Targeting PI3K/p-Akt/eNOS, Nrf2/HO-1, and NF-κB/p53 signaling pathways by angiotensin 1-7 protects against liver injury induced by ischemia-reperfusion in rats

The liver is an important organ, and hepatic ischemia-reperfusion (IR) injury is a frequent pathophysiological process that can cause significant morbidity and mortality. Thus, our study aimed to investigate the effect of targeting PI3K/p-Akt/eNOS (phosphoinositide 3-kinase/phospho-protein kinase B/endothelial nitric oxide synthase), Nrf2/HO-1 (nuclear factor-erythroid 2-related factor-2/heme oxygenase-1), and NF-κB/p53 (nuclear factor-κB/tumor protein 53) signaling pathways by using angiotensin (1-7) [ang-(1-7)] against hepatic injury induced by IR. Thirty-two male rats were included in sham group, ang-(1-7)-treated group, hepatic IR group, and hepatic IR group treated with ang-(1-7). The levels of hepatic ang-(1-7), angiotensin II (Ang II), angiotensin-converting enzyme 2 (ACE2), HO-1, malondialdehyde (MDA), PI3K, and p-Akt were assessed. The expressions of eNOS and B-cell leukemia/lymphoma-2 (BCL-2) in the liver were determined. Histological assessment and immunohistochemical expression of NF-κB, p53, and Nrf2 were carried out. The levels of reduced glutathione (GSH), aspartate aminotransferase (AST), alanine aminotransferase (ALT), tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6) in serum were estimated. Results showed that administration of ang-(1-7) to hepatic IR rats led to significant amelioration of hepatic damage through a histological evaluation that was associated with significant upregulation of the expressions of PI3K/p-Akt/eNOS and Nrf2/HO-1 with downregulation of NF-κB/p53 signaling pathways. In conclusion, PI3K/p-Akt/eNOS and Nrf2/HO-1 signaling pathways are involved in the protective effects of ang-(1-7) against hepatic damage induced by IR. Therefore, ang-(1-7) can be used to prevent hepatic IR, which occurs in certain conditions such as liver transplantation, hemorrhagic shock, and severe infection.

Effect of fluoxetine on the testes of adult albino rats and the possible protective role of curcumin

Fluoxetine (FLX) is extensively used for the treatment of a diversity of psychiatric disorders, mainly depression. However, it can adversely affect male fertility. This study was done to clarify the changes which take place in the testes after the oral administration of FLX and to evaluate the possible preventative role of curcumin. Seventy-six adult male albino rats were randomly divided into four equal groups. Control group: kept without any treatment. Curcumin group: received daily dose of curcumin (150 mg/kg body weight) through oral gavage for 8 weeks. FLX group. They were given daily dose of FLX (10 mg/kg body weight) given through oral gavage for 8 weeks. FLX and curcumin group. They were given FLX together with curcumin with the same previous doses through oral gavage daily for 8 weeks. By the end of the experiment, blood samples were collected for the biochemical study of testosterone. All the animals were anaesthetized by ether inhalation, and the testis specimens were dissected out and weighed. The specimens were subjected to histopathological, immunohistochemical, and morphometrical evaluation. FLX decreased serum testosterone, diminished both epithelial height and diameter of seminiferous tubules, increased collagen fiber deposition in testicular tissue and induced positive immune reaction to B-cell lymphoma-2-associated X protein. In the FLX and curcumin group, the FLX-induced changes were less remarkable. Exposure to FLX led to pronounced testicular alterations. Co-administration of curcumin with FLX ameliorated these changes.

Inflammation induced preterm labor and birth

Preterm birth which occurs before 37 weeks gestation is one of the most common obstetrical complication in humans. After many studies, it appears that "not one answer fits all" regarding the risk factors, causes and the treatments for this syndrome. However, it is becoming more evident that one of the major risk factors is inflammation and/or infection in the fetoplacental unit. In animal models (usually consisting of mice injected with lipopolysaccharide at 14 days of gestation), IL-22 and IL-6 have been identified as factors related to preterm birth. There are some clinical tests available to determine the risk for preterm labor and delivery, which can be identified before, during early, or at mid-gestation. However, treatment of preterm birth with antibiotics so far has not been "curable" and studies using anti-inflammatory treatments are not readily available. More studies regarding causes and treatments for preterm labor and delivery in humans are necessary to prevent neonatal deaths and/or developmental abnormalities associated with this common syndrome.

Dysregulated uterine natural killer cells and vascular remodeling in women with recurrent pregnancy losses

PROBLEM

Angiogenesis and vascular remodeling in secretory endometrium represent one of the crucial steps in pregnancy establishment, for which uterine NK (uNK) cells have an important role. Impairment of these steps may proceed to implantation and instigate initial pathology of recurrent pregnancy losses (RPL). In this study, we aim to investigate vascular development and density of uNK cells in secretory endometrium of women with RPL.

METHODS OF STUDY

Mid-secretory phase endometrial tissues from women with RPL (n = 15) and fertile controls (n = 7) were investigated. CD56⁺ and CD16⁺ uNK cells, CD31⁺ vascular endothelial cells and smooth muscle myosin (SMM)⁺ . Vascular smooth muscle cells (VSMC) expressing SMM were investigated using immunohistochemistry and western blot. High-throughput quantitative real-time polymerase chain reaction (qRT-PCR) was used as well.

RESULTS

CD56⁺ uNK number was significantly higher in women with RPL compared to controls (P < 0.0001). uNK cell density by immunohistochemistry was positively correlated with CD56 mRNA expression by qRT-PCR (r²  = 0.43, P = 0.0137). The number of blood vessels represented by the expression of either CD31 or SMM was higher in women with RPL as compared to controls (P < 0.05 and P < 0.0001, respectively), and correlated with the number of uNK cell (r²  = 0.18, P < 0.04, and r²  = 0.65, P < 0.0001, respectively). The wall thickness of spiral arteries was significantly higher in women with RPL as compared with that of controls (P = 0.0027).

CONCLUSION

Increased uNK cells in mid-secretory endometrium are associated with increased vascularization and defective vascular transformation of spiral arteries in women with RPL.

Identification of Giardia lamblia and the human infectious-species of Cryptosporidium in drinking water resources in Western Saudi Arabia by nested-PCR assays

The presence of Cryptosporidium and/or Giardia in drinking water represents a major public health problem. This study was the first report concerned with the occurrence of these protozoa in drinking water in Saudi Arabia. The study was undertaken in Al-Taif, a high altitude region, Western Saudi Arabia. Eight underground wells water, six desalinated water and five domestic brands of bottled water samples, 10 liter each, were monthly collected between May 2013 and April 2014. All samples (n = 228), were processed using an automated wash/elution station (IDEXX Laboratories, Inc.). Genomic DNA was directly isolated and purified from samples concentrates with QIAamp® Stool Mini Kit (Qiagen). The target protozoan DNA sequences were amplified using two previously published nested-PCR protocols. Of all the analyzed water, 31 samples (≈14%) were found contaminated with the target protozoa. Giardia lamblia was detected in ≈10% (7/72) of desalinated water and in ≈9% (9/96) of wells water. On the other hand, Cryptosporidium was identified in ≈8% (8/72) of desalinated water and in ≈7% (7/96) of wells water. All bottled water samples (n = 60) were (oo)cysts-free. Protozoan (oo)cysts were more frequently identified in water samples collected in the spring than in other seasons. The methodology established in our study proved sensitive, cost-effective and is amenable for future automation or semi-automation. For better understanding of the current situation that represent an important health threat to the local inhabitants, further studies concerned with (oo)cyst viability, infectivity, concentration and genotype identification are recommended.

Clinical chorioamnionitis is characterized by changes in the expression of the alarmin HMGB1 and one of its receptors, sRAGE

OBJECTIVE

High mobility group box-1 (HMGB1) protein is an alarmin, a normal cell constituent, which is released into the extracellular environment upon cellular stress/damage and capable of activating inflammation and tissue repair. The receptor for advanced glycation end products (RAGE) can bind HMGB1. RAGE, in turn, can induce the production of pro-inflammatory cytokines; this may be modulated by the soluble truncated forms of RAGE, including soluble RAGE (sRAGE) and endogenous secretory RAGE (esRAGE). The objectives of this study were to determine whether: 1) clinical chorioamnionitis at term is associated with changes in amniotic fluid concentrations of HMGB1, sRAGE and esRAGE; and 2) the amniotic fluid concentration of HMGB1 changes with labor or as a function of gestational age.

METHODS

Amniotic fluid samples were collected from the following groups: 1) mid-trimester (n = 45); 2) term with (n = 48) and without labor (n = 22) without intra-amniotic infection; and 3) term with clinical chorioamnionitis (n = 46). Amniotic fluid concentrations of HMGB1, sRAGE and esRAGE concentrations were determined by ELISA.

RESULTS

1) the median amniotic fluid HMGB1 concentration was higher in patients at term with clinical chorioamnionitis than in those without this condition (clinical chorioamnionitis: median 3.8 ng/mL vs. term in labor: median 1.8 ng/mL, p = 0.007; and vs. term not in labor: median 1.1 ng/mL, p = 0.003); 2) in contrast, patients with clinical chorioamnionitis had a lower median sRAGE concentration than those without this condition (clinical chorioamnionitis: median 9.3 ng/mL vs. term in labor: median 18.6 ng/mL, p = 0.001; and vs. term not in labor median: 28.4 ng/mL, p < 0.001); 3) amniotic fluid concentrations of esRAGE did not significantly change in patients with clinical chorioamnionitis at term (clinical chorioamnionitis: median 5.4 ng/mL vs. term in labor: median 6.1 ng/mL, p = 0.9; and vs. term not in labor: median 9.5 ng/mL, p = 0.06); and 4) there was no significant difference in the median AF HMGB1 concentration between women at term in labor and those not in labor (p = 0.4) and between women in the mid-trimester and those at term not in labor (mid-trimester: median 1.5 ng/mL; p = 0.2).

CONCLUSION

An increase in the amniotic fluid HMGB1 concentration and a decrease in sRAGE were observed in clinical chorioamnionitis at term. This finding provides evidence that an alarmin, HMGB1, and one of its receptors, sRAGE, are engaged in the process of clinical chorioamnionitis at term. These changes are quite different from those observed in cases of intra-amniotic infection/inflammation in preterm gestations.

Transabdominal evaluation of uterine cervical length during pregnancy fails to identify a substantial number of women with a short cervix

OBJECTIVE

To assess the diagnostic performance of transabdominal sonographic measurement of cervical length in identifying patients with a short cervix.

METHODS

Cervical length was measured in 220 pregnant women using transabdominal and transvaginal ultrasound (US). Reproducibility and agreement between and within both methods were assessed. The diagnostic accuracy of transabdominal US for identifying cases with a cervical length <25 mm was evaluated.

RESULTS

Twenty-one out of 220 cases (9.5%) had a cervical length <25 mm by transvaginal US. Only 43% (n = 9) of patients with a short cervix were correctly identified by transabdominal US. In patients with a cervical length of <25 mm by transvaginal US, transabdominal measurement of the cervix overestimated this parameter by an average of 8 mm (95% LOAs, -26.4 to 10.5 mm). Among women without a short cervix, transabdominal US underestimated cervical length on average (LOA) by 1.1 mm (95% LOAs, -11.0 to 13.2 mm). Transvaginal US was also more reproducible (intraclass correlation coefficient: (ICC) (0.96; 95% CI, 0.94 to 0.97) based on comparisons between 2D images and immediately acquired 3D volume datasets relative to transabdominal US (ICC: 0.71; 95% CI, 0.57 to 0.84). Transvaginal US detected 13 cases with funneling and six cases with sludge whereas only three cases of funneling and one of sludge were detected by transabdominal US.

CONCLUSION

Transabdominal measurement overestimated cervical LOA by 8 mm among women with a short cervix and resulted in the underdiagnosis of 57% of cases.

Late-onset preeclampsia is associated with an imbalance of angiogenic and anti-angiogenic factors in patients with and without placental lesions consistent with maternal underperfusion

OBJECTIVE

An imbalance between maternal angiogenic/anti-angiogenic factors concentrations has been observed in preeclampsia (PE) and other obstetrical syndromes. However, the frequency of pathologic findings in the placenta and the changes in maternal plasma angiogenic/anti-angiogenic factor concentrations differ between late- and early-onset PE. The aim of this study was to determine if the maternal plasma concentrations of placental growth factor (PlGF), soluble endoglin (sEng), and soluble vascular endothelial growth factor receptor-1 and 2 (sVEGFR-1 and sVEGFR-2) are different in late-onset PE with and without placental pathologic findings consistent with maternal underperfusion.

STUDY DESIGN

A cross-sectional study was conducted including 64 uncomplicated women and 66 women with late-onset PE (>34 weeks) who had blood samples and placenta available for pathologic examination. Patients with late-onset PE were divided into those with and without placental histologic findings consistent with maternal underperfusion as proposed by the Society for Pediatric Pathology. Maternal plasma concentrations of PlGF, sEng, sVEGFR-1 and sVEGRF-2 were determined by ELISA. Non-parametric statistics were used for analysis.

RESULTS

1) the prevalence of placental histological findings consistent with maternal underperfusion among women with late-onset PE was higher than that of those with an uncomplicated pregnancy (47% (31/66) vs. 7.8% (5/64), respectively; p < 0.01); 2) patients with late-onset PE and histological findings consistent with maternal underperfusion had a significantly lower median plasma concentration of PlGF, plasma PlGF/sVEGFR-1 ratio and plasma PlGF/sEng ratio than those with late-onset PE without placental underperfusion lesions (each p < 0.05); 3) the most common pathological findings in the placenta of patient with PE were lesions consistent with villous changes (77%, 24/31); and 4) isolated vascular lesions in the placenta were found only in 2 cases (6.5%), and the rest had a combination of villous and vascular lesions.

CONCLUSIONS

Nearly half of the patients with late-onset PE have placental lesions consistent with maternal underperfusion. These lesions are associated with an imbalance in the maternal concentration of angiogenic/anti-angiogenic factors. We propose that there is a link between maternal underperfusion and an anti-angiogenic state characterized by the changes in the concentrations of angiogenic and anti-angiogenic factors in women with late onset PE.

Interleukin-19 in fetal systemic inflammation

OBJECTIVE

The fetal inflammatory response syndrome (FIRS) is considered the fetal counterpart of the systemic inflammatory response syndrome (SIRS), which can be caused by infection and non-infection-related insults. Although the initial response is mediated by pro-inflammatory signals, the control of this response is achieved by anti-inflammatory mediators which are essential for the successful outcome of the affected individual. Interleukin (IL)-19 is capable of stimulating the production of IL-10, a major anti-inflammatory cytokine, and is a potent inducer of the T-helper 2 (Th2) response. The aim of this study was to determine if there is a change in umbilical cord plasma IL-19 and IL-10 concentrations in preterm neonates with and without acute funisitis, the histologic counterpart of FIRS.

METHODS

A case-control study was conducted including 80 preterm neonates born after spontaneous labor. Neonates were classified according to the presence (n = 40) or absence of funisitis (n = 40), which is the pathologic hallmark of FIRS. Neonates in each group were also matched for gestational age. Umbilical cord plasma IL-19 and IL-10 concentrations were determined by ELISA.

RESULTS

1) The median umbilical cord plasma IL-19 concentration was 2.5-fold higher in neonates with funisitis than in those without funisitis (median 87 pg/mL; range 20.6-412.6 pg/mL vs. median 37 pg/mL; range 0-101.7 pg/mL; p < 0.001); 2) newborns with funisitis had a significantly higher median umbilical cord plasma IL-10 concentration than those without funisitis (median 4 pg/mL; range 0-33.5 pg/mL vs. median 2 pg/mL; range 0-13.8 pg/mL; p < 0.001); and 3) the results were similar when we included only patients with funisitis who met the definition of FIRS by umbilical cord plasma IL-6 concentrations ≥ 17.5 pg/mL (p < 0.001).

CONCLUSION

IL-19 and IL-10 are parts of the immunologic response of FIRS. A subset of fetuses with FIRS had high umbilical cord plasma IL-19 concentrations. In utero exposure to high systemic concentrations of IL-19 may reprogram the immune response.

Anatomical study of the cervical nerve roots for posterior foraminotomy: cadaveric study

BACKGROUND

Anatomical study of the relationship among the cervical nerve roots, intervertebral disc, and lateral mass is important for the neurosurgeon to avoid complications of posterior cervical foraminotomy.

METHODS

Six adult cadavers were studied. The muscles of the back of the neck were removed to expose the cervical vertebrae posteriorly from C3 to C7. We measured the length, height, extent, and angulations of the nerve roots from the medial point of the facet (MPF) after a total laminectomy, then after one-half facetectomy. The height, width, anteroposterior diameter of the lateral mass, then the height and anteroposterior diameter of the neural foramen were also measured.

RESULTS

After total laminectomy from C3 to C7, all measures were taken from MPF showed that the mean length of the exposed root was 6.5-8.8 mm while vertical distance was 4-5.4 mm and the horizontal distance was 5.1-7.1 mm. Following a medial one-half facetectomy; the mean length of the exposed root was 8.9-12.3 mm, the vertical distance was 5.5-7.3 mm while the horizontal distance was 7.1-9.8 mm. The mean angulations of the nerve roots were 50.9-53.3º. There was a significant difference after total laminectomy and medial one-half facetectomy.

CONCLUSION

Anatomic and morphologic study of the cervical nerve roots and their relationships to the lateral mass and the intervertebral disc are useful landmarks to reduce the operative complications of the posterior foraminotomy.

Placental lesions associated with maternal underperfusion are more frequent in early-onset than in late-onset preeclampsia

OBJECTIVE

Preeclampsia (PE) has been classified into early- and late-onset disease. These two phenotypic variants of PE have been proposed to have a different pathophysiology. However, the gestational age cut-off to define "early" vs. "late" PE has varied among studies. The objective of this investigation was to determine the prevalence of lesions consistent with maternal underperfusion of the placenta in patients with PE as a function of gestational age.

STUDY DESIGN

A nested case-control study of 8307 singleton pregnant women who deliver after 20 weeks of gestation was constructed based on a cohort. Cases were defined as those with PE (n=910); controls were pregnant women who did not have a hypertensive disorder in pregnancy (n=7397). The frequency of maternal underperfusion of the placenta (according to the criteria of the Society for Pediatric Pathology) was compared between the two groups. Logistic regression was used for analysis. Estimated relative risks (RRs) were calculated from odds ratios.

RESULTS

1) The prevalence of lesions consistent with maternal underperfusion was higher in patients with PE than in the control group [43.3% vs. 15.9%, unadjusted odds ratio 4.0 (95% CI 3.5-4.7); P<0.001]; 2) the estimated RR of maternal underperfusion lesions in PE was higher than in the control group [RR=2.8 (95% CI 2.5-3.0)]; 3) the lower the gestational age at delivery, the higher the RR for these lesions; 4) early-onset PE, regardless of the gestational age used to define it (<32, 33, 34, 35 or 37 weeks) had a significantly higher frequency of placental lesions consistent with maternal underperfusion than late-onset PE (P<0.001 for all).

CONCLUSIONS

1) The earlier the gestational age of preeclampsia at delivery, the higher the frequency of placental lesions consistent with maternal underperfusion; 2) our data suggest that demonstrable placental involvement as determined by pathologic examination differs in early- and late-onset preeclampsia; and 3) this phenomenon appears to be a continuum, and we could not identify a clear and unambiguous gestational age at which lesions consistent with underperfusion would not be present.

Damage-associated molecular patterns (DAMPs) in preterm labor with intact membranes and preterm PROM: a study of the alarmin HMGB1

OBJECTIVE

Preterm parturition is a syndrome caused by multiple etiologies. Although intra-amniotic infection is causally linked with intrauterine inflammation and the onset of preterm labor, other patients have preterm labor in the absence of demonstrable infection. It is now clear that inflammation may be elicited by activation of the Damage-Associated Molecular Patterns (DAMPs), which include pathogen-associated molecular patterns (PAMPs) as well as "alarmins" (endogenous molecules that signal tissue and cellular damage). A prototypic alarmin is high-mobility group box 1 (HMGB1) protein, capable of inducing inflammation and tissue repair when it reaches the extracellular environment. HMGB1 is a late mediator of sepsis, and blockade of HMGB1 activity reduces mortality in an animal model of endotoxemia, even if administered late during the course of the disorder. The objectives of this study were to: (1) determine whether intra-amniotic infection/inflammation (IAI) is associated with changes in amniotic fluid concentrations of HMGB1; and (2) localize immunoreactivity of HMGB1 in the fetal membranes and umbilical cord of patients with chorioamnionitis.

METHODS

Amniotic fluid samples were collected from the following groups: (1) preterm labor with intact membranes (PTL) with (n=42) and without IAI (n=84); and (2) preterm prelabor rupture of membranes (PROM) with (n=38) and without IAI (n=35). IAI was defined as either a positive amniotic fluid culture or amniotic fluid concentration of interleukin-6 (IL-6) ≥ 2.6ng/mL. HMGB1 concentrations in amniotic fluid were determined by ELISA. Immunofluorescence staining for HMGB1 was performed in the fetal membranes and umbilical cord of pregnancies with acute chorioamnionitis.

RESULTS

(1) Amniotic fluid HMGB1 concentrations were higher in patients with IAI than in those without IAI in both the PTL and preterm PROM groups (PTL IAI: median 3.1 ng/mL vs. without IAI; median 0.98 ng/mL; p <0.001; and preterm PROM with IAI median 7.3 ng/mL vs. without IAI median 2.6 ng/mL; p=0.002); (2) patients with preterm PROM without IAI had a higher median amniotic fluid HMGB1 concentration than those with PTL and intact membranes without IAI (p <0.001); and (3) HMGB1 was immunolocalized to amnion epithelial cells and stromal cells in the Wharton's jelly (prominent in the nuclei and cytoplasm). Myofibroblasts and macrophages of the chorioamniotic connective tissue layer and infiltrating neutrophils showed diffuse cytoplasmic HMGB1 immunoreactivity.

CONCLUSIONS

(1) intra-amniotic infection/inflammation is associated with elevated amniotic fluid HMGB1 concentrations regardless of membrane status; (2) preterm PROM was associated with a higher amniotic fluid HMGB1 concentration than PTL with intact membranes, suggesting that rupture of membranes is associated with an elevation of alarmins; (3) immunoreactive HMGB1 was localized to amnion epithelial cells, Wharton's jelly and cells involved in the innate immune response; and (4) we propose that HMGB1 released from stress or injured cells into amniotic fluid may be responsible, in part, for intra-amniotic inflammation due to non-microbial insults.

Enzyme-linked immunospot assays provide a sensitive tool for detection of cytokine secretion by monocytes

Blood monocytes as well as tissue-differentiated macrophages play a pivotal role in controlling immune reactions. Monocytes regulate the extent, nature, and duration of immune responses by secretion of cytokines. Interleukin 6 (IL-6), tumor necrosis factor alpha (TNF-alpha), IL-10, and IL-12 are of particular interest, since IL-12 shifts the immune response towards a Th1 type, facilitating the production of, e.g., TNF-alpha and IL-6, while IL-10 counteracts Th1 responses and promotes the production of Th2-related cytokines such as IL-4. A tight regulation of these four cytokines keeps the balance and decides whether Th1 or Th2 will predominate in immune reactions. Enzyme-linked immunospot (ELISPOT) assays are among the most-sensitive and -specific methods available for cytokine research. They permit ex vivo identification of individual cells actively secreting cytokines. In the present study we prepared monocytes from healthy subjects' blood and adapted ELISPOT assays to define optimal conditions to detect and enumerate monocytes secreting IL-6, TNF-alpha, IL-10, and IL-12. The optimal time for monocyte incubation was 24 h, and optimal monocyte numbers (in cells per well) were 2,000 for IL-6, 1,000 for TNF-alpha, 50,000 for IL-10, and 100,000 for enumeration of IL-12 secreting monocytes. Among healthy subjects, 10% +/- 5% of the monocytes secreted IL-6, 12% +/- 12% secreted TNF-alpha, 0.1% +/- 0.1% secreted IL-10, and 0.2% +/- 0.3% secreted IL-12 (values are means +/- standard deviations). In conclusion, ELISPOT assays constitute a valuable tool to enumerate monocytes secreting IL-6, TNF-alpha, IL-10, and IL-12 and probably to enumerate monocytes secreting other cytokines and proteins.

The chloroplast genome of bleached mutants of Euglena gracilis

Bleached mutants of Euglena gracilis, traditionally thought to be completely deprived of chloroplast DNA, have been shown to contain a defective chloroplast genome, present at a very low copy number, and preferentially retaining ribosomal RNA genes. We propose to call these mutants phi-, because of their resemblance with the rho- mutants of yeast.

Comparative studies of chloroplastic and nuclear DNA repair abilities after ultraviolet irradiation of Euglena gracilis

Studies of nuclear and chloroplastic-DNA repair after ultraviolet irradiation of Euglena gracilis show that photoreactivation is very efficient at both the nuclear and chloroplastic level. Liquid-holding or split-dose experiments and treatment with caffeine reveal, furthermore, that dark-repair is very efficient in nuclear DNA but not in chloroplastic DNA (ctDNA). The possibility of a chloroplastic dark-repair of restricted efficiency is discussed. Determination of chloroplastic DNA content by reassociation kinetics indicates that an important degradation follows UV irradiation during liquid holding in the dark.