The Health System Dynamics Framework: The introduction of an analytical model for health system analysis and its application to two case-studies

Frameworks can clarify concepts and improve understanding of underlying mechanisms in the domain of health systems research and strengthening. Many existing frameworks have a limited capacity to analyze interactions and equilibriums within a health system overlooking values as an underlying steering mechanism. This paper introduces the health system dynamics framework and demonstrates its application as a tool for analysis and modelling. The added value of this framework is: 1) consideration of different levels of a health system and tracing how interventions or events at one level influence other elements and other levels; 2) emphasizes the importance of values; 3) a central axis linking governance, human resources, service delivery and population, and 4) taking into account the key elements of complexity in analysis and strategy development. We urge  the analysis of individual health systems and meta-analysis, for a better understanding of their functioning and strengthening. 

Effect of mutations found in carbohydrate-deficient glycoprotein syndrome type IA on the activity of phosphomannomutase 2

Seven mutant forms of human phosphomannomutase 2 were produced in Escherichia coli and purified. These mutants had a Vmax of 0.2-50% of the wild enzyme and were unstable. The least active protein (R141H) bears a very frequent mutation, which has never been found in the homozygous state whereas the second least active protein (D188G) corresponds to a mutation associated with a particularly severe phenotype. We conclude that total lack of phosphomannomutase 2 is incompatible with life. Another conclusion is that the elevated residual phosphomannomutase activity found in fibroblasts of some patients is contributed by their mutated phosphomannomutase 2.

Urbanisation of yellow fever in Santa Cruz, Bolivia

BACKGROUND

Reinvasion by Aedes aegypti of cities in the Americas poses a threat of urbanisation of yellow fever. After detection of yellow-fever infection in a resident of the city of Santa Cruz, Bolivia, in December, 1997, we investigated all subsequent suspected cases.

METHODS

We introduced active surveillance of yellow fever in the Santa Cruz area. Hospitals and selected urban and rural health centres reported all suspected cases. Patients were serologically screened for yellow fever, dengue, hepatitis A and B, and leptospirosis. We collected clinical and epidemiological information from patients' records and through interviews. We also carried out a population-based serosurvey in the neighbourhood of one case.

FINDINGS

Between December, 1997, and June, 1998, symptomatic yellow-fever infection was confirmed in six residents of Santa Cruz, five of whom died. Five lived in the southern sector of the city. Two had not left the city during the incubation period, and one had visited only an area in which sylvatic transmission was deemed impossible. Of the 281 people covered in the serosurvey 16 (6%) were positive for IgM antibody to yellow fever. Among five people for whom this result could not be explained by recent vaccination, there were two pairs of neighbours.

INTERPRETATION

Urban transmission of yellow fever in Santa Cruz was limited in space and time. Low yellow-fever immunisation coverage and high infestation with A. aegypti in the city, and the existence of endemic areas in the region present a risk for future urban outbreaks. We recommend immediate large-scale immunisation of the urban population, as well as tightened surveillance and appropriate vector control.

Kinetic properties and tissular distribution of mammalian phosphomannomutase isozymes

Human tissues contain two types of phosphomannomutase, PMM1 and PMM2. Mutations in the PMM2 gene are responsible for the most common form of carbohydrate-deficient glycoprotein syndrome [Matthijs, Schollen, Pardon, Veiga-da-Cunha, Jaeken, Cassiman and Van Schaftingen (1997) Nat. Genet. 19, 88-92]. The protein encoded by this gene has now been produced in Escherichia coli and purified to homogeneity, and its properties have been compared with those of recombinant human PMM1. PMM2 converts mannose 1-phosphate into mannose 6-phosphate about 20 times more rapidly than glucose 1-phosphate to glucose 6-phosphate, whereas PMM1 displays identical Vmax values with both substrates. The Ka values for both mannose 1,6-bisphosphate and glucose 1,6-bisphosphate are significantly lower in the case of PMM2 than in the case of PMM1. Like PMM1, PMM2 forms a phosphoenzyme with the chemical characteristics of an acyl-phosphate. PMM1 and PMM2 hydrolyse different hexose bisphosphates (glucose 1,6-bisphosphate, mannose 1,6-bisphosphate, fructose 1,6-bisphosphate) at maximal rates of approximately 3.5 and 0.3% of their PMM activity, respectively. Fructose 1,6-bisphosphate does not activate PMM2 but causes a time-dependent stimulation of PMM1 due to the progressive formation of mannose 1,6-bisphosphate from fructose 1,6-bisphosphate and mannose 1-phosphate. Experiments with specific antibodies, kinetic studies and Northern blots indicated that PMM2 is the only detectable isozyme in most rat tissues except brain and lung, where PMM1 accounts for about 66 and 13% of the total activities, respectively.

[Epidemic outbreak of dengue virus 2/Jamaica genotype in Bolivia]

OBJECTIVE

To confirm an epidemic outbreak of Dengue virus in the city of Santa Cruz, Bolivia, and to determine the serotype of the virus, to estimate the rate of attack and the proportion of symptomatic infections.

MATERIAL AND METHODS

In March 1997, a seroepidemiological survey was conducted with random sampling in a central district of the city of Santa Cruz, Bolivia. Information on recent acute illness and febrile episodes was gathered, and venous blood samples were obtained. Levels of antidengue IgM were determined by MAC Elisa and the virus was typified with RT-PCR.

RESULTS

IgM antibodies were detected in 6.5% of adults (CI 95% 3.4-9.6) and 5.1% of children (CI 95% 2.0-8.2). Circulating virus was identified as Dengue serotype 2, subgroup Jamaica. Less than half of the infected children experienced a symptomatic infection compared to almost 90% of adults.

CONCLUSIONS

The estimated attack rates are compatible with a Dengue epidemic outbreak in Santa Cruz. The introduction of the serotype 2/ subgroup Jamaica virus into the country increases the risk of hemorrhagic Dengue.

Short communication: dengue serotype 2 subtype III ('Jamaica') epidemic in Santa Cruz, Bolivia

BACKGROUND

During the past decade, dengue and dengue haemorrhagic fever (DHF) have become a public health problem in various Latin American countries. Indications of increased dengue cases in the city of Santa Cruz, Bolivia, early in 1997 were promptly investigated.

METHODS

We conducted a sample sero-survey in one district of the city. Levels of antidengue IgM were determined and genetic analysis was performed on virus isolates.

RESULTS

IgM antibodies were detected in 6.5% (95% CI: 3.4%-9.6%) of adults (over 15 years old) and 5.1% (2.0%-8.2%) of children (5-7 years old). Dengue virus serotype 2 subtype III ('Jamaica') was isolated.

CONCLUSIONS

The estimated attack rates are compatible with a dengue epidemic in Santa Cruz. Isolation of dengue-2 'Jamaica' virus documents the further spread of this subtype from the Caribbean via Brazil into South America. Increased DHF preparedness seems mandatory.

A new class of phosphotransferases phosphorylated on an aspartate residue in an amino-terminal DXDX(T/V) motif

When incubated with their substrates, human phosphomannomutase and L-3-phosphoserine phosphatase are known to form phosphoenzymes with chemical characteristics of an acyl-phosphate. The phosphorylated residue in phosphomannomutase has now been identified by mass spectrometry after reduction of the phosphoenzyme with tritiated borohydride and trypsin digestion. It is the first aspartate in a conserved DVDGT motif. Replacement of either aspartate of this motif by asparagine or glutamate resulted in complete inactivation of the enzyme. The same mutations performed in the DXDST motif of L-3-phosphoserine phosphatase also resulted in complete inactivation of the enzyme, except for the replacement of the second aspartate by glutamate, which reduced the activity by only about 40%. This suggests that the first aspartate of the motif is also the phosphorylated residue in L-3-phosphoserine phosphatase. Data banks contained seven other phosphomutases or phosphatases sharing a similar, totally conserved DXDX(T/V) motif at their amino terminus. One of these (beta-phosphoglucomutase) is shown to form a phosphoenzyme with the characteristics of an acyl-phosphate. In conclusion, phosphomannomutase and L-3-phosphoserine phosphatase belong to a new phosphotransferase family with an amino-terminal DXDX(T/V) motif that serves as an intermediate phosphoryl acceptor.

Comparison of PMM1 with the phosphomannomutases expressed in rat liver and in human cells

Carbohydrate-deficient glycoprotein syndrome type I (CDGI) is most often due to phosphomannomutase deficiency; paradoxically, the human phosphomannomutase gene PMM1 is located on chromosome 22, whereas the CDGI locus is on chromosome 16. We show that phosphomannomutases present in rat or human liver share with homogeneous recombinant PMM1 several kinetic properties and the ability to form an alkali- and NH2OH-sensitive phosphoenzyme with a subunit mass of approximately 30,000 Mr. However, they have a higher affinity for the activator mannose-1,6-bisphosphate than PMM1 and are not recognized by anti-PMM1 antibodies, indicating that they represent a related but different isozyme. Phosphomannomutases belong to a novel mutase family in which the active residue is a phosphoaspartyl or a phosphoglutamyl.

PMM (PMM1), the human homologue of SEC53 or yeast phosphomannomutase, is localized on chromosome 22q13

We have cloned the human homologue of SEC53 or yeast phosphomannomutase (HGMW-approved symbol PMM1) from a liver cDNA library. This cDNA encodes a protein of 262 amino acids with a predicted molecular mass of 29 kDa and 54% identity with yeast phosphomannomutase. Expression of the human cDNA in Escherichia coli yielded an active phosphomannomutase, which was purified to homogeneity. Northern blot analysis of human tissues showed strong expression in liver, heart, brain, and pancreas and a lower expression in skeletal muscle. The gene was assigned to chromosome 22q13.1 by the use of hybrid cell lines and by fluorescence in situ hybridization. Most patients presenting with carbohydrate-deficient glycoprotein syndrome type 1 (CDG1 or Jaeken disease) have a greatly reduced phosphomannomutase activity; the gene encoding this enzyme is a likely candidate for CDG1. Since the CDG1 locus maps else where in the genome (16p13), mutations in the phosphomannomutase gene encoded by chromosome 22 are not a major cause of CDG1.

Inhibition of phosphomannose isomerase by fructose 1-phosphate: an explanation for defective N-glycosylation in hereditary fructose intolerance

Isoelectrofocusing of serum sialotransferrins from patients with untreated hereditary fructose intolerance (HFI) shows a cathodal shift similar to that in carbohydrate-deficient glycoprotein (CDG) syndrome type I and in untreated galactosemia. This report is on serum lysosomal enzyme abnormalities in untreated HFI that are identical to those found in CDG syndrome type I but different from those in untreated galactosemia. CDG syndrome type I is due to phosphomannomutase deficiency, a defect in the early glycosylation pathway. It was found that fructose 1-phosphate is a potent competitive inhibitor (Ki congruent to 40 microM) of phosphomannose isomerase (EC 5.3.1.8), the first enzyme of the N-glycosylation pathway thus explaining the N-glycosylation disturbances in HFI.

To control or to be controlled? From health locus of control to morphine control during patient-controlled analgesia

We postulated that patients with an internal locus of control, i.e. those who like to control their health problems themselves, would adapt more adequately to the 'patient-controlled analgesia' technique as compared to patients with an external health locus of control, who do not believe in their own control. Since contradicting studies have been published on this matter, we investigated relations between the demand for analgesics, perceived pain in the postoperative phase, and the health locus of control in the postoperative context of cardiac surgery. Findings demonstrate distinct utilization patterns between subjects with internal or external locus of control concerning total morphine consumption, number of unsatisfied demands and reduction of perceived pain.

[Patient, family, nurses and intensive care unit: review of the literature and state of a practice "in the field"]

An increasing interest in psychological and interactional aspects of intensive care unit stay is found in the recent literature. On one hand, seriousness and acuteness of the pathology, on the other hand, environment specificity as well as their respective consequences result in the fact that the ICU is a peculiar context for the patient and his family. The patient experiences a stressful event which probably differs from the one experienced in other types of wards. The family and its needs during this critical period are the focus of an increasing number of studies. A corresponding occupational stress for the caregivers is now widely acknowledged.