Pharmacokinetics of rifabutin during atazanavir/ritonavir co-administration in HIV-infected TB patients in India

SETTING

Rifabutin (RBT) is reported to be as effective as and to have less inducing effect on cytochrome P450 enzymes than rifampicin against tuberculosis (TB). The optimal dose of RBT during ritonavir (RTV) co-administration remains a matter of debate.

OBJECTIVE

To study the pharmacokinetics of 150 mg RBT thrice weekly during concomitant atazanavir/RTV administration in human immunodeficiency virus (HIV) infected TB patients.

METHODS

This observational study was conducted in 16 adult HIV-infected TB patients being treated for TB with an RBT-containing regimen and an antiretroviral therapy regimen with RTV; the dose of RBT was 150 mg thrice weekly. Serial blood draws were performed at pre-dosing and at 1, 2, 4, 6, 8, 12 and 24 h after the drug was administered. Plasma RBT was estimated using high-performance liquid chromatography.

RESULTS AND CONCLUSIONS

Peak RBT concentration was below the lower therapeutic limit (<0.3 μg/ml) in seven patients, while 10 patients had trough concentrations below the minimal inhibitory concentration against Mycobacterium tuberculosis (0.06 μg/ml), suggesting that the RBT dosage may be inadequate. Prospective studies in different settings are required to arrive at the proper therapeutic dose for RBT to be used during co-administration with RTV.

Undergraduate research. Genomics Education Partnership

The Genomics Education Partnership offers an inclusive model for undergraduate research experiences incorporated into the academic year science curriculum, with students pooling their work to contribute to international data bases.

Undergraduate research. Genomics Education Partnership

The Genomics Education Partnership offers an inclusive model for undergraduate research experiences incorporated into the academic year science curriculum, with students pooling their work to contribute to international data bases.

Aspiration versus tube drainage in primary spontaneous pneumothorax: a randomised study

This randomised study was designed to compare clinical outcomes for simple aspiration versus tube thoracostomy, in the treatment of the first primary spontaneous pneumothorax (PSP) attack. A randomised trial, comparing simple aspiration with tube thoracostomy, in 137 patients with a first episode of PSP was carried out. Immediate success was obtained in 40 out of the 65 patients (62%) randomly assigned to undergo simple aspiration and in 49 out of the 72 patients (68%) who had been randomly assigned to undergo tube thoracostomy. The 1-week success rates were: 58 (89%) patients in the intention-to-treat simple aspiration group and 63 (88%) patients in the tube thoracostomy group. In the aspiration group, there were more recurrences during the 3-month follow-up period (15 versus 8%), though the difference was not significant. Recurrence rates at 1 and 2 yrs were 16 (22%) and 20 (31%) for patients who had undergone simple aspiration, respectively, and 17 (24%) and 18 (25%) for patients who had undergone tube thoracostomies, respectively. Complications occurred in 5 (7%) patients who had undergone a tube thoracostomy and 1 (2%) patient who had undergone simple aspiration. Analgesia was required in 22 (34%) patients of the simple aspiration group versus 40 (56%) patients of the tube thoracostomy group. These findings suggest that simple aspiration could be an acceptable alternative to tube thoracostomy in the treatment of primary spontaneous pneumothorax.

Bi-transgenic mice reveal that K-rasVal12 augments a p53-independent apoptosis when small intestinal villus enterocytes reenter the cell cycle

Studies in cell culture systems have indicated that oncogenic forms of Ras can affect apoptosis. Activating mutations of Ras occur in approximately 30% of all human tumors and 50% of colorectal carcinomas. Since these mutations appear at early or intermediate stages in multistep journeys to neoplasia, an effect on apoptosis may help determine whether initiated cells progress towards a more neoplastic state. We have tested the effects of K-rasVal12 on apoptosis in transgenic mice. A lineage-specific promoter was used to direct expression of human K-rasVal12, with or without wild-type (wt) or mutant SV-40 T antigens (TAg), in postmitotic villus enterocytes, the principal cell type of the small intestinal epithelium. Enterocytes can be induced to reenter the cell cycle by TAgWt. Reentry is dependent upon the ability of TAg to bind pRB and is associated with a p53-independent apoptosis. Analyses of K-rasVal12 x TAgWt bi-transgenic animals indicated that K-rasVal12 can enhance this apoptosis threefold but only in cycling cells; increased apoptosis does not occur when K-rasVal12 is expressed alone or with a TAg containing Glu107,108two head right arrow Lys107, 108 substitutions that block its ability to bind pRB. Analysis of bi-transgenic K-rasVal12 x TAgWt mice homozygous for wild-type or null p53 alleles established that the enhancement of apoptosis occurs through a p53-independent mechanism, is not attributable to augmented proliferation or to an increase in abortive cell cycle reentry (compared to TAgWt mice), and is not associated with detectable changes in the crypt-villus patterns of expression of apoptotic regulators (Bcl-2, Bcl-xL, Bak, and Bax) or mediators of epithelial cell-matrix interactions and survival (e.g., alpha5beta1 integrin and its ligand, fibronectin). Coexpression of K-rasVal12 and TAgWt produces dysplasia. The K-rasVal12-augmented apoptosis is unrelated to this dysplasia; enhanced apoptosis is also observed in cycling nondysplastic enterocytes that produce K-rasVal12 and a TAg with a COOH-terminal truncation. The dysplastic epithelium of K-rasVal12 x TAgWt mice does not develop neoplasms. Our results are consistent with this finding: (a) When expressed in initiated enterocytes with a proliferative abnormality, K-rasVal12 facilitates progression to a dysplastic phenotype; (b) by diminishing cell survival on the villus, the oncoprotein may impede further progression; and (c) additional mutations may be needed to suppress this proapoptotic response to K-rasVal12.

Use of normal and transgenic mice to examine the relationship between terminal differentiation of intestinal epithelial cells and accumulation of their cell cycle regulators

A spatially well organized continuum of proliferation, differentiation, and death is displayed along crypt-villus units in the adult mouse small intestine. This continuum provides an opportunity to examine in vivo the mechanisms by which proliferative status changes as a function of cellular differentiation. Immunohistochemical studies of normal FVB/N mice revealed that as epithelial cells complete their terminal differentiation during a 48-72-h migration up villi, there is a marked and rapid fall in the levels of two important regulators of the G1/S transition, cyclin D1 and cyclin-dependent kinase (cdk) 2. However, cellular levels of their partners, cdk4 and cyclin E, remain unchanged as does the level of pRB. Adult FVB/N transgenic mice were studied that contained an intestinal fatty acid binding protein gene promoter (Fabpi) linked to wild type Simian virus 40 large T antigen (SV40 TAgWt) or a mutant TAg with Lys for Glu substitutions at residues 107 and 108 (SV40 TAgK107/8) that fails to bind pRB and related pocket proteins. Both transgenes are expressed only in villus enterocytes. SV40 TAgWt causes these terminally differentiated cells to re-enter the cycle. Re-entry is accompanied by a reduction in un/hypophosphorylated pRB, an induction of cyclin D1 and cdk2, but no change in cdk4, cyclin E, or E2F-1. In contrast, SV40 TAgK107/8 fails to induce re-entry and does not produce changes in un/hypophosphorylated pRB, cyclin D1, or cdk2 accumulation. These results suggest that un/hypophosphorylated pRB is an important mediator of the cell cycle arrest that normally occurs as enterocytes exit the crypt and complete their differentiation. Fabpi-directed expression of E2F-1 does not cause villus enterocytes to return to the cell cycle, alter their suppression of cyclin D1 or cdk2, or affect their state of differentiation, emphasizing the insensitivity of these cells to the effects of E2F-1. Analyses of p53(-/-) and p53(+/+) mice containing Fabpi-SV40 TAgWt and Fabpi-SV40 TAgK107/8 established that the proliferation induced by SV40 TAgWt does not require p53 and is associated with increased (p53-independent) apoptosis. The presence of cyclin E and cdk4 in differentiating villus enterocytes emphasizes that these cells retain part of their proliferative heritage expressed 24-72 h earlier in the crypt. The data suggest that down-regulation of cdk2 and/or cyclin D1 expression may be important for control of proliferative status and/or execution of terminal differentiation.

Radiation-induced cell cycle arrest compromised by p21 deficiency

The protein p21 is a dual inhibitor of cyclin-dependent kinases and proliferating-cell nuclear antigen (PCNA), both of which are required for passage through the cell cycle. The p21 gene is under the transcriptional control of p53 (ref. 5), suggesting that p21 might promote p53-dependent cell cycle arrest or apoptosis. p21 has also been implicated in cell senescence and in cell-cycle withdrawal upon terminal differentiation. Here we investigate the role of p21 in these processes using chimaeric mice composed partly of p21-/- and partly of p21+/+ cells. Immunohistochemical studies of the p21+/+ and p21-/- components of adult small intestine indicated that deletion of p21 has no detectable effect on the migration-associated differentiation of the four principal intestinal epithelial cell lineages or on p53-dependent apoptosis following irradiation. However, p21-/- mouse embryo fibroblasts are impaired in their ability to undergo G1 arrest following DNA damage.

Cell lineage-specific and differentiation-dependent patterns of CCAAT/enhancer binding protein alpha expression in the gut epithelium of normal and transgenic mice

The proliferation and differentiation programs of gut epithelial cells are expressed rapidly and perpetually along an anatomically well defined pathway. The mouse intestine thus provides an excellent in vivo model system to define the contributions of CCAAT enhancer binding protein alpha (C/EBP alpha) and related bZIP proteins to these processes. Immunocytochemical studies revealed that C/EBP alpha is produced in villus-associated enterocytes located in the duodenum and jejunum of adult mice. The protein is located in the cytoplasmic and nuclear compartments of these cells. C/EBP alpha is not detectable in proliferating and nonproliferating epithelial cells situated in small intestinal crypts nor is it evident in any gut epithelial cell lineage located in the ileum and colon. The related C/EBP beta and C/EBP delta proteins are not detectable by sensitive immunocytochemical methods in epithelial cells distributed along the duodenal-to-colonic axis. Developmental surveys indicate that C/EBP alpha is confined to postmitotic, villus-associated epithelial cells during conversion of the polyclonal intervillus epithelium to monoclonal crypts. Analyses of intestinal isografts reveal that these developmental stage-specific, lineage-specific, differentiation-dependent, and regional patterns of C/EBP alpha expression can be established and maintained in the absence of exposure to luminal contents. Transgenic mice containing nucleotides -1178 to +28 of the rat intestinal fatty acid binding protein gene (I-FABP-1178 to +28) linked to the simian virus 40 large tumor antigen (T antigen) gene express T antigen in villus-associated enterocytes. This results in reentry of enterocytes into the cell cycle and a silencing of C/EBP alpha expression without an apparent effect on the accumulation of several markers of this lineage's terminal differentiation program or on gut morphogenesis. These findings indicate that there is a relationship between expression of C/EBP alpha in enterocytes and their exit from the cell cycle and suggest that I-FABP-1178 to +28/simian virus 40 T antigen transgenic mice could provide a screening assay for examining the role of C/EBP alpha in regulating the activity of genes known to be transcribed during differentiation of this gut epithelial cell lineage.

Evidence for sterol-independent regulation of low-density lipoprotein receptor activity in Hep-G2 cells

The relationship between the serum factor(s)-mediated induction of low-density lipoprotein (LDL) receptor activity and changes in cellular cholesterol metabolism was examined in the human hepatoma cell line Hep-G2. Relative to incubation with serum-free media [Eagle's minimal essential medium (MEM) control], short-term (less than 8 h) incubation with medium containing 15% of either calf serum (MEM + serum) or the d greater than 1.25 fraction of calf serum (MEM + d greater than 1.25) produced a time- and concentration-dependent increase in the uptake of 125I-LDL. Immunoblotting with anti-(LDL receptor) antibodies demonstrated that this was correlated with a 2-fold increase in the amount of the mature 136,000 Da LDL receptor protein in detergent-solubilized Hep-G2 cell membranes. Incubation with MEM + serum, but not MEM + d greater than 1.25, increased the efflux of radiolabelled cholesterol from Hep-G2 cells. However, the induction of 125I-LDL uptake by MEM + d greater than 1.25 (2.3-fold) and MEM + serum (2.2-fold) was virtually identical. Addition of the d less than 1.063 lipoproteins of calf serum to MEM + d greater than 1.25 at their original or three times their serum concentration decreased the induction of 125I-LDL uptake by MEM + d greater than 1.25 by only 20-30%. Together, these results suggest that the stimulation of 125I-LDL uptake was not due to the presence of high-density lipoprotein, the absence of LDL or the stimulation of cholesterol efflux. MEM + serum stimulated 125I-LDL uptake in cells cholesterol-loaded by incubation with rat very-low-density lipoprotein with beta electrophoretic mobility (beta-VLDL). Compared to incubation with the MEM control, either MEM + serum or MEM + d greater than 1.25 produced time-dependent increases in the activity of 3-hydroxy-3-methylglutaryl-CoA reductase which also occurred in cholesterol-loaded cells. However, cholesterol biosynthesis, whether measured from 3H2O, [14C]acetate or [3H]mevalonic acid, was not increased. Incubation with MEM + serum or MEM + d greater than 1.25 did not affect [3H]oleate incorporation into cellular cholesteryl esters, hydrolysis of intracellular [3H]cholesteryl esters or the cellular mass of unesterified or esterified cholesterol. Incubation with MEM + serum or MEM + d greater than 1.25 produced a transient increase in the level of LDL receptor mRNA, reaching a maximum of 5-10-fold by 2 h and decreasing to near baseline levels by 4 h. Actinomycin D blocked the serum-factor-mediated induction of LDL receptor mRNA.(ABSTRACT TRUNCATED AT 400 WORDS)

Assessing the effect of mortality change in an age group on the expectation of life at birth

"This article compares four procedures in assessing the effect of the change in mortality conditions in an age group between two periods on the expectation of life at birth. The differences and similarities are pointed out. The outcome of applying the different approaches on the difference in the expectation of life at birth of the life tables of Sweden for the periods 1901-10 and 1936-40 is also discussed."

'Continuation rate', 'use-effectiveness' and their assessment for the diaphragm and jelly method

Abstract The application of the life-table technique in the calculation of use-effectiveness of a contraceptive was proposed by Potter in 1963.(1) The technique was also found to be useful in assessing the duration for which the use of a contraceptive was continued. The keen interest that existed in the use of IUD in the mid-1960's was reflected in the terminology developed for assessment of the continuity of use. 'Retention rate' was a frequently used index.(2) Because of the development of the concept of segments whose end-period determined either termination of the use of a method or its continuance on a cut-off date, 'closure rate' and 'termination rate' have been used as measures of the discontinuance of the use of methods primarily of the IUD.(3) While discussing concepts relating to acceptance, use and effectiveness of family planning methods, more generally, an expert group suggested that 'continuation' should be used to denote that a client (or a couple) had begun to practise a method and that the method was still being practised.(4) Since this group defined 'an acceptor' as a person taking service and/or advice, i.e. having an IUD insertion or a sterilization operation or receiving supplies (or advice on methods such as 'rhythm' or coitus-interruptus with the intent of using the method), the base for the assessment of continuation rates, according to this group, would be only those acceptors who had begun using the method. The lifetable method has also been used for the study of the continuation rate for pill acceptors.(5) Balakrishnan, et al., made a study of continuation rates of oral contraceptives using the multiple decrement life-table technique.(6).

Some problems in determining the number of acceptors needed in a family planning programme to achieve a specified reduction in the birth rate

Abstract The paper attempts to revive professional interest in a problem originally considered by Lee and Isbister and which has assumed added importance recently because of the increasing number of national family planning programmes that are being instituted, which require the determination of the number of acceptors needed in a family planning programme in order to achieve a specified reduction in the birth rate. The publication of subsequent papers on births averted by programmes, notably by Potter and Wolfers, each of whom had made some criticisms of the paper by Lee and Isbister, has tended to obscure the differences in the nature between the problem raised by Lee and Isbister, and that discussedby Potter or Wolfers. The paper tries to bring out these differences and points out one of the limitations of the estimates of births averted obtained by using either Potter's or Wolfers's methods, viz. the inability to determine the time period to which the birth reduction refers, thereby further complicating the issues involved in assessing the social and economic implications of births averted by a family planning programme. The paper also points out some of the unrecognizedtechnical considerations which arise in dealingwith the 'target-setting' problem raised by Lee and Isbister and suggeststhat stochasticmodel studies might offera clue for evolving practical methods for tackling this problem.