Genetic analysis of the yeast NUD1 endo-exonuclease: a role in the repair of DNA double-strand breaks

The deoxyribonucleases (DNases) have been shown genetically to be important in the vital processes of DNA repair and recombination. The NUD1 gene, which codes for an endo-exonuclease of Saccharomyces cerevisiae, was analyzed for its role in the DNA double-strand break (DSB) repair processes. While the nud1 strain is only slightly sensitive to ionizing radiation, expression of the HO-endonuclease to introduce a DSB at the MAT locus in that strain results in cell death. Cell survival is inversely proportional to the duration of HO-endonuclease expression. Analysis of the surviving colonies from the nud1 strain indicated that many of the survivors are sterile and that the proportion of these sterile survivors increases with the time of HO-endonuclease expression. On the other hand, the surviving colonies from the isogenic NUD1 strain are mating-proficient. Interestingly, double mutants of nud1 rad52 are more resistant to ionizing irradiation than the rad52 strain and have a cell-survival fraction of 32% for rad52-1 nud1 and 9% for rad52::URA3 nud1 following prolonged HO-endonuclease expression, indicating that nud1 has a suppressor effect on the DSB-induced lethality in rad52. Polymerase chain reaction analysis showed that many of the nud1 survivors contained small alterations within the MAT locus, suggesting that the survivors arose through the process of non-homologous end-joining. These results suggest that the endo-exonuclease acts at a DSB to promote DNA repair via the homologous recombination pathway. Received: 20 July / 20 September 1998     

Incidence and predictors of loss to follow-up among adult HIV-infected patients taking antiretroviral therapy at North Shewa zone public Hospitals,Northeast Ethiopia: A retrospective follow-up study

BackgroundPatients who are lost to follow-up while on treatment compromise their own health and the long-term success of antiretroviral therapy (ART) programs. Besides, loss to follow-up (LTFU) increases HIV-related morbidity and mortality. Therefore, this study aimed to determine the incidence of LTFU and its predictors among adult HIV positive patients on anti-retroviral therapy at North Shoa zone public hospitals, Northeast Ethiopia.MethodsA retrospective follow up study of 517 people living with HIV/AIDS and attending an ART clinic between 2015 and 2020 was conducted at North Shewa zone, public hospitals. Kaplan-Meier failure function together with log rank test was used to compare failure function. Multivariable Cox proportion hazards regression model was used to determine predictors of LTFU.ResultThe incidence density rate of lost to follow up among HIV positive adult on ART was found to be 8.9 per 100 adult years observation (95%CI; 7.45, 10.68). In multivariable cox proportional regression analysis, WHO clinical stage-IV (AHR = 1.50; 95% CI: 1.08, 3.75), comorbidity disease (AHR = 0.54; 95% CI; 0.30, 0.97), body mass index less than 18kg/m2 (AHR = 1.60; 95% CI; 1.02, 2.51), cotrimoxazole preventive therapy (AHR = 1.57; 95% CI;1.09, 2.53), and a low CD4 count (AHR = 1.66; 95% CI; 1.29, 3.49) were found to be a significant predictors of lost to follow up.ConclusionThe current study showed that the incidence rate of loss to ART follow-up was high. Body mass index score less than 18kg/m2, advanced WHO clinical stage, CD4<200cell/mm³, had comorbidity disease, and cotrimoxazole therapy were a significant predictors of lost to ART follow up. Therefore, appropriate mitigation measures in the at-risk group need to be instigated to advance retention rate.     

Phage Display-directed Discovery of LEDGF/p75 Binding Cyclic Peptide Inhibitors of HIV Replication

The interaction between the human immunodeficiency virus (HIV) integrase (IN) and its cellular cofactor lens epithelium-derived growth factor (LEDGF/p75) is crucial for HIV replication. While recently discovered LEDGINs inhibit HIV-1 replication by occupying the LEDGF/p75 pocket in IN, it remained to be demonstrated whether LEDGF/p75 by itself can be targeted. By phage display we identified cyclic peptides (CPs) as the first LEDGF/p75 ligands that inhibit the LEDGF/p75–IN interaction. The CPs inhibit HIV replication in different cell lines without overt toxicity. In accord with the role of LEDGF/p75 in HIV integration and its inhibition by LEDGINs, CP64, and CP65 block HIV replication primarily by inhibiting the integration step. The CPs retained activity against HIV strains resistant to raltegravir or LEDGINs. Saturation transfer difference (STD) NMR showed residues in CP64 that strongly interact with LEDGF/p75 but not with HIV IN. Mutational analysis identified tryptophan as an important residue responsible for the activity of the peptides. Serial passaging of virus in the presence of CPs did not yield resistant strains. Our work provides proof-of-concept for direct targeting of LEDGF/p75 as novel therapeutic strategy and the CPs thereby serve as scaffold for future development of new HIV therapeutics.     

Insulin-like Growth Factor and its Therapeutic Potential for Diabetes Complications - Mechanisms and Metabolic Links: A Review

BACKGROUNDThe insulin-like growth factor (IGF) system is an important system in normal physiological functioning of the body. In diabetes mellitus, alterations of IGF-binding protein (IGFBP) levels have been described, mainly in vascular complications.AIMThe aim of this review was to explore the role of the IGF system in reducing diabetes complications and its role as potential therapeutic target.RESULTSIGF-1 plays a role in neuronal growth and developmental processes. Low concentrations of IGF-1 have been associated with neuropathy and other diabetes complications. Moreover, impaired IGF synthesis and function may result in cellular senescence and impaired vascular endothelial proliferation, adhesion, and integration. Of note, high IGF-1 bioavailability may prevent or delay the inception of diabetes-associated complications in diabetes patients. The mechanism of normal functioning IGF-1 is induced by increasing nitric oxide synthesis and potassium ion channel opening in cardiovascular physiology, which improves impaired small blood vessel function and reduces the occurrence of diabetes complications associated with reduced concentrations of IGF-1.CONCLUSIONSIGF may be considered an alternative therapy for diabetes and diabetes-associated complications. Therefore, future studies should focus on the mechanism of action and therapeutic potential of IGFs in reducing the risk of development and progression of the disease in different clinical settings.     

Sphingomyelinase and ceramide analogs induce vasoconstriction and leukocyte-endothelial interactions in cerebral venules in the intact rat brain: Insight into mechanisms and possible relation to brain injury and stroke

This study was designed to test the hypothesis that the sphingomyelin-ceramide signaling pathway may be important in proinflammatory-like responses in the intact brain. Effects of neutral sphingomyelinase (N-SMase), ceramide analogs, phosphorylcholine and ceramide metabolites were studied on rat brain cerebral (cortical) venule lumen sizes, leukocyte rolling, velocity and endothelial cell wall adhesion, microvessel permeability, microvessel rupture and focal hemorrhages using in vivo high resolution TV microscopy. Perivascular and close intra-arterial administration of N-SMase, C(2)-, C(8)-, and C(16)-ceramide, but not either phosphorylcholine, C(6)-ceramide, nervonic (C(24):1) ceramide, lignoceric (C(24):0) ceramide, C(8)-ceramide-1-phosphate, glucosylceramide or 1-0-acylceramide, resulted in potent, concentration-dependent constriction (and spasm) of cortical venules, followed by increased leukocyte rolling, decreased leukocyte velocities, increased leukocyte-endothelial wall adhesion, increased venular wall permeability, postcapillary venule rupture and, often, micro-hemorrhaging at high concentrations; angiotensin II, serotonin and PGF(2alpha) didn't demonstrate these characteristics. Pretreatment with either one of three different antioxidants, including inhibitors of NF-kappaB activation, or two different Ca(2+) channel blockers either prevented or attenuated the adverse venular effects of N-SMase and the ceramides. Likewise, pretreatment with either a PKCalpha-beta antagonist or a MAP kinase antagonist also attenuated the adverse venular effects. These results suggest that N-SMase and several ceramides can result in potent venular cerebrovasospasm, leukocyte-endothelial chemoattraction, and microvessel wall permeability changes in the intact rat brain. These proinflammatory-like actions suggest that N-SMase and ceramides could produce brain-vascular damage by reperfusion injury triggering lipid peroxidation, release of reactive oxygen species and activation of diverse signaling pathways: PKCalpha-beta isozymes, MAP kinase and NF-kappaB.     

Serum enzyme levels and influencing factors in three indigenous Ethiopian sheep breeds

Serum enzymes were studied in 377 apparently healthy sheep from three indigenous sheep breeds of Ethiopia. The effect of breed, age, sex and season on alanine aminotransferase (ALT)/glutamic pyruvic transaminase (GPT), aspartate aminotransferase (AST)/glutamic oxalacetic transaminase (GOT), alkaline phosphatase (ALP) and acid phosphatase (AcP) levels was assessed. The mean serum enzymes levels of the indigenous Menz, Tukur and Wello sheep breeds ranged from 17.2–17.7 IU l⁻¹, AST/GOT from 50.4–56.6 IU l⁻¹, ALP from 93.2–103.9 IU l−¹, and AcP from 2.47–2.56 IU l⁻¹, were within the normal range for sheep elsewhere. Season had significant influence on all serum enzymes except for the AcP in Menz breed. Sex had significant effect on AST/GOT for Menz and on ALP for all sheep breeds, with consistently higher values in males than in females. Age was significant only on ALP in the Menz and Tukur breeds. The serum enzyme levels of these indigenous sheep breeds can be used as normal reference values for Ethiopian sheep breeds adapted to similar agro-ecology and production system.     

Assessment of the implementation of HIV-rapid test kits at different levels of health institutions in Ethiopia

OBJECTIVE: Evaluation and monitoring of Human Immunodeficiency Virus (HIV) testing reagents at the point of service is helpful to prevent the occurrence of problems related to testing and interpretation. To evaluate the implementation of HIV rapid test kits at the point of services in voluntarily counseling and testing (VCT) and diagnostic centers in Ethiopia. METHODS: The assessment was the third phase of evaluation of HIV rapid test kits in Ethiopia followed from phase-I and phase-II. Known proficiency testing panels, well-structured questionnaire (addressing type of tests, human resource and problems related to tests), onsite supervision and retesting of samples collected from sites were used to evaluate the performances of reagents and laboratories. RESULTS: Forty-four health institutions were included. Thirty-six (90.0%) health institutions had trained human resource on HIV testing. In 27 (61.4%) three types of HIV rapid test kits (Determine, Capillus and Unigold) were available. Serial-algorithm was used in all the laboratories. In 31 (70.4%) of them external quality control specimens were not used. Twenty two (50.0%) of the laboratories reported frequent shortage of reagents. All (100%) were able to identify negative specimens distributed. Positive proficiency panel samples were identified in 37 (94.8%) of the 39 laboratories. There was 98.3% agreement at a screening level between the sites and the central laboratory. Rate of discrepancy between screening and confirmatory assays was found to be 3.0% and 2.1% at the sites and at central laboratory, respectively. CONCLUSION: The test kits showed a good performance at the point of services in the field sites. However, continuous assessment of HIV test kits at the point of service and training of professionals on newly arrived techniques are recommended to have effective testing performance with acceptable sensitive and specific testing algorithm. Effective quality assurance program should be in place to support programs such as VCT, prevention of mother-to-child-transmission and antiretroviral therapy.     

Wheeze, allergic sensitization and geohelminth infection in Butajira, Ethiopia

BACKGROUND: The effect of geohelminth infection on wheeze and allergen sensitization is inconsistent across different epidemiological studies. OBJECTIVE: To investigate the association between self-reported wheeze, self-reported asthma, allergic sensitization and geohelminth infection in urban and rural areas of Butajira, southern Ethiopia. METHODS: Questionnaire data on wheeze, asthma and a range of confounding variables was gathered in a cross-sectional study of 7649 people aged 5 years or more from the Butajira Rural Health Project database. Allergic skin sensitization to Dermatophagoides pteronyssinus and cockroach was measured, and a stool sample collected for qualitative and quantitative geohelminth analysis. RESULTS: Wheeze was weakly associated with allergic sensitization to D. pteronyssinus and cockroach (odds ratios (OR) 1.21, 95% confidence interval (CI) 0.98-1.51, and 1.27, 95% CI 1.00-1.62, respectively). Self-reported asthma was related to sensitization to D. pteronyssinus only (OR 4.09, 95% CI 2.86-5.84). Geohelminths were present in 33.8% of participants, and the median egg load in infested individuals was 6 eggs/g. Overall, presence of any geohelminths was associated with a diminished risk of cockroach sensitization (adjusted OR 0.82, 95% CI 0.68-0.99) but there were no significant protective effects of any geohelminth infection against wheeze or asthma. CONCLUSION: In a developing country community with relatively low geohelminth prevalence and intensity, we found weak association between allergic sensitization and wheeze, but no evidence of a protective effect of geohelminths against wheeze or asthma.     

Treatment outcome of tuberculosis patients under directly observed treatment in Addis Ababa,Ethiopia

BackgroundTuberculosis is one of the leading causes of mortality among infectious diseases worldwide. For effective tuberculosis control, it is a pre-requisite to detect the cases as early as possible, and to ensure that the tuberculosis patients complete their treatment and get cured. However, in many resource-constrained settings treatment outcome for tuberculosis has not been satisfactory.ObjectiveThe aim of the study was to assess the treatment outcome of tuberculosis patients and investigate the association of demographic and clinical factors with treatment success of patients enrolled in Directly Observed Treatment Short Course program in government owned health centers over the course of five consecutive years in Addis Ababa, Ethiopia.MethodsA register based historical cohort study covering the period of July 2004 to June 2009 was conducted to determine the treatment outcome of Directly Observed Treatment Short Course in government owned health centers in Addis Ababa. Sex and age of tuberculosis patients, health center at which the patient was treated, year of treatment, type of tuberculosis for which the patient was treated, type of treatment offered to the patient, follow-up status and documented treatment outcome were extracted from the Directly Observed Treatment Short Course clinics of three randomly selected health centers.ResultRecords of 6450 registered tuberculosis patients (n = 3147 males and 3433 females) were included in this document review. Of these patients 18.1% were reported as being cured, 64.6% were documented as treatment completed, 3.7% died during follow-up, 5.1% were reported as defaulters, 0.4% were documented as treatment failure and 8.2% were transferred out to another health institution. Treatment center and year of enrollment were significantly associated with treatment success.ConclusionYear of enrollment and treatment center were significantly associated with treatment success. Although the overall treatment success obtained in this study is in line with the World Health Organization (WHO) target, continuous follow-up of patients with frequent supportive supervision during the course of treatment, and further investigate the cause for the observed difference in treatment success across treatment centers are recommended.