Insurance type and satisfaction with medical care among HIV-infected men

Patient satisfaction is a valuable indicator of the quality of medical care. We assessed the impact of type of health insurance on satisfaction with seven aspects of medical care among 593 HIV-infected men without AIDS, drawn from three sites in San Francisco, California and Denver, Colorado. After adjustment for site of medical care, patient age, race, income, education, and CD4 lymphocyte count, there were few differences in satisfaction between men with fee-for-service and those with managed care insurance. Men with fee-for-service insurance were significantly more satisfied with their interpersonal relations with their clinicians (p = 0.01) but less satisfied with their finances (p = 0.0001) than persons with managed care. Uninsured men were significantly less satisfied with several aspects of care than insured persons. There were no significant differences in satisfaction between men with managed care and those with public insurance. HIV-infected persons who have a choice of insurance should carefully weigh their options, recognizing the implicit trade-offs between types of insurance. Those who choose fee-for-service insurance can expect to be more satisfied with interpersonal relations with their medical providers but less satisfied with financial aspects of their plans. Efforts to address the low satisfaction of uninsured persons are needed.

In situ extracorporeal shockwave lithotripsy for ureteral calculi: investigation of factors influencing stone fragmentation and appropriate number of sessions for changing treatment modality

To determine the factors influencing stone fragmentation and to suggest when to change treatment modality for ureteral calculi refractory to repetitive in situ extracorporeal shockwave lithotripsy (SWL), we analyzed 369 patients treated primarily by the second-generation lithotripter, Siemens Lithostar, from March 1989 to December 1993. Three hundred forty-two (92.7%) of the patients were ultimately free of stones after repetitive in situ SWL. The cumulative stone-free rates of the first, second, and third session were 64%, 81%, and 88%, respectively, and the increment in the cumulative stone-free rate thereafter with further repeated in situ SWL was minimal (p < 0.01). The cumulative stone-free rate at the third session was 89%, 87%, and 86% for proximal, middle, and lower ureteral stones, respectively (p > 0.05). The cumulative stone-free rate at the third session was 100%, 90%, 87%, 70%, 67%, and 50% for stones <5 mm, 6 to 10 mm, 11 to 15 mm, 16 to 20 mm, 21 to 25 mm, and >25 mm, respectively (p < 0.001). According to the radiopacity of the stone, the cumulative stone-free rate at the third session was 96% for stones with minimal opacity, 94% for those with moderate opacity, and 70% for highly opaque stones (p < 0.001). The cumulative stone-free rate at the second session was 100% without ureteral obstruction; 80% with mild, 57% with moderate, and 67% with severe obstruction; and 50% in patients with nonappearance of the kidney (p < 0.05). From these observations, it could be concluded that the factors influencing fragmentation were the size and radiopacity of the calculi and the degree of ureteral obstruction, whereas the location of the calculi did not influence the cumulative stone-free rate of repetitive in situ SWL. It is preferable to restrict in situ SWL to three sessions in patients with ureteral calculi refractory to shockwaves. An early change of treatment modality either to ureteroscopic manipulation or to open surgery would be recommended if there were risk factors as listed above.

Human RAD2 homolog 1 5'- to 3'-exo/endonuclease can efficiently excise a displaced DNA fragment containing a 5'-terminal abasic lesion by endonuclease activity

Repair of abasic lesions, one of the most common types of damage found in DNA, is crucial to an organism's well-being. Studies in vitro indicate that after apurinic-apyrimidinic endonuclease cleaves immediately upstream of a baseless site, removal of the 5'-terminal sugar-phosphate residue is achieved by deoxyribophosphodiesterase activity, an enzyme-mediated beta-elimination reaction, or by endonucleolytic cleavage downstream of the baseless sugar. Synthesis and ligation complete repair. Eukaryotic RAD2 homolog 1 (RTH1) nuclease, by genetic and biochemical evidence, is involved in repair of modified DNA. Efficient endonucleolytic cleavage by RTH1 nuclease has been demonstrated for annealed primers that have unannealed 5'-tails. In vivo, such substrate structures could result from repair-related strand displacement synthesis. Using 5'-tailed substrates, we examined the ability of human RTH1 nuclease to efficiently remove 5'-terminal abasic residues. A series of upstream primers were used to increasingly displace an otherwise annealed downstream primer containing a 5'-terminal deoxyribose-5-phosphate. Until displacement of the first annealed nucleotide, substrates resisted cleavage. With further displacement, efficient cleavage occurred at the 3'-end of the tail. Therefore, in combination with strand displacement activity, RTH1 nucleases may serve as an important alternative to other pathways in repair of abasic sites in DNA.

Mechanism of tracking and cleavage of adduct-damaged DNA substrates by the mammalian 5'- to 3'-exonuclease/endonuclease RAD2 homologue 1 or flap endonuclease 1

The mammalian 5'- to 3'-exonuclease/endonuclease, called RAD2 homologue 1 or flap endonuclease 1, has a unique cleavage activity, dependent on specific substrate structure. On a primer-template, in which the primer has an unannealed 5'-tail, endonucleolytic cleavage near the annealing point releases the tail intact. Entering at the 5'-end, the nuclease tracks along the entire tail to the point of cleavage. Genetic analyses suggest that this nuclease removes DNA adducts in vivo (Sommers, C. H., Miller, E. J., Dujon, B., Prakash, S., and Prakash, L. (1995) J. Biol. Chem. 270, 4193-4196). Micrococcal nuclease footprinting shows that after tracking the nuclease protects a region of the tail 25 nucleotides long, adjacent to the cleavage site. Substrates with adducts at specific locations were used to assess the mechanism of RAD2 homologue 1 nuclease tracking and its ability to cleave modified DNA. Either a conventional cis-diamminedichloroplatinum (II) (CDDP) or a bulky CDDP derivative was placed within or beyond the region protected by the nuclease. The nuclease cleaved the tail of both substrates. In contrast, a CDDP adduct just adjacent to the expected cleavage point was inhibitory. A CDDP adduct at the very 5'-end of the tail was also cleaved. The nuclease could remove tails containing adducts on the sugar-phosphate backbone. Apparently, the nuclease is designed to slide over various types of damage on single stranded DNA and then cut past the damaged site.

Interactive computer-aided assignment of multiple probes to cytogenetic bands by simultaneous dual color fluorescence in situ hybridization and DAPI banding

A macro function was developed to run in conjunction with the popular image analysis package NIH Image, to allow simultaneous determination of mapping positions of one or two separate probes with respect to cytogenetic bands by dual color fluorescence in situ hybridization (FISH) and DAPI banding, and by determination of their fractional distance from pter (FLpter). In order to allow maximal flexibility, a user-defined line along the chromosome is used for measurements. Algorithms were developed to detect the ends of the chromosome and the cytogenetic bands. Results of the analysis are presented in graphical form, comprising a display of the DAPI intensity along the chromosome, the positions of the probe(s), the locations of bands as determined by analysis of the second derivative of the DAPI intensity profile, and a standard ideogram of the chromosome for comparison. The approach was validated and compared to visual assignment of probes to DAPI bands using the cosmid clone PYGM, which has been previously mapped to chromosome 11q13, and has been used as a landmark for mapping for other probes.

Some new 1,2-benzothiazine derivatives with analgesic and anti-inflammatory activities

Twenty-three new 7-halo-4-hydroxy-2H(or alkyl)-N-(3-aralkyl-2-thio- 1-hydantoinyl)-2H-1,2-benzothiazine-3-carboxamide 1,1-dioxide derivatives were synthesized through the condensation of 7-halo-4-hydroxy-2H(or alkyl)-1,2-benzothiazine-3-carboxylic acid methyl ester 1,1-dioxides with 1-amino-2-thio-3-aralkyl-imidazolidine-4-one. The analgesic and anti-inflammatory activities of the synthesized compounds were investigated by acetic acid-induced writhing syndrome and carrageenan rat paw edema tests. In analgesic activities most compounds exhibited higher activities than acetylsalicylic acid, but in anti-inflammatory activities most compounds except compounds 24, 36, 39 showed lower activities than indometacin.

Kinetic analysis of human flap endonuclease-1 by flow cytometry

Human flap endonuclease-1 (FEN-1) is a structure-specific endonuclease and exonuclease which is essential for DNA replication and repair. We have cloned a human FEN-1 gene, overexpressed it in Escherichia coli, purified the recombinant protein to near homogeneity, and characterized its cleavage of a flap DNA structure using a novel analytical approach based on flow cytometry. With this approach, we were able to measure continuously the kinetics of DNA cleavage by FEN-1 and to separate experimentally the binding and catalysis functions of the enzyme. When the reaction was initiated by the addition of FEN-1, the cleavage kinetics were dependent on enzyme concentration and appeared to saturate at high concentrations. When enzyme and substrate were preincubated in the presence of EDTA and the reaction initiated by the addition of Mg2+, rapid kinetic flow cytometry measurements showed that cleavage is fast (t1/2 approximately 6 s, k = 0.10 s-1). Using the single-turnover kinetics as a measure of the amount of enzyme-substrate complex present, we estimated the Kd for the FEN-1-flap DNA substrate to be 7.5 nM in the absence of Mg2+ and the rate constant for dissociation of the enzyme-substrate complex to be 0.07 s-1. Computer fitting of the experimental data to a kinetic model confirms these estimates for the individual steps and suggests some interesting features of enzymology using a surface-bound substrate.

Molecular cloning and structural analysis of the functional mouse genomic XPG gene

The mouse XPG gene is a homolog of the human DNA excision repair gene known to be defective in the hereditary sun-sensitive disorder xeroderma pigmentosum (group-G). Defects in mouse XPG have been shown to directly affect the sensitivity of cultured cells to chemotherapy agents and may play a role in tumor cell drug resistance in vivo. A full-length cosmid clone of mouse XPG was isolated by complementation of the UV sensitivity and repair defect in CHO-UV135 cells. Exon mapping determined that the gene consisted of 15 exons within 32 kb of genomic DNA. Sequencing of intron-exon boundaries revealed that mouse XPG possesses a rare class of intron previously identified in only four other eukaryotic genes; it utilizes AT and AC dinucleotides instead of the expected GT and AG within the splice junctions. Promoter analysis determined that mouse XPG is expressed constitutively and probably initiates transcription from multiple start sites, yet, unlike the yeast homolog RAD2, we found no evidence that it is UVC inducible in cultured cells. Amino acid comparison with human XPG identified a highly conserved acidic region of homology not previously described.

Ultraviolet-induced movement of the human DNA repair protein, Xeroderma pigmentosum type G, in the nucleus

Xeroderma pigmentosum type G (XPG) is a human genetic disease exhibiting extreme sensitivity to sunlight. XPG patients are defective XPG endonuclease, which is an enzyme essential for DNA repair of the major kinds of solar ultraviolet (UV)-induced DNA damages. Here we describe a novel dynamics of this protein within the cell nucleus after UV irradiation of human cells. Using confocal microscopy, we have localized the immunofluorescent, antigenic signal of XPG protein to foci throughout the cell nucleus. Our biochemical studies also established that XPG protein forms a tight association with nuclear structure(s). In human skin fibroblast cells, the number of XPG foci decreased within 2 h after UV irradiation, whereas total nuclear XPG fluorescence intensity remained constant, suggesting redistribution of XPG from a limited number of nuclear foci to the nucleus overall. Within 8 h after UV, most XPG antigenic signal was found as foci. Using beta-galactosidase-XPG fusion constructs (beta-gal-XPG) transfected into HeLa cells, we have identified a single region of XPG that is evidently responsible both for foci formation and for the UV dynamic response. The fusion protein carrying the C terminus of XPG (amino acids 1146-1185) localized beta-gal specific antigenic signal to foci and to the nucleolus regions. After UV irradiation, antigenic beta-gal translocated reversibly from the subnuclear structures to the whole nucleus with kinetics very similar to the movements of XPG protein. These findings lead us to propose a model in which distribution of XPG protein may regulate the rate of DNA repair within transcriptionally active and inactive compartments of the cell nucleus.

Physical interaction between human RAD52 and RPA is required for homologous recombination in mammalian cells

The yeast RAD52 protein is essential for DNA double-strand break repair, and meiotic and mitotic recombination. RPA is a protein complex of three subunits (70, 34, and 11 kDa) that has been shown to be involved in DNA replication, nucleotide excision repair, and homologous recombination. Here, we demonstrate a physical interaction between human RAD52 and RPA in vivo and in vitro. In addition, the domain (amino acids 221-280) in RAD52 protein that mediates the interaction with the 34-kDa subunit of RPA was also determined. Overexpression of mutant RAD52 proteins lacking the interaction domain (amino acids 221-240, 241-260, and 261-280) failed to induce homologous recombination in monkey cells. We have previously shown that overexpression of human RAD52 induced homologous recombination in these cells. These results suggest that direct physical interactions between RAD52 and RPA are essential for homologous recombination in mammalian cells.

Depression and use of mental health services among HIV-infected men

Depression is a serious, common, and treatable condition among HIV-infected persons. We examined the prevalence and predictors of depression and use of mental health services among 475 HIV-infected men without AIDS. Participants were drawn from three sites in San Francisco and Denver that did not provide ongoing medical care or mental health services. Depression was measured using the Center for Epidemiology Studies Depression scale (CES-D). Overall, 176 men (37.1%) were classified as depressed based on having a CES-D score above the standard cut-off of > or = 16. In logistic regression analysis, persons with HIV-related symptoms (OR = 3.4; 95% CI = 2.0.-5.6), low social support (OR = 2.5; 95% CI = 1.6-3.9), who were unemployed (OR = 1.9; 95% CI = 1.1-3.3), and with CD4 count < 200 cells (OR = 1.9; 95% CI = 1.1-3.3), were significantly more likely to be depressed. Only 40.3% of depressed men had seen a mental health clinician in the previous year and only 6.3% were taking an antidepressant. Among depressed men, in logistic regression analysis, men who were unemployed (OR = 2.4; 95% CI = 1.2-4.7) and those with health insurance (OR = 2.2; 95% CI = 1.1-4.5) were more likely to have received these services. Increased evaluation and treatment of HIV-infected persons for depression is needed.

Diagnosis of Yersinia pseudotuberculosis infection by polymerase chain reaction

BACKGROUND

The diagnosis of Yersinia pseudotuberculosis infection is usually based on serologic and/or bacteriologic tests. However, successfully culturing Y. pseudotuberculosis is difficult, and serologic tests in many cases require at least two serial sera obtained during 1-week intervals to confirm rising agglutination antibody titers.

METHODS

We applied a nested polymerase chain reaction method for rapid diagnosis of Y. pseudotuberculosis infection. The DNAs extracted from the peripheral blood and urine of patients and from mountain water, a suspected source of infection, were used as templates for the polymerase chain reaction with consequent amplification of a fragment of the inv gene in the chromosomal DNA of Y. pseudotuberculosis.

RESULTS

The overall rate of diagnosis with the polymerase chain reaction, which was based on a positive result with a single blood sample or one or more positive results with serial samples, was 93.3%. The polymerase chain reaction was also positive in two mountain water samples that were thought to be a source of infection.

CONCLUSION

Based on our results the nested polymerase chain reaction method can be used clinically for rapid and precise diagnosis of Y. pseudotuberculosis infection.

Multiple nuclear localization signals in XPG nuclease

We report here evidence for the mechanism of nuclear localization of XPG nuclease in human cells. Several candidate nuclear localization signal (NLS) peptides have been proposed for XPG protein. We have identified XPG peptides containing functional NLS and a potential nuclear retention signal (NRS) using in situ immunofluorescene localization of transiently expressed beta-galactosidase fusion proteins. Two XPG regions with putative NLS [amino acid (AA) coordinates: NLS-B (AA 1057-1074) and NLS-C (AA 1171-1185)] were each shown to independently localize the beta-gal extensively (> 80%) to the nucleus of HeLa cells. The C-terminus peptide containing NLS-C, an NLS conserved evolutionarily between yeasts and humans, also directed sub-localization of beta-galactosidase to intranuclear foci reminiscent of native XPG protein, as well as to peri-nucleolar regions. Peptides in the putative XPG 'NLS domain' (AA approximately 1051-1185) apparently function in concert for nuclear localization and also for retention of XPG in nuclear matrix-associated foci. Evidence presented elsewhere (Park et al., 1995) indicates that the peptide containing NLS-C (AA 1146-1185) also regulates the dynamic localization of XPG in the nucleus following UV-irradiation.

Essential amino acids for substrate binding and catalysis of human flap endonuclease 1

Human flap endonuclease 1 (FEN-1) is a member of the structure-specific endonuclease family and is involved in DNA repair. Eight restrictively conserved amino acids in FEN-1 have been converted individually to an alanine to elucidate their roles in specific DNA substrate binding and catalysis. Flap endonuclease activity of the wild type and mutant enzymes was measured by kinetic flow cytometry. Mutants D34A, D86A, and D181A lost their cleavage activity completely but retained substrate binding ability, as measured by their ability to inhibit the wild type enzyme in a competition assay. This indicates that these amino acids contribute to integrity of the enzyme active site. Loss of both binding and cleavage competency for the flap substrate by mutants E156A, G231A, and D233A suggests that these amino acids are involved in substrate binding. Mutants R103A and D179A retained wild type-like enzyme activity.

Molecular analysis and comparison of radiation-induced large deletions of the HPRT locus in primary human skin fibroblasts

Genetic alterations in gamma-ray- and alpha-particle-induced HPRT mutants were examined by multiplex polymerase chain reaction (PCR) analysis. A total of 39-63% of gamma-ray-induced and 31-57% of alpha-particle-induced mutants had partial or total deletions of the HPRT gene. The proportion of these deletion events was dependent on radiation dose, and at the resolution limits employed there were no significant differences between the spectra induced by equitoxic doses of alpha particles (0.2-0.4 Gy) and gamma rays (3 Gy). The molecular nature of the deletions was analyzed by the use of sequence tagged site (STS) primers and PCR amplification as a "probe" for specific regions of the human X chromosome within the Xq26 region. These STSs were closely linked and spanned regions approximately 1.7 Mbp from the telomeric side and 1.7 Mbp from the centromeric side of the HPRT gene. These markers include: DXS53, 299R, DXS79, yH3L, 3/19, PR1, PR25, H2, yH3R, 1/44, 1/67, 1/1, DXS86, D8C6, DXS10 and DXS144. STS analyses indicated that the maximum size of total deletions in radiation-induced HPRT mutants can be greater than 2.7 Mbp and deletion size appears to be dependent on radiation dose. There were no apparent differences in the sizes of the deletions induced by alpha particles or gamma rays. On the other hand, deletions containing portions of the HPRT gene were observed to be 800 kbp or less, and the pattern of the partial deletion induced by alpha particles appeared to be different from that induced by gamma rays.

Specific interactions between the human RAD51 and RAD52 proteins

Processing of DNA damage by the DNA double-strand break repair pathway in mammalian cells is accomplished by multiprotein complexes. However, the nature of these complexes and details of the molecular interactions are not fully understood. Interaction of the yeast RAD51 and RAD52 proteins plays a crucial role in yeast DNA homologous recombination and DNA double-strand break repair. Here, specific interactions between human RAD51 and RAD52 proteins are demonstrated both in vivo, using the yeast two-hybrid system and immunoprecipitation of insect cells co-infected with RAD51 and RAD52 recombinant viruses, and in vitro, using affinity chromatography with purified recombinant proteins. These results suggest that RAD52 may modulate the catalytic activities of RAD51 protein such as homologous pairing and strand exchange through a direct physical interaction. In addition, the domain in RAD52 that mediates this interaction was determined in vitro and in vivo. The RAD51-interacting region (amino acids 291-330) of the human RAD52 protein shows no homology with the yeast RAD52 protein, indicating that the interaction between RAD51 and RAD52 is species-specific.

MRI in presumed cervical anterior spinal artery territory infarcts

We report the MRI findings in two patients with presumed cervical spinal cord infarcts in the anterior spinal artery territory. MRI revealed abnormal signal intensities and/or band-like enhancement in the anterior two-thirds of the cervical spinal cord, corresponding to the vascular territory of the anterior spinal artery. Clinically there was an anterior spinal cord syndrome.

Lyphatic absorption in CAPD patients with loss of ultrafiltration capacity

During continuous ambulatory peritoneal dialysis (CAPD) treatment, loss of ultrafiltration capacity (UFC) is a common complication that can be associated with increased peritoneal fluid absorption rate. The aim of the present study was to investigate the relative importance of lymphatic absorption for total peritoneal fluid absorption in patients with permanent loss of UFC associated with a high peritoneal absorption rate (KE, ml/min; high-KE group, n = 4). Clinically stable CAPD patients (n = 23) as well as patients with loss of UFC associated with increased diffusive mass transport coefficients (KBD, ml/min; high-KBD group, n = 8) served as control groups. The patients were investigated with a 6-hour dwell study with 3.86% glucose solution. The total fluid absorption rate was estimated by the disappearance rate (KE) of 131I-radioiodinated human serum albumin (RISA) from the peritoneal cavity, and the lymphatic absorption rate was estimated by the rate of RISA appearance in plasma (KPP, ml/min). The values of KE and KPP in the high-KE group (4.65 +/- 0.93 and 0.42 +/- 0.31 ml/min, respectively) were markedly higher than in the clinically stable CAPD patients (1.77 +/- 0.60 and 0.15 +/- 0.06 ml/min, respectively; both p < 0.001 vs. the high-KE group). In the high-KBD group, KE was lower (2.19 +/- 0.38 ml/min, p < 0.001) compared to the high-KE group, whereas KPP was similar (0.26 +/- 0.09 ml/min, NS). The fraction of KE which could be accounted for by KPP was on average only 9 +/- 5% in the high-KE group and did not differ from the fractions in the clinically stable patients or in the high-KBD group (9 +/- 5 and 12 +/- 4%, respectively). In 5 patients in whom plasma RISA activity was measured for 24 h from the beginning of the 6-hour dwell study, a continuous increase of the RISA level in plasma was observed during this time period. We conclude that although KPP was increased in patients with UFC loss associated with high KE, it accounted for only a minor part of KE. Furthermore, the relatively slow but prolonged appearance of RISA in plasma indicates that the interstitial compartment may serve as a reservoir of macromolecules which are slowly absorbed by local lymphatics. The present study supports previous findings that direct lymphatic absorption is only of relatively minor importance for the fluid absorption in peritoneal dialysis.

Sieving coefficients for small solutes during experimental peritoneal dialysis in rats

A single 4-hour experimental peritoneal dialysis was performed in 6 normal Sprague-Dawley rats to investigate sieving coefficients (S) for small solutes during peritoneal dialysis. A modified 3.86% Dianeal solution with approximately the same concentrations of urea, sodium, and potassium as in the rat plasma (isochratic solution) was used to avoid diffusion of investigated solutes and to achieve sufficient ultrafiltration. As a control, a 4-hour peritoneal dialysis in 7 normal Sprague-Dawley rats was performed using the conventional 3.86% Dianeal solution. The infusion volume was 30 ml. A dilution of radioiodinated serum albumin was used to determine the intraperitoneal dialysate volume. S was calculated (1) from the mass and volume balances for the initial 30 min of the exchange with the isochratic solution (SI, isochratic method) and (2) by using a membrane model based on the thermodynamic theory of mass transport (SM). The diffusive mass transport coefficient KBD for the solutes investigated was estimated using the membrane model. The SI values for urea, sodium, and potassium were similar with the isochratic solution. For urea and sodium, the S values were within the physiological range 0-1, whereas the S values for glucose were close to 0 and for potassium were negative. SM for glucose, urea, and sodium using the conventional solution did not differ from the values obtained with the isochratic solution; however, SM for potassium was significantly lower than with the isochratic solution. SI and SM for potassium and sodium were correlated. The KBD values for glucose, urea, and sodium using the isochratic solution did not differ from the values obtained with the conventional solution, whereas the KBD values for potassium were significantly higher with the isochratic solution as compared with the conventional solution. We conclude that the net sieving coefficients SI and SM for urea and sodium were lower than unity in the rats dialyzed with the two solutions and did not differ from the previously reported S values measured in continuous ambulatory peritoneal dialysis patients with the isochratic solution. However, the transport of potassium was abnormal with the isochratic solution, suggesting mechanisms other than passive diffusive and convective potassium transport.

The effect of dialysate acidity on peritoneal solute transport in the rat

OBJECTIVE

To investigate the possible effect of unphysiologically low pH in dialysis fluid on peritoneal transport.

DESIGN

A 4-hour single-cycle experimental session of peritoneal dialysis was performed in six Sprague-Dawley rats using Dianeal 3.86% solution modified by adding 5 mmol/L of sodium hydroxide, neutral pH solution (NpHS) (pH 7.4). The intraperitoneal volume (VD) and peritoneal bulk fluid reabsorption (Qa) were calculated using a marker, 131I-labeled human serum albumin (RISA). The diffusive mass transport coefficient (KBD) as well as sieving coefficient (S) for glucose, urea, sodium, and potassium were calculated using the Babb-Randerson-Farrell model. The same study was performed in seven rats using Dianeal 3.86% solution, acidic pH solution (ApHS) (pH 5.7) to provide control values.

RESULTS

The dialysate pH was stable with NpHS; 45 min after the infusion of ApHS it increased rapidly and reached the physiological value 7.4. Dialysate volume and KBD values for sodium and potassium with NpHS were significantly higher than with ApHS, while the KBD values for glucose and urea did not differ between the two solutions. S values for sodium and urea did not differ between the two solutions, while the values for glucose and potassium with NpHS were significantly higher and lower, respectively, than the values with ApHS (0.92 +/- 1.04 vs 0.04 +/- 0.63 and 0.56 +/- 060 vs 1.15 +/- 0.39, p < 0.05). The absorption of glucose from the dialysis solution expressed as a percentage of the initial amount of dialysate glucose was significantly lower with NpHS than with ApHS at 30 min (17.3 +/- 1.7% vs 29.7 +/- 2.0%, p < 0.05).

CONCLUSION

We conclude that the peritoneal transport of fluid and small solutes might to some extent be influenced by the acidity of the dialysis solution. The vasodilatory effect of acidic dialysis solution might be the most important mechanism for these differences. However, a larger KBD value and a lower S value for potassium and higher S values for glucose during dialysis with the neutral dialysis solution may indicate that transport mechanisms other than simple passive transport are involved in peritoneal transport for glucose and electrolytes.

XPG protein has a structure-specific endonuclease activity

Biochemically active human DNA repair protein, xeroderma pigmentosum G (XPG), was overexpressed in insect cells by a recombinant baculovirus. The recombinant baculovirus produced XPG with a mobility of approximately 185 kDa in a denaturing polyacrylamide gel. Indirect immunofluorescence studies demonstrated that the recombinant full-length XPG protein was expressed predominantly as a nuclear protein. The recombinant XPG protein was purified to apparent homogeneity using Q-sepharose, S-300 size exclusion, and Mono Q column chromatography. XPG protein showed a structure-specific DNA endonuclease activity, and a preferential affinity to single-stranded DNA and RNA compared to double-stranded DNA.

Association between Vogt-Koyanagi-Harada syndrome and HLA-DR1 and -DR4 in Hispanic patients living in southern California

BACKGROUND

Vogt-Koyanagi-Harada (VKH) syndrome is associated with human leukocyte antigen (HLA)-B54, -DR4, -DR beta 1*0405, -DQ4, and -DR53 in Japanese patients. Disease-associated HLA specificities may differ among races. This study examined HLA associations with VKH syndrome in Hispanic patients living in southern California, a racial subgroup at increased risk for the disease.

METHODS

Human leukocyte antigen specificities were determined on 25 Hispanic patients with VKH syndrome and compared with HLA specificities of 217 healthy Hispanic control subjects. Inclusion criteria for study patients were nontraumatic panuveitis with exudative retinal detachments, with or without extraocular manifestations. Tests were performed using standard cytotoxic assays.

RESULTS

HLA-DR4 was present in 14 (56%) patients with VKH syndrome and in 62(29%) control subjects (relative risk = 1.96). HLA-DR1 was present in 9 (36%) patients with VKH syndrome and in 19 (9%) control subjects (relative risk = 4.11). HLA-DR1 and DR4 share a common epitope within the DR beta 1 gene. HLA-DR1 and/or DR4 were present in 21 (84%) patients with VKH syndrome and in 76 (35%) control subjects (relative risk = 2.40).

CONCLUSIONS

HLA-DR1 and -DR4 were found in a significantly disproportionate number of Hispanic patients with VKH syndrome living in southern California. HLA-DR4, although not HLA-DR1, has been previously associated with VKH syndrome in other groups. These associations suggest a common immunogenic predisposition to VKH among different racial groups, and suggest that a common epitope shared by DR1 and DR4 may be involved in the pathogenesis of the disease.

Expression of human RAD52 confers resistance to ionizing radiation in mammalian cells

Processing of mutagenic DNA damages by the double strand breaks (DSB) in eukaryotes is most likely achieved by multiple pathways, including homologous recombination. Although RAD52 has been shown to be important for DSB repair in yeasts, its role in DSB repair in mammalian cells has not been demonstrated. This study reports for the first time that the overexpression of human RAD52 confers enhanced resistance to gamma-rays and induces homologous intrachromosomal recombination in cultured monkey cells. Recombination frequency synergistically increased by the combination of overexpression of RAD52 and ionizing radiation. These observations suggest that homologous recombination mediated by RAD52 is involved in double-stranded break repair in mammalian cells.

Albumin-based solutions for peritoneal dialysis: investigations with a rat model

To evaluate albumin, an osmotic agent for peritoneal dialysis, the peritoneal fluid and solute transport were investigated during a 4-h single cycle peritoneal dialysis with albumin-based dialysis solutions. Two different albumin solutions were used in 15 normal Sprague-Dawley rats: isotonic 7.5% albumin solution (ADS 1, n = 7) and a combined 7.5% albumin and 1.35% glucose solution (ADS 2; n = 8). A standard 1.36% Dianeal solution was used to provide control values (n = 6). The rate of the intraperitoneal volume change (Qv) was positive during the initial 90 min with ADS 2 and during the initial 60 min with Dianeal 1.36% solution but negative with ADS 1. The peritoneal bulk flow reabsorption rate, Qa, was similar in all three groups. The estimated rate of transcapillary ultrafiltration (Qu = Qv + Qa) was positive with all three solutions throughout the dialysis. With ADS 1, Qu increased gradually during the initial 90 min and then remained stable, but it decreased with ADS 2 and Dianeal 1.36% solution. Qu with ADS 2 did not differ from that with Dianeal 1.36% solution during the initial 60 min, but it was significantly higher during the latter part of dialysis. The value of Qu during the last 2 h of dialysis was 0.026 +/- 0.010 and 0.025 +/- 0.009 ml/min with ADS 1 and ADS 2, respectively, and it was significantly higher than that with Dianeal 1.36% solution (0.005 +/- 0.007 ml/min; p < 0.017).(ABSTRACT TRUNCATED AT 250 WORDS)

Diffusive and convective solute transport in peritoneal dialysis with glucose as an osmotic agent

To investigate possible effects of glucose concentration, dwell time, and peritoneal reabsorption on the combined diffusive and convective peritoneal solute transport, dialysate to plasma concentration ratios (D/P) and solute clearances were evaluated for 6-h peritoneal dwell studies with 1.36, 2.27, and 3.86% glucose solutions. The diffusive mass transport coefficient, KBD, and sieving coefficient, S, were estimated using the Babb-Randerson-Farrell model of peritoneal transport. Dialysate volumes over time and peritoneal reabsorption rates, KE, were assessed using radiolabeled iodinated serum albumin (RISA). The transport parameters were estimated with and without peritoneal reabsorption of solutes taken into account. To test the stability of the transport parameters throughout a single peritoneal dwell, KBD and S values were estimated for the initial 3-120 min, the final 120-360 min, and the entire 3-360 min dwell period for dialysis with 3.86% glucose solution. The transport parameters did not differ between the three dialysis fluids although clearances of small solutes were higher with the 3.86% solution. Values of KBD, but not S, were dependent on the correction for peritoneal reabsorption of solutes. Computer simulations showed that S could be estimated even with the 1.36% glucose solution. A significant change of the transport parameters, with increased values of KBD during the initial period of the dwell, was found for urea, potassium, sodium, and total protein during dialysis with the 3.86% solution. S values for urea and potassium were close to 1 during the initial period whereas unphysical (higher than 1) S values were found for the whole dwell period. The transient increase of KBD during the initial part of the dwell may reflect changes in the peritoneal barrier possibly induced by fresh dialysis fluid. In conclusion, the transport parameters KBD and S are not influenced by the concentration of glucose in the dialysis fluid. Moreover, the estimation of KBD but not of S is dependent on the assumed rate of peritoneal reabsorption. Finally, the current results challenge the assumption that KBD and S are constant throughout a peritoneal dialysis exchange.