The human homolog of Saccharomyces cerevisiae CDC45

In budding yeast Saccharomyces cerevisiae CDC45 is an essential gene required for initiation of DNA replication. A structurally related protein Tsd2 is necessary for DNA replication in Ustilago maydis. We have identified and cloned the gene for a human protein homologous to the fungal proteins. The human gene CDC45L is 30 kilobases long and contains 15 introns. The 16 exons encode a protein of 566 amino acids. The human protein is 52 and 49.5% similar to CDC45p and Tsd2p, respectively. The level of CDC45L mRNA peaks at G1-S transition, but total protein amount remains constant throughout the cell cycle. Consistent with a role of CDC45L protein in the initiation of DNA replication it co-immunoprecipitates from cell extracts with a putative replication initiator protein, human ORC2L. In addition, subcellular fractionation indicates that the association of the protein with the nuclear fraction becomes labile as S phase progresses. The CDC45L gene is located to chromosome 22q11.2 region by cytogenetics and by fluorescence in situ hybridization. This region, known as DiGeorge syndrome critical region, is a minimal area of 2 megabases, which is consistently deleted in DiGeorge syndrome and related disorders. The syndrome is marked by parathyroid hypoplasia, thymic aplasia, or hypoplasia and congenital cardiac abnormalities. CDC45L is the first gene mapped to the DiGeorge syndrome critical region interval whose loss may negatively affect cell proliferation.

Isolated myoepithelial duodenal hamartoma presenting with upper gastrointestinal bleed

Myoepithelial duodenal hamartoma, a rare lesion, usually occurs as a part of diffuse gastrointestinal tract polyposis in Peutz-Jegher's and Gardner's syndromes. Solitary duodenal hamartoma in the absence of other manifestations of polyposis syndrome is rare. We report one such patient presenting with massive gastrointestinal bleeding.

Human CDC6/Cdc18 associates with Orc1 and cyclin-cdk and is selectively eliminated from the nucleus at the onset of S phase

In a two-hybrid screen for proteins that interact with human PCNA, we identified and cloned a human protein (hCdc18) homologous to yeast CDC6/Cdc18 and human Orc1. Unlike yeast, in which the rapid and total destruction of CDC6/Cdc18 protein in S phase is a central feature of DNA replication, the total level of the human protein is unchanged throughout the cell cycle. Epitope-tagged protein is nuclear in G1 and cytoplasmic in S-phase cells, suggesting that DNA replication may be regulated by either the translocation of this protein between the nucleus and the cytoplasm or the selective degradation of the protein in the nucleus. Mutation of the only nuclear localization signal of this protein does not alter its nuclear localization, implying that the protein is translocated to the nucleus through its association with other nuclear proteins. Rapid elimination of the nuclear pool of this protein after the onset of DNA replication and its association with human Orc1 protein and cyclin-cdks supports its identification as human CDC6/Cdc18 protein.

The evolutionarily conserved zinc finger motif in the largest subunit of human replication protein A is required for DNA replication and mismatch repair but not for nucleotide excision repair

The largest subunit of the replication protein A (RPA) contains an evolutionarily conserved zinc finger motif that lies outside of the domains required for binding to single-stranded DNA or forming the RPA holocomplex. In previous studies, we showed that a point mutation in this motif (RPAm) cannot support SV40 DNA replication. We have now investigated the role of this motif in several steps of DNA replication and in two DNA repair pathways. RPAm associates with T antigen, assists the unwinding of double-stranded DNA at an origin of replication, stimulates DNA polymerases alpha and delta, and supports the formation of the initial short Okazaki fragments. However, the synthesis of a leading strand and later Okazaki fragments is impaired. In contrast, RPAm can function well during the incision step of nucleotide excision repair and in a full repair synthesis reaction, with either UV-damaged or cisplatin-adducted DNA. Two deletion mutants of the Rpa1 subunit (eliminating amino acids 1-278 or 222-411) were not functional in nucleotide excision repair. We report for the first time that wild type RPA is required for a mismatch repair reaction in vitro. Neither the deletion mutants nor RPAm can support this reaction. Therefore, the zinc finger of the largest subunit of RPA is required for a function that is essential for DNA replication and mismatch repair but not for nucleotide excision repair.

Promoting adherence to an electronic home spirometry research program after lung transplantation

Adherence with any long-term treatment or research protocol is a challenge; this has been found to be the case with lung transplant recipients participating in an electronic home spirometry research program. Because the purpose of the current study is to develop a system for detecting early infection and rejection in lung transplant recipients, regular transmission of data by subjects to the research data center is imperative to the success of the study. Various adherence-promoting strategies have been developed by the research team to increase subject adherence with the program. An increased adherence rate has been reported after implementation of these various strategies, yet work remains to promote continually regular participation in the program by all subjects. It remains a challenge for the research team to devise creative and effective strategies for increasing adherence to regular spirometer use to provide data to develop a computerized system for detecting early infection and rejection of transplanted lung tissue.

Efficacy of oral hyposmolar glucose-based and rice-based oral rehydration salt solutions in the treatment of cholera in adults

BACKGROUND

Recent animal experiments and clinical trials have shown that both osmolarity and rice as the organic components are important factors for net intestinal absorption of an oral rehydration salt solution.

METHODS

In a controlled clinical trial 123 male adult patients with severe cholera, after initial rehydration with intravenous Ringer's lactate solution, were randomly assigned to receive one of the four oral rehydration salt solutions: WHO ORS, ORS containing 70 mmol/l Na+ and 16.2 g/l glucose, rice ORS containing 50 g/l rice and 90 mmol/l Na+, and rice ORS containing 50 g/l rice and 70 mmol/l Na+. All patients received 300 mg of doxycycline as a single dose.

RESULTS

Patients who received rice-low-sodium ORS subsequently had lower (P < 0.05) stool output, ORS consumption, and diarrhoea duration than the other three ORS groups.

CONCLUSIONS

We conclude that rice-based low-sodium ORS is superior for treating adult cholera.

Initiation of DNA replication in eukaryotic cells

The recent identification of proteins that recognize origins of DNA replication and control the initiation of eukaryotic DNA replication has provided critical molecular tools to dissect this process. Dynamic changes in the assembly and disassembly of protein complexes at origins are important for the initiation of DNA replication and occur throughout the cell cycle. Herein, we review the key proteins required for the initiation of DNA replication, their involvement in the protein complex assembly at replication origins, and how the cell cycle machinery regulates this process.

The evolutionarily conserved zinc finger motif in the largest subunit of human replication protein A is required for DNA replication and mismatch repair but not for nucleotide excision repair

The largest subunit of the replication protein A (RPA) contains an evolutionarily conserved zinc finger motif that lies outside of the domains required for binding to single-stranded DNA or forming the RPA holocomplex. In previous studies, we showed that a point mutation in this motif (RPAm) cannot support SV40 DNA replication. We have now investigated the role of this motif in several steps of DNA replication and in two DNA repair pathways. RPAm associates with T antigen, assists the unwinding of double-stranded DNA at an origin of replication, stimulates DNA polymerases alpha and delta, and supports the formation of the initial short Okazaki fragments. However, the synthesis of a leading strand and later Okazaki fragments is impaired. In contrast, RPAm can function well during the incision step of nucleotide excision repair and in a full repair synthesis reaction, with either UV-damaged or cisplatin-adducted DNA. Two deletion mutants of the Rpa1 subunit (eliminating amino acids 1-278 or 222-411) were not functional in nucleotide excision repair. We report for the first time that wild type RPA is required for a mismatch repair reaction in vitro. Neither the deletion mutants nor RPAm can support this reaction. Therefore, the zinc finger of the largest subunit of RPA is required for a function that is essential for DNA replication and mismatch repair but not for nucleotide excision repair.

Molecular motor and electrokinetic contributions to outer hair cell electromotility

The outer hair cell of the inner ear is believed to be responsible for the high sensitivity and selectivity of mammalian hearing. Molecular motors are generally believed to cause the electrically-driven length change (electromotility) of the outer hair cell. It has been suggested that electrokinetic effects might also play a significant role in electromotility, along with the molecular motors. This paper describes a new technique that can be used to experimentally determine the percentage of the electromotile response that is caused by electrokinetic effects. The technique is based on the novel idea that molecular motor activity cannot in itself generate a net force on the cell, but that electrokinetic effects can. Our method is the first that can separate molecular motor behavior from electrokinetic behavior, during experiments on the outer hair cell.

Identification of HsORC4, a member of the human origin of replication recognition complex

A new member of human origin recognition complex (ORC) has been cloned and identified as the human homologue of Saccharomyces cerevisiae ORC4. HsORC4 is a 45-kDa protein encoded by a 2.2-kilobase mRNA whose amino acid sequence is 29% identical to ScORC4. HsORC4 has a putative nucleotide triphosphate binding motif that is not seen in ScORC4. HsORC4P also reveals an unsuspected homology to the ORC1-Cdc18 family of proteins. HsORC4 mRNA expression and protein levels remain constant through the cell cycle. HsORC4P is coimmunoprecipitated from cell extracts with another subunit of human ORC, HsORC2P, consistent with it being a part of the putative human origin recognition complex.

p21CIP1 and Cdc25A: competition between an inhibitor and an activator of cyclin-dependent kinases

Cdc25A, a phosphatase essential for G1-S transition, associates with, dephosphorylates, and activates the cell cycle kinase cyclin E-cdk2. p21CIP1 and p27 are cyclin-dependent kinase (cdk) inhibitors induced by growth-suppressive signals such as p53 and transforming growth factor beta (TGF-beta). We have identified a cyclin binding motif near the N terminus of Cdc25A that is similar to the cyclin binding Cy (or RR LFG) motif of the p21CIP1 family of cdk inhibitors and separate from the catalytic domain. Mutations in this motif disrupt the association of Cdc25A with cyclin E- or cyclin A-cdk2 in vitro and in vivo and selectively interfere with the dephosphorylation of cyclin E-cdk2. A peptide based on the Cy motif of p21 competitively disrupts the association of Cdc25A with cyclin-cdks and inhibits the dephosphorylation of the kinase. p21 inhibits Cdc25A-cyclin-cdk2 association and the dephosphorylation of cdk2. Conversely, Cdc25A, which is itself an oncogene up-regulated by the Myc oncogene, associates with cyclin-cdk and protects it from inhibition by p21. Cdc25A also protects DNA replication in Xenopus egg extracts from inhibition by p21. These results describe a mechanism by which the Myc- or Cdc25A-induced oncogenic and p53- or TGF-beta-induced growth-suppressive pathways counterbalance each other by competing for cyclin-cdks.

Roles of the structure and orientation of ligands and ligand mimics inside the ligand-binding pocket of the vitamin D-binding protein

1alpha,25-Dihydroxyvitamin D3, the vitamin D hormone, manifests its diverse biological properties by specifically binding to the vitamin D sterol-binding pockets of vitamin D-binding protein (DBP) and vitamin D receptor. In the past, several affinity, photoaffinity, and chemical modification studies have been carried out to probe the vitamin D sterol-binding pocket of DBP and to evaluate the relationship between the structure of this pocket and the functions of the protein. In the present study, we examined the steric requirements inside this pocket by considering conformational structures of various bromoacetate derivatives of 25-hydroxyvitamin D3 and 1alpha,25-dihydroxyvitamin D3 and their abilities to covalently and specifically modify this pocket. We observed that, although 25-hydroxyvitamin D3 3beta-bromoacetate (25-OH-D3-3-BE), 1alpha,25-dihydroxyvitamin D3 3beta-bromoacetate [1alpha,25(OH)2D3-3-BE], 1alpha,25-dihydroxyvitamin D3 1alpha-bromoacetate [1alpha,25(OH)2D3-1-BE], and 1alpha,25-dihydroxyvitamin D3 1alpha,3beta-dibromoacetate [1alpha,25(OH)2D3-1,3-di-BE] bound DBP in a specific manner, only [3H]-25-OH-D3-3-BE and [3H]-1alpha,25(OH)2D3-3-BE affinity labeled the protein. BNPS-skatole cleavages of [3H]-25-OH-D3-3-BE- and 3H-1alpha,25(OH)2D3-3-BE-labeled DBP samples produced the same labeled peptide (N-terminal), demonstrating the specificity of labeling by these analogs. Energy-minimized conformational structures of these bromoacetate derivatives indicated significant changes in the A-ring conformations of these analogs. These structural changes were invoked to explain the inability of [3H]-1alpha,25(OH)2D3-1-BE and [3H]-1alpha,25(OH)2D3-1,3-di-BE to affinity label DBP. Overall, these studies suggested that the vitamin D sterol-binding pocket in DBP is sterically quite restrictive. This information could be potentially important in designing future vitamin D-based drugs for several diseases.

p21Cip1/Waf1 disrupts the recruitment of human Fen1 by proliferating-cell nuclear antigen into the DNA replication complex

Fen1 or maturation factor 1 is a 5'-3' exonuclease essential for the degradation of the RNA primer-DNA junctions at the 5' ends of immature Okazaki fragments prior to their ligation into a continuous DNA strand. The gene is also necessary for repair of damaged DNA in yeast. We report that human proliferating-cell nuclear antigen (PCNA) associates with human Fen1 with a Kd of 60 nM and an apparent stoichiometry of three Fen1 molecules per PCNA trimer. The Fen1-PCNA association is seen in cell extracts without overexpression of either partner and is mediated by a basic region at the C terminus of Fen1. Therefore, the polymerase delta-PCNA-Fen1 complex has all the activities associated with prokaryotic DNA polymerases involved in replication: 5'-3' polymerase, 3'-5' exonuclease, and 5'-3' exonuclease. Although p21, a regulatory protein induced by p53 in response to DNA damage, interacts with PCNA with a comparable Kd (10 nM) and a stoichiometry of three molecules of p21 per PCNA trimer, a p21-PCNA-Fen1 complex is not formed. This mutually exclusive interaction suggests that the conformation of a PCNA trimer switches such that it can either bind p21 or Fen1. Furthermore, overexpression of p21 can disrupt Fen1-PCNA interaction in vivo. Therefore, besides interfering with the processivity of polymerase delta-PCNA, p21 also uncouples Fen1 from the PCNA scaffold.

Expression of cell cycle-regulated proteins in prostate cancer

Markers of cellular proliferation have proven to be useful prognostic markers in several tumor types. Recently, immunoreactivity for cyclins was found to provide an independent marker of tumor proliferation in breast cancer. In this study, we sought to determine the pattern of immunoreactivity for cyclins A, B, E, and Ki-67 in surgically resected prostate cancer and to determine their possible prognostic significance. Twenty-eight tumors of American Urological Association stages B and C were selected for study. Immunoreactivity for cyclins A and B was detected in most tumors and was present at significantly reduced levels as compared with breast cancer. Staining for cyclin E was present in four tumors and was present only in focal areas in two of the four. Such focal variation in expression of cell cycle regulators may reflect genetic instability in a tumor. Immunoreactivity for cyclins A and B was correlated with both Ki-67 index (the percentage of cells with Ki-67 immunoreactivity) and with each other. A Ki-67 index greater than 4.0 was associated with shorter time to prostate-specific antigen-detected relapse (P = 0.026). The fraction of cells staining for cyclins A and B divided by the fraction of cells staining for Ki-67 [(A+B)/K] was highly predictive of relapse, with values less than 0.50 associated with more rapid progression (P < 0.001). This latter result remained statistically significant after controlling for Gleason score by stratification. Our results suggest that immunoreactivity for markers of cellular proliferation may provide useful prognostic information in localized prostate cancer, and they need to be validated in a larger numbers of patients.

Cyclin-binding motifs are essential for the function of p21CIP1

The cyclin-dependent kinase (Cdk) inhibitor p21 is induced by the tumor suppressor p53 and is required for the G1-S block in cells with DNA damage. We report that there are two copies of a cyclin-binding motif in p21, Cy1 and Cy2, which interact with the cyclins independently of Cdk2. The cyclin-binding motifs of p21 are required for optimum inhibition of cyclin-Cdk kinases in vitro and for growth suppression in vivo. Peptides containing only the Cy1 or Cy2 motif partially inhibit cyclin-Cdk kinase activity in vitro and DNA replication in Xenopus egg extracts. A monoclonal antibody which recognizes the Cy1 site of p21 specifically disrupts the association of p21 with cyclin E-Cdk2 and with cyclin D1-Cdk4 in cell extracts. Taken together, these observations suggest that the cyclin-binding motif of p21 is important for kinase inhibition and for formation of p21-cyclin-Cdk complexes in the cell. Finally, we show that the cyclin-Cdk complex is partially active if associated with only the cyclin-binding motif of p21, providing an explanation for how p21 is found associated with active cyclin-Cdk complexes in vivo. The Cy sequences may be general motifs used by Cdk inhibitors or substrates to interact with the cyclin in a cyclin-Cdk complex.

Phosphorylation of human replication protein A by the DNA-dependent protein kinase is involved in the modulation of DNA replication

The single-stranded DNA-binding protein, Replication Protein A (RPA), is a heterotrimeric complex with subunits of 70, 32 and 14 kDa involved in DNA metabolism. RPA may be a target for cellular regulation; the 32 kDa subunit (RPA32) is phosphorylated by several cellular kinases including the DNA-dependent protein kinase (DNA-PK). We have purified a mutant hRPA complex lacking amino acids 1-33 of RPA32 (rhRPA x 32delta1-33). This mutant bound ssDNA and supported DNA replication; however, rhRPA x 32delta1-33 was not phosphorylated under replication conditions or directly by DNA-PK. Proteolytic mapping revealed that all the sites phosphorylated by DNA-PK are contained on residues 1-33 of RPA32. When wild-type RPA was treated with DNA-PK and the mixture added to SV40 replication assays, DNA replication was supported. In contrast, when rhRPA x 32delta1-33 was treated with DNA-PK, DNA replication was strongly inhibited. Because untreated rhRPA x 32delta1-33 is fully functional, this suggests that the N-terminus of RPA is needed to overcome inhibitory effects of DNA-PK on other components of the DNA replication system. Thus, phosphorylation of RPA may modulate DNA replication indirectly, through interactions with other proteins whose activity is modulated by phosphorylation.

Dissection of functional domains of the human DNA replication protein complex replication protein A

Replication protein A (RPA) is a mammalian single-stranded DNA binding factor essential for DNA replication, repair, and recombination. It is composed of three subunits of 70, 34, and 13 kDa (Rpa1, Rpa2, and Rpa3, respectively). Deletion mapping of the Rpa2 subunit identified the domain required for interaction with Rpa1 and Rpa3 which does not include the N-terminal domain that is phosphorylated during S phase. Deletion mapping of Rpa1 defined three domains. The C-terminal third of the Rpa1 polypeptide binds Rpa2 which itself forms a bridge between Rpa1 and Rpa3. The N-terminal third of Rpa1 bound single-stranded DNA under low stringency conditions only (0.1 M NaCl), while a central domain binds to single-stranded DNA under both low and high stringency conditions (0.5 M NaCl). Binding to p53 requires the N-terminal third of Rpa1 with some contribution from the C-terminal third. The evolutionarily conserved putative zinc finger near the C terminus of Rpa1 was not required for binding to single-stranded DNA, Rpa2, or p53. However, all three subdomains of Rpa1 and the zinc finger were essential for supporting DNA replication in vitro. These experiments are a first step toward defining peptide components responsible for the many functions of the RPA protein complex.

Loss of transactivation and transrepression function, and not RPA binding, alters growth suppression by p53

The tumor suppressor protein p53 activates transcription from promoters with specific p53 binding elements, represses transcription from promoters without such elements and interacts with and inhibits the single-stranded DNA binding activity of the human DNA replication factor RPA. All these activities involve the N terminal 70 amino acids of p53. Dissection of the domains of p53 which bind RPA suggest that multiple sub-domains of the protein synergize to give strong RPA binding. Point-mutations in one of these sub-domains of p53 significantly diminish its ability to interact with RPA. A multimer of a peptide from p53 which includes these residues, or of a peptide from the acidic activation domain of the prototypic trans-activator protein VP16, can itself bind to RPA. Comparison of sequences of these multimeric peptides suggests that aromatic amino acids flanked by negatively charged residues are important for binding RPA. Several alleles of p53 with point mutations in the N terminal region were analysed for their relative abilities to bind RPA, activate or repress transcription, and suppress growth of p53 null SaOs2 and H1299 cells. Both mutants of p53 with decreased RPA binding suppressed cell growth as well as wild-type p53, suggesting that p53 can suppress growth without interacting with RPA. The allele that lost most of the transcription activation function also lost most of its transcription repression activity suggesting that interaction with the same basal transcription factors are involved in both functions. This same allele bound RPA well but was defective in growth suppression. Therefore, transcription activation and/or repression appear to be more important for the growth suppression function of p53 than RPA binding.

Oxygen tension profiles in isolated hamster retractor muscle at different temperatures

Oxygen tension (P0(2)) profiles within unperfused hamster retractor muscles were obtained at 25, 30, and 37 degrees by using sharpened, recessed oxygen microelectrodes. The microelectrode was driven vertically into freshly excised muscle lying on a flat, impermeable boundary inside a diffusion chamber. Intramuscular P0(2) profiles were measured as a function of electrode depth in 10-mu m steps during both inward and outward penetrations when the upper surface of the muscles was exposed to humidified gases containing 10, 21, 50, and 100% 0(2). The ratio of the 0(2) consumption (M) to the 0(2) permeability (K, Krogh diffusion coefficient = D alpha, diffusion coefficient-solubility product) was estimated by curve-fitting the experimental steady-state distribution of 0(2) through muscles to the analytic solution of the diffusion equation assuming that M obeys zero-order kinetics and K is constant, uniform, and independent of P0(2). The ratios of M/K were independent of temperature and were found to be independent of surface P0(2) and muscle thickness. The average value of M/K was 3.9 +/- 0.45 (SE; n = 30) x 10(5) mm Hg/cm(2), which is consistent with that estimated from previous measurements of M and D using different non-steady-state techniques (Bentley et aL, 1993). These results are consistent with other in vitro 0(2) consumption measurements (Sullivan and Pittman, 1984) and do not provide evidence for nonclassical respiratory activity in resting mammalian skeletal muscle.

A 39 amino acid fragment of the cell cycle regulator p21 is sufficient to bind PCNA and partially inhibit DNA replication in vivo

The cell cycle regulator p21 interacts with and inhibits the DNA replication and repair factor proliferating cell nuclear antigen (PCNA). We have defined a 39 amino acid fragment of p21 which is sufficient to bind PCNA with high affinity (Kd 10-20 nM). This peptide can inhibit DNA replication in vitro and microinjection of a GST fusion protein containing this domain inhibited S phase in vivo. Despite its high affinity for PCNA, the free 39 amino acid peptide does not have a well-defined structure, as judged from circular dichroism and nuclear magnetic resonance measurements, suggesting an induced fit mechanism for the PCNA-p21 interaction. The association of the small peptide with PCNA was thermolabile, suggesting that portions of p21 adjoining the minimal region of contact stabilize the interaction. In addition, a domain containing 67 amino acids from the N-terminus of PCNA was defined as both necessary and sufficient for binding to p21.

Influence of non-Newtonian behavior of blood on flow in an elastic artery model

Two different non-Newtonian models for blood, one a simple power law model exhibiting shear thinning viscosity, and another a generalized Maxwell model displaying both shear thinning viscosity and oscillatory flow viscoelasticity, were used along with a Newtonian model to simulate sinusoidal flow of blood in rigid and elastic straight arteries. When the spring elements were removed from the viscoelastic model resulting in a purely viscous shear thinning fluid, the predictions of flow rate and WSS were virtually unaltered. Hence, elasticity of blood does not appear to influence its flow behavior under physiological conditions in large arteries, and a purely viscous shear thinning model should be quite realistic for simulating blood flow under these conditions. When a power law model with a high shear rate Newtonian cutoff was used for sinusoidal flow simulation in elastic arteries, the mean and amplitude of the flow rate were found to be lower for a power law fluid compared to a Newtonian fluid experiencing the same pressure gradient. The wall shear stress was found to be relatively insensitive to fluid rheology but strongly dependent on vessel wall motion for flows driven by the same pressure gradient. The effect of wall motion on wall shear stress could be greatly reduced by matching flow rate rather than pressure gradient. For physiological flow simulation in the aorta, an increase in mean WSS but a reduction in peak WSS were observed for the power law model compared to a Newtonian fluid model for a matched flow rate waveform.

Evaluation of agonist-antagonist properties of nitrogen mustard and cyano derivatives of delta 8-tetrahydrocannabinol

delta 8-Tetrahydrocannabinol (delta 8-THC) is a naturally occurring cannabinoid with a characteristic pharmacological profile of in vivo effects. Previous studies have shown that modification of the structure of delta 8-THC by inclusion of a nitrogen-containing functional group alters this profile and may alkylate the cannabinoid receptor, similar to the manner in which beta-funaltrexamine (beta-FNA) alkylates the micro-opioid receptor. Two novel analogs of delta 8-THC were synthesized: a nitrogen mustard analog with a dimethylheptyl side chain (NM-delta 8-THC) and a cyano analog with a dimethylpentyl side chain (CY-delta 8-THC). Both analogs showed high affinity for brain cannabinoid receptors and when administered acutely, produced characteristic delta 9-THC-like effects in mice, including locomotor suppression, hypothermia, antinociception and catalepsy. CY-delta 8-THC shared discriminative stimulus effects with CP 55,940; for NM-delta 8-THC, these effects also occurred, but were delayed. Although both compounds attenuated the effects of delta 9-THC in the mouse behavioral tests, evaluation of potential antagonist effects of these compounds was complicated by the fact that two injections of delta 9-THC produced similar results, suggesting that acute tolerance or desensitization might account for the observations. NM-delta 8-THC, but not CY-delta 8-THC, attenuated the discriminative stimulus effects of CP 55,940 in rats several days following injection. Hence, addition of a nitrogen-containing functional group to a traditional cannabinoid structure does not eliminate agonist effects and may produce delayed attenuation of cannabinoid-induced pharmacological effects.

EXPERIENCE WITH THE LARYNGEAL MASK AIRWAY IN ANAESTHESIA

Laryngeal mask airway was used in 100 adult patients of either sex (ASA I/II) undergoing various surgical procedures. The duration of surgery varied from 17 to 145 minutes. The course of anaesthesia was smooth and uneventful in all cases. The failure rate of insertion of LMA was 7%. The overall incidence of complications was 12%. LMA insertion was associated with statistically insignificant change in haemodynamic parameters.

Community perception of mosquitos and mosquito control in some areas of urban Delhi and rural Alwar, Rajasthan

There is little information regarding community perception of mosquitos and and their control in India. A qualitative study based on In depth discussions with the people in Urban Delhi, and rural Alwar was carried out in August-September, 1995. In the Ghazipur and Munirka areas of Delhi, 63 respondent groups with 171 head counts, and 59 respondent groups and 305 persons in Alwar were met. Community responses to uniform set of questions on mosquito types, seasonality, biting, breeding places, ongoing control activities, and methods of personal protection were recorded. Most people in the areas surveyed viewed mosquitos primarily as a biting nuisance, and secondarily as agents of disease and debilitators of health. In general the knowledge regarding mosquitos was deficient. An overwhelming tendency to attribute mosquitogenic conditions to the unsavoury features of one's physical environment was observed in both areas. The methods of personal protection and attitudes to organised control are discussed.

Relation of speed of a mile run, maximum energy cost of running, and maximum oxygen consumption: a field study

OBJECTIVE

To compare the maximum energy cost of running (MECR) estimated from the speed of a mile run and the maximum oxygen consumption (VO2max) with a field step test.

METHODS

MECR was defined as the maximum VO2, derived from the equation VO2 = 5.3 mph + 3.9 (ml.min-1.kg-1), when the subject performs a maximal, exhausting run and attains maximum speed. The equation is based on a straight line relation between speed and VO2. In this study MECR was obtained from a mile run and was compared with VO2max by extrapolation using a step test. Both tests were performed in the field.

RESULTS AND CONCLUSIONS

The variation in the MECR with VO2max was within +/- 10%. It therefore appears that the speed of a mile run is a good criterion of VO2max or estimated MECR for the measurement of physical fitness, and for the selection, recruitment, and assignment of an individual in field sports.

Cross-task cross talk in memory and perception

The application of the additive factors method depends on finding factors that selectively influence processing stages. When all the processes for a task are in series, a factor directly influencing a process might change its output and thereby have indirect influence on succeeding processes. We investigate whether such indirect influence is possible between processes associated with different tasks being performed together. In two dual-task memory scanning and arithmetic experiments with digits as the stimuli for both tasks, information relevant for only one of the tasks nonetheless affected performance of the other. When the same digit was relevant for the two tasks, cross-task facilitation and interference were observed in some cases. Displaying the same digit for both tasks led to relatively fast response times, paralleling the effect of flankers in the response competition paradigm. But repetition of digits in memory slowed responses. It is suggested that the need for control processes to keep task information segregated is responsible for the pattern of effects.

A theoretical analysis of intracellular oxygen diffusion

Oxygen diffusion rates within cells may be heterogeneous, with more rapid diffusion occurring along intracellular pathways of high oxygen solubility, such as mitochondria. Recent experimental data indicate that tissue oxygen permeability rises sharply in a temperature range associated with phase transitions in lipid membranes suggesting that membranes may function as oxygen "pathway". The experimental data have been analyzed using theoretical models of diffusion in two-phase media. By assuming muscles to be composed entirely of aqueous cytosol and lipids, cytosolic permeability was determined as a function of temperature by matching the experimental values of tissue permeability with those of model predictions using in vitro values of lipid permeability. Cytosolic permeability ranged from 50% of water permeability (low temperature) to 90% of water permeability (high temperature) and its temperature dependence was distinctly different from that of water. An upper bound for cytosolic permeability was calculated using a physiologic value for protein volume fraction, and lipid permeability was obtained using this cytosolic permeability. A model with a parallel arrangement of lipid and cytosol yielded a value of lipid permeability that was 71% higher than the in vitro value. Intracellular permeabilities calculated from tissue permeability values were found to be inconsistent with experimentally reported values for rat cardiac myocytes. Comparison of three different muscles exhibited the same trend of higher permeability with higher lipid content. It is concluded that both lipid and cytosol permeabilities and, hence, tissue permeabilities are different among different muscles and one should exercise caution when data from one muscle is used to calculate or extrapolate values in other muscles. It is conceivable that muscles with very high mitochondrial content, such as diaphragm and cardiac muscles may exhibit an oxygen permeability which is significantly higher than commonly accepted values. These results warrant additional measurements of tissue oxygen permeability at 37 degrees C, especially for oxidative muscles with high lipid content.

Cyclins as markers of tumor proliferation: immunocytochemical studies in breast cancer

We have developed methods to use anticyclin A, B, and E antibodies as reagents to specifically detect proliferating cells in specific phases of the cell cycle in formalin-fixed, paraffin-embedded sections of tissues and cells. Staining of 48 archival cases of breast cancer showed that these antibodies estimate the tumor proliferation fraction and therefore are potentially useful for the prediction of prognosis. A subset of cancers had a high frequency of tumor cells expressing cyclins A and E, out of proportion to other proliferation markers, suggesting that these tumors may have deregulated cyclin expression. In addition to recognizing authentic cyclin E in the nucleus of proliferating cells, anticyclin E antibody cross-reacted with a cytoplasmic protein in nonproliferating endothelial cells. This cross-reaction allows the simultaneous visualization and quantitation of microvessels in the tumors, measuring a second potential predictor of breast cancer prognosis, tumor angiogenesis.

Rpa4, a homolog of the 34-kilodalton subunit of the replication protein A complex

Replication protein A (RPA) is a complex of three polypeptides of 70, 34, and 13 kDa isolated from diverse eukaryotes. The complex is a single-stranded DNA-binding protein essential for simian virus 40-based DNA replication in vitro and for viability in the yeast Saccharomyces cerevisiae. We have identified a new 30-kDa human protein which interacts with the 70- and 13-kDa subunits of RPA, with a yeast two-hybrid/interaction trap method. This protein, Rpa4, has 47% identity with Rpa2, the 34-kDa subunit of RPA. Rpa4 associates with the 70- and 13-kDa subunits to form a trimeric complex capable of binding to single-stranded DNA. Rpa4 is preferentially expressed in placental and colon mucosa tissues. In the placenta, Rpa4 is more abundant than the 70-kDa Rpa1 subunit and is not associated with either Rpa1 or with any other single-stranded DNA-binding protein. In proliferating cells in culture, Rpa4 is considerably less abundant than Rpa1 and Rpa2. Northern (RNA) blot analysis suggest that there are alternatively processed forms of the RPA4 mRNA, and Southern blot analysis indicates that beside RPA4 there may be other members of the RPA2 gene family.

Separate domains of p21 involved in the inhibition of Cdk kinase and PCNA

The protein p21 (WAF1, CIP1 or sdi1), induced by the tumour-suppressor protein p53, interacts with and inhibits two different targets essential for cell-cycle progression. One of these is the cyclin-Cdk family of kinases and the other is the essential DNA replication factor, proliferating-cell nuclear antigen (PCNA). We report here that separate domains of p21 are responsible for interacting with and inhibiting the two targets. An amino-terminal domain inhibits cyclin-Cdk kinases and a carboxy-terminal domain inhibits PCNA. Using these separated domains, we have determined that p21 inhibits different biological systems through different targets. The PCNA-binding domain is sufficient for inhibition of DNA replication based on simian virus 40, whereas the Cdk2-binding domain is sufficient for inhibition of DNA replication based on Xenopus egg extract and for growth suppression in transformed human cells.

Risk factors for development of dehydration in young children with acute watery diarrhoea: a case-control study

In a case-control study to understand the risk factors for development of life-threatening dehydration, a total of 379 children comprising 243 cases (moderate or severe dehydration) and 136 controls (non or mild dehydration) up to 2 years of age suffering from acute watery diarrhoea were studied. By univariate analysis, the presence of vibrios in stool, withdrawal of breast feeding during diarrhoea, not giving fluids, including oral rehydration solution (ORS), during diarrhoea, frequent purging ( > 8/day), vomiting ( > 2/day) and undernutrition were identified as risk factors. However, by multivariate analysis after controlling for confounders, withdrawal of breast feeding during diarrhoea (odds ratio (OR) = 6.8, p < 0.00001) and not giving ORS during diarrhoea (OR = 2.1, p < 0.006) were identified as significant risk factors. The confounding variables which also contributed significantly to increasing the risk were age ( < or = 12 months; OR = 2.7, p = 0.001), frequent purging ( > 8/day; OR = 4.1, p < 0.00001), vomiting ( > 2/day; OR = 2.4, p = 0.001) and severe undernutrition (%median < or = 60 weight-for-age of Indian Academy of Paediatrics classification; OR = 3.1, p = 0.001). We feel that these findings will be useful for Global and National Diarrhoeal Diseases Control Programmes for formulating intervention strategies for preventing death due to diarrhoeal dehydration.

Dose proportionality of bisoprolol enantiomers in humans after oral administration of the racemate

Dose proportionality of racemic bisoprolol and the stereoselectivity of its enantiomers were studied after single oral dosing of 5 to 40 mg of bisoprolol hemifumarate in eight healthy male volunteers in an open-label, randomized, four-way cross-over trial. There were dose-proportional increases in mean peak plasma concentration (Cmax) and area under the plasma concentration versus time curve (AUC) values for the racemate and the individual enantiomers. No statistically significant differences were detected between the mean half life (t 1/2), Cmax, and time to reach Cmax (tmax) of the R- and S-isomers at each of the four dose levels studied. These findings support dose proportionality and absence of stereoselective pharmacokinetics for bisoprolol in the dose range studied.

Cross-modal compatibility effects with visual-spatial and auditory-verbal stimulus and response sets

Within the visual-spatial and auditory-verbal modalities, reaction times to a stimulus have been shown to be faster if salient features of the stimulus and response sets correspond than if they do not. Accounts that attribute such stimulus-response compatibility effects to general translation processes predict that similar effects should occur for cross-modal stimulus and response sets. To test this prediction, three experiments were conducted examining four-choice reactions with (1) visual spatial-location stimuli assigned to speech responses, (2) speech stimuli assigned to keypress responses, and (3) symbolic visual stimuli assigned to speech responses. In all the experiments, responses were faster when correspondence between salient features of the stimulus and response sets was maintained, demonstrating that similar principles of translation operate both within and across modalities.

Inhibition of DNA replication factor RPA by p53

The tumour suppressor p53 specifically interferes with the onset of S phase. The mechanism of the growth suppression action of the protein is unclear, though recent evidence points to transcriptional activation and repression functions of the protein. A competing hypothesis suggests that p53 interacts with the DNA replication apparatus and directly interferes with DNA replication. The major evidence for this hypothesis is that p53 interacts with the simian virus 40 (SV40)-encoded protein T antigen and interferes with the ability of T antigen to unwind the SV40 origin of DNA replication, and recruit DNA polymerase alpha to the replication initiation complex. Here we report that p53 physically interacts with and inhibits the function of a cellular DNA replication factor, the single-stranded DNA-binding protein complex RPA.

Do the same stimulus-response relations influence choice reactions initially and after practice?

A two-choice reaction task was used to evaluate changes in stimulus-response translation with practice. In Experiment 1, four groups of Ss practiced with either a direct or indirect mapping of left-right stimuli to left-right responses and either a crossed or uncrossed hand placement and transferred to one of the four Mapping x Placement conditions. Stimulus-response location and response location-effector relations affected performance initially and after practice. In Experiments 2 and 3, Ss switched every 42 trials between conditions for which only the stimulus location-effector (Experiment 2) or stimulus-response location relation (Experiment 3) remained constant. Switching produced interference in Experiment 2 but not in Experiment 3, corroborating the influence of the stimulus-response location relation on performance. Mediation based on spatial codes continues to be a factor in the performance of practiced Ss.

The separability of space and time: dimensional interaction in the memory trace

The speeded-classification paradigm, adapted from the study of perceptual interactions, was used to examine interactions among features of the short-term memory trace. In each of four experiments, a trial began with the presentation of a pair of stimuli, each member of which occurred either first or second in time and above or below a fixation point. One of the two stimuli was then presented again, and the task was to classify its prior temporal (Experiments 1 and 3) or spatial (Experiments 2 and 4) position. The main question of interest asked whether subjects could selectively attend to one of these occurrence dimensions while ignoring irrelevant variation along the other. The results suggested that whereas subjects can selectively ignore temporal or spatial variation when no recall of the irrelevant dimensions value is required, they suffer interference when values on both dimensions must be remembered. The obtained patterns of interference are consistent with postperceptual interactions of the spatial and temporal components of the memory trace.

Do the same stimulus-response relations influence choice reactions initially and after practice?

A two-choice reaction task was used to evaluate changes in stimulus-response translation with practice. In Experiment 1, four groups of Ss practiced with either a direct or indirect mapping of left-right stimuli to left-right responses and either a crossed or uncrossed hand placement and transferred to one of the four Mapping x Placement conditions. Stimulus-response location and response location-effector relations affected performance initially and after practice. In Experiments 2 and 3, Ss switched every 42 trials between conditions for which only the stimulus location-effector (Experiment 2) or stimulus-response location relation (Experiment 3) remained constant. Switching produced interference in Experiment 2 but not in Experiment 3, corroborating the influence of the stimulus-response location relation on performance. Mediation based on spatial codes continues to be a factor in the performance of practiced Ss.

Initial intensive therapy for multibacillary leprosy patients--in retrospect

We analysed the results of 4845 multibacillary (MB) patients being treated with multidrug treatment (MDT) in the Srikakulam District of Andhra Pradesh, India. Of these, 2309 (47.7%) patients were given an initial 14-day intensive therapy with rifampicin, clofazimine and dapsone, followed by the WHO recommended pulse therapy. The rest of the cases were given only pulse therapy. The improvement in terms of bacteriological clearance and the proportion of cases declared released from treatment (RFT) was found to be significantly higher among patients treated with only pulse therapy. Clinic attendance was found to be better and more regular in patients treated with intensive therapy, and no relapses were seen with either therapy. The implications of these findings on the operational aspects of programme implementation are discussed.

Influence of Composition and Processing History on the Cellular Morphology of the Foamed Olefinic Thermoplastic Elastomers

Foam extrusion of a series of dynamically vulcanized polypropylene (PP)/ethylene-propylene-diene terpolymer (EPDM) blends (commercially available Santoprene) by using chemical blowing agents have been studied. Results suggest that foaming occurs only within the thermoplastic phase and for each composition there exists a limiting density which controls the maximum volume expansion. This limiting density is controlled only by the composition and is independent of the blowing agent concentration, extrusion conditions, and the geometry. For the softest and the hardest blends, maximum volume expansion was found to be about 20 and 100%, respectively. Considerable differences in cell structure were also observed with change in the blend composition. As the rubber content increases, bubbles change their shapes from spherical to highly elongated channels where long axes are primarily along the extrusion direction. When the shapes of the bubbles are viewed by cutting the specimen, the bubbles were found to become highly irregular as the rubber content was increased. The fractal dimension of the perimeter profiles revealed that increases in rubber content give increases in the characteristic fractal dimension. Additionally, wide angle x-ray pole figure analysis, which gives an average orientation behavior of the material, indicates that low levels of preferential crystalline chain orientation develop in the extradates. This preferential orientation was found to vary from skin to core.

Foaming of Vulcanized PP/EPDM Blends Using Chemical Blowing Agents

Using two different chemical blowing agents, foaming behavior of partially vulcanized PP/EPDM blends with high EPDM ratio has been studied. The objective was to induce foaming within the EPDM phase prior to complete curing. The results suggest that with proper choice of blowing agent and by optimum balance of curative loading, foams with densities as low as 0.55 g/cm3 could be obtained. This corresponds to nearly 90 percent density reduction which is significantly greater than the 15 to 20% afforded by similar fully-vulcanized dynamically cured blends reported previously. The degree of cure in the rubber phase was determined to play a key role in determining the overall foamability. In particular, the foamability of the blend was found to decrease linearly with increase in the gel content. In addition, the compounding technique also plays a major role in controlling foamability of these blends. Attempts at extrusion foaming of these blends, however, were successful only for blends with a rather low degree of cure.