The bentiromide test using plasma p-aminobenzoic acid for diagnosing pancreatic insufficiency in young children. The effect of two different doses and a liquid meal

The bentiromide test was evaluated using plasma p-aminobenzoic acid as an indirect test of pancreatic insufficiency in young children between 2 months and 4 years of age. To determine the optimal test method, the following were examined: (a) the best dose of bentiromide (15 mg/kg or 30 mg/kg); (b) the optimal sampling time for plasma p-aminobenzoic acid; and (c) the effect of coadministration of a liquid meal. Sixty-nine children 91.6 +/- 1.0 years) were studied, including 34 controls with normal fat absorption and 35 patients (34 with cystic fibrosis) with fat maldigestion due to pancreatic insufficiency. Control and pancreatic insufficient subjects were studied in three age-matched groups: (a) low-dose bentiromide (15 mg/kg) with clear fluids; (b) high-dose bentiromide (30 mg/kg) with clear fluids; and (c) high-dose bentiromide with a liquid meal. Plasma p-aminobenzoic acid was determined at 0, 30, 60, and 90 minutes then hourly for 6 hours. The dose effect of bentiromide with clear liquids was evaluated. High-dose bentiromide best discriminated control and pancreatic insufficient subjects, due to a higher peak plasma p-aminobenzoic acid level in controls, but poor sensitivity and specificity remained. High-dose bentiromide with a liquid meal produced a delayed increase in plasma p-aminobenzoic acid in the control subjects probably caused by retarded gastric emptying. However, in the pancreatic insufficient subjects, use of a liquid meal resulted in significantly lower plasma p-aminobenzoic acid levels at all time points; plasma p-aminobenzoic acid at 2 and 3 hours completely discriminated between control and pancreatic insufficient patients. Evaluation of the data by area under the time-concentration curve failed to improve test results. In conclusion, the bentiromide test is a simple, clinically useful means of detecting pancreatic insufficiency in young children, but a higher dose administered with a liquid meal is recommended.

Biosynthesis of the precursor of a soluble human insulin receptor ectodomain in insect Sf9 cells infected with a recombinant baculovirus

In contrast to transfected mammalian cells, insect Sf9 cells infected with a recombinant Baculovirus inefficiently process and secrete a soluble derivative of the extracellular domain of the human insulin receptor. The high-mannose form of the receptor precursor that accumulates intracellularly is not grossly aberrant or malfolded, as its interaction with a diverse panel of monoclonal antibodies are comparable to secreted precursor and proteolytically processed receptor, both of which bear partially trimmed oligosaccharide chains. Thus the inefficient step in the biosynthesis of this protein in Sf9 cells is either at, or just preceding, the trimming of its high-mannose oligosaccharide chains.

Insulin receptor tyrosine kinase structure and function

Six years have now elapsed since efforts to establish heterologous cell expression systems for studies of the human insulin receptor were begun. As is apparent from the results summarized in Figs. 1 and 2, a significant number of studies have been devoted to the analysis of receptor mutations, both experimentally derived (i.e. by mutagenesis) and those identified in human patients, as well as to the generation of soluble derivatives of the major functional domains of the receptor for use in biophysical studies. While it is certainly clear that these methods can be expected to yield an ever-increasing body of data concerning insulin receptor structure/function, it is equally apparent that attention to a number of basic experimental limitations inherent in these approaches will be required to resolve a number of fundamental questions and disagreements concerning particular receptor mutations. Given the level of interest in the insulin receptor that has persisted over the past several decades, one expects that these efforts will be forthcoming, and that our understanding of this complex transmembrane receptor will, with time, improve.

A soluble insulin receptor kinase catalyzes ordered phosphorylation at multiple tyrosines of dodecapeptide substrates

At present, the requirements for efficient phosphorylation of exogenous substrates by protein-tyrosine kinases are largely unknown. The proton resonances of each of the 3 tyrosines of the dodecapeptide substrate RRDIYETDYYRK are well resolved in the aromatic region of the 1H NMR spectra: thus, it is feasible to directly monitor phosphorylation at each site. A soluble approximately 48-kDa derivative of the human insulin receptor cytoplasmic protein-tyrosine kinase domain phosphorylates this peptide at all 3 tyrosine sites and does so in a highly ordered and progressive manner (Y9, then Y10 and finally Y5), proceeding to full stoichiometry at each site before phosphorylating the next. This experimental system now provides an approach by which to follow the stereochemical requirements and dynamics of substrate phosphorylation by a protein-tyrosine kinase in solution in real time.

Molecular basis of the activation of the tumorigenic potential of Gag-insulin receptor chimeras

A previous study showed that the human insulin receptor (IR) could be activated by insertion of a 3' portion of the cDNA encoding the beta subunit into a retrovirus genome to form a Gag-IR fusion protein. While capable of transforming cells in culture, this IR cDNA-containing virus, called UIR, was not able to induce tumors in animals. Subsequently, we isolated a spontaneous sarcomagenic variant called UIR19t from the parental UIR. UIR19t was molecularly cloned, sequenced, and found to harbor two mutations. A 44-amino acid deletion immediately upstream from the transmembrane domain of the Gag-IR fusion protein removes all the extracellular sequence of the IR remaining in the original UIR construct. In addition, a single nucleotide deletion at the 3' end results in truncation and replacement of the carboxyl-terminal 12 amino acids by 4 new amino acids. The specific kinase activity of UIR19t is 4- to 5-fold higher than that of the parental UIR. However, no new cellular substrates were detected in UIR19t-transformed cells as compared to UIR cells. Viruses containing either the 5' or the 3' deletion mutation were constructed and assessed for their biological function. Our data indicate that the 5' deletion alone is sufficient to confer tumorigenic ability. We conclude that sequence immediately upstream from the transmembrane domain imposes a negative effect on the transforming and tumorigenic potential of the Gag-IR fusion protein.

Phosphorylation of tyrosines 1158, 1162 and 1163 on a synthetic dodecapeptide by the insulin receptor protein-tyrosine kinase

To investigate the mechanism of tyrosine phosphorylation by the insulin receptor protein-tyrosine kinase, we utilized a synthetic dodecapeptide substrate (RRDIYETDYYRK; amino acids 1155-1165) containing the three major insulin receptor autophosphorylation sites. (1) We show that all three tyrosines on this peptide are rapidly phosphorylated and that phosphorylation is probably initiated at tyrosine 9. This peptide thus serves as a useful tool to study the mechanism of transphosphorylation by the insulin receptor. (2) A proteolytic activity was detected in purified receptor preparations that removed basic residues from the peptide and prevented it binding to phosphocellulose paper. Such activity could pose a serious problem when using peptide substrates to assay for protein kinases in other acellular systems.

Two-dimensional phosphopeptide analysis of the autophosphorylation cascade of a soluble insulin receptor tyrosine kinase. The tyrosines phosphorylated are typical of those observed following phosphorylation of the heterotetrameric insulin receptor in intact cells

A soluble derivative of the human insulin receptor cytoplasmic domain, as expressed in insect cells via a Baculovirus vector, is an active protein-tyrosine kinase. In the present study, we find that three forms of the enzyme (48, 43, and 38 kDa) can be partially purified by MonoQ fast protein liquid chromatography. Two-dimensional thin layer phosphopeptide mapping reveals that the 48-kDa enzyme undergoes a rapid autophosphorylation on the same tyrosines (residues 1158, 1162, 1163, 1328, and 1334) that have previously been shown to be major autophosphorylation sites on the native insulin receptor beta-subunit in intact cells. Furthermore, the 48- and 43-kDa proteins are phosphorylated on serine residues by a serine kinase(s) that copurifies through MonoQ fast protein liquid chromatography. Tyrosine autophosphorylation sites 1328 and 1334 and virtually all serine phosphorylation sites are absent in the 38-kDa kinase. Partial tryptic proteolysis of the 48-kDa kinase generates a core 38-kDa enzyme that undergoes autophosphorylation almost exclusively on tyrosines 1158, 1162, and 1163. Phosphorylation of these tyrosine residues occurs in a cascade manner analogous to that found in the intact insulin receptor beta-subunit.

The regulatory role of known tyrosine autophosphorylation sites of the insulin receptor kinase domain. An assessment by replacement with neutral and negatively charged amino acids

Autophosphorylation of the insulin receptor has been previously documented to activate the phosphotransferase activity of the receptor from 20- to 200-fold. Biochemical studies have correlated activation of the receptor kinase with the autophosphorylation of tyrosines residues 1158, 1162, and 1163. To further assess the role of these 3 tyrosines in the activation process, we have studied the effect of their substitution with either the neutral amino acids phenylalanine or alanine or with the negatively charged amino acids aspartate and glutamate. In several other proteins, it has been shown that substitution of phosphorylated residues with negatively charged amino acids can mimic the phosphorylation state of the protein. In agreement with previous studies, tyrosines at positions 1162 and 1163 were found to be crucial in the kinase activation process. In contrast, mutant receptors with tyrosine 1158 changed to either phenylalanine or aspartate were still activated to the same extent as the wild-type receptor. An increased basal exogenous kinase activity was observed upon replacement of tyrosines 1162 and 1163 with, in increasing order of potency, aspartate = glutamate less than alanine = phenylalanine. These results indicate that phosphorylation of tyrosines 1162/1163 but not 1158 play a critical role in the activation of the receptor kinase and that the mechanism of activation of the receptor kinase by autophosphorylation is more complex than just an introduction of a cluster of negative charges in this region of the receptor. In addition, the finding of an increased basal kinase activity in receptors lacking tyrosines 1162 and 1163 could explain the reported ability of this receptor to mediate certain biological responses.

A synthesized (biosocial) theory of rape

Features of contemporary theories of rape are integrated with information on neurohormonal variables to formulate a synthesized theory of rape. It consists of four propositions: (a) Rape is motivated by two largely unlearned drives (a sex drive and a drive to possess and control). (b) Natural selection has favored men who more readily learn forced copulatory tactics than women and women who are more inclined than men to resist forced copulations. (c) The tendency to use forced copulatory tactics is largely a function of the strength of an individual's sex drive plus estimates of the probability of success minus the probability of being punished, divided by sensitivity to aversive stimuli. (d) Genes that have evolved primarily on the Y chromosome affect neurohormonal functioning in ways that alter the strength of the sex drive and sensitivity to aversive stimuli and thereby affect individual probabilities of committing rape.

Teicoplanin compared to flucloxacillin for antibiotic treatment of neutropenic patients

Ninety-eight neutropenic patients were randomized to receive piperacillin and gentamicin in combination with either teicoplanin or flucloxacillin. Sixty-seven of these patients, most of whom had myeloma, were given this combination as prophylaxis 5 d after high dose chemotherapy, 35 receiving flucloxacillin and 32 receiving teicoplanin. Of 31 patients with leukaemia who were febrile and neutropenic following induction chemotherapy or bone marrow transplantation, 18 received flucloxacillin and 13 received teicoplanin. For those given flucloxacillin, the mean number of days to change of antibiotics was 7.8 in the prophylaxis group and 5.1 in the treatment group. In the teicoplanin arm, the mean number of days to change antibiotics was 6.8 in the prophylaxis group and 6.1 in the treatment group. Two patients in the flucloxacillin arm developed drug rashes. Four patients developed rigors after teicoplanin administration and one asthmatic became wheezy. One patient had a progressive rise in creatinine, but overall the patients having teicoplanin did not have any appreciable increase of renal toxicity compared to the flucloxacillin arm. Blood cultures were positive prior to commencement in the treatment group in nine patients, and during treatment in six patients. Organisms grown were Gram-positive in 14 patients. Teicoplanin appears to be as effective as flucloxacillin when each is used in combination with piperacillin and gentamicin in the treatment of neutropenic patients, with similar rates of toxicity.

Effects of cisapride in patients with cystic fibrosis and distal intestinal obstruction syndrome

In a double-blind, placebo-controlled, crossover trial, we investigated the effects of the prokinetic drug cisapride in patients with cystic fibrosis and chronic recurrent distal intestinal obstruction syndrome (DIOS). After a baseline period, 17 patients (12.9 to 34.9 years; 12 boys) received, in random order, cisapride (7.5 to 10 mg) and placebo three times daily by mouth, each for 6 months. Gastrointestinal symptoms (flatulence, abdominal pain, fullness, abdominal distension, nausea, anorexia, heartburn, diarrhea, vomiting and regurgitation) were scored three times monthly and physical examinations assessed. At baseline and at each 6-month period, assessment included food intake for 7 days, 3-day stool collection, pulmonary function tests, and abdominal radiographs. During cisapride therapy compared with placebo, there were significant reductions in flatulence (p less than 0.005), fullness, and nausea (p less than 0.05). Patients with the worst symptom scores benefited most from cisapride. With cisapride, 12 patients felt better and three worse (p less than 0.05); physicians judged 11 patients improved and two worse (p less than 0.05). No side effects were noted. There were no significant differences between cisapride and placebo periods in nutritional status, x-ray scores, pulmonary function, food intake (fat, protein, calories), stool size and consistency, and fecal losses of fat, bile acids, chymotrypsin, and calories. For acute episodes of DIOS, intestinal lavage was needed 6 times in 4 patients during treatment with cisapride, and 11 times in 6 patients receiving placebo. In comparison with unselected patients with cystic fibrosis and pancreatic insufficiency who were receiving enzyme supplements and who had no distal intestinal obstruction, fecal fat losses (percentage of intake) were almost twice as high in the study group with DIOS (31.2 +/- 20.6% vs 16.2 +/- 17.6%; p less than 0.01). We conclude that in the dosage used, long-term treatment with cisapride appears to improve chronic abdominal symptoms in patients with cystic fibrosis and DIOS, but fails to abolish the need for intestinal lavage. Cisapride treatment had no effect on digestion and nutritional status of cystic fibrosis patients with pancreatic insufficiency.

The p38 and p34 polypeptides of growth cone particle membranes are the alpha- and beta-subunits of G proteins

Growth cone particle (GCP) membranes prepared from fetal day 17 rat brain are comprised of 5 major polypeptides as analyzed by SDS-PAGE: tubulin (p52), actin (p42), pp46/GAP-43 and two unidentified species, p38 and p34. Antibodies specific for the alpha- and beta-subunits of G proteins recognize p38 and p34, respectively, on immunoblots following one- and two-dimensional electrophoretic separation. That G protein subunits comprise major species of GCP membrane-associated polypeptides suggests a role for G proteins in transmembrane signaling in nerve growth cones.

Deletion analysis of the human insulin receptor ectodomain reveals independently folded soluble subdomains and insulin binding by a monomeric alpha-subunit

A series of 13 deletions within the extracellular domain of the human insulin receptor delineates the boundaries of subdomains that fold de novo into stable proteins that are efficiently secreted and retain the epitopes required for interaction with two conformation-specific monoclonal antibodies. While most of these proteins fail to bind insulin, a truncation that includes only the alpha-subunit is secreted as a monomer that binds the hormone with an affinity only slightly less than that of the complete heterotetrameric extracellular domain. These results thus demarcate landmarks within the primary sequence which will now guide further analysis of the structure and function of this complex domain of the receptor.

Evaluation of the injury profile of personnel in a busy urban EMS system

The occupational injury profile of emergency medical technicians (EMTs) and paramedics is not well described. We retrospectively studied 254 injuries over a 3.5-year period in a busy urban EMS system. Low back strain was the most common injury (93/254, 36%), with EMTs suffering a significantly higher injury rate than paramedics (0.33 v 0.17 injuries/person-years at risk, P = .03). Lifting caused 58/93 (62.4%) of back injuries, and most occurred at the scene to which personnel were dispatched (58/93, 62.4%). The back injuries were recurrent in 31% of personnel. The data showed trends toward higher overall injury rates among EMTs compared with paramedics (0.83 v 0.55, P = 0.057) and women compared with men (0.86 v 0.50, P = 0.11). There was a significantly higher injury rate among personnel less than 30 years of age compared with those 30 years or older (0.65 v 0.39, P = 0.01). Over 25% of the personnel injured had more than one injury per year. There was no correlation between injury rates and job experience. Approximately 96 injuries accounted for 481 compensation days with low back strain the cause of 375 days (78%). Our findings suggest a high incidence of occupational injury in EMS personnel with EMTs and persons under 30 years of age at higher risk. Guidelines for prevention programs are suggested.

Evidence for insulin-dependent activation of S6 and microtubule-associated protein-2 kinases via a human insulin receptor/v-ros hybrid

The abilities of a series of six mutants of the human insulin receptor, an insulin receptor/v-ros hybrid (IR-ros) and the P68gag-ros transforming protein to stimulate S6 protein kinase have been assessed. Insulin receptor mutants in which either 1 or 2 tyrosine residues have been replaced with phenylalanine (YF1, YF3) have lost some or all of the capacity to mediate the activation of S6 kinase in response to insulin. None of the four mutants that contain deletions (spBam, spBamYF3, iBgl, T-t) elicit an insulin-dependent stimulation of S6 kinase. A previous study of the IRros hybrid receptor demonstrated that it was unable to cause either insulin-stimulated thymidine incorporation or glucose uptake (Ellis, L., Morgan, D. O., Jong, S.-M., Wang, L.-H., Roth, R. A., and Rutter, W. J. (1987) Proc. Natl. Acad. Sci. U. S. A. 84, 5101-5105). In contrast, the IRros chimera appears to mediate the activation of S6 protein kinase by insulin. In further evaluating the biological activities of the IRros hybrid, we have examined its effects on a microtubule-associated protein-2 (MAP2) kinase that is thought to be an early target in the cascade of reactions leading to increased S6 phosphorylation (Sturgill, T. W., Ray, L. B., Erickson, E., and Maller, J. L. (1988) Nature 334, 715-718). We find that the IRros receptor stimulates the MAP2 protein kinase from 3- to 6-fold in insulin-treated cells, conferring more than a 30-fold increase in the insulin sensitivity of MAP2 kinase activation.

Speech clarity/intelligibility: test-retest reliability of magnitude-estimation scaling

The reliability of magnitude-estimation scaling as a measure of overall clarity of speech was investigated. 40 subjects (M age = 19 yr.) provided magnitude-estimation responses for nine audiotaped versions of a nonsense sentence varying systematically in number of correct consonant phonemes. There was no significant difference in the magnitude-estimation responses of the subjects during two test sessions separated by one week. Analysis suggested that magnitude-estimation scaling is a reliable measure of speech clarity/intelligibility. This finding is discussed in relation to speech samples varying in aspects other than number of consonant phonemes correct and possible further clinical research applications.

The impact of gestational length on human milk selenium concentration and glutathione peroxidase activity

Longitudinal changes in selenium (Se) and protein concentrations and glutathione peroxidase (GSH-Px) activity of milk collected from healthy mothers of term (n = 12), preterm (n = 10), and very preterm (n = 12) infants were assessed. All infants were size appropriate for gestational age. Milk samples representative of colostrum (d 3), transitional (d 7), and mature milk (d 21 and 42) were assayed. The content of Se in the colostrum secreted by mothers of preterm infants was significantly greater than the Se content of milk secreted by the same mothers at d 21 and 42 of lactation. Mothers of term and very preterm infants, however, produced colostrum with significantly higher levels of Se than milk produced at d 7 (p less than 0.05), d 21 (p less than 0.01), or d 42 (p less than 0.001). Significant differences between the protein concentrations measured in early lactation and in late lactation were evident in all maternal groups. Protein content did not differ significantly among groups at anytime during lactation. An age-related difference was detected in milk GSH-Px activities of mature milk (d 21). Mature milk produced by mothers of very preterm infants on d 21 of lactation contained significantly greater enzyme activity (p less than 0.05) than milk produced by mothers of term infants at the same stage of lactation. Activity of GSH-Px in milk from mothers of very preterm and preterm infants paralleled previously noted changes in long-chain polyunsaturated fatty acid content in human milk with the progression of lactation.(ABSTRACT TRUNCATED AT 250 WORDS)

Autophosphorylation activates the soluble cytoplasmic domain of the insulin receptor in an intermolecular reaction

The cytoplasmic protein-tyrosine kinase domain of the insulin receptor (residues 959-1355) has been expressed as a soluble protein in Sf9 insect cells via a Baculovirus expression vector (Ellis, L., Levitan, A., Cobb, M.H., and Ramos, P. (1988) J. Virol. 62, 1634-1639). The purified protein is a monomer as judged by its behavior in sucrose gradients and on gel filtration in the presence or absence of protamine. The initial rate of autophosphorylation using 3 mM MgCl2 is increased 20-30-fold by protamine. A maximum of 4-5 mol of phosphate are incorporated per mol of enzyme. The activity of the enzyme as a function of phosphorylation state was studied for three substrates: a synthetic dodecapeptide derived from the sequence of the major autophosphorylation site in the insulin receptor, poly(Glu, Tyr), 4:1, and histone 2B. Autophosphorylation of the protein to a stoichiometry of 4-5 mol of phosphate/mol increases its enzymatic activity as much as 200-fold; a 30-fold increase in activity occurs upon addition of 1 mol of phosphate/mol. The activities of unphosphorylated enzyme with the three substrates are 3.4, 2.3, and 0.44 nmol/min/mg, respectively. The activities of the autophosphorylated enzyme with the three substrates are 175, 274, and 45 nmol/min/mg, respectively. Exposure of the autophosphorylated enzyme to ADP results in a loss of phosphate from the enzyme which is associated with a decrease in enzymatic activity. Autophosphorylation of the kinase in the presence or absence of protamine displays a marked dependence on enzyme concentration. Furthermore, the rate of autophosphorylation decreases as the viscosity of the solution increases. Taken together, these data suggest that phosphorylation occurs via an intermolecular reaction.

Secretion of the extracellular domain of the human insulin receptor from insect cells by use of a baculovirus vector

To explore the utility of the baculovirus/insect-cell system for the expression of a soluble secreted human insulin-receptor (hIR) extracellular ligand-binding domain, we have engineered a recombinant virus encoding an hIR deletion mutant which is truncated eight residues from the beginning of the predicted transmembrane domain (i.e. 921 residues). Within 24 h after infection of Sf9 cells with virus, insulin-binding activity begins to accumulate in the culture medium, and reaches a maximum between 48 and 72 h. The intracellular transit and processing of this secreted receptor, designated 'AchIR01', is quite slow. After 24 h in pulse-chase experiments approximately 50% of the metabolically labelled protein is still inside the cell. This protein accumulates as a non-cleaved hIR precursor which is glycosylated, but the carbohydrate is entirely endoglycosidase H (endoH)-sensitive (i.e. high mannose). Approximately one-half of the receptor in the culture medium (i.e. approximately 25% of the total) is in the form of non-cleaved precursor, and about one half of its carbohydrate chains are now endoH-resistant. The remainder of the protein is proteolytically processed hIR (alpha-plus truncated beta-subunits). None of these hIR species exhibit O-linked carbohydrate. Only the processed form of the receptor in the medium binds insulin. This insulin-binding protein is secreted as a dimer (alpha beta)2, and binds insulin with an affinity which is comparable with that of both the wild-type hIR as well as the secreted form of the hIR expressed in mammalian cells. Despite the rather inefficient processing and altered glycosylation of the AchIR01 protein in insect cells, this high-affinity insulin-binding protein accumulates in the medium at levels (mg/litre) of about 100 times that achieved in a mammalian-cell system.

Expression in heterologous cells of the unusual cytoplasmic domain of rat brain 5B4/NCAM-ld

Monoclonal antibody 5B4 recognizes a carboxy-terminal epitope common to large (approximately 180 kDa) and short (approximately 140 kDa) forms of neural cell adhesion molecules (NCAM-ld and NCAM-sd, respectively). The deduced primary sequence of rat brain 5B4/NCAM-ld predicts a large cytoplasmic domain (390 amino acids, Mr 39,284) of striking amino acid composition (52% proline, alanine, serine and threonine) and little predicted alpha or beta secondary structure: its function is unknown. To directly test the deduced topology of the protein, and especially the solubility and stability of its unusual cytoplasmic domain, we have constructed a cDNA expression vector designed to express this domain independently as a soluble protein (designated 5B4cyt) in a heterologous cell system (simian Cos cells). 5B4cyt is indeed soluble, but migrates anomalously on SDS-PAGE under denaturing and reducing conditions as two species of approximately 77 and approximately 80 kDa. In pulse chase experiments, the approximately 77 kDa band chases into the approximately 80 kDa band with a t1/2 of approximately 1 h. The difference in mobility is apparently a consequence of the rapid phosphorylation of the approximately 77 kDa species. The approximately 88 kDa phospho-form is reasonably stable with a t1/2 of approximately 6 h. These results are consistent with the deduced topology of 5B4/NCAM-ld, and demonstrate the feasibility of this experimental approach for exploring the biochemistry and structure of its unusual cytoplasmic domain.

Isolation and sequence of lambda gt11 cDNA clones encoding the 5B4 antigen expressed on sprouting neurons

Monoclonal antibody (mAb) 5B4 recognizes a developmentally regulated membrane glycoprotein (Mr approximately 185,000-255,000) expressed on sprouting neurons. The amino acid sequence deduced from lambda gt11 cDNA clones encoding the transmembrane and cytoplasmic domains of the 5B4 antigen is co-linear with that of chick NCAM-ld. The significant level of overall sequence identity (75%) demonstrates that the 5B4 antigen is rat brain NCAM. The 5B4 epitope maps to the carboxy-terminus common to both NCAM-ld and NCAM-sd.

Effects of auditory masking on lingual vibrotactile magnitude-estimation scaling responses of young children

Studies of lingual vibrotactile magnitude-estimation scaling have focused primarily on the responses of normal young adults. Little is known about the scaling responses of young children to suprathreshold vibratory stimulation because of the complexities of the experimental procedure. Binaural auditory masking is one aspect of the procedure that has recently been studied in adults. The purpose of this study was to investigate the effects of binaural auditory masking on lingual vibrotactile magnitude-estimation responses of young children. Four children whose mean age was 4.6 yr. completed magnitude-estimation scaling tasks for eight lingual vibrotactile suprathreshold intensity levels (6, 10, 16, 20, 26, 30, 36, 40 dB SL) under masking and no masking conditions. Results suggest possible effects of auditory masking on the lingual vibrotactile magnitude-estimation scaling responses of these young children that have not been found for such responses of adults.

Membrane proteins of the nerve growth cone and their developmental regulation

The membrane polypeptides of growth cone fragments ("growth cone particles," GCPs) isolated from fetal rat brain by subcellular fractionation have been analyzed in further detail. The major polypeptides of salt-washed GCP membranes detected by 1-dimensional gel electrophoresis (Ellis et al., 1985b) resolve in 2-dimensional gels as a spot of 52 kDa that comigrates with beta-tubulin and reacts with anti-beta-tubulin; a 46 kDa, pl 4.3, polypeptide (pp46) that has no equivalent in the soluble fraction and is identical to one of the GCP's major phosphoproteins (Katz et al., 1985) and to GAP43 (Willard et al., 1985); a spot of 42 kDa that comigrates with actin; and a species of 34 kDa (p34) without soluble equivalent. The prominent 38 kDa doublet identified in 1-dimensional gels is difficult to resolve in 2-dimensional gels. The major phosphoproteins pp80ac, pp46, and pp40 (Katz et al., 1985), as well as p34 partition into the oil phase of Triton X-114 extracts, suggesting that they are integral membrane proteins, at least in our experimental conditions. The properties of pp46 reported here are in conflict with the highly hydrophilic amino acid sequence predicted for GAP43/B50/F1 (Basi et al., 1987; Karns et al., 1987). Growth-cone and presynaptic membrane proteins are compared as follows. After eye injection of 35S-methionine, GCPs and synaptosomes are isolated from the target areas of optic nerve of fetal and adult rats, respectively. Polypeptides are separated by 1- and 2-dimensional gel electrophoresis and the radiolabeled species identified fluorographically. The comparison of labeled GCP and synaptosome polypeptides shows that all 5 major Coomassie blue-stained polypeptides of GCP membranes (52, 46, 42, 38, 34 kDa) are intensely labeled after eye injection. However, in synaptosomes, these polypeptides are weakly labeled if at all; instead, an intensely labeled polypeptide of 28 kDa, and several additional species not seen in GCPs, have appeared. Therefore, the major growth cone membrane proteins are developmentally regulated, and the rates of synthesis and transport into the axonal ending of neuronal polypeptides change dramatically at the time of synaptogenesis.

Delinquency, sidedness, and sex

One hundred and thirty male and 213 female college students responded to a self-report delinquency and crime measure and to a scale of sidedness preferences. Consistent with most of the literature on official delinquency and crime, left handedness was positively associated with involvement in several forms of delinquency (including some degree of criminality) among males. Other measures of sidedness among males largely failed to correlate with delinquency, however. Among females, sidedness was much less systematically related to delinquency than among males.

Effect of auditory masking on lingual vibrotactile thresholds and magnitude estimation scaling responses

Auditory masking has become a frequently employed part of the procedure used in vibrotactile research. Research investigating the effect of auditory masking on lingual vibrotactile thresholds of sensitivity has shown that there is little difference between lingual vibrotactile thresholds under masking and no masking conditions. The purpose of the present study was to extend the investigation of the effect of auditory masking to include lingual vibrotactile suprathreshold scaling responses. 20 young adult subjects of mean age 19 yr. completed lingual vibrotactile-threshold and magnitude-estimation scaling tasks under conditions of bilateral auditory masking and no masking. Similar lingual vibrotactile-threshold values and magnitude-estimation power-function exponents for the conditions of masking and no masking were noted.

Respiratory syncytial virus

RSV is now understood to be the most significant viral respiratory pathogen of infants and is capable of causing both bronchiolitis and pneumonia. It is a particular risk to hospitalized infants as the virus is easily spread through close contact. The most vulnerable infants are those who suffer with either congenital heart disease or bronchopulmonary dysplasia who easily fall prey to pulmonary complications of infection. Strict environmental control and the use of protective clothing and eyewear should be implemented to decrease the nosocomial spread of RSV. Available diagnostic studies include viral isolation, fluorescent antibody stains, and enzyme immunoassays. Treatment of the disease is usually supportive but hospitalized patients frequently benefit from aerosolized ribavirin therapy. Hopefully, current vaccine trials will be successful and this pathogen will not only be treatable but will also be preventable.

Estrogen and insulin synergism in neurite growth enhancement in vitro: mediation of steroid effects by interactions with growth factors?

Addition of estradiol to organotypic cultures of the fetal murine hypothalamus, preoptic area and cerebral cortex has been shown to elicit a striking enhancement of neurite growth which appears restricted to estrogen receptor-containing explant regions. The mechanisms underlying this response are unknown. An important question is whether the neurite enhancement which follows exposure to estradiol is due directly to the interaction of estrogen with the cell that was stimulated (the receptor-containing cell) or whether intermediate steps involving the possible interaction of estrogen and the endogenous polypeptide neurite-promoting growth factors or their receptors may play an important role. Recent findings in the cultures suggest that the effect of estrogen on neurite growth may involve synergistic interactions between estradiol and insulin-related peptides and may be important in regulating estrogen-responsive neurite growth in the central nervous system. Concurrent addition of estradiol and high levels of insulin (10 micrograms/ml or 50 micrograms/ml) to cultures of the olfactory bulb, hypothalamus, preoptic area and cerebral cortex of the fetal rat and mouse results in a dramatic acceleration and increase of neurite outgrowth which appears localized to estrogen receptor-containing explant regions. The supraphysiological concentrations of insulin required to elicit this response suggest that the factor(s) involved is unlikely to be insulin per se. Insulin may activate the receptor of different but closely related molecules such as the insulin-like growth factors (IGF)-I or -II to which it exhibits a relatively low affinity. Interactions between hormones and endogenous growth factors have been implicated in the modulation or mediation of an increasing number of endocrine-dependent, differentiative processes in vivo and in vitro.(ABSTRACT TRUNCATED AT 250 WORDS)

Efficient expression in insect cells of a soluble, active human insulin receptor protein-tyrosine kinase domain by use of a baculovirus vector

The human insulin receptor (IR) is a transmembrane glycoprotein, whose cytoplasmic domain contains an insulin-activated protein-tyrosine kinase (EC 2.7.1.112). By the use of an appropriately engineered baculovirus expression vector, a soluble cytoplasmic derivative of this domain was expressed in the insect cell line Spodoptera frugiperda (Sf9). At 24 to 48 h after Sf9 cells were infected with recombinant virus, a protein of the size expected for this domain (approximately 48 kilodaltons) constituted a major band when total cell lysates of metabolically labeled cells were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and fluorography. This protein (designated AchIRPTK) was immunoprecipitated by three monoclonal antibodies, each of which recognizes a distinct antigenic site of the IR cytoplasmic domain and requires the native structure of the protein for recognition and one of which binds at or near the physiologically relevant site(s) of IR autophosphorylation. In vivo, AchIRPTK was phosphorylated on both tyrosine and serine residues. When affinity purified, the kinase was active in vitro; it autophosphorylated exclusively on tyrosine residues, and phosphorylated the exogenous substrates histone H2b and poly(Glu-Tyr). The expression of an active IR protein-tyrosine kinase molecule in this heterologous cell system provides an efficient experimental method for producing this domain in quantity for enzymatic and structural studies.

Truncation of the ectodomain of the human insulin receptor results in secretion of a soluble insulin binding protein from transfected CHO cells

The insulin receptor is an integral transmembrane glycoprotein comprised of two alpha-(approximately 135 kDa) and two beta-(approximately 95 kDa) subunits, which is synthesized as a single polypeptide chain precursor (alpha beta). The primary sequence of the human insulin receptor (hIR) protein, deduced from the nucleotide sequence of cloned human placental mRNAs, predicts two large domains (929 and 403 residues) on either side of a single membrane spanning domain (23 residues); each of these major domains has a distinct function (insulin binding and protein/tyrosine kinase activity, respectively). To experimentally test this deduced topology, and to explore the potential for independent domain function by the hIR extracellular domain, we have constructed an expression plasmid encoding an hIR deletion mutant which is truncated 8 residues from the beginning of the predicted transmembrane domain (i.e., 921 residues). This domain of the hIR is in fact processed into alpha- and truncated beta-subunits and secreted with high efficiency from transfected CHO cell lines which express this mutant hIR, and the protein accumulates as an (alpha beta)2 dimer in the medium. This molecule is recognized by a battery of 13 monoclonal antibodies to epitopes on the IR extracellular domain, four of which block insulin binding and two of which require the native conformation of the IR for recognition. Further, this domain binds insulin with an apparent dissociation constant comparable to that of the wild-type hIR. However, the secreted dimer displays a linear Scatchard plot, while that of the wild-type membrane-associated hIR is curvilinear.(ABSTRACT TRUNCATED AT 250 WORDS)

Heterologous transmembrane signaling by a human insulin receptor-v-ros hybrid in Chinese hamster ovary cells

A hybrid receptor molecule composed of the extracellular ligand-binding domain of the human insulin receptor and the transmembrane and cytoplasmic (protein-tyrosine kinase) domains of the chicken sarcoma virus UR2 transforming protein p68gag-ros has been constructed and expressed in Chinese hamster ovary (CHO) cells. The hybrid is processed normally into alpha and hybrid beta subunits, is expressed on the cell surface at high levels, and binds insulin with near-wild-type affinity. Furthermore, insulin stimulates the phosphorylation on tyrosine residues of the hybrid beta subunit in vivo and the phosphorylation of an exogenous substrate [poly(Glu,Tyr)] in vitro. Thus the hybrid is capable of heterologous transmembrane signaling. However, the hybrid mediates neither the insulin-activated uptake of 2-deoxyglucose nor the incorporation of [3H]thymidine into DNA, suggesting that the physiological response(s) mediated by ligand-activated protein-tyrosine kinases may utilize distinct intracellular mechanisms for postreceptor signaling.

Activation of transforming potential of the human insulin receptor gene

A retrovirus containing part of the human insulin receptor (hIR) gene was constructed by replacing ros sequences in the avian sarcoma virus UR2 with hIR cDNA sequences coding for 46 amino acids of the extracellular domain and the entire transmembrane and cytoplasmic domains of the beta subunit of hIR. The resulting virus, named UIR, contains the hIR sequence fused to the 5' portion of the UR2 gag gene coding for p19. UIR is capable of transforming chicken embryo fibroblasts and promoting formation of colonies in soft agar; however, it does not form tumors in vivo. A variant that arose from the parental UIR is capable of efficiently inducing sarcomas in vivo. UIR-transformed cells exhibit higher rates of glucose uptake and growth than normal cells. The 4-kilobase UIR genome codes for a membrane-associated, glycosylated gag-hIR fusion protein of 75 kDa designated P75gag-hir. P75gag-hir contains a protein tyrosine kinase activity that is capable of undergoing autophosphorylation and of phosphorylating foreign substrates in vitro; it is phosphorylated at both serine and tyrosine residues in vivo.

Antibody-induced down-regulation of a mutated insulin receptor lacking an intact cytoplasmic domain

Insulin receptor down-regulation was studied in various Chinese hamster ovary (CHO) cell lines expressing transfected human insulin receptor cDNAs. In addition to a cell line expressing the normal receptor (CHO.T line), three lines expressing mutated receptors were studied: the CHO.T-t line, which expresses a receptor with a degraded cytoplasmic domain due to the removal of the C-terminal 112 amino acids, and the CHO.YF1 and CHO.YF3 lines, in which important autophosphorylation sites of the receptor kinase (tyrosines-1162 and -1163) have been replaced by phenylalanine. A monoclonal anti-receptor antibody, but not insulin itself, was found to down-regulate cell surface receptor levels in all four cell lines by 60-80% after 18-h treatment at 37 degrees C. Down-regulation of the CHO.T and CHO.T-t receptors occurred at similar antibody concentrations and with a similar time course, although the maximum level of CHO.T-t down-regulation (60%) was generally lower than the level of CHO.T down-regulation (80%). Pulse-chase labeling of these two cell types with [35S]methionine revealed that antibody treatment of both CHO.T and CHO.T-t cells resulted in a similar increase in the rate of degradation of mature receptor subunits. These results indicate that antibody-induced down-regulation of the insulin receptor in these cells can occur in the absence of various autophosphorylation sites of the receptor and that the mechanism of antibody-induced down-regulation is different from that for insulin.

A membrane-anchored cytoplasmic domain of the human insulin receptor mediates a constitutively elevated insulin-independent uptake of 2-deoxyglucose

Insulin stimulates the autophosphorylation of the beta-subunit of the insulin receptor (IR) on tyrosine residues. Mutations which compromise IR autophosphorylation in vivo result in a decrease of the insulin-activated uptake of 2-deoxyglucose. These results are consistent with previous results which implicate IR autophosphorylation in the generation of the insulin response by cells. To further explore the specificity of the IR tyrosine phosphokinase (TPK) domain in IR function, we have altered the human IR (hIR) cDNA to encode truncated insulin-independent TPKs, which are expressed in chinese hamster ovary (CHO) cells as either membrane-anchored or cytosolic proteins. Both mutant hIRs exhibit TPK activity in vitro, although the cytosolic form is approximately 20 times more active. The carbohydrate moiety of the membrane-anchored form is of the high mannose type, consistent with an intracellular localization for this mutant hIR. The two mutant hIRs mediate very different physiological responses in transfected cells: the membrane-anchored, but not the cytosolic, hIR TPK mediates a constitutively elevated (135% the maximum insulin-stimulated response in CHO cells) insulin-independent uptake of 2-deoxyglucose. These results thus suggest that the hIR TPK is in fact specific for this aspect of IR function and, when membrane-associated, can mediate the insulin-independent uptake of 2-deoxyglucose. Neither of these mutant hIRs appears to transform CHO cells.

The human insulin receptor cDNA: a new tool to study the function of this receptor

The human insulin receptor (hIR) is an integral transmembrane glycoprotein comprised of two alpha and two beta subunits. An immediate consequence of insulin binding to the extracellular alpha subunit is the autophosphorylation of tyrosine residues on the intracellular domain of the beta subunit. The placental hIR cDNA has been cloned and sequenced, providing the primary structural features of the protein. In order to investigate the functions of the beta subunit and particularly the role of autophosphorylation and tyrosine phosphokinase (TPK) activity (a feature shared by other receptors and oncogene proteins) in transmembrane signalling, we designed an expression system of the hIR cDNA in eucaryotic cells. Superexpressing CHO cell lines that contain about 10(6) functional hIR/cell have been developed. In these cells half maximum stimulation of glucose uptake occurs at 5 X 10(-10)M insulin, whereas normal CHO cells require 5 X 10(-12)M insulin. In this expression system we have carried out site-directed mutagenesis experiments in which domains of the molecule have been deleted or particular amino acids have been replaced by others. The replacement of either or both the tyrosine residues 1162 and 1163 compromise an autophosphorylated site that is important for kinase function and the insulin response. Expression of an isolated membrane-bound form of the beta-subunit produces a 6 fold increase in glucose uptake. This insulin-independent effect disappears if the twin tyrosines are mutated or if the beta subunit is expressed in the cytoplasm. These studies also show that the C terminal 112 amino acid portion of the beta subunit is important for the stability of this protein.

The 5B4 antigen expressed on sprouting neurons contains alpha-2,8-linked polysialic acid

Monoclonal antibody 5B4 recognizes a large (approximately 185,000-255,000 Da) developmentally regulated membrane glycoprotein, whose expression on fetal rat neurons is coincident with neuronal sprouting. By the use of two prokaryotic-derived probes specific for recognizing alpha-2,8-linked polysialosyl units, we demonstrate the presence of this unusual carbohydrate moiety (a characteristic of neural cell adhesion molecules, NCAMs) on the fetal form of the 5B4 antigen. The 5B4 antigens expressed in adult rat brain (approximately 140,000 and 180,000 Da) do not contain polysialic acid.

Linking functional domains of the human insulin receptor with the bacterial aspartate receptor

A hybrid receptor has been constructed that is composed of the extracellular domain of the human insulin receptor fused to the transmembrane and cytoplasmic domains of the bacterial aspartate chemoreceptor. This hybrid protein can be expressed in rodent (CHO) cells and displays several functional features comparable to wild-type insulin receptor. It is localized to the cell surface, binds insulin with high affinity, forms oligomers, and is recognized by conformation-specific monoclonal antibodies. Although most of the expressed protein accumulates as a 180-kDa proreceptor, some processed 135-kDa receptor can be detected on the cell surface by covalent cross-linking. Expression of the hybrid receptor inhibits the insulin-activated uptake of 2-deoxyglucose by CHO cells. Thus, this hybrid is partially functional and can be processed; however, it is incapable of native transmembrane signaling. The results indicate that the intact domains of different types of receptors can retain some of the native features in a hybrid molecule but specific requirements will need to be satisfied for transmembrane signaling.