synthesis reduced the OP-1-stimulated ALP activity by about 50%. Inhibition of synthesis of any one of the type I receptor plus the BMPR-II receptor did not reduce the OP-1-stimulated ALP activity significantly beyond that observed by inhibition of BMPR-II alone. Under these conditions, nodule formation was affected similarly, thus supporting the observations made with the ALP measurements. The present results suggest that the ActR-I, BMPR-IA, and BMPR-IB receptors and the BMPR-II receptor are expressed and functional for OP-1 in FRC cells and that regulation of synthesis of these receptors may be a mechanism by which a specific cell type responds to OP-1. The turnover rate of these receptor proteins might be relatively long and another type II receptor(s) for OP-1 might be functional in FRC cells.

Yeast ribosomal proteins L4, L17, L20, and L25 exhibit different binding characteristics for the yeast 35S precursor rRNA

In vitro synthesized radioactive yeast 35S precursor rRNA (35S pre-rRNA) molecules were used to determine the binding characteristics of 13 proteins from the yeast 60S ribosome subunit. L4, L17, L20 and L25 were found to bind the 35S pre-rRNA molecule in vitro in the absence of any other cellular components as determined by a modified membrane filtration assay and an agarose gel mobility shift assay. In all cases, RNA-protein complex formation was proportional to the amount of protein added to the binding reaction mixture. Binding to the pre-rRNA could be saturated yielding a molar RNA/protein ratio approaching one. Non-radioactive 35S pre-rRNA transcript competed for the binding in a dosage-dependent manner. Presence of 18S rRNA species and poly(A) did not affect their binding to the 35S RNA. However, in the presence of the 25S rRNA species, the four proteins exhibited distinct binding characteristics for the pre-rRNA molecule. L4 did not bind the 25S rRNA but interacted specifically with the 35S pre-rRNA molecule with a binding constant of 4.4x10(6)/M. L17 bound the pre-rRNA molecule preferentially (Ka=17x10(6)/M) but also bound the mature 25S rRNA species (Ka=10x10(6)/M). L20 bound both the pre-rRNA molecule and the 25S rRNA species equally well (Ka=11-12x10(6)/M). L25 also bound both the 35S pre-rRNA and the mature 25S rRNA with slightly different affinities, with Ka=3.1 vs. 2.5x10(6)M, respectively. We speculate that L4, L17, and L25 are among the early assembled ribosomal proteins but L4 may be one of the first ribosomal proteins that bind to the 35S pre-rRNA molecule during ribosome biogenesis.

Osteogenic protein-1 regulates insulin-like growth factor-I (IGF-I), IGF-II, and IGF-binding protein-5 (IGFBP-5) gene expression in fetal rat calvaria cells by different mechanisms

Osteogenic protein-1 (OP-1 or BMP-7) stimulates new bone formation in vivo and induces cell proliferation and differentiation of osteoblasts in vitro. Previous studies from our laboratory revealed that OP-1 led to a two- to threefold increase in steady-state insulin-like growth factor-I (IGF-I) and IGF-II mRNA levels and a fivefold decrease in IGF-binding protein-5 (IGFBP-5) mRNA levels in primary cultures of fetal rat calvaria (FRC) cells. In the present study, we determined whether the effects of OP-1 were at the transcriptional or posttranscriptional level. OP-1 increased the half-life of the IGF-I mRNA from 6 to 17 h without changing the level of IGF-I nuclear pre-mRNA. In transiently transfected FRC cells, the luciferase activity driven by the -1122/+362 or the -133/+362 IGF-I exon 1 promoter fragment was not changed by OP-1. Similar results were observed using the -1500/+44 or -362/+44 IGF-I exon 2 promoter constructs. Effects of OP-1 on IGF-I mRNA were independent of cell division, as they remained elevated in the presence of hydroxyurea. Cycloheximide inhibited moderately the OP-1-induced increase in IGF-I mRNA, suggesting partial dependency on protein synthesis. On the other hand, the IGF-II nuclear pre-mRNA levels were increased by OP-1 but the half-life of the mature IGF-II mRNA was not affected. Effects of OP-1 on IGF-II mRNA were also independent of cell division, but were dependent on protein synthesis. OP-1 caused a 43-50% reduction in the level of IGFBP-5 nuclear pre-mRNA transcripts and a 40% decrease in the IGFBP-5 promoter activity in FRC cells transfected with the -1278/+1 IGFBP-5 promoter fragment. The half-life of the mature IGFBP-5 mRNA was not affected by OP-1. Hydroxyurea did not prevent the OP-1-induced reduction in IGFBP-5 mRNA. The level of IGFBP-5 mRNA was barely detectable in the presence of cycloheximide, and further suppressive effect of OP-1 on IGFBP-5 mRNA could not be determined. In conclusion, OP-1 regulates IGF-I gene expression at the posttranscriptional level, but regulates IGF-II and IGFBP-5 gene expression at the transcriptional level.

Foreign bodies in tracheobronchial tree in children: a review of cases over a twenty-year period

BACKGROUND

Foreign body inhalation into the tracheobronchial tree of children is rather rare but serious problem. It may be hazardous and even cause fatal sequelae in the children if misdiagnosed and not managed promptly.

METHODS

We retrospectively reviewed the records of 81 patients with foreign bodies inhaled into the larynx, trachea and bronchi. The children were all treated during the 20-year period from July 1976 through June 1996 at Chang Gung Memorial Hospital. Of these patients, 82% were 36 months of age or younger. The male to female ratio was 3:1. All of the patients initially received flexible fiberoptic bronchoscopy to identify the foreign objects. The foreign bodies were removed by jet ventilation bronchoscopy with apneic techniques under general anesthesia.

RESULTS

Peanuts were found to be the most common causative foreign body agent which occurred in 53 instances (65%). The most common manifestation was coughing, with subsequent dyspnea and audible wheezing. The foreign bodies were lodged in the left bronchus more than in the right. The most obvious radiologic evidence observed in aspirated children were emphysematous changes at same side of the foreign bodies caused by "expansile check-valve" phenomenon. Four patients showed radio-opaque objects on chest roentgenograms. Six patients required second extraction procedures due to the retained foreign bodies. Neither serious complications nor deaths occurred in these patients due to the foreign body inhalation.

CONCLUSION

Early diagnosis and management is essential in children with foreign bodies in the airways to prevent morbidity or death. Small materials or food bits should be kept far away from young child.

The trauma response of children and adolescents. Future directions in research

Although trauma research in children lags behind that of adults and is often preliminary or unreplicated, current work promises rich understanding of the neurobiologic and psychologic mechanisms underlying the trauma response of the young. Epidemiologic and longitudinal, prospective, controlled studies sensitive to cultural and developmental differences are needed to illuminate the natural history of posttraumatic stress disorder and to show how trauma and its response interact with family, school, and community factors. Promising profound implications for society, such data would enable mental health professionals, educators, and policy makers to develop standards for prevention, detection, and intervention to optimize children's developmental trajectory.

Osteogenic protein-1 and insulin-like growth factor I synergistically stimulate rat osteoblastic cell differentiation and proliferation

Previous studies have shown that osteogenic protein-1 (OP-1; also known as BMP-7) alters the steady state levels of messenger RNA (mRNA) encoding insulin-like growth factor I (IGF-I), IGF-II, and IGF-binding proteins (IGFBPs) in primary cultures of fetal rat calvaria (FRC) cells. In the present study, the effects of exogenous IGF-I on bone cell differentiation and mineralized bone nodule formation induced by OP-1 were examined. Exogenous IGF-I synergistically and dose dependently enhanced OP-1 action in stimulating [3H]thymidine incorporation, alkaline phosphatase activity, PTH-dependent cAMP level, and bone nodule formation. Maximal synergism between OP-1 and IGF-I was observed when both factors were added simultaneously. Synergism was not observed when FRC cells were pretreated with IGF-I for 24 h, followed by OP-1 treatment. These findings suggest that IGF-I acted on OP-1-sensitized FRC cells. To examine the mechanism(s) by which this sensitization may occur, levels of mRNA encoding OP-1 receptor, IGF-I receptor, and IGFBPs were measured. The mRNA levels of both type I and II OP-1 receptors were elevated by OP-1, but were not changed further by combined OP-1 and IGF-I treatment. IGF-I receptor gene expression was not changed by OP-1, IGF-I, or a combination of both factors. OP-1 alone or together with IGF-I increased the steady state IGFBP-3 mRNA level and reduced the steady state mRNA levels of IGFBP-4, -5, and -6. IGF-I alone did not change the steady state mRNA levels of IGFBP-3, -4, and -6, but elevated that of IGFBP-5. Des(1-3)-IGF-I, which has a lower affinity for IGFBPs, was more effective than the full-length IGF-I in enhancing the OP-1-induced alkaline phosphatase activity. Exogenous IGFBP-5 inhibited the OP-1-induced alkaline phosphatase activity and reduced the synergistic stimulatory effect of IGF-I and OP-1. These findings strongly suggest that the OP-1-induced down-regulation of IGFBPs, especially that of IGFBP-5, is an important mechanism by which OP-1 and IGF-I synergize to stimulate FRC cell differentiation.

Involvement of lysine 270 and lysine 271 of yeast 5S rRNA binding protein in RNA binding and ribosome assembly

Contributions of the highly conserved K270 and its neighboring K271 in the C-terminal region of the yeast ribosomal protein L1 to 5S rRNA binding and ribosome assembly were examined by in vivo and in vitro studies on the consequences of 14 substitution mutations. All mutant proteins with a single amino-acid substitution at either position were able to bind 5S rRNA in vitro to an extent comparable to the wild-type. Yeast cells expressing these mutant proteins, except the K270G mutant, grew at nearly normal rates. Mutations of K270 appeared to produce more demonstrable effects than those of K271. The double mutant K270,271G bound RNA poorly and yeast cells expressing the mutant protein grew 30% slower. Double mutants K270,271E and K270,271R were lethal, although the mutant protein was assembled into the 60S ribosomal subunits. The resultant subunits were not stable leading eventually to cell death. The in vitro RNA binding ability of the respective protein was reduced by 60% and 20%. Taken together, the present data identified K270 and K271 as important amino-acid residues in the function of the yeast ribosomal protein L1.

Osteogenic protein-1-mediated insulin-like growth factor gene expression in primary cultures of rat osteoblastic cells

Osteogenic protein-1 (OP-1) is a member of the bone morphogenetic protein family and has been shown to induce new bone formation in vivo. In the present study, we determined whether the expression of the IGF system, a significant growth factor system in bone, was altered by OP-1 in primary cultures of fetal rat calvarial cells. Levels of messenger RNA (mRNA) encoding insulin-like growth factor I (IGF-I), IGF-II, IGF-I receptor, and IGF-binding proteins (IGFBP-1 to -6) were determined after OP-1 treatment. The level of total IGF-I mRNA was elevated in an OP-1 concentration (0-1000 ng/ml)-dependent manner, with maximal stimulation of IGF-I mRNA of 2- to 3-fold apparent 24 h after treatment. The increase in the IGF-I mRNA level involved a preferential stimulation of transcripts initiated at start site 2 in the exon 1 promoter. The level of IGF-II mRNA also increased by approximately 2-fold in OP-1 treated cells in a concentration-dependent manner. The level of IGF-I receptor mRNA was not altered by treatment. Whereas IGFBP-1 mRNA was not detected in these cells, IGFBP-2 mRNA was expressed, but the expression was not changed after treatment for 48 h in the concentration range (0-1000 ng/ml) tested. The IGFBP-3 mRNA level was increased slightly 48 h after OP-1 treatment in a concentration-dependent manner. The IGFBP-4, -5, and -6 mRNA levels decreased dramatically in an OP-1 concentration-dependent manner. In addition, coincubation of antisense oligonucleotides corresponding to IGF-I or -II mRNA sequence with OP-1 reduced the OP-1 induced elevation in alkaline phosphatase activity. The present results suggest that the differentiation of rat osteoblastic cells in response to OP-1 is mediated in part by increased IGF-I -II gene expression and alterations in the gene expression of different IGFBPs.

The accessibility of yeast ribosomal protein L1 as probed by proteolysis and site-directed mutagenesis is different in intact 60 and 80 S ribosome

Accessible regions of protein L1 in intact 60 and 80 S ribosomes from Saccharomyces cerevisiae were first detected by controlled proteolysis. The N-terminal region of L1 in either 60 S or 80 S particles, was inaccessible to proteases, but the central and C-terminal regions were accessible. The accessibility of the central region differed depending on the ribosome state. These regions were further examined by determination of the chemical reactivity of specific cysteine residues introduced into these regions by site-directed mutagenesis. All cysteine mutant proteins were capable of binding yeast 5 S rRNA in vitro and the ribosomes containing the mutant proteins were functional in vivo. Residues Cys-257 and Cys-275 were modified in both the 60 and 80 S ribosomes but the modification rates were different in the two ribosome states. Both residues Cys-62 and Cys-286 were inaccessible in 80 S or 60 S ribosomes. Taken together, the present study identified several accessible regions of L1 in intact ribosomes and further showed that the accessibility of some of the regions was altered upon ribosomal subunit association. The most likely interpretation of these results is that the conformation of the ribosomal protein L1 was altered upon ribosomal subunit association.

Multiple regions of yeast ribosomal protein L1 are important for its interaction with 5 S rRNA and assembly into ribosomes

Yeast ribosomal protein L1 binds to 5 S rRNA and can be released from 60 S ribosomal subunits as an intact ribonucleoprotein particle. To identify residues important for binding of Saccharomyces cerevisiae rpL1 to 5 S rRNA and assembly into functional ribosomes, we have isolated mutant alleles of the yeast RPL1 gene by site-directed and random mutagenesis. The rpl1 mutants were assayed for association of rpL1 with 5 S rRNA in vivo and in vitro and assembly of rpL1 into functional 60 S ribosomal subunits. Consistent with previous data implicating the importance of the carboxyl-terminal 47 amino acids of rpL1 for binding to 5 S rRNA in vitro, we find that deletion of the carboxyl-terminal 8, 25, or 44 amino acids of rpL1 confers lethality in vivo. Missense mutations elsewhere in rpL1 also affect its function, indicating that multiple regions of rpL1 are important for its association with 5 S rRNA and assembly into ribosomes.

Contributions of multiple basic amino acids in the C-terminal region of yeast ribosomal protein L1 to 5 S rRNA binding and 60 S ribosome stability

Previous studies suggest that the C-terminal region of ribosomal protein L1 from Saccharomyces cerevisiae is important for its interaction with the 5 S rRNA molecule. Within this region are several highly conserved basic amino acids including Lys276, Lys279, Lys289, Arg282, Arg285. To examine potential contributions of these amino acids to RNA-protein interaction and ribosomal assembly, effects of substitutions of these residues by methionine either individually or in combinations were examined. A methionine substitution of any one of the lysine residues did not significantly affect RNA binding in vitro. The mutant RNPs were as stable as the wild-type RNP. Yeast transformants expressing these mutant proteins grew at the same rate as the wild-type. However, mutant proteins containing substitutions of any two of these basic amino acids bound RNA weakly. The resultant RNPs were significantly less stable than the wild-type. Whereas cells expressing mutant L1 with a single substitution at 289 was not lethal, cells expressing mutant L1 with any double substitutions involving Lys289 as one of the substituted amino acids were lethal. These data suggest that Lys289 plays a key role in the binding of ribosomal protein L1 to 5 S rRNA. The other basic residues, particularly Arg282, and Arg285, in this region also contribute to RNA binding. These residues are predicted to locate on the same side of an alpha helix. We would like to propose a structural model for the yeast RNP that involves multiple contact sites located on one side of the helix in the C terminus of the protein and the 5 S rRNA. These basic amino acids also participate, directly or indirectly, in the interaction of the RNP complex with other components of the 60 S ribosomal subunit.

An in vitro system for studying RNA-protein interaction: application to a study of yeast ribosomal protein L1 binding to 5S rRNA

Previous attempts to study the binding of yeast ribosomal protein L1 with 5S rRNA in vitro have been impeded by the failure to form RNA-protein complexes with purified protein and RNA. To circumvent this difficulty, we have developed an in vitro system that allowed RNP formation. The system involved in vitro expression of the protein L1 from its cloned gene in the presence of exogenous yeast 5S rRNA. A protein of the expected size (34 kDa) was synthesized by in vitro transcription and translation. A specific 5S rRNA-protein L1 complex (RNP) was formed when the rRNA molecule was present during protein L1 synthesis. However, the full-length protein L1 failed to bind 5S rRNA. The extent of RNP formation was proportional to the concentration of the exogenous yeast 5S rRNA in the reaction. The RNP displayed properties identical to those isolated from mature 60S ribosome subunits. Addition of yeast 5.8S rRNA did not result in the formation of a specific RNP. Using this in vitro system, we examined the ability of several deletion mutant proteins to bind yeast 5S rRNA and concluded that protein L1 missing residues 261 to 295 from the C-terminus could not bind yeast 5S rRNA. This in vitro system should be useful for future studies on the molecular nature of 5S rRNA-protein L1 interaction.

Structure analysis of the 5' external transcribed spacer of the precursor ribosomal RNA from Saccharomyces cerevisiae

Full-length precursor ribosomal RNA molecules were produced in vitro using as a template, a plasmid containing the yeast 35 S pre-rRNA gene under the control of the phage T3 promoter. The higher-order structure of the 5'-external transcribed spacer (5' ETS) sequence in the 35S pre-rRNA molecule was studied using dimethylsulfate, 1-cyclohexyl-3-(2-morpholinoethyl)-carbodiimide metho-p-toluenesulfonate, RNase T1 and RNase V1 as structure-sensitive probes. Modified residues were detected by primer extension. Data produced were used to evaluate several theoretical structure models predicted by minimum free-energy calculations. A model for the entire 5'ETS region is proposed that accommodates 82% of the residues experimentally shown to be in either base-paired or single-stranded structure in the correct configuration. The model contains a high degree of secondary structure with ten stable hairpins of varying lengths and stabilities. The hairpins are composed of the Watson-Crick A.T and G.C pairs plus the non-canonical G.U pairs. Based on a comparative analysis of the 5' ETS sequence from Saccharomyces cerevisiae and Schizosaccharomyces pombe, most of the base-paired regions in the proposed model appear to be phylogenetically supported. The two sites previously shown to be crosslinked to U3 snRNA as well as the previously proposed recognition site for processing and one of the early processing site (based on sequence homology to the vertebrate ETS cleavage site) are located in single-stranded regions in the model. The present folding model for the 5' ETS in the 35 S pre-rRNA molecule should be useful in the investigations of the structure, function and processing of pre-rRNA.

Yeast 5S rRNA binding to ribosomal protein L1a alters the fluorescence of tryptophan residues lying outside the binding site

The yeast ribosomal protein L1a contains two tryptophan residues located at positions 95 and 183. Spectrofluorometric analysis showed that the average tryptophan environment is moderately polar. Quenching studies of the yeast 5S rRNA-L1a protein complex (RNP) with acrylamide and iodide revealed tryptophan heterogeneity. The two tryptophan residues are located in the non-RNA-binding region of the L1a molecule. However, dissociation of the yeast 5S rRNA-L1a protein RNP complex to its components resulted in a decline of tryptophan fluorescence. The observation implied that the environment of the tryptophan-containing L1a regions which were not known to be involved in RNA binding was influenced by association with the 5S rRNA molecule.

Instrumented laxity test for the evaluation of posterior cruciate ligament reconstructed knee

By making anterior and posterior drawer tests using "Laxity tester" is an objective way to evaluate the resting position of tibia plateau and knee laxity. This study followed up 16 cases of PCL reconstructed or pull-out repaired knees for an average of two years and seven months. A force of 20 1b was applied to evaluate knee laxity at 30 degree and 90 degree knee flexion. From paired t-test, the stability of reconstructed knees was not statistically different from that of control contralateral normal knees. The functional scores measured by the Gillquist scoring system for injured knees after reconstruction were satisfactory. Therefore the restabilized PCL deficient knees by the modified Clancy method or pull-out repair yielded good evaluation scores. The data of contralateral normal knee laxity obtained in this study was used as reference in pre-operative and post-operative evaluation of PCL injured knee.

The initiation codon AUG binds at a hydrophobic site on yeast 40S ribosomal subunits as revealed by fluorescence studies with bis (1,8-anilinonaphthalenesulfonate)

Binding studies of yeast 40S ribosome with bis (1,8-anilinonaphthalenesulfonate) (bis-ANS) revealed the binding of 3-4 molecules of bis-ANS per ribosome with a dissociation constant (Kd) of 1.45 microM. Binding of AUG to the 40S subunits resulted in a concentration-dependent decrease in the bis-ANS fluorescence without displacing all of the bound bis-ANS from the ribosomes. The residual bis-ANS fluorescence at saturation with AUG corresponds to about 3 molecules of bis-ANS per ribosome. Thus AUG displaces one of the bound bis-ANS molecules. The data suggest that AUG binds at a hydrophobic site on the yeast 40S subunit.

Higher-order structure of the 5.8 S rRNA sequence within the yeast 35 S precursor ribosomal RNA synthesized in vitro

Dimethylsulfate, 1-cyclohexyl-3-(2-morpholinoethyl)-carbodiimide metho-p-toluene-sulfonate, RNase T1 and RNase V1 have been used as structure-sensitive probes to examine the higher-order structure of the 5.8 S rRNA sequence within the yeast 35 S precursor ribosomal RNA molecule. Data produced have been used to evaluate several theoretical structure models for the 5.8 S rRNA sequence within the precursor rRNA. These models are generated by minimum free energy calculations. A model is proposed that accommodates 83% of the residues experimentally shown to be in either base-paired or single-stranded structure in the correct configuration. Several alternative suboptimal secondary structures have been evaluated. Moreover, the chemical reactivities of several residues within the 5.8 S rRNA sequence in the precursor rRNA molecule differ from those of the corresponding residues in the mature rRNA molecule. This finding provides experimental evidence to support the notion that the 5.8 S rRNA sequence within the precursor rRNA undergoes structural reorganization following rRNA processing.

Internal transcribed spacer 1 of the yeast precursor ribosomal RNA. Higher order structure and common structural motifs

The higher order structure of the first internal transcribed spacer between the 18S and the 5.8S rRNA sequences in the Saccharomyces cerevisiae precursor ribosomal RNA has been investigated. Sites of potential base pairing in the RNA region have been determined by using a combination of enzymatic and chemical structure sensitive probes. Data generated have been used to evaluate secondary structure models predicted by minimum free energy calculations. Several alternative suboptimal structures were also evaluated. The derived model contains several stable hairpins. Theoretical secondary structural models for the corresponding RNA region from S. carlsbergensis, S. pombe, N. crassa, X. laevis, and mung bean have also been derived from identical calculations and assumptions. Certain structural motifs appear to be conserved despite extensive divergence in the base sequence. The yeast model should be a useful prototype for investigation of structure and function of precursor ribosomal RNA molecules.

Structural analysis of the internal transcribed spacer 2 of the precursor ribosomal RNA from Saccharomyces cerevisiae

Full-length precursor ribosomal RNA molecules (6440 bases) were produced in vitro using a plasmid containing the yeast 35 S pre-rRNA operon under the control of phage T7 promoter. The higher-order structure of the internal transcribed spacer 2 (ITS-2) region (between the 5.8 S and 25 S rRNA sequence) in the pre-rRNA molecule was investigated using a combination of enzymatic and chemical structural probes. The data were used to evaluate several structural models predicted by a minimum free-energy calculation. The results supported a model in which the 3' end of the 5.8 S rRNA and the 5' end of the 25 S rRNA are hydrogen-bonded better than the one in which the ends are not. The model contains a high degree of secondary structure with several stable hairpins. Similar structural models for the ITS-2 regions of Schizosaccharomyces pombe, Saccharomyces carlsbergensis, mung bean and Xenopus laevis were derived. Certain common folding features appear to be conserved, in spite of extensive sequence divergence. The yeast model should be useful as a prototype in future investigations of the structure, function and processing of pre-rRNA.

Probing the yeast 5 S RNA-protein complex by fluorescence and controlled proteolytic digestion

The nature of the interaction between the RNA and the protein component in the yeast 5 S rRNA-L1a complex was assessed using fluorescence and controlled proteolytic and RNase digestion. (a) Influence of L1a on the RNA conformation was monitored by ethidium fluorescence and controlled RNase T1 digestion. The complex was digested with alpha-chymotrypsin, Staphylococcus aureus protease V8, subtilisin, or trypsin. Both termini of L1a in the complex were readily accessible to proteases. Proteolytic digestion of the complex resulted in a reduction in fluorescence intensity if ethidium was added after proteolysis. No change was observed when ethidium was allowed to react with the complex prior to proteolysis. Neither the rate of proteolysis nor the resultant peptide pattern was affected by the presence of ethidium. T1 digestion of intact RNP and trypsin-treated RNP produced different oligonucleotide patterns. Both the fluorescence and the T1 digestion data suggest that the conformation of the RNA moiety was influenced by the protein. (b) Influence of the RNA molecule on L1a conformation in the complex was monitored by limited proteolysis. Whereas the protein in the complex was relatively sensitive to proteases, free protein was completely resistant to digestion under identical conditions. The trypsin sensitivity of L1a in complexes containing different truncated 5 S RNA molecules was studied also. Upon removal of residues 31-49 of the 5 S RNA molecule, L1a in the complex became resistant to proteolysis. These results are interpreted in a model in which specific regions of both the RNA and the protein are involved in the interaction.

Probing the RNA structure within the yeast 5 S RNA.L1a protein complex by fluorescence and enzymatic digestion

Conformational states of the ribosomal 5 S RNA molecule and its associated protein L1a in the yeast RNA-protein (RNP) complex were determined using controlled RNase T1 digestion in conjunction with fluorescence probes, ethidium bromide and bisanilinonaphthalenesulfonic acid. Fluorescence measurements indicated that the RNA molecule in the RNP complex appeared to exhibit a slightly lower degree of secondary structure than that in the free form. Controlled digestion of the intact RNP complex with RNase T1 resulted in an initial increase in ethidium fluorescence followed by a gradual decrease. In free RNA, a similar profile, except that a larger increase in ethidium fluorescence at the initial stage of digestion, was observed. During digestion of the RNP complex, increases in bisanilinonaphthalenesulfonic acid fluorescence and in light scattering were observed. These findings implied that as regions of the 5 S RNA molecule were perturbed, hydrophobic regions in the protein became exposed. Polyacrylamide gel analysis of the digestion products revealed a temporal appearance of discrete RNA fragments. Sequence analysis of these fragments generated information about the structural arrangement of the RNA molecule within the RNP complex. Results from the present investigation indicate that interactions between the 5 S RNA and protein L1a can stabilize functionally relevant conformations of the components that are individually labile. Properties of the separated components also suggest that special conditions, such as those suggested by Steitz et al. (Steitz, J. A., Berg, C., Hendrick, J. P., LaBranche-Chabot, H., Metspalu, A., Rinke, J., and Yario, T. (1988) J. Cell Biol. 106, 545-556) may be involved for these components to associate during ribosomal assembly.

Studies of RNA-protein interactions in the yeast 5 S ribonucleoprotein particles by fluorescence and tritium exchange. Implications for ribosomal assembly

Studies of the conformational properties of the yeast 5 S RNA-protein complex were initiated in an attempt to understand loss of ability of its individual protein and RNA components to reassociate. The 5 S RNA-L1a protein complex from 60 S ribosomal subunits of Saccharomyces cerevisiae could be dissociated by high concentrations of magnesium. The degree of dissociation could be monitored by polyacrylamide gel electrophoresis. The complex was completely dissociated at about 390 mM magnesium, but was stable at 4 degrees C in 25 mM EDTA up to 48 h. The overall conformation of the complex was monitored using tritium exchange. The tritium exchange behavior was dramatically changed as the complex was dissociated. To determine contribution of each component to the observed overall change reflected in the tritium exchange behavior, ethidium bromide (EtBr) and bis-anilinonaphthalene-sulfonic acid fluorescence were used to monitor the RNA and the protein moiety, respectively. Upon dissociation of the complex, the fluorescence intensity resulting from EtBr binding to RNA decreased, whereas the intensity due to bis-anilinonaphthalene-sulfonic acid binding to the protein increased. Turbidity was observed during dissociation of the complex. These results indicate that disruption of interactions between the 5 S RNA and protein L1a resulted in an exposure of solvent-accessible apolar regions in the protein molecule. Such exposure led to insolubility of protein and irreversibility in interaction between individual components. Properties of the separated components also suggest that special conditions may be required for these components to associate during ribosomal assembly.

Molecular cloning of cDNA for human prostatic acid phosphatase

A human liver cDNA library in lambda gt11 was screened with polyclonal antiserum to human acid phosphatase isoenzyme 2a/4. About eleven positive clones have been obtained. Two clones, lambda Hap21 and lambda Hap22 were further characterized: clone lambda Hap21 contained a 0.8-kb cDNA insert and clone lambda Hap22 a 1.8-2.0-kb insert. XbaI digestion of lambda Hap22 generated two fragments of 1.0 and 0.9 kb. BglII digestion resulted in a 1.2-kb fragment and several smaller fragments of undetermined size. Clone lambda Hap22 contained all the genes carried by lambda gt11(lac5cI857nin5Sam100) and the 2-kb insert. An Escherichia coli(lambda Hap22) lysogen was generated, and its acid phosphatase activity was approximately ten-fold higher than that in the control nonlysogenic lysate. Western-blot analysis of total proteins present in this E. coli(lambda Hap22) lysate revealed that the non-induced lambda Hap22 prophage directed the synthesis of an approx. 175-kDa protein. This protein was recognized by antibody to the human acid phosphatase isoenzyme 2a/4 and anti-beta-galactosidase and was produced only upon induction with IPTG. These results indicated that lambda Hap22 carried a major portion of the gene coding for the human acid phosphatase isoenzyme 2a and/or 4 and this protein fragment of acid phosphatase was sufficient to manifest enzymatic activity.

Interaction between ethanol and low dietary zinc during gestation and lactation in the rat

Pregnant rats were fed individual liquid diets throughout gestation and lactation. The diets contained either 2 or 10 micrograms zinc/ml diet with or without 30% of the kilocalories supplied from ethanol. The low zinc diet produced a moderate zinc deficiency in dams evidenced by decreases in tissue zinc content, serum alkaline phosphatase activity and urinary zinc concentration. Despite the presence of high zinc content in the diet, ethanol antagonized the maternal zinc status to a level typical of that produced by the low zinc diet. The lowest zinc status, however, was found when low dietary zinc and ethanol were combined. The maternal interaction between ethanol and zinc also depressed offspring serum zinc and alkaline phosphatase activity in a similar manner. Ethanol, however, did not affect tissue content of calcium, magnesium or phosphorus, which indicates that ethanol is a specific antagonist of zinc utilization during gestation and lactation.

Formulation of a liquid diet for ethanol studies involving gestation and lactation in the rat

This report describes the preparation of a liquid diet for rat studies involving ethanol ingestion during gestation and lactation. The control diet was formulated to contain 30% of energy from casein including methionine at 0.5 mg/kcal, 11.5% of energy from corn oil, 58.5% of energy from dextrose, cellulose, and adequate vitamins and minerals. Calculations for the isocaloric substitution of dextrose with ethanol are described as well as the use of xanthan gum to disperse and emulsify ordinary solid diet components. The use of this liquid diet as the sole source of nutrition for the rat during gestation and lactation produced energy intakes, gestational weight gains, litter sizes, percent survival to weaning and weaning weights similar to those expected of a conventional diet even when ethanol was substituted for dextrose to provide 30% of total energy.