Oxidative stress in human aging and mitochondrial disease-consequences of defective mitochondrial respiration and impaired antioxidant enzyme system

Respiratory function of mitochondria is compromised in aging human tissues and severely impaired in the patients with mitochondrial disease. A wide spectrum of mitochondrial DNA (mtDNA) mutations has been established to associate with mitochondrial diseases. Some of these mtDNA mutations also occur in various human tissues in an age-dependent manner. These mtDNA mutations cause defects in the respiratory chain due to impairment of the gene expression and structure of respiratory chain polypeptides that are encoded by the mitochondrial genome. Since defective mitochondria generate more reactive oxygen species (ROS) such as O2- and H2O2 via electron leak, we hypothesized that oxidative stress is a contributory factor for aging and mitochondrial disease. This hypothesis has been supported by the findings that oxidative stress and oxidative damage in tissues and culture cells are increased in elderly subjects and patients with mitochondrial diseases. Another line of supporting evidence is our recent finding that the enzyme activities of Cu,Zn-SOD, catalase and glutathione peroxidase (GPx) decrease with age in skin fibroblasts. By contrast, Mn-SOD activity increases up to 65 years of age and then slightly declines thereafter. On the other hand, we observed that the RNA, protein and activity levels of Mn-SOD are increased two- to three-fold in skin fibroblasts of the patients with CPEO syndrome but are dramatically decreased in patients with MELAS or MERRF syndrome. However, the other antioxidant enzymes did not change in the same manner. The imbalance in the expression of these antioxidant enzymes indicates that the production of ROS is in excess of their removal, which in turn may elicit an elevation of oxidative stress in the fibroblasts. Indeed, it was found that intracellular levels of H2O2 and oxidative damage to DNA and lipids in skin fibroblasts from elderly subjects or patients with mitochondrial diseases are significantly increased as compared to those of age-matched controls. Furthermore, Mn-SOD or GPx-1 gene knockout mice were found to display neurological disorders and enhanced oxidative damage similar to those observed in the patients with mitochondrial disease. These observations are reviewed in this article to support that oxidative stress elicited by defective respiratory function and impaired antioxidant enzyme system plays a key role in the pathophysiology of mitochondrial disease and human aging.

The effect of dexamethasone on postoperative pain and emesis after intrathecal neostigmine

We evaluated the effect of a single dose of dexamethasone on the incidence and severity of postoperative nausea and vomiting (PONV) after intrathecal injection of tetracaine plus neostigmine. Sixty ASA physical status I patients scheduled for inguinal herniorrhaphy were studied with a randomized, double-blinded, placebo-controlled protocol. The dexamethasone group (Group D) received 10 mg of dexamethasone IV before performance of spinal anesthesia, whereas the placebo group (Group P) received saline. Spinal anesthesia was performed with intrathecal injection of 15 mg tetracaine plus neostigmine 100 microg in both groups. Pain, PONV, and other side effects were evaluated 24 h after surgery. The duration and severity of analgesia and the incidence of PONV were not significantly different between the two groups. Our results demonstrate that a single dose of dexamethasone (10 mg) did not potentiate the analgesic effect or reduce the incidence of PONV after intrathecal injection of tetracaine and neostigmine.

IMPLICATIONS

The results of our evaluation of the effect of IV dexamethasone versus saline control on analgesia and nausea and vomiting after intrathecal neostigmine and tetracaine suggest that IV dexamethasone did not enhance the analgesic effect of neostigmine or reduce the incidence of emesis after intrathecal administration.

Long-term outcomes of renal transplantation: a result of the original endowment of the donor kidney and the inflammatory response to both alloantigens and injury

Recent data suggest that long-term allograft survival might be affected by two factors. The first is the endowment of the allograft, which consists of two elements: the nephron mass and the ability of these nephrons to repair injuries sustained during the transplant process. The second factor is renal inflammation. Although inflammation is traditionally ascribed to alloreactivity, recent data have shown that there is also a renal inflammatory response to early injury after transplantation, to brain death in the donor, and as part of the maladaptive response to nephron loss. These two factors contribute to the detrimental effects of delayed graft function or acute rejection on the long-term survival seen in most studies, and the beneficial effects of anti-inflammatory agents on the maladaptive response to nephron loss.

Nitric oxide inhibits INFgamma-induced increases in CIITA mRNA abundance and activation of CIITA dependent genes--class II MHC, Ii and H-2M. Class II TransActivator

BACKGROUND

Nitric oxide (NO) has been recently implicated as a powerful inhibitor of immune responses during allograft rejection, and some autoimmune and infectious diseases. We previously showed that one potential regulatory effect of NO is inhibition of IFNgamma-stimulated expression of Class II MHC on macrophages. Activation of this gene is mediated by the "Class II TransActivator" (CIITA). We now ask whether NO inhibits CIITA and thus the family of genes regulated by CIITA--Class II MHC, Ii, and H-2M. The latter two genes participate in antigen processing and formation of the cell-surface peptide-Class II MHC complex.

METHODS

Murine macrophages--both peritoneal macrophages and the RAW264.7 macrophage line--were stimulated in vitro with IFNgamma. NO production was measured by the Greiss reagent. Transcription of Class II MHC was measured by nuclear run-on assay. mRNA abundance of Class II MHC, Ii, H-2M, and CIITA was measured by Northern blotting and RT-PCR.

RESULTS

NO inhibits IFNgamma-induced increases in the abundance and transcription of the Class II MHC Ab gene. The increases in mRNA abundance of CIITA, Ii, and H-2M are also inhibited. As a control, we found that NO did not inhibit LPS-induce increases in TNFalpha mRNA abundance.

CONCLUSIONS

NO inhibits IFNgamma-induced increases in CIITA, and thus inhibits the CIITA-regulated genes: Class II MHC, Ii, and H-2M. Early during rejection, NO production by macrophages may result after stimulation by IFNgamma produced by CD4+ T cells, and be an effector of allograft damage. High concentrations of NO may then act as a feedback inhibitor which decreases antigen presentation by macrophages and thus decreases CD4 T cell activation.

Human genetic factors related to susceptibility to mild malaria in Gabon

Several human genetic factors, including red blood cell polymorphisms (ABO blood group, sickle-cell trait, G6PD deficiency) as well as point mutations in the mannose binding protein (MBP) and in the promoter regions of both the TNF-alpha and NOS2 genes, influence the severity of disease due to infection with Plasmodium falciparum. We assessed their impact on mild P. falciparum malaria, as part of a longitudinal investigation of clinical, parasitological and immunological parameters in a cohort of 300 Gabonese schoolchildren. We found the following frequencies: blood group O (0.54), sickle-cell trait (0.23), G6PD deficiency (0.09), MBP gene mutations (0.34), TNF-alpha promoter mutations (at positions -238: 0.17 and -308: 0.22) and NOS2 promoter mutation (0.18). Blood group O or hemoglobin AA were associated with protection against higher parasitemia. Girls with normal G6PD enzyme activity were protected against clinical malaria attacks. In addition, we demonstrated for the first time that the mutation at position -238 of the gene coding for the promoter region of TNF-alpha was positively correlated with the level of the antibody response specific for epitopes of the antigens MSA-2 and RAP-1 of P. falciparum.

Enteric adenovirus infection in children in Taipei

Enteric adenoviruses (EAds), including type 40 (Ad40) and 41 (Ad41), can cause acute and severe diarrhea in young children. To delineate the epidemiological features of pediatric EAds infection in Taiwan, we conducted a retrospective study of all cases of EAds gastroenteritis in children treated at National Taiwan University Hospital for the period from July 1993 to December 1997. Stool samples were tested for the presence of Ad40 or Ad41 by enzyme immunoassay (EIA). A total of 64 cases of EAds infection in 63 children aged from 8 days to 81 months old with a median age of 9.5 months treated during the study period were identified. The male-to-female ratio was 1.63 (39/24). No obvious seasonal clustering of EAds cases was noted. Most patients (76.6%) were infected before the age of 2 years. Clinical features included diarrhea (96.9%), fever (54.7%), vomiting (45.3%), mild dehydration (43.8%), symptoms of upper respiratory tract infection (21.9%), and abdominal pain (12.5%). Analysis of fecal samples in patients with diarrhea showed watery diarrhea in 72.2%, diarrhea with mucus in 20%, diarrhea with blood in 3.1% and diarrhea with mucus and blood in 1.6 % of all patients. Nearly one-half (43.5%) of the patients had diarrhea for more than 7 days. Thirty-seven patients (57.8%) were hospitalized due to gastroenteritis or other unrelated diseases, and 11 patients (17.2%) acquired enteric adenovirus infection during hospitalization for other underlying disease. Twelve patients (18.8%) had mixed infections, which included rotavirus, respiratory syncytial virus (RSV) and Salmonella species. There were no deaths in this series. The findings of this study suggest that EAds are important etiologic microbes of pediatric gastroenteritis.

Rotavirus gastroenteritis in children: 5-year experience in a medical center

Rotavirus infection is the leading cause of childhood gastroenteritis. We retrospectively reviewed cases of rotavirus gastroenteritis at National Taiwan University Hospital from January 1993 to December 1997. During the study period there were 429 patients with rotavirus infection with ages ranging from 1 day to 16 years with a median of 13 months. The male-to-female ratio was 1.2:1. Infection occurred before the age of 2 years old in 76% of patients. The seasonal peak occurred in the late winter and early spring during 1993 to 1996, but the case number increased in late spring and summer in 1997. The G serotype of the rotavirus was identified in 302 patients (70%). Vomiting and dehydration developed more frequently following infection with G1 rotaviruses, while an increased frequency of seizures was noted following G2 infection; the differences were not statistically significant. One patient had two episodes of infection; the first one was caused by G1 rotavirus, and the strain causing the second infection could not be typed. In conclusion, the results suggest that there is a strong seasonal variation in the incidence and characteristics of rotavirus infection in Taipei area. The infections caused by G1 and G2 rotaviruses were clinically indistinguishable.

Independent occurrence of somatic mutations in mitochondrial DNA of human skin from subjects of various ages

The incidence (frequency of occurrence) and abundance (percentage of mutant out of total mtDNA population) of two different somatic mtDNA mutations in human skin were investigated in 44 subjects ranging from 19 to 87 years of age. Using quantitative allele-specific polymerase chain reaction (AS-PCR) to analyse the A-->G base substitution at nucleotide 3243, 50% of the samples showed detectable levels of that particular mutation, with abundances ranging from 0.01% to 0.12%. In the same set of skin samples, the overall incidence of the 4977 bp "common" deletion was also approximately 50%. Where detected, the abundance of this deletion ranged from 0.0002% to 0.1%. Comparative analyses of the incidence and abundance of these two mutations, collectively and in individual skin samples, led to these two conclusions: (1) there is independent occurrence of these two mtDNA mutations in human skin, and (2) whereas the 4977 bp deletion shows an age-associated accumulation in human skin, no age association is apparent for the 3243 A-->G base substitution. Furthermore, in general, there is a much lower incidence of somatic mutations in mtDNA of human skin as compared to that in postmitotic tissues such as skeletal muscle.

Increase of mitochondria and mitochondrial DNA in response to oxidative stress in human cells

Mitochondrial respiratory function is impaired in the target tissues of patients with mitochondrial diseases and declines with age in various human tissues. It is generally accepted that respiratory-chain defects result in enhanced production of reactive oxygen species and free radicals in mitochondria. Recently, we have demonstrated that the copy number of mitochondrial DNA (mtDNA) is increased in the lung tissues of elderly human subjects. The mtDNA copy number was suggested to be increased by a feedback mechanism that compensates for defects in mitochondria harbouring mutated mtDNA and a defective respiratory system. However, the detailed mechanism remains unclear. In this study, we treated a human lung fibroblast cell line, MRC-5, with H(2)O(2) at concentrations of 90-360 microM. After the treatment for 24-72 h, we found that cells were arrested at G(0) and G(1) phases but that mitochondrial mass and mtDNA content were significantly increased in a concentration- and time-dependent manner. Moreover, the oxidative stress induced by buthionine sulphoximine was also found to cause an increase in mitochondrial mass of the treated cells. Increased uptake of a vital mitochondrial dye Rhodamine 123 and enhanced tetrazolium [MTT, 3-(4, 5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide] reduction revealed that the mitochondria increased by H(2)O(2) treatment were functional. In addition, the increase in the mitochondrial mass was also observed in cell-cycle-arrested cells induced by mimosine, lovastatin and genistein. Taken together, these findings suggest that the increase in mitochondrial mass and mtDNA content are the early molecular events of human cells in response to endogenous or exogenous oxidative stress through cell-cycle arrest.

Increase of mitochondria and mitochondrial DNA in response to oxidative stress in human cells

Mitochondrial respiratory function is impaired in the target tissues of patients with mitochondrial diseases and declines with age in various human tissues. It is generally accepted that respiratory-chain defects result in enhanced production of reactive oxygen species and free radicals in mitochondria. Recently, we have demonstrated that the copy number of mitochondrial DNA (mtDNA) is increased in the lung tissues of elderly human subjects. The mtDNA copy number was suggested to be increased by a feedback mechanism that compensates for defects in mitochondria harbouring mutated mtDNA and a defective respiratory system. However, the detailed mechanism remains unclear. In this study, we treated a human lung fibroblast cell line, MRC-5, with H(2)O(2) at concentrations of 90-360 microM. After the treatment for 24-72 h, we found that cells were arrested at G(0) and G(1) phases but that mitochondrial mass and mtDNA content were significantly increased in a concentration- and time-dependent manner. Moreover, the oxidative stress induced by buthionine sulphoximine was also found to cause an increase in mitochondrial mass of the treated cells. Increased uptake of a vital mitochondrial dye Rhodamine 123 and enhanced tetrazolium [MTT, 3-(4, 5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide] reduction revealed that the mitochondria increased by H(2)O(2) treatment were functional. In addition, the increase in the mitochondrial mass was also observed in cell-cycle-arrested cells induced by mimosine, lovastatin and genistein. Taken together, these findings suggest that the increase in mitochondrial mass and mtDNA content are the early molecular events of human cells in response to endogenous or exogenous oxidative stress through cell-cycle arrest.

Identification of a locus for disseminated superficial actinic porokeratosis at chromosome 12q23.2-24.1

Disseminated superficial actinic porokeratosis is an autosomal dominant cutaneous disorder characterized by many uniformly small, minimal, annular, anhidrotic, and keratotic lesions. The genetic basis for this disease is unknown. Using a genomewide search in a large Chinese family, we identified a locus at chromosome 12q23.2-24. 1 responsible for disseminated superficial actinic porokeratosis. The fine mapping study indicates that the disseminated superficial actinic porokeratosis gene is located within a 9.6 cM region between markers D12S1727 and D12S1605, with a maximum two-point LOD score of 20.53 (theta = 0.00) at D12S78. This is the first locus identified for a genetic disease where the major phenotype is porokeratosis. The study provides a map location for isolation of a gene causing disseminated superficial actinic porokeratosis.

Docosahexaenoic acid decreases IRF-1 mRNA and thus inhibits activation of both the IRF-E and NFkappa d response elements of the iNOS promoter

BACKGROUND

Nitric oxide produced by inducible nitric oxide synthase (iNOS) may be cytotoxic during cardiac, hepatic, and renal acute allograft rejection. Because the incidence of rejection is decreased by fish oils that contain docosahexaenoic acid (DHA), we investigated the effects of DHA on iNOS. Using nuclear run-on assays and iNOS-promoter constructs, we previously showed that docosahexaenoic acid (DHA) inhibits activation of the iNOS gene by murine macrophages that had been stimulated in vitro by IFNgamma plus lipopolysaccharide.

METHODS

In our current investigation, our purpose has been to determine how DHA inhibits iNOS gene activation in murine macrophages, by using gel retardation and Northern blotting techniques. We studied the effects of DHA on the formation nuclear protein complexes that interact with the critical iNOS promoter's response elements for IRF-1 (IRF-E -923 to -913 bp) and NF-kappaB (NFkappa d -85 to -75 bp).

RESULTS

We now show that DHA inhibited increases of IRF-1 mRNA abundance in response to IFNgamma plus lipopolysaccharide. As expected, we found that this prevented formation of the nuclear protein complex that binds to the IRF-E DNA response element. We also found that inhibition of IRF-1 inhibited formation of the nuclear protein complex that binds to the NFkappa d DNA response element.

CONCLUSIONS

DHA decreases the abundance of IRF-1 mRNA in stimulated cells. That, in turn, results in the decreased nuclear protein binding to the major iNOS promoter response elements (IRF-E and NF-kappaB). We found that this occurred because IRF-1 is a component of both the nuclear protein complex that binds to IRF-E and the nuclear protein complex that binds to NFkappa d.

Diagnosis of Ebola haemorrhagic fever by RT-PCR in an epidemic setting

This study reports the first field evaluation of a new diagnostic technique for Ebola virus disease with sensitivity and specificity. Ebola virus causes rare but fulminating outbreaks in Equatorial Africa. Rapid differentiation from other infections is critical for timely implementation of public health measures. Patients usually die before developing antibodies, necessitating rapid virus detection. A reverse transcriptase-polymerase chain reaction (RT-PCR) assay was developed, implemented and evaluated at Centre International de Recherches Médicales de Franceville (CIRMF) in Gabon, to detect Ebola viral RNA in peripheral blood mononuclear cells (PBMC). Twenty-six laboratory-confirmed patients during and 5 after the acute phase of Ebola haemorrhagic fever, 15 healthy controls and 20 febrile patients not infected with Ebola virus were studied. RT-PCR results were compared with ELISA antigen capture, and Ebola specific IgM and IgG antibody detection. Ebola virus RNA was amplified from 26/26 specimens from the acute phase, 3/5 during recovery, 0/20 febrile patients and 1/15 negative controls. Sensitivity of RT-PCR in identifying acute infection and early convalescence compared with antigen or IgM detection was 100% and 91% respectively, and specificity compared with antigen detection and IgM assay combined was 97%. Antigen capture detected only 83% of those identified by PCR, and IgM only 67%. Ebola virus RNA was detected in all 13 fatalities, only 5 of whom had IgM and none IgG. RT-PCR detected Ebola RNA in PBMC one to three weeks after disappearance of symptoms when antigen was undetectable. RT-PCR was the most sensitive method and able to detect virus from early acute disease throughout early recovery.

Pertussis seroepidemiology in Taipei

PURPOSE

We evaluated the seroprevalence of pertussis among apparently healthy Taipei residents.

METHODS

From January 1992 through December 1994, we recruited subjects from a well baby clinic (children < 3 years), kindergartens, primary, and secondary schools and colleges (3-20 years), a health exam clinic (> 20 years), and obstetric clinics (pregnant women). Subjects were stratified into 12 groups according to age and pregnant women were considered separately. The serum antibody titers against filamentous hemagglutinin (FHA) and pertussis toxin (PT) were measured by enzyme-linked immunosorbent assay.

RESULTS

The anti-PT and anti-FHA titers were elevated in the 4 to 6-month and 19 to 20-month age groups, coinciding with regular pertussis vaccinations. The anti-PT titers rose again in the 3 to 4-year age group, reflecting a higher prevalence of natural pertussis infection. The anti-PT titers gradually decreased among older age groups, although a peak occurred in the 11 to 15-year age group. The sequential changes in anti-FHA titers followed those of anti-Pt titers in the younger age groups, but the anti-FHA titers were persistently elevated beyond 15 years of age. The antibody levels were similar in the two sexes, except that anti-PT titers were higher in males of 19 to 20 months and 21 to 30 years of age. Anti-PT titers were equivalent between neonates (0-2 months) and pregnant women, but anti-FHA titers were much lower in neonates.

CONCLUSIONS

The seroprevalence patterns in this study indicate that young children, adolescents, and even adults remain at risk of pertussis, despite the current immunization program. Booster vaccinations after completion of the current four-dose immunization schedule, possibly continuing into adolescence, should be considered to block the transmission of infection.

Geographical differences in human herpesvirus 8 seroepidemiology: a survey of 1,201 individuals in Asia

Since the discovery of human herpesvirus 8 (HHV8) as a contributory cause of Kaposis sarcoma, the clinical role of this virus has been actively investigated. An understanding of HHV8 seroepidemiology is critical for the study of its pathogenesis within a specific environment. A sero-survey is described in Taiwan of 1,201 individuals ranging in age from under 1 year to over 70. Indirect immunofluorescence assay was used to determine antibody titers against both latent and lytic antigens of HHV8. The results indicate that very few individuals (3-4%) were exposed to HHV8 before 10 years of age. Infection rate peaked (19.2%) between the ages of 21 to 40. Females showed a slightly higher seroprevalence for HHV8 than males, but the difference was not statistically significant. Pregnancy did not correlate with increased HHV8 infection rate nor with augmented HHV8 antibody titers. It is concluded that HHV8 in Taiwan is predominantly an infectious agent for adults. In this geographical locale, HHV8 is similar to herpes simplex virus type 2 in its likely transmission occurring presumptively through sexual routes. However, the study also indicates that a smaller portion of HHV8-transmission could occur through nonsexual contacts.

Spectrum of beta thalassemia mutations and their linkage to beta-globin gene haplotypes in the Indo-Mauritians

The beta thalassemia alleles in 53 thalassemic Indo-Mauritian patients and their families consisting of 23 homozygous beta-thalassemia, 9 HbE/beta-thalassemia, 18 HbS/beta-thalassemia, 1 HbD/beta-thalassemia, 1 deltabeta/beta-thalassemia and 1 HbH/beta-thalassemia from the island of Mauritius were studied. Characterization by polymerase chain reaction-based reverse dot blot hybridization technique revealed that the IVS1-5 (G-->C) mutation accounted for 74% of the beta thalassemic alleles, while six other mutations occurred at much lower frequencies: HbE codon 26 (G-->A); 10.4%, codon 8/9 (+G); 3.5%, codon 30 (AGG-->ACG) also called IVSI (-1).G-->C; 3.5%, codon 15 (G-->A); 3.5%, codon 41/42 (-CTTT); 2.4% and -28 (A-->G); 2.4%. Association of these mutations to specific beta globin gene sequence framework and haplotype allowed to trace their ancestral link. These data are useful in future molecular screening of the population in view of implementing a thalassemia prevention and control program in Mauritius.

Syngeneic renal transplantation increases the number of renal dendritic cells in the rat

Dendritic cells participate in the regulation of CD4 and CD8 T cells during transplant rejection. Understanding what causes increased numbers of dendritic cells to appear in the renal transplant is therefore important. We performed syngeneic renal transplants between rats. We used the monoclonal antibody OX62 to detect dendritic cells, and OX6 to detect major histocompatability complex (MHC) Class II in the renal transplant. One week after transplant, dendritic cells appeared. This indicates that the injury of transplantation itself is sufficient to increase the number of dendritic cells in the kidney in a model where there is no alloreactivity.

Factors influencing resistance to reinfection with Plasmodium falciparum

A treatment-reinfection study design was used to investigate the relationships between host immunologic and/or genetic factors and resistance to reinfection with Plasmodium falciparum. Sixty-one children in Gabon were enrolled in a cross-sectional study to measure the prevalence of each human plasmodial species. All were given amodiaquine for radical cure of parasites, and 40 were subsequently followed-up for 30 weeks. Successive blood smears were examined to measure the delay of reappearance in blood of asexual stages of P. falciparum parasites. Presence of infection during the cross-sectional survey was associated with male sex, non-deficient glucose-6-phosphate dehydrogenase activity, plasma interleukin-10 level, and anti-LSA-Rep antibody concentration. Resistance to reinfection was related to the presence of anti-LSA-J antibodies, and the absence of anti-LSA-Rep antibodies. Moreover, P. malariae-infected subjects were usually co-infected with P. falciparum, and were also more rapidly reinfected with P. falciparum after treatment, compared with those without P. malariae infection.

Immunogenicity of oral poliovirus vaccine in Taiwan

Previous studies have shown that the immune response to trivalent oral poliovirus vaccine (OPV) varies widely from country to country. However, there has been no report on the immunogenicity of this vaccine in Taiwanese children. In this study, 98 children were followed up for 17 months to study the antibody responses following four doses of trivalent OPV. The results showed that, after two doses of vaccine, all children were protected against poliovirus type 1 and 2. All except two children also developed protective antibodies against poliovirus type 3. After three doses, the antibody levels in all subjects were above protective concentrations. The fourth dose, given at 18 months of age, further boosted the antibody titers. These findings show that the OPV currently used in Taiwan is highly immunogenic in Taiwanese children.

Transplant surgery injury recruits recipient MHC class II-positive leukocytes into the kidney

BACKGROUND

CD4 T cells, which are stimulated by the "indirect pathway" of antigen-presentation, participate in rejection. These T cells are sensitized by recipient major histocompatibility complex (MHC) class II-positive leukocytes that migrate into the transplant. Therefore, an important early step in rejection is the immigration of these recipient MHC class II-positive leukocytes into the renal transplant. The regulation of this early step is not understood. We now test the hypothesis that such leukocytes immigrate into the renal transplant in response to ischemic injury occurring during the transplant procedure.

METHODS

We transplanted Brown Norway (BN) kidneys into F1 Lewis/Brown Norway (L/BN) recipients. The F1 recipients are tolerant to the parental BN antigens, and any infiltration of recipient MHC class II-positive leukocytes results from injury occurring during transplantation surgery. In addition, ischemia/reperfusion injury was also induced by temporarily occluding the native renal arteries for 30 minutes. Transplanted kidneys and native kidneys, which suffered ischemia/reperfusion injury, were studied by immunohistochemistry on days 3, 7, 14, and 28 after surgery. Staining by the new monoclonal antibody (mAb) OX62 and antibodies to MHC class II identified dendritic cells. In addition, the following monoclonal antibodies identified: gamma/delta T cells, V65; B cells, OX33; cells that may be macrophages, dendritic cells, or dendritic cell precursors, ED1 (+) and OX62 (-); and recipient class II MHC, OX3.

RESULTS

After transplantation, the serum creatinine increased to 4 mg/dl and then decreased, which was consistent with reversible injury during transplantation and the absence of rejection. We found that the injury of transplantation itself resulted in the infiltration of recipient MHC class II-positive leukocytes into the transplanted kidney. This infiltrate peaked at days 7 to 14 after surgery. The inflammation was peritubular and patchy and involved cortex and outer medulla. Double staining for OX62 and OX3 identified some of the infiltrating leukocytes as dendritic cells. Other recipient leukocytes were MHC class II positive, ED1 positive, and OX62 negative. We also found that MHC class II leukocytes, including dendritic cells, infiltrated native kidneys injured by ischemia/reperfusion injury.

CONCLUSION

To our knowledge, this is the first demonstration that injury to the kidney during transplantation recruits recipient MHC class II-positive leukocytes into the kidney. Some of these leukocytes are dendritic cells.

Phase separation of rigid-rod suspensions in shear flow

We analyze the behavior of a suspension of rigid-rod-like particles in shear flow using a modified version of the Doi model, and construct diagrams for phase coexistence under conditions of constant imposed stress and constant imposed strain rate, among paranematic, flow-aligning nematic, and log-rolling nematic states. We calculate the effective constitutive relations that would be measured through the regime of phase separation into shear bands. We calculate phase coexistence by examining the stability of interfacial steady states and find a wide range of possible "phase" behaviors.

Genetic polymorphism of the mannose-binding protein gene in children with sickle cell disease: identification of three new variant alleles and relationship to infections

Mannose-binding protein (MBP) is a serum lectin that participates in the innate immune response. MBP deficiency may constitute a risk factor in the development of infections. Three MBP structural variants have been identified with a dominant effect on MBP serum concentration. Similarly, polymorphisms in the promoter of the corresponding gene (HSMBP1B) have been related to variations of MBP concentration in serum. Children with sickle cell disease (SCD) have an increased susceptibility to infections with encapsulated organisms resulting in meningitis, septicaemia, and osteomyelitis. We have investigated the HSMBP1B genotype in 242 children with SCD living in Paris. Apart from the known variant alleles, we identified three novel ones and report their distribution in our sample population. In addition, we found rather unexpectedly an increased frequency of the variant alleles in patients who had not suffered severe infections.

Penicillin-nonsusceptible Streptococcus pneumoniae infections in children

The emergence of penicillin-nonsusceptible Streptococcus pneumoniae (PNSSP) has brought a new clinical challenge. In Taiwan, reports of the prevalence and clinical features of PNSSP infections in children are limited. This study reviewed the resistance patterns of all clinical isolates of S. pneumoniae obtained from patients under 17 years of age from January 1993 through July 1998 in a medical center. Their clinical features and treatment responses were analyzed, with special attention paid to those patients with invasive PNSSP infections. Totally, 170 clinical isolates of S. pneumoniae were obtained from 168 patients aged under 17 years. Among those infections, there were 56 sinusitis (including 4 sinusitis with bacteremia), 44 pneumonia (including 23 pneumonia with bacteremia or empyema), 23 otitis media (including 5 otitis media with bacteremia), 9 simple bacteremia, 9 conjunctivitis, 8 meningitis, 4 peritonitis, 3 skin infections and the other 14 isolates were colonization. One hundred eleven isolates (65.3%) showed reduced penicillin susceptibility by the disk diffusion method. A trend of increasing percentiles of PRSP was noted: 27.3% (3/11) in 1993, 37.5% (9/24) in 1994, 55.5% (10/18) in 1995, 77.5% (31/40) in 1996, 66.0% (31/47) in 1997, and 87.1% (27/31) in 1998. Minimum inhibitory concentration (MIC) determinations by the E-test showed some of the isolates were intermediately resistant. Prior antibiotic usage was associated with a higher incidence of PNSSP infections. However, most children responded well to antimicrobial treatment.