Relative bioavailability of iron from two different iron tablets used in the Indonesian Iron Supplementation Program

The relative bioavailability of two different iron tablets which are used in the Indonesian iron supplementation program was determined, because low bioavailability of iron might decrease the impact of the program. In two studies volunteers (n = 12, n = 6) received 120 mg elemental iron either as two iron tablets, each containing 60 mg elemental iron, or as an aqueous Fe(II)-sulphate solution in a randomized cross-over design. Plasma iron concentrations were measured before, and 1, 2, 4, 6, 8 and 10 hours after dosing. For each of the tablets and solutions, the positive area under the concentration/time curve (AUC+), the peak plasma level (Cmax), the time to reach the peak plasma level (tmax) and the relative bioavailability were determined. Relative bioavailability of both tablets was high (106.9 +/- 24.3%) and 116.3 +/- 43.1%). This indicates a good therapeutical efficacy of both tablets. In case where low effectiveness of iron supplementation programs is recorded, factors other than low bioavailability of iron in the tablets must be responsible.

Body composition of Indonesian adults assessed by skinfold thickness and bioelectrical impedance measurements and by a body mass index equation

Body composition was assessed in Indonesian male (n=29) and female (n=17) students and rural women (n=35) using skinfold thickness measurements, bioelectrical impedance measurements (BIA) with two different equations, and a body mass index equation. Correlation between different methods was significant (P<0.01). In rural women and female students fat mass by skinfold measurements was respectively 2.5± 2.9 kg (P<0.01) and 2.2± 2.3 kg (P<0.01) lower than by BIA. In male students the difference between skinfold and BIA measurements was 0.8± 2.6 kg. Disagreement between methods increased with larger fat mass. In some individuals differences between assessed values were substantial. It is concluded that, especially under field conditions, results obtained by different methods are not interchangeable.

A phase variant of Bordetella pertussis with a mutation in a new locus involved in the regulation of pertussis toxin and adenylate cyclase toxin expression

A novel nonhemolytic phase variant of Bordetella pertussis was characterized. This strain is strongly impaired in the transcription of the pertussis and adenylate cyclase toxins, whereas other known virulence-related factors such as the filamentous hemagglutinin, the fimbriae, and the outer membrane protein pertactin are expressed and regulated normally. Complementation and allelic exchange experiments demonstrated that the mutation is localized neither in the bvg locus involved in virulence regulation nor in the genes responsible for synthesis and transport of the toxins pertussis and adenylate cyclase. Instead, the mutation impairing transcription of at least the two toxin genes is located in a new genetic locus, which acts together with the BvgA/S two-component regulatory system on the expression of a subset of virulence genes. Further analysis suggested that most presumably the mutation affects a sequence-specific DNA-binding protein which contributes to transcriptional activation. The mutant was nonlethal in a murine respiratory model, which corresponds well with the lack of expression of the toxins. However, the clearing rate of this mutant from the lungs of mice was much lower than that of a bvg mutant, suggesting that factors other than the toxins may play a role in the persistence of the bacteria in the respiratory tract of mice.

Decreased rate of stunting among anemic Indonesian preschool children through iron supplementation

Effects of iron supplementation on growth and hematological status of Indonesian anemic preschool children with low weight-for-age were investigated. A treatment group (n = 39) received daily supplements of 30 mg Fe and 20 mg vitamin C, whereas a control group (n = 37) received 20 mg vitamin C only for a period of 2 mo. Supplement allocation was double blind. At the start and finish of the study, body weight, height, food intake, and hemoglobin and serum ferritin concentrations were determined. Only the treatment group showed a significant increase in all hematological values (P < 0.001). Height and weight of all children increased (P < 0.01). Increases in height and height-for-age Z score in the treatment group were larger (P = 0.001) than the increase in the control group. The positive effect of iron supplementation on linear growth was not caused by increased food intake, but seems to be influenced by decreased morbidity. Iron supplementation may be a relatively inexpensive way to help decrease the high prevalence of stunting.

Prior glucose deprivation increases the first phase of glucose-induced insulin response: possible involvement of endogenous ATP and (or) ADP

A possible implication of endogenously released ATP and (or) ADP in insulin response to glucose stimulation was investigated in the isolated rat pancreas. The first phase of insulin response to the same glucose concentration (8.3 mM) was much higher in pancreas previously perfused in the absence of glucose than in pancreas previously perfused with 4.2 mM glucose. A P2 purinoceptor antagonist, 2,2'-pyridylisatogen tosylate, strongly reduced the higher first phase resulting from glucose deprivation; similarly, it reduced exogenous ATP-potentiated insulin response to a glucose increase from 4.2 to 8.3 mM. In contrast, 2,2'-pyridylisatogen tosylate did not modify the first phase of insulin response to 8.3 or 12.5 mM glucose in pancreas previously perfused with 4.2 mM glucose. Our results suggest that endogenous ATP and (or) ADP released in pancreatic islets in the absence of glucose could activate P2 purinoceptors and increase the magnitude of the first phase of insulin response to a glucose stimulation.

Characterization of an IS-like element from Mycobacterium tuberculosis

A DNA sequence, present in members of the Mycobacterium tuberculosis complex, has been identified and characterized. The distribution of this DNA sequence among mycobacterial species was analysed by DNA hybridization and PCR experiments. As the sequence was detected only in bacteria belonging to the M. tuberculosis complex, it may be useful for the rapid discrimination of mycobacteria. Interestingly, the sequence has some characteristics of an insertion element (IS) and codes for a hypothetical protein with significant homologies to proteins encoded by several IS elements of other organisms, namely IS427 and IS869 from Agrobacterium tumefaciens, IS402 from Pseudomonas cepacia, Tn4811 from Streptomyces lividans and ISRm4 from Rhizobium meliloti. Together, these elements form a previously unrecognized family of transposable elements. This finding suggests the possibility of horizontal gene transfer between pathogenic mycobacteria and other organisms including Gram-negative plant-pathogenic bacteria.

Glutamate stimulates glucagon secretion via an excitatory amino acid receptor of the AMPA subtype in rat pancreas

The effect of L-glutamate was studied on glucagon secretion from rat isolated pancreas perfused with 2.8 mM glucose. L-Glutamate (3.10(-5)-10(-4)M) induced an immediate, transient and concentration-dependent glucagon release. The three non-N-methyl-D-aspartate (NMDA) receptor agonists, kainate (3.10(-5)-3.10(-3)M), alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) (3.10(-5)-10(-4)M) and quisqualate (3.10(-6)-10(-5)M), all elicited a peak-shaped glucagon response. Compared to glutamate, AMPA and quisqualate exhibited a similar efficacy, whereas kainate caused a 4-fold higher maximal glucagon response. In contrast, NMDA (10(-3)M) was ineffective. The selective antagonist of non-NMDA receptors, 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX; 5.10(-5)M), totally prevented the glucagon response to 10(-4) M glutamate (IC50 congruent to 0.8 +/- 0.3 10(-6)M) and 3.10(-4)M kainate. Furthermore, quisqualate at a maximal effective concentration (3.10(-4)M) inhibited the response to kainate (10(-3)M). This study showed that L-glutamate stimulates glucagon release in rat pancreas by activating a receptor of the AMPA subtype.

Optical limiting by chemically enhanced bacteriorhodopsin films

The optical limiting properties of a thin film (~150 microm) of chemically enhanced bacteriorhodopsin under cw laser illumination is investigated. The effective nonlinearity n(2) of the film is measured with the z-scan method. Anomalous absorption at different wavelengths as a function of illumination intensity is observed.

Different mechanisms are involved in neuropeptide Y-induced pancreatic vasoconstriction and inhibition of insulin secretion

We have studied the mechanisms whereby neuropeptide Y (NPY) inhibits insulin secretion and induces vasoconstriction in the isolated perfused rat pancreas. Neither prazosin (alpha 1-adrenoceptor antagonist; 6 microM) nor yohimbine (alpha 2-adrenoceptor antagonist; 0.6 microM) affected the effects of neuropeptide Y (1 nM). Also the Ca2+ channel antagonist, verapamil (5 microM), which itself decreased insulin output by 55%, could not affect the neuropeptide Y-induced inhibition of insulin secretion. However, verapamil impaired the neuropeptide Y-induced decrease in pancreatic outflow rate. Finally, neuropeptide Y (1 and 10 nM) suppressed the insulin secretion induced by dibutyryl cAMP (100 microM) and the cyclic nucleotide suppressed the neuropeptide Y-induced vasoconstriction. We conclude that the secretory and vascular effects of neuropeptide Y are mediated by different processes in the perfused rat pancreas: inhibition of insulin secretion seems mediated by a mechanism distal to and/or different from cAMP generation, whereas vasoconstriction seems to involve uptake of extracellular Ca2+ and to be sensitive to dibutyryl cAMP. Both effects occur independently of adrenoceptor receptors.

Differential regulation of Bordetella pertussis virulence factors

Bordetella pertussis, the causative agent of whooping cough, regulates its virulence factors coordinately according to environmental parameters such as temperature and certain chemicals. A regulatory locus has been characterized which is essential for this regulation. This bvg locus codes for a two-component regulatory system composed of the sensor protein BvgS and the transcriptional activator protein BvgA. It has been shown that the BvgA and BvgS proteins are sufficient for the transcriptional regulation of some virulence factors such as the filamentous haemagglutinin (FHA) involved in adhesion. The recent identification of new regulatory mutants demonstrates that the regulation of some virulence factors such as the pertussis toxin (PTX) and the adenylate cyclase toxin (CYA) is more complex and involves additional regulatory factor(s). This finding suggests that the regulation of the various virulence factors is coordinated at the highest level of regulation, but there may be differences in the fine regulation of some of the factors such as the adhesins and the toxins.

A special-purpose processor for gene sequence analysis

Advances in computational biology have occurred primarily in the areas of software and algorithm development; new designs of hardware to support biological computing are extremely scarce. This is due, we believe, to the presence of a non-trivial knowledge gap between molecular biologists and computer designers. The existence of this gap is unfortunate, as it has long been known that for certain problems, special-purpose computers can achieve significant cost/performance gains over general-purpose machines. We describe one such computer here: a custom accelerator for gene sequence analysis. The accelerator implements a version of the Needleman-Wunsch algorithm for nucleotide sequence alignment. Sequence lengths are constrained only by available memory; the product of sequence lengths in the current implementation can be up to 2(22). The machine is implemented as two NuBus boards connected to a Mac IIf/x, using a mixture of TTL and FPGA technology clocked at 10 MHz. The boards are completely functional, and yield a 15-fold performance improvement over an unassisted host.

Signal transduction and virulence regulation in human and animal pathogens

Pathogens have developed many strategies for survival in animals and humans which possess very effective defense mechanisms. Although there are many different ways, in which pathogenic bacteria solved the problem to overcome the host defense, some common features of virulence mechanisms can be detected even in phylogenetically very distant bacteria (Finlay and Falkow (1989) Microb. Rev. 6, 1375-1383). One important feature is that the regulation of expression of virulence factors and the exact timing of their expression is very important for many of the pathogenic bacteria, as most of them have to encounter different growth situations during an infection cycle, which require a fast adaptation to the new situation by the expression of different factors. This review gives an overview about the mechanisms used by pathogenic bacteria to accomplish the difficult task of regulation of their virulence potential in response to environmental changes. In addition, the relationship of these virulence regulatory systems with other signal transduction mechanisms not involved in pathogenicity is discussed.

Low compliance with an iron-supplementation program: a study among pregnant women in Jakarta, Indonesia

The efficiency of an established iron-supplementation program for pregnant women in Jakarta, Indonesia was investigated. Hemoglobin, serum ferritin, and packed cell volume (PCV) were measured at the start of the study and after 2 mo supplementation with 300 mg ferrous sulphate/d. The women (n = 45) were questioned about compliance and stool samples were checked for iron content to control for tablet intake. Twelve women dropped out. Prevalence of anemia (42%) did not decrease during the study period. Of the remaining 33 women, 64% (n = 21) claimed to have taken all iron tablets. This was only confirmed by positive stool tests in 12 women. Serum ferritin and PCV increased in women with positive stool tests (P < 0.05 and P < 0.01, respectively) after supplementation. It is concluded that compliance was low and that the iron dose needs to be increased. Supplementation programs need reliable monitoring and evaluation systems.

A comparison of visual and digital image-processing methods in quantifying the severity of coffee leaf rust (Hemileia vastatrix)

Using disease diagrams, visual assessments of coffee leaf rust from Papua New Guinea overestimated severity by >2 times when >20% leaf area was rusted. Nevertheless, a significant linear relationship was established between visual and planimeter assessments of coffee rust severity. Colour image analysis, using a Matrox digitiser, was more accurate than visual estimates or black and white imaging systems in discriminating between rusted and healthy leaf tissues in colour transparency photographs of rusted coffee leaves. Electronic flash photography of rusted coffee leaves produced images with reflections from the waxy leaf surface which made it difficult to discriminate between healthy tissues and the background.

Quality of care in decentralized primary care clinics: a conceptual framework

In an attempt to provide high quality medical care, despite limited resources, health care providers in various countries have introduced decentralization into their health care services. It has been assumed that the delegation of authority to the local levels of the organization will enhance their ability to respond to local needs, and improve cost containment without compromising the quality of care. However, to date, few empirical studies have explored the relationship between decentralization and such projected outcomes. In this article we present a conceptual framework for analyzing possible consequences of decentralization on dimensions of quality of primary health care. We also suggest a framework for defining decentralization programs by their key components, and employ these frameworks to analyze a specific decentralization program being implemented in Israel's largest health maintenance organization (HMO). While we identify the dimensions most likely to be affected, we also conclude that data presently available do not permit a definitive prediction of whether the overall effect of decentralization on quality of care will be positive or negative. The potential reaction of a unit to the elements of change introduced by a decentralization program is influenced by the structural, cultural and management characteristics of that unit. Therefore, future attempts to decentralize health care organizations should be accompanied by close monitoring.

Evidence for a direct inhibitory effect of PYY on insulin secretion in rats

Peptide YY (PYY) has been shown to inhibit stimulated insulin secretion under in vivo conditions in the mouse, the rat, and the dog. In the present study, we investigated the effects of PYY on insulin secretion from the isolated perfused rat pancreas and isolated rat islets. In isolated pancreas perfused in presence of 8.3 mM glucose, PYY at 10(-10) and 10(-9) M, but not at 10(-8) M, inhibited insulin secretion. In the presence of 5.5 mM glucose, PYY (10(-9) M) did not modify basal insulin release but reduced the biphasic insulin response to arginine (10 mM). PYY also markedly reduced the pancreatic vascular flow rate; this effect was observed at all three concentrations tested in a dose-dependent manner. In isolated islets, glucose (15 mM)-stimulated insulin secretion was inhibited by PYY at 10(-7) M. We conclude that in the perfused rat pancreas, PYY inhibits insulin secretion and induces vasoconstriction without a causal relationship. In addition, our results on isolated islets suggest that the inhibitory action of PYY on insulin secretion is exerted through a direct islet action.

Functional analysis of the pertussis toxin promoter

The expression of the pertussis toxin ptx operon is positively regulated in cis by a promoter region of about 170 base pairs and in trans by the bvg locus, which codes for the transcriptional activator protein BvgA. The promoter contains two direct repeats which are essential for its activity. When the position of these direct repeats relative to the transcription start point was changed, the activity of the promoter was strongly impaired. The repeated sequences therefore do not represent enhancer-like elements similar to those which have been identified in other positively regulated promoters; instead, the integrity of the whole promoter region seems to be an important feature of ptx regulation. A transcription interference assay was carried out to analyze in vivo binding of regulatory proteins to the ptx promoter. The results suggest that the direct repeats are the recognition sequence of a protein, which binds to them only under conditions in which the promoter is activated. In vitro DNA binding experiments with BvgA protein purified from an overproducing Escherichia coli strain were performed. However, no binding of BvgA to the ptx promoter was observed under conditions where binding of BvgA to the fha and bvg promoters occurred. This suggests that factors in addition to the bvg system are involved in the regulation of the Bordetella virulence regulon.

Expression of bacterial cytotoxin genes in mammalian target cells

We have studied the expression of the gene fragments encoding the enzymatically active portion of three bacterial cytotoxins: exotoxin A (ETA) of Pseudomonas aeruginosa, and pertussis toxin (PT) and adenylate cyclase toxin (CYA) of Bordetella pertussis, in sensitive mammalian target cells. Expression of active ETA and CYA was lethal to the producing cells and stable transfectants of Cos-1 cells containing the corresponding genes could not be obtained. The expression of the PTS1 subunit was tolerated by the producing mammalian cells. Since PT is cytotoxic because of ADP-ribosylation of G-proteins, we assume that the endogenously expressed PTS1 may not find the cellular target G proteins or PTS1 alone may not be sufficient for ADP-ribosylation of these proteins in vivo.