Influence of CYP2B6 516G>T polymorphism and interoccasion variability (IOV) on the population pharmacokinetics of efavirenz in HIV-infected South African children.

OBJECTIVE: To investigate the influence of CYP2B6 516G>T polymorphism, as a covariate, and of interoccasion variability (IOV) on the oral clearance (CL/F) of efavirenz (EFV) in treatment-naïve black South African children over a period of 24 months post-antiretroviral therapy (ART) initiation. METHODS: HIV-infected black children (n = 60, aged 3-16 years), with no prior exposure to ART, eligible to commence ART and attending an outpatient clinic were enrolled into this study. Blood samples were taken at mid-dose interval at 1, 3, 6, 12, 18 and 24 months post-ART initiation. EFV plasma samples were determined with an adapted and validated LC/MS/MS method. Genotyping of the CYP2B6 G516T single nucleotide polymorphism (SNP) was performed using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). NONMEM was used for the population pharmacokinetic modelling. RESULTS: EFV concentrations below 1 µg/mL accounted for 18% (116/649), EFV concentrations >4 µg/mL accounted for 29.5% (192/649) and concentrations within the therapeutic range (1-4 µg/mL) represented 52.5% (341/649) of all the samples determined. The covariates age, weight and CYP2B6 G516Tgenotype were included in the final model with population estimates for CL/F determined as 2.46, 4.60 and 7.33 L/h for the T/T, G/T and G/G genotype groups respectively. CONCLUSIONS: The inclusion of both age and weight to predict accurate EFV CL values for the respective genotype groups within this paediatric population was required, whereas the addition of gender and body surface area did not improve the predictions. The importance of introducing IOV in a PK model for a longitudinal study with sparsely collected data was again highlighted by this investigation.

The composition of egg yolk absorbed by fasted ostrich (Struthio camelus L.) chicks from 1 to 7 days posthatching and for ostrich (Struthio camelus L.) chicks from 1 to 16 days posthatching on a prestarter broiler diet.

This study was performed to obtain information on yolk utilization in fasted and fed ostrich chicks posthatching. The fasted trial lasted for 7 d, whereas the fed trial continued for 16 d. Fasted ostrich chicks showed a decrease of 31.3 g of BW, with yolk weight decreasing by 28.9 g daily after hatching. Yolk weight comprised 28% of 1-d-old ostrich chick BW and decreased to 12% at 7 d of age. Only 44.4% of the fasted ostrich chick yolk was assimilated over the trial period. Crude protein content of the yolk decreased by 13.2 g daily. Fat content increased by 1.77% daily, whereas total yolk fat weight decreased with 8.91 g daily. Slaughter weight of fed ostrich chicks increased, with yolk weight decreasing by 16.3 g daily. Yolk content for fed ostrich chicks was 26% of BW at 2 d of age. Ostrich chicks absorb 30% of yolk over the first 4 d, 67% after 8 d, and only deplete the yolk after 14 d posthatch. Fasted ostrich chicks absorbed the yolk content at a rate of 28.9 g/d, compared with 22.3 g/d over the first 8 d and 16.3 g/d over the 16 d for fed ostrich chicks. The CP content of the yolk decreased by 6.84 g daily in fed ostrich chicks, whereas fat content of the yolk increased by 1.39% daily, although total yolk fat weight decreased by 6.61 g daily. Yolk weight and total CP decreased faster over the first 7 d in the fasted ostrich chicks compared with the fed ostrich chicks, which indicated that the decrease in yolk weight could be attributed to absorption of protein from the yolk. Fat content decreased faster over the first 8 d from the yolk of the fed ostrich chicks compared with that from the yolk of the fasted ostrich chicks, which could indicate that external feed has a positive influence on the absorption of fat from the yolk content.

Expression of the H-subunit and L-subunit of ferritin in bone marrow macrophages and cells of the erythron during cellular immune activation.

BACKGROUND: The expression of the two types of ferritin subunits, the H-subunit and L-subunit, has been shown to be differentially regulated by cytokines. The primary aim of the present study was to quantitatively measure the expression of the H-subunit and L-subunit of ferritin in bone marrow macrophages and cells of the erythron in patients with chronic T-helper cell type-1 immune stimulation. METHODS: The expression of the H-subunit and L-subunit of ferritin in bone marrow macrophages and cells of the erythron was quantitatively evaluated by post-embedding immunolocalisation with immunogold transmission electron microscopy. RESULTS: The present study showed up-regulation of the H-subunit of ferritin in the bone marrow macrophage in patients with pronounced cellular immune activation (94.7±37.3 counts/µm(2); n=31 vs 72.4±34.0 counts/µm(2); n=13, p-value=0.037). CONCLUSION: This supports a possible role for H-subunit rich ferritins in the hypoferraemia of chronic disease.

Pro- and anti-inflammatory cytokines during immune stimulation: modulation of iron status and red blood cell profile.

Forty-eight patients were subdivided according to C-reactive protein (CRP) levels, resulting in 19 patients with normal (2.8 ± 2.8 mg/L) and 29 with elevated (82.2 ± 76.2 mg/L) CRP levels. The elevated CRP group had iron and red blood cell (RBC) profiles characteristic of chronic immune stimulation (CIS), and the normal CRP group, profiles of true iron deficiency. Normal relationships between storage iron, bioavailable iron, and RBC indices were absent in the elevated CRP group-implying the role of iron as major determinant of the RBC profile to be diminished during CIS. The elevated CRP group had significant increases in proinflammatory cytokines (INF-γ, TNF-α, Il-1ß, Il-6, and Il-8). Anti-inflammatory cytokine levels were normal, except for Il-10, supporting previous indications that Il-10 contributes to reducing bioavailable iron. Regression analysis suggested decreases in transferrin to be related to increases in Il-8 and an increase in ferritin to be related to a decrease in Il-12 levels. TGF-ß levels were positively related to transferrin and negatively to ferritin.

Engineering pathways for malate degradation in Saccharomyces cerevisiae.

Deacidification of grape musts is crucial for the production of well-balanced wines, especially in colder regions of the world. The major acids in wine are tartaric and malic acid. Saccharomyces cerevisiae cannot degrade malic acid efficiently due to the lack of a malate transporter and the low substrate affinity of its malic enzyme. We have introduced efficient pathways for malate degradation in S. cerevisiae by cloning and expressing the Schizosaccharomyces pombe malate permease (mae1) gene with either the S. pombe malic enzyme (mae2) or Lactococcus lactis malolactic (mleS) gene in this yeast. Under aerobic conditions, the recombinant strain expressing the mae1 and mae2 genes efficiently degraded 8 g/L of malate in a glycerol-ethanol medium within 7 days. The recombinant malolactic strain of S. cerevisiae (mae1 and mleS genes) fermented 4.5 g/L of malate in a synthetic grape must within 4 days.

Ferritin and ferritin isoforms I: Structure-function relationships, synthesis, degradation and secretion.

Ferritin is the intracellular protein responsible for the sequestration, storage and release of iron. Ferritin can accumulate up to 4500 iron atoms as a ferrihydrite mineral in a protein shell and releases these iron atoms when there is an increase in the cell's need for bioavailable iron. The ferritin protein shell consists of 24 protein subunits of two types, the H-subunit and the L-subunit. These ferritin subunits perform different functions in the mineralization process of iron. The ferritin protein shell can exist as various combinations of these two subunit types, giving rise to heteropolymers or isoferritins. Isoferritins are functionally distinct and characteristic populations of isoferritins are found depending on the type of cell, the proliferation status of the cell and the presence of disease. The synthesis of ferritin is regulated both transcriptionally and translationally. Translation of ferritin subunit mRNA is increased or decreased, depending on the labile iron pool and is controlled by an iron-responsive element present in the 5'-untranslated region of the ferritin subunit mRNA. The transcription of the genes for the ferritin subunits is controlled by hormones and cytokines, which can result in a change in the pool of translatable mRNA. The levels of intracellular ferritin are determined by the balance between synthesis and degradation. Degradation of ferritin in the cytosol results in complete release of iron, while degradation in secondary lysosomes results in the formation of haemosiderin and protection against iron toxicity. The majority of ferritin is found in the cytosol. However, ferritin with slightly different properties can also be found in organelles such as nuclei and mitochondria. Most of the ferritin produced intracellularly is harnessed for the regulation of iron bioavailability; however, some of the ferritin is secreted and internalized by other cells. In addition to the regulation of iron bioavailability ferritin may contribute to the control of myelopoiesis and immunological responses.

Ferritin and ferritin isoforms II: protection against uncontrolled cellular proliferation, oxidative damage and inflammatory processes.

Ferritin is a major iron storage protein involved in the regulation of iron availability. Each ferritin molecule comprises 24 subunits. Various combinations of H-subunits and L-subunits make up the 24-subunit protein structure and these ferritin isoforms differ in their H-subunit to L-subunit ratio, as well as in their metabolic properties. Ferritin is an acute-phase protein and its expression is up-regulated in conditions such as uncontrolled cellular proliferation, in any condition marked by excessive production of toxic oxygen radicals, and by infectious and inflammatory processes. Under such conditions ferritin up-regulation is predominantly stimulated by increased reactive oxygen radical production and by cytokines. The major function of ferritin in these conditions is to reduce the bio-availability of iron in order to stem uncontrolled cellular proliferation and excessive production of reactive oxygen radicals. Ferritin is not, however, indiscriminately up-regulated in these conditions as a marked shift towards a predominance in H-subunit rich ferritins occurs. Preliminary indications are that, while the L-subunit primarily fulfils the conventional iron storage role, the H-subunit functions primarily as rapid regulator of iron availability, and perhaps indirectly as regulator of other cellular processes. It is suggested that the optimum differential expression of the two subunits differ for different cells and under different conditions and that the expression of appropriate isoferritins offers protection against uncontrolled cellular proliferation, oxidative stress and against side effects of infectious and inflammatory conditions.

Learners' knowledge and and perceptions of voluntary counselling and testing for HIV and AIDS in the Free State Province.

The study investigated the perceptions of the youth regarding Voluntary Counselling and Testing (VCT) and sexual aspects related to HIV and AIDS. The study was grounded in qualitative methodology, using 4 focus group interviews for data collection triangulating the results with field notes and literature. The participants of the four focus groups proved to be well informed on the topic and had clear perceptions concerning several aspects. They were very positive regarding the advantages of VCT for the prevention and management of HTV and AIDS. The participants recognised the need for the youth to be better informed about VCT and HIV and AIDS. They were much concerned by the lack of parental involvement in sexual education as well as the permissiveness of the youth who partook in alcohol and drug abuse as well as prostitution. Participants of the study stated that this problem was exacerbated by poverty and poor socio economic conditions.

Supportive neurodevelopmental evidence for ADHD as a developmental disorder.

A baby is dependent on its primary caregiver (hereafter referred to as 'mother') for its emotional regulation. The development of emotional self-regulation is dependent on the growth and myelinisation of connections between cortical (control) and limbic (emotion) structures in the infant brain. The subcortical sympathetic limbic system is dominant from birth, and it is only at 14-18 months of age that the parasympathetic cortical inhibitory part develops. The maturation of specifically the right orbitofrontal cortex, which dominates both the sympathetic and parasympathetic limbic systems, is essential for the regulation of emotion for the rest of an individual's life. Behavioral hyperactivity, impulsivity and inattention are considered normal for children in the early practising phase (10-14 months). This stage is characterised by sympathetic dominance stimulated by the ventral tegmental limbic circuit. We hypothesise that children with Attention Deficit Hyperactivity Disorder remain stuck in this phase, and accordingly do not enter the next stage of emotional development, i.e., the late practising period, in which the lateral tegmental limbic circuit, which stimulates the parasympathetic system develops. Parental reactions, which may contribute to this block in emotional development, include: largely ignoring their child, until the child does something the parent disapproves of, then scolding the child, without consoling the child again afterwards. This leads susceptible children to develop defensive hyperactivity and inattention in order to avoid a shame state they are unable to cope with. Implications for therapy are that caregivers should be taught firstly to give lots of positive attention to their child, and if necessary to scold, to console the child immediately afterwards. If this can be achieved consistently, the child will have the chance to develop their parasympathetic lateral limbic circuit, and eventually right orbitofrontal dominance over both limbic circuits, which translates into the ability to self-regulate their emotional states.

Prediction of the chemical composition of freeze dried ostrich meat with near infrared reflectance spectroscopy.

Near infrared reflectance spectroscopy (NIRS) was used to predict the chemical composition of freeze-dried ostrich meat samples. Tenderloin (M. ambiens), big drum (M. iliofibularis) and fan fillet (M. gastrocnemius) samples (n=160) were included in the study. Samples were minced, freeze-dried and analysed according to standard laboratory procedures for ash, dry matter (DM), crude protein (CP) and fat content. Samples were scanned (1100-2500 nm) and partial least-square regression (PLSR) was used to predict the chemical composition. Multiple correlation coefficients (r) and standard errors of calibration (SEC) for the chemical analysis of freeze-dried ostrich meat were: ash (0.72; 0.29%); DM (0.72; 1.01%); CP (0.98; 0.55%); and fat (0.99; 0.29%). The r values for the validation set and the standard error of performance (SEP) for the different constituents were: ash (0.71; 0.23%); DM (0.84; 0.72%); CP (0.97; 0.64%); and fat (0.99; 0.18%). Calibrations were accurate for CP and fat.

South African medical schools: Current state of selection criteria and medical students' demographic profile.

BACKGROUND: Selection of medical students at South African (SA) medical schools must promote equitable and fair access to students from all population groups, while ensuring optimal student throughput and success, and training future healthcare practitioners who will fulfil the needs of the local society. In keeping with international practices, a variety of academic and non-academic measures are used to select applicants for medical training programmes in SA medical schools. OBJECTIVES: To provide an overview of the selection procedures used by all eight medical schools in SA, and the student demographics (race and gender) at these medical schools, and to determine to what extent collective practices are achieving the goals of student diversity and inclusivity. METHODS: A retrospective, quantitative, descriptive study design was used. All eight medical schools in SA provided information regarding selection criteria, selection procedures, and student demographics (race and gender). Descriptive analysis of data was done by calculating frequencies and percentages of the variables measured. RESULTS: Medical schools in SA make use of academic and non-academic criteria in their selection processes. The latter include indices of socioeconomic disadvantage. Most undergraduate medical students in SA are black (38.7%), followed by white (33.0%), coloured (13.4%) and Indian/Asian (13.6%). The majority of students are female (62.2%). The number of black students is still proportionately lower than in the general population, while other groups are overrepresented. CONCLUSION: Selection policies for undergraduate medical programmes aimed at redress should be continued and further refined, along with the provision of support to ensure student success.

Site of renal action of xipamide.

Xipamide, hydrochlorothiazide, and furosemide were given to normal volunteers on a double-blind basis. During maximal water diuresis, there was a reduction in free water clearance and an increase in osmolar clearance after administration of xipamide and hydrochlorothiazide, but not in the case of furosemide. During maximal hydropenia, both xipamide and hydrochlorothiazide increased free water reabosorption in a linear relationship to osmolar clearance, while furosemide increased osmolar clearance with little change in free water reabsorption. It was concluded, therefore, that, as with hydrochlorothiazide, the site of action of xipamide was on the distal convoluted tubule, and that of furosemide on the loop of Henle.

Mutation of Gly-444 inactivates the S. pombe malic enzyme.

A mutant malic enzyme gene, mae2-, was cloned from a strain of Schizosaccharomyces pombe that displayed almost no malic enzyme activity. Sequence analysis revealed only one codon-altering mutation, a guanine to adenine at nucleotide 1331, changing the glycine residue at position 444 to an aspartate residue. Gly-444 is located in Region H, previously identified as one of eight highly conserved regions in malic enzymes. We found that Gly-444 is absolutely conserved in 27 malic enzymes from various prokaryotic and eukaryotic sources, as well as in three bacterial malolactic enzymes investigated. The evolutionary conservation of Gly-444 suggests that this residue is important for enzymatic function.

Red blood cell fatty acid profile of chronic renal failure patients receiving maintenance haemodialysis treatment.

The fatty acid profile of chronic renal failure (CRF) patients on maintenance haemodialysis treatment (MHT) is abnormal and results point towards an essential fatty acid (EFA) deficiency. However, controversies still exist as to which of the essential fatty acids (EFAs) or EFA-products are decreased. In this study, the results of a comprehensive analysis of the fatty acids, performed on the red blood cells of 14 CRF patients on MHT, are presented. The red blood cell membrane fatty acids determined in this study include a range of saturated fatty acids (SFAs), mono-unsaturated fatty acids (MUFAs) and poly-unsaturated fatty acids (PUFAs). Results confirmed the suggested presence of an essential fatty acid deficiency in CRF patients on MHT. It showed the total content of the n-6 fatty acids (31.66 +/- 3.21 vs 34.67 +/- 2.05), as well as the total content of the PUFAs (37.22 +/- 4.08 vs 40.93 +/- 2.35), to be significantly decreased. The total MUFA content was, in contrast, significantly increased (16.87 +/- 0.91 vs 15.49 +/- 1.18). The EFA deficiency profile seen in this study points towards that of a chronic inflammatory condition. This is borne out by the fact that all three precursors of the eicosanoids--the mediators of various inflammatory and immune responses--were reduced in the presence of an increase in MUFAs as well as SFAs. The possibility of the fatty acid profile of CRF patients on MHT being that of a chronic inflammatory condition is supported by the fact that continuous complement-dependent and complement-independent immune activation, due to bio-incompatibility between blood cells and the dialysis membranes, is known to occur during the dialysis process.

Whole blood serotonin levels in chronic renal failure.

Whole blood serotonin levels were investigated in a control group (n = 35) and in a group of chronic renal failure patients (n = 127) on various treatment regimen i.e. conservative treatment (n = 39), maintenance haemodialysis (n = 35) and after renal transplantation (n = 53). The whole blood serotonin levels, as determined by high performance liquid chromatography, were significantly lower in the chronic renal failure patients than in the control group (p = 0.0001). Whole blood serotonin levels were significantly lower in the white subjects than in the black subjects of the study (p = 0.0001).

Plasma vitamin E levels in a chronically hemolyzing group of dialysis patients.

Plasma vitamin E levels and the ascorbate cyanide test were assessed in 15 chronic hemodialysis (HD) patients (group A) exposed to persistently elevated chloramine levels in the dialysis water. The vitamin E levels in these patients, who had evidence of oxidant induced hemolytic anemia, were compared to 15 chronic HD patients exposed to low chloramine levels (group B) and 17 controls (group C). Vitamin E levels were found to be significantly lower in group A than in either groups B or C (p less than 0.001). Within group A, levels were lower in those patients who had a positive ascorbate cyanide test (p less than 0.05). Upon removal of chloramines from the dialysis water, vitamin E levels in group A were no longer significantly different from those found in groups B or C.

Isoniazid pharmacokinetics in patients in chronic renal failure.

INH pharmcokinetics was studied in 2 groups of patients in chronic renal failure. In the group on conservative treatment, INH half life was prolonged, but was not related to the degree on renal impairement. In the hemodialysis group 73% of the INH given was removed by dialysis within 5 hours. If INH is to be used in the presence of renal failure, individual half life estimations should be performed in order to determine dosage frequency. In patients on hemodialysis, therapy should be given post dialysis. Alternatively, drugs not dependent on renal failure, e.g. rifampicin, may be preferable.

Associations between psychological profiles and diseases: examining hemispheric dominance and autonomic activation as underlying regulators.

Personality profiles are often typical for specific illnesses, e.g., the type A personality and heart disease. We hypothesize that many more such patterns exist, and have developed a scheme in which many diseases can be classified, depending on hemispheric dominance (i.e., integrated, intellectualising or emotional) and type of autonomic control (i.e., dominance of either sympathetic or parasympathetic system, or an increase in both types of autonomic outflow). Our hypothesis is based on recent findings in neurophysiology, involving the early rearing environmental effects on the developing orbitofrontal cortex, and attachment theory. We conclude with implications for therapy, and a discussion of the limitations of our hypothesis.

Intracellular free calcium in the neutrophils of maintenance haemodialysis patients.

Chronic renal failure has on occasion been referred to as a state of calcium toxicity. The aim of this study was to investigate the status of intracellular free Ca2+ in the neutrophils of chronic renal failure patients on maintenance haemodialysis treatment. Factors previously suggested to influence intracellular free Ca2+ were investigated including PTH levels, oxidative stress and recombinant human erythropoietin administration. The study involved 14 chronic renal failure patients on the haemodialysis programme of the Pretoria Academic hospital. Intracellular free Ca2+ and transmembrane Ca2+ fluxes were investigated by fluorescence spectrophotometry. Increases above control values were found in intracellular free Ca2+ (P-value 0.0242) and in the transmembrane Ca2+ flux upon fMLP stimulation (P-value 0.0002). The results showed significant differences in intracellular free Ca2+ between patients on rHuEPO and patients not on rHuEPO. The apparently rHuEPO-induced increase in intracellular free Ca2+ persisted in the presence of calcium channel blockers. No overt indications of oxidative stress could be detected by the antioxidant vitamin levels. It is concluded that factors other than those associated with uraemia, such as rHuEPO administration, might contribute to the often reported increase in intracellular free Ca2+ in these patients. Further studies to investigate the relationship between intracellular free Ca2+, rHuEPO and calcium channel blockers are suggested.

Gastro intestinal hyperpermeability: a review.

OBJECTIVE: To present a wide overview of the recent developments in the understanding of the aetiopathogenesis of gastrointestinal hyperpermeability. DATA SOURCES: Medline, from 1985, was sourced for relevant articles. Review articles were included in order to minimise the number of references in the reference list. STUDY SELECTION: Results from experiments and observations on humans and other mammalian species were studied. DATA SYNTHESIS: The major mechanisms elucidated in the aetiopathogenesis of the gastrointestinal hyperpermeability were integrated and consolidated into a flow diagram and the major factors responsible for normal permeability presented for comparison. CONCLUSION: The occurrence of increased gastrointestinal hyperpermeability is probably vastly underestimated. In addition to the hyperpermeability commonly associated with chronic gastro intestinal disorders, an increase in gastrointestinal permeability may occur in any condition of metabolic depletion, enterocyte ATP-depletion, stimulation of gastrointestinal pro-inflammatory cytokine production and disturbances of the normal gastrointestinal flora as with prolonged use of antibiotics.