The RadB protein from Pyrococcus does not complement E. coli recA mutations in vivo

A previous publication claimed that the radB gene called Pk-REC from Pyrococcus furiosus complemented an E. coli recA mutation. We found that a sequencing error had led to the test of a mutant form of Pk-REC. The wild-type radB gene from P. furiosus cloned in a similar expression vector to the mutant Pk-REC also appeared to complement an E. coli recA mutation. However, the cloned P. furiosus gdh (glutamate dehydrogenase) gene showed the same activity. We therefore concluded that overexpression of any protein can produce an artificial growth inhibition or stationary phase in recA mutant cells, which allows cells to recover from UV damage due to the action of repair systems that do not require RecA-like activity.

Malignant peritoneal mesothelioma deciduoid or anaplastic variant? Point to ponder

A case of peritoneal mesothelioma displaying unusual morphology, occurring in a 53 year old woman is described. The role of immunohistochemistry and electron microscopy in the evaluation of this tumor is stressed. The appropriate terminology to be used and possible etiologic factor are also discussed.

Nerve cell markers in ossifying fibromyxoid tumour of soft parts

Reported herein are two benign ossifying fibromyxoid tumors (OFMTs) of the soft tissues in axilla and terminal phalanx respectively. Both cases on immunohistochemistry (IHC) showed reactivity for vimentin, S-100 protein and glial fibrillary acidic protein (GFAP) antibodies. In addition, a focal/diffuse strong positivity for neurofilament (NF) and neuron specific enolase (NSE) was observed. Electron microscopy in one instance revealed abundant intermediate filaments, primitive cell junctions and a focally present external lamina. In the light of nerve cell differentiation of these tumors and the similarity of IHC profile and EM features of OFMT to a poorly differentiated malignant peripheral nerve sheath tumor (MPNST); it is suggested that OFMT is a variably differentiated PNST rather than a simple Schwannian neoplasm as is believed.

The synaptic vesicle protein, cysteine-string protein, is associated with the plasma membrane in 3T3-L1 adipocytes and interacts with syntaxin 4

Adipocytes and muscle cells play a major role in blood glucose homeostasis. This is dependent upon the expression of Glut4, an insulin-responsive facilitative glucose transporter. Glut4 is localised to specialised intracellular vesicles that fuse with the plasma membrane in response to insulin stimulation. The insulin-induced translocation of Glut4 to the cell surface is essential for the maintenance of optimal blood glucose levels, and defects in this system are associated with insulin resistance and type II diabetes. Therefore, a major focus of recent research has been to identify and characterise proteins that regulate Glut4 translocation. Cysteine-string protein (Csp) is a secretory vesicle protein that functions in presynaptic neurotransmission and also in regulated exocytosis from non-neuronal cells. We show that Csp1 is expressed in 3T3-L1 adipocytes and that cellular levels of this protein are increased following cell differentiation. Combined fractionation and immunofluorescence analyses reveal that Csp1 is not a component of intracellular Glut4-storage vesicles (GSVs), but is associated with the adipocyte plasma membrane. This association is stable, and not affected by either insulin stimulation or chemical depalmitoylation of Csp1. We also demonstrate that Csp1 interacts with the t-SNARE syntaxin 4. As syntaxin 4 is an important mediator of insulin-stimulated GSV fusion with the plasma membrane, this suggests that Csp1 may play a regulatory role in this process. Syntaxin 4 interacts specifically with Csp1, but not with Csp2. In contrast, syntaxin 1A binds to both Csp isoforms, and actually exhibits a higher affinity for the Csp2 protein. The results described raise a number of interesting questions concerning the intracellular targeting of Csp in different cell types, and suggest that the composition and synthesis of GSVs may be different from synaptic and other secretory vesicles. In addition, the interaction of Csp1 with syntaxin 4 suggests that this Csp isoform may play a role in insulin-stimulated fusion of GSVs with the plasma membrane.

Endometrial stromal sarcoma with sex-cord like features

Endometrial stromal sarcomas are rare, low grade, malignant uterine tumours. Sometimes, they manifest an epithelial like or sex-cord like differentiation. This is a report of one such case in a 35 year old female.

Histoplasmosis capsulatum as a cause of lower gastrointestinal bleeding in common variable immunodeficiency

Infection with Histoplasma capsulatum is the most common systemic fungal infection in the United States, but symptomatic gastrointestinal disease is rare. Gastrointestinal involvement is seen in patients with an established immunosuppressed state that predates any infection. We report a patient presenting with gastrointestinal bleeding ultimately diagnosed with disseminated histoplasmosis. Work-up led to the diagnosis of common variable immunodeficiency, a diagnosis not previously described as associated with gastrointestinal histoplasmosis. Resolution of the colonic ulcer was documented after appropriate antifungal therapy, underscoring the importance of including this infectious process in the differential of a patient without other risk factors for colonic ulceration.

Malignant peritoneal mesothelioma deciduoid or anaplastic variant? A point to ponder

A case of peritoneal meosthelioma displaying unusual morphology, occurring in a 53 years old woman is described. The role of immunohistochemistry and electron microscopy in the evaluation of this tumour is stressed. The appropriate terminology to be used and possible etiologic factor are also discussed.

EGF activates ErbB-2 and stimulates phosphatidylinositol 3-kinase in human airway smooth muscle cells

The epidermal growth factor (EGF)-receptor (EGFR) family includes four homologous transmembrane receptor protein tyrosine kinases, EGFR, ErbB-2, ErbB-3, and ErbB-4. This receptor family plays a pivotal role in regulating cell proliferation, differentiation, and transformation. Ligand-induced activation of these receptors results in formation of homo- and heterodimers, which undergo transphosphorylation and transactivation. The aim of this study was to characterize the role of EGFR family members in signaling EGF-induced human airway smooth muscle (HASM) cell proliferation. Here, we show that EGF stimulates activation of EGFR and transactivation of ErbB-2 in quiescent HASM cells. Phosphatidylinositol (PI) 3-kinase, a critical signaling enzyme that modulates HASM cell growth, is preferentially associated with ErbB-2, and EGF-stimulated transactivation of ErbB-2 induces PI 3-kinase activation. ErbB-3 and ErbB-4 are present in HASM cells; however, EGF has no effect on their activation. Betacellulin, a ligand for EGFR, ErbB-3, and ErbB-4, induced DNA synthesis of HASM cells and stimulated signaling through the activation of EGFR and ErbB-2 but not of ErbB-3 and ErbB-4. Heregulin, a specific ligand for ErbB-3 and ErbB-4, did not effect DNA synthesis and did not activate its specific receptors. These data suggest that EGF imparts signals that involve activation of ErbB-2 and are associated with ErbB-2 PI 3-kinase activation. Despite the mRNA and protein expression of all members of the EGFR family, ligand-stimulated signaling induced activation of EGFR and ErbB-2 but not of ErbB-3 and ErbB-4.

The future of pediatric psychopharmacology

The future of pediatric psychopharmacology will be a collaborative effort among the public, the federal government, the pharmaceutical industry, and clinical scientists. Clinical scientists and the NIH have initiated the process. The federal regulatory guidelines are in place but may need to be amended further to truly facilitate needed research. The pharmaceutical industry is making efforts to study medications in childhood psychiatric disorders. More new drugs are being tested in humans. Many of the new agents offer the promise of more clinical benefit with milder side effects. The future is indeed promising.

The relationship of school breakfast to psychosocial and academic functioning: cross-sectional and longitudinal observations in an inner-city school sample

OBJECTIVE

To determine if a relationship exists between participation in a school breakfast program and measures of psychosocial and academic functioning in school-aged children.

METHODS

Information on participation in a school breakfast program, school record data, and in-depth interviews with parents and children were collected in 1 public school in Philadelphia, Pa, and 2 public schools in Baltimore, Md, prior to the implementation of a universally free (UF) breakfast program and again after the program had been in place for 4 months. One hundred thirty-three low-income students had complete data before and after the UF breakfast program on school breakfast participation and school-recorded measures, and 85 of these students had complete psychosocial interview data before and after the UF breakfast program. Teacher ratings of behavior before and after the UF breakfast program were available for 76 of these students.

RESULTS

Schoolwide data showed that prior to the UF breakfast program, 240 (15%) of the 1627 students in the 3 schools were eating a school-supplied breakfast each day. Of the 133 students in the interview sample, 24 (18%) of the students ate a school-supplied breakfast often, 26 (20%) ate a school-supplied breakfast sometimes, and 83 (62%) ate a school-supplied breakfast rarely or never. Prior to the UF breakfast program, students who ate a school-supplied breakfast often or sometimes had significantly higher math scores and significantly lower scores on child-, parent-, and teacher-reported symptom questionnaires than children who ate a school-supplied breakfast rarely or never. At the end of the school term 4 months after the implementation of the UF breakfast program, school-supplied breakfast participation had nearly doubled and 429 (27%) of the 1612 children in the 3 schools were participating in the school breakfast program each day. In the interview sample, almost half of the children had increased their participation. Students who increased their participation in the school breakfast program had significantly greater increases in their math grades and significantly greater decreases in the rates of school absence and tardiness than children whose participation remained the same or decreased. Child and teacher ratings of psychosocial problems also decreased to a significantly greater degree for children with increased participation in the school breakfast program.

CONCLUSION

Both cross-sectional and longitudinal data from this study provide strong evidence that higher rates of participation in school breakfast programs are associated in the short-term with improved student functioning on a broad range of psychosocial and academic measures.

Use of mismatched grating pairs in chirped-pulse amplification systems

We demonstrate for the first time to our knowledge the use of mismatched grating pairs between the stretching and compression systems in a chirped-pulse amplification laser. Pulses as short as 57 fs are generated with 2000-lines/mm gratings in the compressor and 1200-lines/mm gratings in the stretcher.

Motorbike toe: a toddler's sporting injury

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Functional studies of human GLUT5: effect of pH on substrate selection and an analysis of substrate interactions

The adsorption of D-fructose within the lumen of the human small intestine is thought to be mediated by the GLUT5 isoform of the human facilitative sugar transporter family. This isoform has been expressed in oocytes and shown to be capable of D-fructose transport. Some debate remains regarding the absolute substrate specificity of this isoform. To that end, we have undertaken an analysis of the functional properties of this protein when expressed in Xenopus oocytes. We have examined the pH dependence of transport activity, the ability to transport D-fructose versus deoxyglucose, and employed a range of sugar analogues to probe the nature of the exofacial substrate binding site. Our data show that the human GLUT5 isoform functions exclusively as a D-fructose transporter between pH 4.5 and 8. The Km for D-fructose was found to be 15 +/- 4 mM at pH 7. 5, and was relatively unaltered even at pH 4.5. Analysis of the effects of a range of compounds on GLUT5 function suggests that this isoform transports D-fructose preferentially in the furanose ring form.

Structure-function studies of the brain-type glucose transporter, GLUT3: alanine-scanning mutagenesis of putative transmembrane helix VIII and an investigation of the role of proline residues in transport catalysis

The brain-type glucose transporter (GLUT3) is a high-affinity transporter for D-glucose and D-galactose and is a member of a family of mammalian sugar transporters, each of which are proposed to adopt a secondary structure containing 12 transmembrane helices. In an effort to understand structure-function relationships within such transporters, we have employed alanine-scanning mutagenesis to examine the functional importance of each residue within putative transmembrane helix VIII of the human GLUT3 isoform. Each residue in this helix was replaced individually with alanine, and the functional properties of the mutants were examined by microinjection of in vitro transcribed mRNA into Xenopus oocytes. We show that substitution of residues 305, 306, 308-314, and 316-325 with alanine had minimal effect on the functional activity of the transporter, as determined by measurement of the Km for deoxyglucose transport and the Ki for maltose. In contrast, Asn-315 > Ala-315 exhibited a significant increase in the Km for deoxyglucose independently of any effect on the Ki for maltose. This data suggests that, despite the strong sequence conservation in this helix among the GLUT family, no individual residue is absolutely required for transport catalysis by this isoform. We have also examined the role of proline residues in transport catalysis mediated by GLUT3. Substitution of Pro-203 (helix VI), Pro-206, Pro-209 (cytoplasmic loop between helices VI and VII), Pro-381, Pro-383 and Pro-385 (helix X), Pro-399 (intracellular loop between helices X and XI), or Pro-451 (in the carboxy terminus, close to the end of helix XII) with alanine did not change the Km for deoxyglucose transport for any mutant. However, both Pro-381 and Pro-385 when mutated to alanine exhibited a reduction in the Ki for cytochalasin B. In addition, the Ki for maltose inhibition of deoxyglucose transport was increased for mutants Pro206Ala, Pro381Ala, Pro383Ala, and Pro451Ala. These results will be discussed in terms of proposed structural models for the transporters.

Compensation of self-phase modulation in chirped-pulse amplification laser systems

Small amounts of self-phase modulation can lead to significant pulse distortions in chirped-pulse amplifiers. However, we show the surprising result that the strong chirp of the pulse can be exploited to remove these distortions completely by linear pulse shaping before amplification.

Structure-function analysis of liver-type (GLUT2) and brain-type (GLUT3) glucose transporters: expression of chimeric transporters in Xenopus oocytes suggests an important role for putative transmembrane helix 7 in determining substrate selectivity

The liver-type (GLUT2) and brain-type (GLUT3) human facilitative glucose transporters exhibit distinct kinetics (K(m) values for deoxyglucose transport of 11.2 +/- 1.1 and 1.4 +/- 0.06 mM, respectively) and patterns of substrate transport (GLUT2 is capable of D-fructose transport, GLUT3 is not) [Gould, G. W., Thomas, H. M., Jess, T. J., & Bell, G. I. (1991) Biochemistry 30, 5139-5145]. We have generated a range of chimeric glucose transporters composed of regions of GLUT2 and GLUT3 with a view to identifying the regions of the transporter which are involved in substrate recognition and binding. The functional characteristics of these chimeras were determined by expression in Xenopus oocytes after microinjection of cRNA. Replacement of the region from the start of putative transmembrane helix 7 to the C-terminus of GLUT3 with the corresponding region from GLUT2 results in a chimera with the ability to transport fructose and exhibits a K(m) for 2-deoxyglucose transport of close to that observed for wild-type GLUT2 (8.3 +/- 0.3 mM compared to 11.2 +/- 1.1 mM). Replacement of the region in GLUT3 from the end of helix 7 to the C-terminus with the corresponding region from GLUT2 resulted in a species which was unable to transport fructose and whose K(m) for 2-deoxyglucose was indistinguishable from wild-type GLUT3. We have determined the affinity for 2-deoxyglucose, D-fructose, and D-galactose of these and other chimeras. In addition, the Ki for maltose, a competitive inhibitor of 2-deoxyglucose transport, which binds to the exofacial sugar binding site was determined for these chimeras. The results obtained support a model in which the seventh putative transmembrane-spanning helix is intimately involved in the selection of transported substrate and in which this region plays an important role in determining the K(m) for 2-deoxyglucose. Additional data is presented which suggests that a region between the end of putative transmembrane helix 7 and the end of helix 10, together with sequences in the N-terminal half of the protein may also participate in substrate recognition and transport catalysis.