Insulin receptor phosphorylation, insulin receptor substrate-1 phosphorylation, and phosphatidylinositol 3-kinase activity are decreased in intact skeletal muscle strips from obese subjects

To determine whether the impaired insulin-stimulated glucose uptake in obese individuals is associated with altered insulin receptor signaling, we measured both glucose uptake and early steps in the insulin action pathway in intact strips of human skeletal muscle. Biopsies of rectus abdominus muscle were taken from eight obese and eight control subjects undergoing elective surgery (body mass index 52.9 +/- 3.6 vs 25.7 +/- 0.9). Insulin-stimulated 2-deoxyglucose uptake was 53% lower in muscle strips from obese subjects. Additional muscle strips were incubated in the basal state or with 10(-7) M insulin for 2, 15, or 30 min. In the lean subjects, tyrosine phosphorylation of the insulin receptor and insulin receptor substrate-1 (IRS-1), measured by immunoblotting with anti-phosphotyrosine antibodies, was significantly increased by insulin at all time points. In the skeletal muscle from the obese subjects, insulin was less effective in stimulating tyrosine phosphorylation (maximum receptor and IRS-1 phosphorylation decreased by 35 and 38%, respectively). Insulin stimulation of IRS-1 immunoprecipitable phosphatidylinositol 3-kinase (PI 3-kinase) activity also was markedly lower in obese subjects compared with controls (10- vs 35-fold above basal, respectively). In addition, the obese subjects had a lower abundance of the insulin receptor, IRS-1, and the p85 subunit of PI 3-kinase (55, 54, and 64% of nonobese, respectively). We conclude that impaired insulin-stimulated glucose uptake in skeletal muscle from severely obese subjects is accompanied by a deficiency in insulin receptor signaling, which may contribute to decreased insulin action.

A randomized trial comparing fluconazole with clotrimazole troches for the prevention of fungal infections in patients with advanced human immunodeficiency virus infection. NIAID AIDS Clinical Trials Group

BACKGROUND

Cryptococcal meningitis and other serious fungal infections are common complications in patients infected with the human immunodeficiency virus (HIV). Fluconazole is effective for long-term suppression of many fungal infections, but its effectiveness as primary prophylaxis had not been adequately evaluated.

METHODS

We conducted a prospective, randomized trial that compared fluconazole (200 mg per day) with clotrimazole troches (10 mg taken five times daily) in patients who were also participating in a randomized trial of primary prophylaxis for Pneumocystis carinii pneumonia.

RESULTS

After a median follow-up of 35 months, invasive fungal infections had developed in 4.1 percent of the patients in the fluconazole group (9 of 217) and in 10.9 percent of those in the clotrimazole group (23 of 211; relative hazard, as adjusted for the CD4+ count, 3.3; 95 percent confidence interval, 1.5 to 7.6). Of the 32 invasive fungal infections, 17 were cryptococcosis (2 in the fluconazole group and 15 in the clotrimazole group; adjusted relative hazard, 8.5; 95 percent confidence interval, 1.9 to 37.6). The benefit of fluconazole was greater for the patients with 50 or fewer CD4+ cells per cubic millimeter than for the patients with higher counts. Fluconazole was also effective in preventing esophageal candidiasis (adjusted relative hazard, 5.8; 95 percent confidence interval, 1.7 to 20.0; P = 0.004) and confirmed and presumed oropharyngeal candidiasis (5.7 and 38.1 cases per 100 years of follow-up in the fluconazole and clotrimazole groups, respectively; P < 0.001). Survival was similar in the two groups.

CONCLUSIONS

Fluconazole taken prophylactically reduces the frequency of cryptococcosis, esophageal candidiasis, and superficial fungal infections in HIV-infected patients, especially those with 50 or fewer CD4+ lymphocytes per cubic millimeter, but the drug does not reduce overall mortality.

Six new candidate members of the alpha/beta twisted open-sheet family detected by sequence similarity to flavodoxin

Strong sequence similarity has been reported among WrbA (the Trp repressor-binding protein of Escherichia coli); Ycp4, a protein of unknown function from the budding yeast Saccharomyces cerevisiae; P25, the pap1-dependent protein of the fission yeast Schizosaccharomyces pombe; and the translation product of a partial cDNA sequence from rice seedling root (Oryza sativa, locus Ricr02421a; here referred to as RicR). Further homology search with the profile method indicates that all the above sequences are related to the flavodoxin family and, in turn, allows detection of the recently proposed flavodoxin-like proteins from E. coli, MioC and the hypothetical protein YihB. We discuss sequence conservation with reference to the known 3-dimensional structures of flavodoxins. Conserved sequence and hydrophobicity patterns, as well as residue-pair interaction potentials, strongly support the hypothesis that these proteins share the alpha/beta twisted open-sheet fold typical of flavodoxins, with an additional alpha/beta unit in the WrbA family. On the basis of the proposed structural homology, we discuss the details of the putative FMN-binding sites. Our analysis also suggests that the helix-turn-helix motif we identified previously in the C-terminal region of the WrbA family is unlikely to reflect a DNA-binding function of this new protein family.

Molecular mapping of the Edwards syndrome phenotype to two noncontiguous regions on chromosome 18

In an effort to identify regions on chromosome 18 that may be critical in the appearance of the Edwards syndrome phenotype, we have analyzed six patients with partial duplication of chromosome 18. Four of the patients have duplications involving the distal half of 18q (18q21.1-qter) and are very mildly affected. The remaining two patients have most of 18q (18q12.1-qter) duplicated, are severely affected, and have been diagnosed with Edwards syndrome. We have employed FISH, using DNA probes from a chromosome 18-specific library, for the precise determination of the duplicated material in each of these patients. The clinical features and the extent of the chromosomal duplication in these patients were compared with four previously reported partial trisomy 18 patients, to identify regions of chromosome 18 that may be responsible for certain clinical features of trisomy 18. The comparative analysis confirmed that there is no single region on 18q that is sufficient to produce the trisomy 18 phenotype and identified two regions on 18q that may work in conjunction to produce the Edwards syndrome phenotype. In addition, correlative analysis indicates that duplication of 18q12.3-q22.1 may be associated with more severe mental retardation in trisomy 18 individuals.

An index of symptoms for infection with human immunodeficiency virus: reliability and validity

The objective of this study was to evaluate the reliability and validity of a brief index to measure symptoms in individuals infected with human immunodeficiency virus (HIV). From an ambulatory clinic that specializes in the care of HIV-infected individuals at a university hospital in northeast Ohio, 148 randomly selected outpatients (predominantly homosexual men) with a broad spectrum of HIV disease were enrolled in a prospective, cohort study. In standard interviews, patients rated the frequency of 36 symptoms related to HIV infection on an ordinal scale from zero (never) to three (daily); these interviews were repeated and outcomes determined every 3 months for one year. Clinical data were abstracted from the medical record with a standard chart review. Using specific criteria, 12 symptoms were selected for the HIV Symptom Index: fatigue, fevers, headache, imbalance, paresthesias, memory loss, cough, nausea, diarrhea, sadness, sleep disturbance, and skin problems. The HIV Symptom score (the sum of frequency ratings for the 12 symptoms) ranged from 0 to 31 with a mean of 9.4 (+/- SD 6.6). The test-retest reliability was high (intraclass correlation coefficient = 0.92) as was the internal consistency (Cronbach's alpha = 0.79). The validity of the index was established with three observations. (1) The HIV Symptom Index makes clinical sense and includes a representative spectrum of symptoms of infection. (2) Symptom Index scores were greater in patients with more advanced disease and in patients who were functionally impaired. (3) The Index was responsive to changes in health as the disease progressed.(ABSTRACT TRUNCATED AT 250 WORDS)

Electrostatic forces contribute to interactions between trp repressor dimers

The trp repressor of Escherichia coli (TR), although generally considered to be dimeric, has been shown by fluorescence anisotropy of extrinsically labeled protein to undergo oligomerization in solution at protein concentrations in the micromolar range (Fernando, T., and C. A. Royer 1992. Biochemistry. 31:3429-3441). Providing evidence that oligomerization is an intrinsic property of TR, the present studies using chemical cross-linking, analytical ultracentrifugation, and molecular sieve chromatography demonstrate that unmodified TR dimers form higher order aggregates. Tetramers and higher order species were observed in chemical cross-linking experiments at concentrations between 1 and 40 microM. Results from analytical ultracentrifugation and gel filtration chromatography were consistent with average molecular weight values between tetramer and dimer, although no plateaus in the association were evident over the concentration ranges studied, indicating that higher order species are populated. Analytical ultracentrifugation data in presence of corepressor imply that corepressor binding destabilizes the higher order aggregates, an observation that is consistent with the earlier fluorescence work. Through the investigation of the salt and pH dependence of oligomerization, the present studies have revealed an electrostatic component to the interactions between TR dimers.

Autonomous subdomains in protein folding

Proteolytic dissection of native trp repressor and horse heart cytochrome c has been used to infer some of the steps in the folding pathways of the intact proteins. For both proteins, small fragments are capable of undergoing spontaneous noncovalent association to form subdomains with native-like secondary and/or tertiary structural features, suggesting that dissection/reassembly may be a general method to gain insight into the structures of folding intermediates. The importance of this approach is its simplicity and potential applicability to studying the folding pathways of a wide range of proteins. The proteases report on the structure and dynamics of the native state, circumventing the need for prior knowledge of the structures of folding intermediates. The observation that small fragments of proteins can associated noncovalently suggests that protein folding can be viewed as an intramolecular "recognition" process. The results imply that substantial information about protein structure and folding is encoded at the level of subdomains, and that chain connectivity has only a minor role in determining the fold.

Cocrystals of Escherichia coli trp repressor bound to an alternative operator DNA sequence

Cocrystals of a 2:1 complex of trp repressor dimers with a DNA duplex containing a single, central operator half-site sequence are described. Crystals with different morphologies grew under diverse crystallization conditions within days to weeks by hanging-drop vapor-diffusion. Twinned rods split along their longitudinal cleft produce single crystals with space group C2 and unit cell dimensions a = 112.34 A, b = 90.16 A, c = 58.65 A and beta = 113.92 degrees. The crystals diffract to 2.4 A and are thus suitable for structural analysis by X-ray diffraction. Several heavy-atom derivative cocrystals have been obtained with iodouridine-substituted DNAs.

Tandem binding in crystals of a trp repressor/operator half-site complex

The crystal structure of trp repressor tandemly bound in a 2:1 complex to a 16-base-pair palindromic DNA containing a central trp operator half-site has been determined and refined to 2.4 A resolution. Despite dramatically different DNA sequence contexts and crystallization conditions, the protein/DNA interface is essentially identical to that seen in the original trp repressor/operator complex structure. Water-mediated sequence recognition by trp repressor is likely to be related to the unusual end-on approach of the recognition helix (E), which allows sharing of the major groove by tandem dimers. The tandem complex model accounts for the mutational sensitivity of all trp operator base pairs. The structure also provides the first detailed view of the tandem interaction, revealing a key role for the amino-terminal arms.

Prenatal detection of de novo paracentric inversion 46, XX inv (14) (q22q32.1) in a normal child: report and review of the literature

We present prenatal diagnosis and follow-up examination of an individual with a de novo paracentric inversion of the long are of chromosome 14. A literature search documented 19 other cases of paracentric inversion of 14q. The outcome of each of these cases is specified together with that of this current case. Four of the 20 cases, all XY, manifested significant abnormalities with mental retardation and microcephaly present in 3 of the 4 cases; 15% (2/13) of familial cases had abnormalities and 40% (2/5) of de novo cases had abnormalities.

A noncovalent peptide complex as a model for an early folding intermediate of cytochrome c

Horse heart cytochrome c is one of a small number of proteins for which the folding pathway has been elucidated in structural detail by pulsed hydrogen exchange and NMR. Those studies indicated that a partially folded intermediate with interacting N- and C-terminal helices is formed at an early stage of folding when most of the chain is still disordered. This report describes a peptide model for this early intermediate, consisting of a noncovalent complex between a heme-containing N-terminal fragment (residues 1-38) and a synthetic peptide corresponding to the C-terminal helix (residues 87-104). Far-UV circular dichroism and proton NMR indicate that the isolated peptides are largely disordered, but when combined, they form a flexible, yet tightly bound complex with enhanced helical structure. These results emphasize the importance of interactions between marginally stable elements of secondary structure in forming tertiary subdomains in protein folding.

Analysis of trp repressor-DNA interactions using gel electrophoresis

Quantitative analysis of the DNA-binding equilibria of E. coli trp repressor by gel electrophoresis led to reevaluation of our understanding of this complex system. In this review, the data leading to controversy about the trp system are discussed, and our current understanding is presented.

Thermodynamics of ligand binding to trp repressor

The thermodynamics of L-tryptophan and operator DNA binding to the tryptophan repressor of Escherichia coli were analyzed by titration microcalorimetry and van't Hoff analysis of footprinting titrations, respectively. At 25 degrees C in 10 mM sodium phosphate, pH 7.6, and 0.1 M NaCl, the binding of L-tryptophan to the repressor is characterized by values of delta G degrees = -6.04, delta H degree = -14.7, and T delta S degree = -8.67 kcal/mol. The temperature dependence of delta H degree yields delta Cp degree = -0.46 +/- 0.08 kcal/(mol.K) per dimer. The binding is noncooperative at all temperatures studied. At 23 degrees C in 2.5 mM sodium phosphate, pH 7.6, and 25 mM NaCl, the binding of operator DNA to the repressor is characterized by values of delta G degree = -13.3 kcal/mol, delta H degree = -1.55 kcal/mol, T delta S degree = 11.8 kcal/mol, and delta Cp degree = -0.54 +/- 0.10 kcal/(mol.K). Changes in water-accessible surface areas upon binding of L-tryptophan or DNA were calculated from X-ray crystal structures. The experimentally observed delta Cp degree values were compared with delta Cp degree values calculated according to several methods based on various proposed relationships between surface area changes and heat capacity changes. Regardless of which method is used, we find poor agreement between the calorimetric results for L-tryptophan binding and the surface areas calculated from X-ray data; the direction of the discrepancy is that the X-ray data underestimate the value of delta Cp degree.(ABSTRACT TRUNCATED AT 250 WORDS)

Reversal of caldesmon binding to myosin with calcium-calmodulin or by phosphorylating caldesmon

Caldesmon, an actin-binding protein from smooth muscle and non-muscle cells, has previously been shown to bind stoichiometrically to smooth muscle myosin in an ATP-dependent manner. We now show quantitatively the effects of Ca(2+)-calmodulin and phosphorylation on the binding of caldesmon to myosin. Ca(2+)-calmodulin reduces the binding of caldesmon to myosin with the same effectiveness as it does the binding of caldesmon to actin. However, Ca(2+)-calmodulin is ineffective in antagonizing the binding of the purified myosin-binding region of caldesmon to myosin. These and other results suggest that Ca(2+)-calmodulin binding to the COOH-terminal region of caldesmon is responsible for reversal of binding to myosin. Phosphorylation of the NH2-terminal region of caldesmon by the co-purifying kinase, calmodulin-dependent protein kinase II, weakens but does not eliminate the binding of caldesmon to smooth muscle myosin. Finally, phosphorylation of smooth muscle myosin by smooth muscle myosin light chain kinase has no effect on the binding of caldesmon to myosin. Since Ca(2+)-calmodulin and phosphorylation of caldesmon weaken the binding of caldesmon to both actin and myosin, these events may be coordinately regulated.

Comparison of VNTR allele frequencies and inclusion probabilities over six populations

There is considerable debate about the methodologies used to estimate VNTR (Variable Number of Tandem Repeats) multi-locus genotype frequencies or odds of inclusion in forensic cases. To compare two of the methods in use, allele frequency distributions among six populations were compared and the effect of population heterogeneity on VNTR multi-locus genotype frequency estimation was examined. Genotype frequencies estimated from single population data were one or two orders of magnitude smaller than those estimated by picking the highest allele frequency in a group of subpopulations to estimate genotype frequencies using a ceiling principle. The average change does not appear to be very sensitive to the set of subpopulations used; four locus frequencies still give inclusion odds of one in a million or less. We think that use of the ceiling principle solves both the statistical problem engendered by subpopulation heterogeneity and the legal problem of assuming that the prepetrator and suspect belong to the same subpopulation. The counterintuitive fact of human genetic polymorphism is that it is easier to identify an individual than it is to identify the subpopulation, ethnic group or race to which that individual belongs.

Treatment of cryptosporidiosis with paromomycin. A report of five cases

Cryptosporidiosis continues to be one of the most devastating complications of the acquired immunodeficiency syndrome, causing severe, chronic diarrhea that is largely refractory to treatment. More than 60 drugs have been tried in the treatment of cryptosporidiosis, none of which have been consistently successful. We describe the successful treatment of cryptosporidiosis in five patients with acquired immunodeficiency syndrome with oral paromomycin at a dose of 1500 to 2000 mg/d. All five patients had resolution of symptoms and normalization of bowel movements, although one patient later relapsed while receiving paromomycin. Three of five patients cleared Cryptosporidium from the stool. Paromomycin is a promising therapy for cryptosporidiosis in acquired immunodeficiency syndrome and further prospective clinical trials are warranted.

Recombinant human erythropoietin in the treatment of anemia associated with human immunodeficiency virus (HIV) infection and zidovudine therapy. Overview of four clinical trials

OBJECTIVE

To assess the effect of recombinant human erythropoietin (r-HuEPO) on anemia in patients with the acquired immunodeficiency syndrome (AIDS) who are receiving zidovudine therapy.

DESIGN

Combined analysis of four 12-week, randomized, double-blind, controlled clinical trials.

SETTING

Multiple centers in the United States.

PATIENTS

Two hundred and ninety-seven anemic (hematocrit < 30%) patients with AIDS who were receiving zidovudine therapy. Of the 297 patients, 255 were evaluable for efficacy, but all patients were included in analysis of safety.

INTERVENTION

Patients were randomly assigned to receive either r-HuEPO (100 to 200 U/kg body weight) or placebo, intravenously or subcutaneously, three times per week for up to 12 weeks.

MEASUREMENTS

Changes in mean hematocrit, transfusion requirement, and quality of life.

RESULTS

Sixty-nine percent of patients had endogenous serum erythropoietin levels less than or equal to 500 IU/L, and 31% had erythropoietin levels greater than 500 IU/L. In patients with low erythropoietin levels (< or equal to 500 IU/l), r-HuEPO therapy decreased the mean number of units of blood transfused per patient when compared with placebo (3.2 units and 5.3 units, respectively; P = 0.003) and increased the mean hematocrit from the baseline level (4.6 percentage points and 0.5 percentage points, respectively; P <0.001). Overall quality of life improved in patients on r-HuEPO therapy (P = 0.13). Patients with erythropoietin levels greater than 500 IU/L showed no benefit from r-HuEPO in any outcome variable. Placebo and r-HuEPO recipients did not differ in the incidence of adverse effects or opportunistic infections.

CONCLUSION

Therapy with r-HuEPO can increase the mean hematocrit and decrease the mean transfusion requirement in anemic patients with AIDS who are receiving zidovudine and have endogenous low erythropoietin levels (< or equal to 500 IU/L). Such therapy is of no apparent benefit in patients whose endogenous erythropoietin levels are higher than 500 IU/L.

What makes information important and its influence on learning in self-directed study

This study investigated what makes text-based information important and what is its influence on learning. College students studied an expository text following their own self-directed study procedures. Data from Exp. 1 (n = 60) and Exp. 2 (n = 40) showed that information was considered important if it (a) began and ended text, (b) began a paragraph, (c) appeared at somewhat equal intervals in text, and (d) contained enumerations of concepts. Subjects recalled information that (a) began the text and (b) contained examples of enumerations. It appeared that text-based variables established what was important and this influenced learning. Implications for the selective attention hypothesis and its volume-of-attention corollary, the cycles hypothesis, and the slot-filling hypothesis are discussed.