Mutation of the Lck-binding motif of Tip enhances lymphoid cell activation by herpesvirus saimiri

The proline-rich SH3-binding (SH3B) motif of the tyrosine kinase-interacting protein (Tip) of herpesvirus saimiri (HVS) is required for binding to the cellular Src family kinase Lck. We constructed a mutant form of HVS in which prolines in the SH3B motif of Tip were altered to alanines. This mutant form of Tip was incapable of binding to Lck. The mutant virus, HVS/Tip mSH3B, retained its ability to immortalize common marmoset lymphocytes in culture. In fact, common marmoset lymphocytes immortalized by the HVS/Tip mSH3B mutant displayed increased expression of HLA-DR lymphocyte activation marker, an altered pattern of tyrosine phosphorylation, increased expression of the tyrosine kinase Lyn, and a shift in electrophoretic mobility of Lck compared to cells immortalized by wild-type HVS. Experimental infection of common marmosets resulted in fulminant lymphoma with both HVS/Tip mSH3B and wild-type HVS. However, HVS/Tip mSH3B produced greater infiltration of affected organs by proliferating lymphoid cells compared to wild-type HVS. These results demonstrate that Tip binding to Lck is not necessary for transformation and that abrogation of Tip binding to Lck alters the characteristics of transformed cells and the severity of the pathologic lesions.

Evaluation of mean skin temperature formulas by infrared thermography

To study the reliability of formulas for calculating mean skin temperature (Tsk), values were computed by 18 different techniques and were compared with the mean of 10,841 skin temperatures measured by infrared thermography. One hundred whole-body infrared thermograms were scanned in ten resting males while changing the air temperature from 40 degrees C to 4 degrees C. Local, regional average and mean skin temperatures were obtained using an image processing system. The agreement frequency, defined as the percentage of the calculated Tsk values which agreed with the corresponding infrared thermographic Tsk within +/- 0.2 degree C, ranged for with the various formulas from 7% to 80%. In many sites, the local skin temperature did not coincide with the regional average skin temperature. When the local skin temperatures which showed the highest percentage similarity to the regional average skin temperature within +/- 0.4 degree C were applied to the formula, the agreement frequency was markedly improved for all formulas. However, the agreement frequency was not affected by changing the weighting factors from specific constants to individually measured values of regional surface area. By applying the physiologically reliable accuracy range of +/- 0.2 degree C in the moderate and +/- 0.4 degree C in the cool condition, agreement frequencies of at least 95% were observed in formulas involving seven or more skin temperature measurement sites, including the hand and foot. We conclude that calculation of a reliable mean skin temperature must involve more than seven skin temperature measurement sites regardless of ambient temperature. Optimal sites for skin temperature measurement are proposed for various formulas.

Transformation of hematopoietic cells by BCR/ABL requires activation of a PI-3k/Akt-dependent pathway

The BCR/ABL oncogenic tyrosine kinase activates phosphatidylinositol 3-kinase (PI-3k) by a mechanism that requires binding of BCR/ABL to p85, the regulatory subunit of PI-3k, and an intact BCR/ABL SH2 domain. SH2 domain BCR/ABL mutants deficient in PI-3k activation failed to stimulate Akt kinase, a recently identified PI-3k downstream effector with oncogenic potential, but did activate p21 RAS and p70 S6 kinase. The PI-3k/Akt pathway is essential for BCR/ABL leukemogenesis as indicated by experiments demonstrating that wortmannin, a PI-3k specific inhibitor at low concentrations, suppressed BCR/ABL-dependent colony formation of murine marrow cells, and that a kinase-deficient Akt mutant with dominant-negative activity inhibited BCR/ABL-dependent transformation of murine bone marrow cells in vitro and suppressed leukemia development in SCID mice. In complementation assays using mouse marrow progenitor cells, the ability of transformation-defective SH2 domain BCR/ABL mutants to induce growth factor-independent colony formation and leukemia in SCID mice was markedly enhanced by expression of constitutively active Akt. In retrovirally infected mouse marrow cells, the BCR/ABL mutant lacking the SH2 domain was unable to upregulate the expression of c-Myc and Bcl-2; in contrast, expression of a constitutively active Akt mutant induced Bcl-2 and c-Myc expression, and stimulated the transcription activation function of c-Myc. Together, these data demonstrate the requirement for the BCR/ABL SH2 domain in PI-3k activation and document the essential role of the PI-3k/Akt pathway in BCR/ABL leukemogenesis.

Effect of indomethacin phonophoresis on the relief of temporomandibular joint pain

The pain-relieving effect of indomethacin phonophoresis on temporomandibular (TMJ) joint pain was evaluated in a double-blind, placebo-controlled clinical trial. Twenty subjects, who have TMJ pain, were included for this study and randomly assigned to either the experimental group (n = 10) or the control group (n = 10). Each treatment consisted of the application of ultrasound massage (1.0 MHz, 0.8 to 1.5 W/cm2 continuous output) for 15 minutes to the painful temporomandibular joint. As a conducting medium, 1% indomethacin cream was used for the experimental group and placebo cream for the control group respectively. Pre- and post-treatment pain levels and pain sensitivity were assessed with visual analogue scales (VAS) and pressure pain threshold (PPT). Mean data indicated that post-treatment VAS was significantly decreased and post-treatment PPT was significantly increased in the experimental group, not in the control group. The results of this study suggest that indomethacin phonophoresis provides significant pain relieving effect over the TMJ pain.

Enhanced downregulation of Lck-mediated signal transduction by a Y114 mutation of herpesvirus Saimiri tip

Tip of herpesvirus saimiri associates with Lck and downregulates Lck function in cellular signal transduction. In this report, we demonstrate that mutation of tyrosine 114 of Tip significantly increases Lck-binding activity. This mutant exhibits a dramatic increase in the suppression of cellular tyrosine phosphorylation and surface expression of lymphocyte antigens in comparison with wild-type Tip. In addition, the expression of TipY114 converted the transforming morphology of fibroblasts induced by oncogenic F505 Lck to a normal cellular morphology. These results further support a mechanism by which the association of Tip with Lck negatively regulates Lck-mediated signal transduction.

Resistance to tobamoviruses in transgenic tobacco plants expressing the coat protein gene of pepper mild mottle virus (Korean isolate)

Red pepper, one of the most important vegetable crops in Korea, is severely affected by viral diseases causing 20-50% reduction in product yield. A pepper strain of tobacco mosaic virus (TMV-p) is the most common virus in red pepper. To study the molecular structure of the TMV-p virus, we generated cDNA clones of the viral genome. Partial sequencing of a few cDNA clones revealed that TMV-p shares a 98% identity at the nucleotide level with the Spanish isolate of pepper mild mottle virus (PMMV-s). This suggests that TMV-p should be reclassified as the Korean isolate of PMMV (PMMV-k). The coat protein (CP) gene together with the 3' untranslated region of the PMMV-k virus was obtained by reverse transcriptase-polymerase chain reaction (RT-PCR) using oligomers deduced from the sequence of PMMV-s. The sequence analysis of the CP gene and the 3' untranslated region further confirmed that PMMV-k is highly related to PMMV-s. The CP gene and the 3' untranslated region of PMMV-k were cloned into a plant expression vector and the construct was introduced into tobacco plants. The transgenic plants expressing the PMMV-k CP gene were delayed in developing systemic disease or failed to develop symptoms at all after inoculation with PMMV-k. Delay of symptoms was also observed when the plants were inoculated with TMV-OM which shares a 74% homology with PMMV-k in the amino acid sequence of the CP region. In a local lesion host, the CP expressing plants exhibited a greatly reduced number of necrotic lesions as compared to control plants after inoculation with TMV-OM. Our results show that CP-mediated viral resistance is readily applicable in the case of PMMV-k and can provide resistance to other viruses in the tobamovirus group.

Visualization of G protein-coupled receptor trafficking with the aid of the green fluorescent protein. Endocytosis and recycling of cholecystokinin receptor type A

A chimeric protein consisting of the cholecystokinin receptor type A (CCKAR) and the green fluorescent protein (GFP) was used for studying receptor localization, internalization, and recycling in live cells in real time in four different cell lines. Fusion of the C terminus of the CCKAR to the N terminus of the GFP did not alter receptor ligand binding affinity, signal transduction, or the pattern of receptor surface expression and receptor-mediated cholecystokinin (CCK) internalization. The use of a new GFP mutant with increased fluorescence allowed the continuous observation of CCKAR-GFP in stably expressing cell lines. Newly obtained biologically active fluorescent derivatives of CCK were used for simultaneous observation of receptor and ligand trafficking in CHO, NIH/3T3, and HeLa cells stably expressing the fluorescent CCKAR and in transiently transfected COS-1 cells. Receptor internalization was predominantly ligand dependent in HeLa, COS-1, and CHO cells, but was mostly constitutive in NIH/3T3 cells, suggesting the existence of cell-specific regulation of receptor internalization. The CCKAR antagonists, L-364,718 and CCK 27-32 amide potently inhibited spontaneous internalization of the receptor. The average sorting time of CCK and the receptor in the endosomes was about 25 min. The receptor recycled back to the cell membrane with an average time of 60 min. While the ligands sorted to lysosomes, no receptor molecules could be detected there, and no receptor degradation was observed during recycling. These results demonstrate the usefulness of GFP tagging for real time imaging of G protein-coupled receptor trafficking in living cells and suggest that this technique may be successfully applied to the study of the regulation and trafficking mechanisms of other receptors.

Decreased immunoglobulin deposition in tumors and increased immature B cells in p53-null mice

Recent studies have hinted that there may be a relationship between p53 and the immune response. In preliminary experiments, we found significantly decreased levels of immunoglobulin deposition in 13 of 16 p53-null tumors compared with 2 of 17 tumors derived from p53 +/- mice. We further explored the effect of p53 on B-cell development and function. p53-null mice contained more splenic white pulp and more immature B cells in the bone marrow compared with p53 +/- mice. p53-null B cells were hyperresponsive to proliferative challenge but were not more resistant to signal-induced apoptosis. Several p53 DNA-binding sites were localized to the regulatory regions of immunoglobulin heavy and light chain genes, including the KII site, which serves as an enhancer for rearrangement of the mouse kappa chain J cluster genes. Levels of p53 protein and the kappa chain sterile transcript increased after exposure of pre-B cells to the DNA damaging agents etoposide and Adriamycin. Our observations suggest that p53 may be involved in B-cell maturation and may relay certain stress signals to affect B-cell function.

Structure of the CAC1 gene and in situ characterization of its expression. The Arabidopsis thaliana gene coding for the biotin-containing subunit of the plastidic acetyl-coenzyme A carboxylase

The CAC1 gene of Arabidopsis thaliana that codes for the biotin carboxyl-carrier subunit of the heteromeric acetyl-coenzyme A carboxylase was isolated and sequenced. CAC1 is a single-copy gene interrupted by six introns. Subcellular immunogold labeling indicates that the biotin carboxyl-carrier subunit is localized in the stroma of the plastids and chloroplasts. The CAC1 mRNA accumulates throughout developing embryos and ovules of siliques at a time of rapid growth and oil accumulation (7 d after flowering), but is present at much lower levels in wall cells and central septal cells of the silique. Immunolocalization studies show that the pattern of accumulation of the biotin carboxyl-carrier subunit within the siliques and leaves is similar to that of the CAC1 mRNA. These observations indicate that the cellular pattern of biotin carboxyl-carrier protein accumulation in the developing silique may be determined by the transcriptional activity of the CAC1 gene.

Effect of physical exercise on renal response to head-out water immersion

Head-out water immersion (HOI) induces various renal functional changes, such as diuresis, natriuresis, and kaliuresis. The present study was undertaken 1) to characterize the renal response to HOI in Koreans who routinely ingest high salt diet and 2) to evaluate the impact of exercise on the renal response to HOI. Six healthy male subjects (average Na+ intake of 232 mEq.day-1) were immersed upto the neck in 34.5 degrees C water and rested in a seated position or exercised on a bicycle ergometer for 3 hours. In resting subjects, we observed a reversible increase in urine flow and a decrease in urine osmolality, with no changes in creatinine clearance. The peak urine flow observed during the second hour of immersion was 4-fold greater than the pre-immersion level. The excretion of total osmotic substances rose progressively during the 3-hour immersion, which was accompanied by a similar change in Na+ excretion. The K+ excretion was slightly elevated. The major component of the immersion diuresis was a water diuresis in the early phase and an osmotic diuresis in the late phase of immersion. In exercising subjects, the diuretic and natriuretic responses to HOI were attenuated and the kaliuretic response was potentiated. Blood hemoglobin concentration and plasma levels of renin, ADH, and aldosterone decreased during immersion-rest, but they remained unchanged or increased during immersion-exercise. These results suggest that 1) the cardiac mechanoreceptor-mediated renal responses to HOI are not changed by chronic high salt diet, and 2) excessive urinary sodium and water losses are prevented by exercise during immersion.

E47 activates the Ig-heavy chain and TdT loci in non-B cells

The E2A proteins, E12 and E47, are basic helix-loop-helix (bHLH) proteins essential for the B-cell lineage. Initially identified as immunoglobulin enhancer-binding proteins, they have also been shown to activate immunoglobulin enhancer-based reporters in transient transfection assays. Here, we examine the relationship between E2A DNA binding activity and activation of the endogenous, chromosomal immunoglobulin heavy chain (IgH) locus. Using sterile I(mu) transcription as an indicator of IgH enhancer activity, we see a direct correlation between E2A DNA binding activity and I(mu) transcription in stable BxT hybrids. We also observe a 1000-fold stimulation of endogenous I(mu) transcription in fibroblasts that express high levels of E47 and less stimulation in cells that express E12. By contrast, none of the other IgH enhancer-binding proteins tested (E2-2, Pu.1, Oct-2, OCA-B, TFE3 and USF) were able to activate I(mu) transcription. E47 overexpression also resulted in transcriptional activation of the endogenous gene encoding TdT, indicating that it, too, is a target of E2A proteins early in the B-cell lineage. Our results indicate that E2A proteins have the distinctive property of activating silent, chromatin-embedded B-cell-specific genes, underscoring their crucial role in B-cell development.

Thermal balance of man in water: prediction of deep body temperature change

Changes in rectal temperature and metabolic rate were continuously monitored in men immersed in water at 15, 20, 25, 30, and 35 degrees C. The subjects (12 healthy male students) wore swimming suits while either resting or doing leg exercise (delta M approximately 60 kcal.h-1.m-2 approximately 70 W.m-2) for 1 h. At all water temperatures below 30 degrees C, the metabolic rate increased but the rectal temperature fell continuously, resulting in hypothermia. The rate of fall in rectal temperature (cooling rate, CR, degrees C.h-1) was inversely proportional to water temperature (Tw, degrees C) according to the equation CR = 3.818-0.109 Tw in resting subjects and CR = 3.434-0.110 Tw in exercising subjects. At a given Tw the cooling rate was greater in resting than in exercising subjects and in lean than in obese subjects. From the relationships between the cooling rate and water temperature the duration of useful activity and the survival time were predicted for resting and exercising subjects of various fatness.

A modified Coomassie blue staining of proteins in polyacrylamide gels with Bismark brown R

A rapid and sensitive protein staining method employing a mixed dye technique has been developed. Solutions of Coomassie brilliant blue R-250 (CB, 0.2%) and Bismark brown R (BBR, 0.05%) were mixed in the volume ratio of 1:0.75 for staining (final molar ratio, 4.5:1). In this staining, BBR inhibits the binding of CB to gel matrix by forming ion-pairing complex with excess CB; therefore, it reduces staining/destaining times and also enhances the staining effect of CB on protein band. As a result, the mixed dye staining enables complete staining/destaining within 20/25 min and detection of up to 25 ng of bovine serum albumin.

Molecular cloning and characterization of the cDNA coding for the biotin-containing subunit of the chloroplastic acetyl-coenzyme A carboxylase

We report the molecular cloning and sequence of the cDNA coding for the biotin-containing subunit of the chloroplastic acetylcoenzyme A (CoA) carboxylase (ACCase) of Arabidopsis thaliana (CAC1). The 3' end of the CAC1 sequence, coding for a peptide of 94 amino acids, which includes a putative biotinylation motif, was expressed in Escherichia coli as a glutathione-S-transferase (GST) fusion protein. The resulting GST-CAC1 fusion protein was biotinylated in vivo, indicating that CAC1 codes for a biotin-containing protein. Antibodies generated to the GST-CAC1 protein reacted solely with the 38-kD biotin-containing polypeptide of Arabidopsis. Furthermore, these antibodies inhibited ACCase activity in extracts from Arabidopsis leaves. The deduced amino acid sequence of CAC1 has an apparent N-terminal chloroplast-targeting transit peptide. The CAC1 protein is coded by a single Arabidopsis gene, and its mRNA accumulates to the highest levels in organs that are undergoing rapid growth. The amino acid sequence of the CAC1 protein is most similar to the biotin carboxyl-carrier protein component of eubacterial ACCases. These characterizations identify CAC1 as the biotin-containing subunit of the plastidic, heteromeric ACCase of Arabidopsis. The results support the ancient origin of the two structurally distinct ACCases of plants.

Intranuclear post-transcriptional down-regulation responsible for loss of a keratin differentiation marker in tumour progression

Apparent loss of differentiation markers characterizes advanced malignant neoplasms. Post-transcriptional down-regulation of keratin message to levels undetectable with a partial cDNA probe to rat keratin K5 had been observed in anaplastic cells (T952/F7) derived from benign keratin-producing cells (A5P/B10) (1). The entire fifth introns of both the K5 and K6 genes were generated from rat genomic DNA by PCR to define expression of these closely related proteins. Sequencing of the PCR products revealed 84% homology in the K5 and K6 exon regions included, but absence of any homology in the introns. Active transcription of K5 could be demonstrated in the anaplastic cells with reverse transcription of nuclear RNA (RTn-PCR) by the presence of PCR-generated products confirmed by sequencing as unspliced and spliced transcripts of rat K5. In situ hybridization with ssDNA probes for the spliced message from this region of the K5 gene demonstrated a punctuate distribution in the cytoplasm of the benign cells and absence of any detectable message in the anaplastic derivatives, ssDNA probes for the unspliced transcript containing intron 5 and the same flanking exon sequences as the spliced probe detected transcription of hnRNA in the anaplastic cells as discrete signals confined to the nuclear compartment. These results show that failure to express mRNA for a differentiation marker in the cytoplasm of anaplastic cells can be due to a mechanism operating in the nuclear compartment after gene transcription and indicate that the mechanism functions shortly after splicing of the transcript.

Modular structural elements in the replication origin region of Tetrahymena rDNA

Computer analyses of the DNA replication origin region in the amplified rRNA genes of Tetrahymena thermophila identified a potential initiation zone in the 5'NTS [Dobbs, Shaiu and Benbow (1994), Nucleic Acids Res. 22, 2479-2489]. This region consists of a putative DNA unwinding element (DUE) aligned with predicted bent DNA segments, nuclear matrix or scaffold associated region (MAR/SAR) consensus sequences, and other common modular sequence elements previously shown to be clustered in eukaryotic chromosomal origin regions. In this study, two mung bean nuclease-hypersensitive sites in super-coiled plasmid DNA were localized within the major DUE-like element predicted by thermodynamic analyses. Three restriction fragments of the 5'NTS region predicted to contain bent DNA segments exhibited anomalous migration characteristic of bent DNA during electrophoresis on polyacrylamide gels. Restriction fragments containing the 5'NTS region bound Tetrahymena nuclear matrices in an in vitro binding assay, consistent with an association of the replication origin region with the nuclear matrix in vivo. The direct demonstration in a protozoan origin region of elements previously identified in Drosophila, chick and mammalian origin regions suggests that clusters of modular structural elements may be a conserved feature of eukaryotic chromosomal origins of replication.

Cloning of the 3'-terminal region encoding movement and coat proteins of a Korean isolate of odontoglossum ringspot virus

The 3'-terminal 1855 nucleotides (nts) of a Korean isolate of odontoglossum ringspot tobamovirus (ORSV-Cy) were cloned and sequenced. The sequence contained two open reading frames, which encode the cell-to-cell movement protein (MP) and coat protein genes, and are 912 nts and 477 nts long, respectively. The MP gene contained a conserved sequence motif of tobamoviruses and putative assembly origin of the viral RNA locating between 1117 nts and 1292 nts from the 3'-end. The 3' untranslated region (UTR) of the virus comprises 414 nts, includes nine pseudoknots and a tRNA-like structure domain containing aminoacyl acceptor arm and the anticodon hairpin loop coding for histidine.

Increasing intracellular concentrations of thymosin beta 4 in PtK2 cells: effects on stress fibers, cytokinesis, and cell spreading

Thymosin beta 4 (T beta 4) binds to G-actin in vitro and inhibits actin polymerization. We studied the effects of increasing T beta 4 concentration within living PtK2 cells, comparing its effects on the disassembly of stress fibers and membrane-associated actin with its ability to inhibit cytokinesis and cell spreading after mitosis. We chose PtK2 cells for the study because these cells have many striking actin bundles in both stress fibers and cleavage furrows. They also have prominent concentrations of membrane-associated actin and remain flattened during mitosis. We have found that PtK2 cells contain an endogenous homologue of T beta 4 at a concentration (approximately 28 microM) sufficient to complex a third or more of the cell's unpolymerized actin. Intracellular T beta 4 concentrations were increased by three different methods: 1) microinjection of an RSV vector containing a cDNA for T beta 4; 2) transfection with the same vector; and 3) microinjection of purified T beta 4 protein. The plasmid coding for T beta 4 was microinjected into PtK2 cells together with fluorescently labeled alpha-actinin as a reporter molecule. Immediately after microinjection fluorescently labeled alpha-actinin was detected in a periodic pattern along the stress fibers just as in control cells injected solely with the reporter. However, after 13 h, cells microinjected with reporter and plasmid showed marked disassembly of the fiber bundles. PtK2 cells transfected with this RSV vector for 2-3 days showed disassembly of stress fibers as detected by rhodamine-phalloidin staining; in these cells the membrane actin was also greatly diminished or absent and the border of the cells was markedly retracted. Microinjection of pure T beta 4 protein into interphase PtK2 cells induced disassembly of the stress fibers within 10 min, while membrane actin appeared only somewhat reduced. If the PtK2 cells were mitotic, similar microinjection of pure thymosin beta 4 protein at times from early prophase to metaphase resulted in an unusual pattern of delayed cytokinesis. Furrowing occurred but at a much slower rate than in controls and the amount of actin in the cleavage furrow was greatly reduced. The cells constricted to apparent completion, but after about 30 min the furrow regressed, forming a binucleate cell, much as after treatment with cytochalasin B or D. Postcytokinesis spreading of these T beta 4-injected cells was often inhibited. These experiments suggest that an insufficient number of actin filaments prolongs the contractile phase of cytokinesis and abolishes the final sealing process.

Ontogeny of protein kinase C in the rat hippocampus: an autoradiographic study with [3H]phorbol 12,13-dibutyrate

The ontogeny of protein kinase C (PKC) in the hippocampus was studied in 1-week-, 4-week-, and 3-month-old Wistar rats with in vitro receptor autoradiography using [3H]phorbol 12,13-dibutyrate ([3H]PDBu). The developmental pattern of [3H]PDBu binding varied within hippocampal subregions. [3H]PDBu binding in stratum oriens of the CA1 and CA3 sectors and stratum lucidum of the CA3 sector increased to adult levels by 4 weeks. In strata moleculare and granulosum of the dentate gyrus, the binding reached peak values at 4 weeks but declined at 3 months. Interestingly, in stratum lacunosum-moleculare of the CA1 sector, the [3H]PDBu binding activity was the highest at 1 week. There were constant binding activities in stratum radiatum of the CA1 and CA3 sectors and the dentate hilus during the postnatal development. These findings may provide evidence that PKC has a distinct role in different subregions of the hippocampus during postnatal development.

Renal response to head-out water immersion in Korean women divers

Head-out water immersion (HOI) induces a profound diuresis and natriuresis, which may endanger the body fluid balance of breath-hold divers during prolonged diving work. To investigate if adaptation is acquired by professional breath-hold divers, we have evaluated renal responses to 3-h HOI in 5 Korean women divers (Amas) and 11 nondiving housewives (controls). In both control and diver groups, the average urine flow during 3-h immersion was four times greater and Na+ excretion was 70%-80% greater than the pre-immersion value [urine flow: 3.7 (SD 1.0) ml.min-1 vs 0.9 (SD 0.4), P < 0.001, in controls; 4.3 (SD 0.9) vs 1.1 (SD 0.4), P < 0.001, in divers; Na+ excretion: 270 (SD 176) mumol.min-1 vs 161 (SD 84), P < 0.025, in controls; 303 (SD 31) vs 164 (SD 62), P < 0.005, in divers]. In all cases, the values for a given period were not significantly different between the two groups. The plasma concentrations of Na+ and osmolality, and renal clearance of creatinine did not change significantly. However, the osmolal clearance increased [from 2.0 (SD 0.8) ml.min-1 to 2.8 (SD 0.7), P < 0.05, in the controls; from 2.2 (SD 0.4) to 2.6 (SD 0.4), P < 0.05, in the divers] and free water clearance changed from negative to positive values [from -1.1 (SD 0.5) ml.min-1 to 1.2 (SD 0.3), P < 0.005, in the controls; from -1.2 (SD 0.4) to 1.6 (SD 1.1), P < 0.01, in the divers] during immersion, again the pattern of change being similar in the two groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Detection of proteins on polyacrylamide gels using calconcarboxylic acid

We describe here a protein staining method in polyacrylamide gels with a new staining dye, 1-(2-hydroxy-4-sulfo-1-naphthylazo)-2-hydroxy-3-naphthoic acid (calconcarboxylic acid, NN). This method can be performed by both simultaneous and postelectrophoretic staining techniques. Simultaneous staining using 0.01% of NN in upper reservoir buffer eliminates the poststaining step, and thus enables detection of the proteins more rapidly and simply. In poststaining, proteins can be stained by a 30-min incubation of a polyacrylamide gel in 40% methanol/7% acetic acid solution of 0.05% NN. These techniques produced protein staining patterns identical to the ones obtained by the conventional poststaining with Coomassie blue R-250 (CB). NN staining can detect as little as 10 ng of bovine serum albumin by poststaining and 25 ng by simultaneous staining, compared to 50 ng detectable by CB poststaining. In comparing the relationship between band intensity and amount of protein, NN staining gave better linearity than CB staining.

Inhibition of human immunodeficiency virus-1 protease by a C2-symmetric phosphinate. Synthesis and crystallographic analysis

The human immunodeficiency virus type 1 (HIV-1) protease is a potential target of acquired immune deficiency syndrome (AIDS) therapy. A highly potent, perfectly symmetrical phosphinate inhibitor of this enzyme, SB204144, has been synthesized. It is a competitive inhibitor of HIV-1 protease, with an apparent inhibition constant of 2.8 nM at pH 6.0. The three-dimensional structure of SB204144 bound to the enzyme has been determined at 2.3-A resolution by X-ray diffraction techniques and refined to a crystallographic discrepancy factor, R (= sigma parallel F(o) magnitude to - Fc parallel/sigma magnitude of F(o)), of 0.178. The inhibitor is held in the enzyme active site by a set of hydrophobic and hydrophilic interactions, including an interaction between Arg8 and the center of the terminal benzene rings of the inhibitor. The phosphinate establishes a novel interaction with the two catalytic aspartates; each oxygen of the central phosphinic acid moiety interacts with a single oxygen of one aspartic acid, establishing a very short (2.2-2.4 A) oxygen-oxygen contact. As with the structures of penicillopepsin bound to phosphinate and phosphonate inhibitors [Fraser, M. E., Strynadka, N. C., Bartlett, P. A., Hanson, J. E., & James, M. N. (1992) Biochemistry 31, 5201-14], we interpret this short distance and the stereochemical environment of each pair of oxygens in terms of a hydrogen bond that has a symmetric single-well potential energy curve with the proton located midway between the two atoms.(ABSTRACT TRUNCATED AT 250 WORDS)

Increase of heat loss by wearing gloves and boots in wet-suited subjects working in cold water

The effect of wearing protective gloves and boots on thermal exchanges of wet-suited subjects in cold water was evaluated. Four male subjects, clad in 5 mm-thick neoprene wet suits and either with or without neoprene gloves (5 mm-thick) and boots (5 mm-thick) were immersed up to the neck in water at 13 degrees C while resting for 3 h or exercising for 2 h. Rectal temperature, oxygen consumption and local (chest, back, upper arm, thigh, forearm, calf, hand and foot) skin temperatures, skin heat fluxes and thermal insulations were determined during immersion. The rectal temperature was not different between conditions but the skin temperature was significantly higher with gloves and boots, especially at the distal extremities (forearm, calf, hand and foot). Consequently, the core-to-skin temperature gradient was reduced by wearing gloves and boots, but the skin heat loss was markedly increased. Calculated overall body insulation was significantly lowered by wearing gloves and boots. These results indicate that in wet-suited subjects resting or exercising in cold (13 degrees C) water, gloves and boots increase the overall rate of body heat loss. Attenuation of cold-induced vasoconstriction is proposed as the mechanism.

G-actin pool and actin messenger RNA during development of the apical processes of the retinal pigment epithelial cells of the chick

It has been suggested that during development an increase in the pool of G-actin may drive the elongation of actin-containing processes which occur in several types of epithelial cells. The apical processes of chick retinal pigment epithelial (RPE) cells elongate during the last 7 days of embryonic life (E15-E21) reaching lengths of 20 microns or more by hatching (E21). F-actin bundles form the cores of these processes. We followed the elongation by measuring F-actin in the cells and cytoskeletons. In correlation with this, we studied by DNAse assay the levels of monomeric actin in supernatants of cell extracts from E13, before elongation starts, to E17, when elongation is well underway. Total F-actin increased 1.9-fold over this time period and cytoskeletal actin increased 2.5-fold. In supernatants from extracts of E13 RPE the monomeric actin concentration was 51 +/- 0.5 micrograms/ml. From estimates of cell volume we calculated the cellular monomeric actin concentration at E13 as at least 510 micrograms/ml (13 microM). We compared this with monomeric actin levels in extracts from RPE at E15 and E17. Allowing for the estimated increase in cell volume, our data show little overall change in cellular monomeric actin concentration at these times. Changes in the level of actin mRNA were measured over the same time period. Normalized to equal RNA, we found a twofold increase in beta actin mRNA and a four- to fivefold increase in message for gamma actin at E17 as compared to E13. In summary, we show that (1) there is a substantial pool of monomeric actin in these epithelial cells before elongation starts; (2) process elongation is not associated with a significant change in the size of this pool; and (3) process elongation is associated with a significant increase in actin mRNA.