Models of mycoplasma respiratory and genital tract infections

Animal models for the study of human diseases must be replaced by in vitro methods, whenever possible. However, when critically evaluated, they remain indispensable for the solution of some specific problems in infectious diseases. These include the pathogenesis, the host response, as well as the study of antimicrobial agents and vaccines. Under these conditions animal models, which closely reflect the situation in man, are especially valuable. Two models may serve as "ideal" examples for the study of human diseases: firstly mouse typhoid for the study of systemic infections with Salmonella typhimurium. This model has been employed for many decades to examine various aspects of human typhoid fever. A second model is the experimental infection of hamsters with Mycoplasma pneumoniae as a model of local infection in the respiratory tract. Mycoplasma and ureaplasma infections of man are frequent, but rarely life threatening. Chick embryos, rats, hamsters, guinea pigs, and monkeys (rhesus monkeys and chimpanzees) are susceptible to experimental infection with M. pneumoniae. Some mouse strains are also colonized with M. pneumoniae after intranasal inoculation, but histopathological alterations similar to the hamster model have not been established in a reproducible way in mice. Hamsters have, therefore, been important for the evaluation of antibiotics and vaccines. Local immunity in the respiratory tract, the possible contribution of the immune response to disease pathogenesis, persistence of the organisms in the respiratory tract after clinical symptoms are cured by antibiotic therapy, and the role of cytokines in protection or disease pathogenesis remain interesting areas for future research, which could be addressed in animal models. The evaluation of the role of mycoplasmas and ureaplasmas in genital tract infections is by far more complex and even more difficult in AIDS and rheumatoid arthritis, because several species of mycoplasmas and Ureaplasma urealyticum can be isolated from a large proportion of healthy individuals. Furthermore, good models for the study of these infections are not available.

The relationship of blood pressure to cardiac hypertrophy: experimental studies in rats

Cardiac hypertrophy is an independent predictor of morbidity and mortality. The exact relationship between blood pressure, hormones and cardiac hypertrophy is unclear. This study was undertaken to determine if intermittent elevation of blood pressure could cause left ventricular hypertrophy. Blood pressure was elevated intermittently by intraperitoneal injections of angiotensin II, noradrenalin and methoxamine. Blood pressure was acutely elevated by 60 mmHg or more for periods lasting up to 1 hour on up to 4 occasions each day. Cardiac index was measured 2 and 4 weeks after the experiment started. The cardiac index was increased by all procedures. The results were complicated by a retardation of growth in some experimental groups, meaning that the cardiac weight did not increase though the index did. In a study looking at the interaction of sodium and angiotensin II high sodium intake caused left ventricular hypertrophy and injections of angiotensin II caused further left ventricular hypertrophy. This study indicated that acute intermittent elevation of blood pressure could cause left ventricular hypertrophy and suggests that wall stress rather than 24 hour workload is the important triggering mechanism.

Premature failure of battery-powered syringe pumps

Failure of battery-powered equipment during the interhospital transfer of patients is potentially life threatening. The time to failure of 60 fully-charged identical syringe pumps (20 from each batch purchased in 1992, 1994 and 1995) was measured. Older pumps were associated with less predictable charge capacity, with 40% of the 1992 pumps failing within 60 min. The premature failure of these pumps is most likely due to poor battery care. It is unsafe to assume that a fully-charged, battery-powered pump will continue to function throughout a long transfer. The routine carriage of spare pumps or a backup power supply is recommended.

Factors affecting dose selection and outcome of cisapride treatment for dyspepsia in primary care. The Austro-Cis Study Group

BACKGROUND

Little is known about the prescribing habits and impact of life style or disease factors on the outcome of cisapride treatment for dyspepsia in primary care.

METHOD

In this large-scale open, multi-centre study in Austria, primary care physicians were asked to prescribe cisapride according to the current prescribing guidelines (standard dose, 5 mg t.d.s.; in case of severe symptoms, 10 mg t.d.s.). Symptom severity was rated by the physicians, after 4 weeks of treatment and after another 4 weeks of follow-up without medication. The global therapeutic result was given by both the physicians and patients.

RESULTS

Among the 3912 recruited patients, 60.0% received cisapride 5 mg t.d.s. and 38.5% received 10 mg t.d.s. The dose selection by the physicians was not only influenced by severity of the symptoms (significantly more patients with severe symptoms receiving the higher dosage when compared to those with milder symptoms (P < 0.001), but also other factors were associated with prescription of the higher dose: including heavy smoking, longer pre-existence of complaints and failing previous treatment. After 4 weeks of treatment, the dyspeptic symptoms improved in about 80% of patients, in both dosage groups. Four weeks after discontinuation of medication, 21% of patients still further improved, while 10% relapsed. The overall therapeutic outcome defined as the percentage of patients with good or excellent results was comparable in both dosage groups and appeared independent of the patient's characteristics, life style or disease factors. However, when only the proportion of "excellent' responders was analysed, this rate significantly decreased the longer the duration of symptoms, the heavier the smoking and with failing previous therapy. This effect was particularly seen with the patients' ratings.

CONCLUSIONS

Although the open-study design does not allow evaluation of the contribution of placebo-effect and calls for cautious interpretation, the data suggest that the use of flexible cisapride doses for management of dyspepsia in primary care results in a good acute and medium-term outcome, with apparently little dependence on life style and disease factors, at least when assessed by physicians.

Role of chloride-homeostasis in the inhibitory control of neuronal network oscillators

1. Spontaneous synaptic activity in networks formed by dissociated neurons from embryonic rat midbrain was analyzed in tight seal whole cell recordings. 2. Application of furosemide (0.5 mM) to the cell and its surrounding area increased the frequency of spontaneous synaptic currents. Incubation of the culture with furosemide resulted in "rhythmic" burst activity. 3. Furosemide (0.1-0.5 mM) changed equilibrium potentials of inhibitory postsynaptic currents, gamma-aminobutyric acid-A (GABAA) or glycine receptor-mediated Cl- currents by a blockade of Cl(-)-outward transport. Furosemide did not alter the slope conductance of GABAA receptor-mediated currents. Membrane conductance and cell excitability were also unaffected. 4. We conclude that furosemide locked the activity of the network in "burst activity" mode through impairment of inhibition resulting from the disturbance of Cl- homeostasis.

Novel magnetic microspheres on the basis of poly(vinyl alcohol) as affinity medium for quantitative detection of glycated haemoglobin

A water-in-oil suspension cross-linking technique using poly(vinyl alcohol) as polymer phase to prepare novel magnetic microbeads is described. By dispersing a conventional Fe3O4 pigment in the polymer phase and subsequently suspending the mixture in a vegetable oil phase with a defined viscosity, spherical magnetic microspheres are obtained. Bead sizes ranging from 1 to 50 microns and above can be obtained by exploiting well defined preparation parameters such as polymer concentration and oil and polymer viscosity. The performance of the magnetic matrices for the separation and quantification of glycated haemoglobin was tested using a m-aminophenylboronic acid matrix. The feasibility of this detection method for blood sugar diagnosis is discussed using a commercial column test kit for comparison.

Effects of modulators of the renin-angiotensin-aldosterone system on cough. Losartan Cough Study Group

OBJECTIVE

To compare the incidence of cough in patients with a history of angiotensin converting enzyme (ACE) inhibitor-related cough who received losartan [a type 1 angiotensin II (Ang II) receptor antagonist], lisinopril (an ACE inhibitor) or hydrochlorothiazide (a diuretic).

DESIGN

An international, multicentre, randomized double-blind, parallel-group controlled trial.

SETTING

Outpatient clinics at 20 tertiary care medical centres in 11 countries.

PATIENTS

One hundred and thirty-five patients with uncomplicated primary hypertension with a history of ACE inhibitor-related cough were randomly assigned to the double-blind treatment phase and completed the study.

INTERVENTION

After confirming that the cough was ACE inhibitor-related by a single-blind rechallenge, followed by a placebo washout period, patients were randomly assigned to receive 50mg losartan, 20mg lisinopril or 25mg hydrochlorothiazide once a day for 8 weeks.

MAIN OUTCOME MEASURES

Cough incidence, severity and frequency were assessed by a self-administered questionnaire and a visual analogue scale.

RESULTS

The percentage of patients who complained of cough was significantly higher with lisinopril than with losartan or hydrochlorothiazide. The mean visual analogue scale scores for patients treated with lisinopril demonstrated that these patients coughed more frequently than those who received losartan or hydrochlorothiazide.

CONCLUSION

The incidence of cough related to the type 1 Ang II receptor antagonist losartan is significantly lower than that observed with lisinopril, and similar to that observed with hydrochlorothiazide in patients with a rechallenged ACE inhibitor cough. Type 1 Ang II receptor antagonists represent a potential new treatment for hypertensive patients in whom ACE inhibitors are indicated, but who develop a cough with these agents.

Muscarinic amplification of fast excitation in hilar neurones and inhibition in granule cells in the guinea-pig hippocampus

1. Effects of the cholinergic agonist, carbachol (CCh), or the acetylcholinesterase inhibitor, eserine, on presumed inhibitory hilar neurones and on inhibition in granule cells were studied by intracellular recording in guinea-pig hippocampal slices. 2. CCh (1-5 microM) strongly enhanced the discharge activity of hilar neurones and spontaneous and evoked IPSPs in granule cells. 3. Eserine, in an atropine-sensitive manner, increased the excitability of hilar neurones through effects on membrane properties and on excitatory synaptic barrage. EPSPs readily triggered long-duration burst discharges. In granule cells, the amplitudes of evoked GABAA and GABAB receptor-mediated IPSPs were enhanced. 4. In the presence of eserine and antagonists for glutamatergic and GABAergic synaptic transmission, train stimulation evoked atropine-sensitive slow EPSPs. In contrast to those in granule cells, slow EPSPs in hilar neurones were invariably preceded by a strong burst-after-hyperpolarization. 5. We suggest that acetylcholine, released from septo-hippocampal fibres, amplifies fast synaptic excitation of inhibitory hilar neurones and inhibition of granule cells. In the dentate area, muscarinic receptor-mediated effects are faster than anticipated from the time course of the slow EPSP.

On the expression of several Lhc genes in garden cress (Lepidium sativum L.)

The polymerase chain reaction was used to prepare gene-specific probes for several Lhc genes coding for chlorophyll a/b-binding proteins of cress (Lepidium sativum L.). Due to the presence of about 150 basepairs of the coding region, the isolated clones could be attributed to Lhc a3 (1 clone), Lhc b1 (5 clones), Lhc b2 (1 clone) and Lhc b3 (1 clone) genes. Probes prepared from the 3'non-coding regions of the clones did not cross-hybridize; they were specific for 3 different Lhc b1 transcripts and one each of Lhc b2, Lhc b3 and Lhc a3 transcripts. The transcript levels were higher in leaves than in cotyledons of light-grown seedlings; they decreased significantly in cotyledons from week 1 to week 4. The levels of 2 Lhc b1 transcripts (detected with probes cd1 and cd2) changed from 1 week old cotyledons (30% cd1, 28% cd2) to 3 months old leaves (14% cd1), 44% cd2), stems (11% cd1, 56% cd2) and fruits (15% cd1, 62% cd2, all values percent of total transcripts), whereas transcript levels of another Lhc b1 gene (detected with probe cd3) and of a Lhc a3 gene remained nearly constant. The level of Lhc b2 and Lhc b3 transcripts were 1-2 orders of magnitude smaller than those of the other Lhc transcripts. The data obtained with cress plants are compared with published data from other plants.

Avenacosidase from oat: purification, sequence analysis and biochemical characterization of a new member of the BGA family of beta-glucosidases

A protein consisting of 60 kDa subunits (As-P60) was isolated from etiolated oat seedlings (Avena sativa L.) and characterized as avenacosidase, a beta-glucosidase that belongs to a preformed defence system of oat against fungal infection. The enzyme is highly aggregated; it consists of 300-350 kDa aggregates and multimers thereof. Dissociation by freezing/thawing leads to complete loss of enzyme activity. The specificity of the enzyme was investigated with para-nitrophenyl derivatives which serve as substrates, in decreasing order beta-fucoside, beta-glucoside, beta-galactoside, beta-xyloside. The corresponding orthonitrophenyl glycosides are less well accepted. No hydrolysis was found with alpha-glycosides and beta-thioglucoside. An anti-As-P60 antiserum was prepared and used for isolation of a cDNA clone coding for As-P60. A presequence of 55 amino acid residues was deduced from comparison of the cDNA sequence with the N-terminal sequence determined by Edman degradation of the mature protein. The presequence has the characteristics of a stroma-directing signal peptide; localization of As-P60 in plastids of oat seedlings was confirmed by western blotting. The amino acid sequence revealed significant homology (> 39% sequence identity) to beta-glucosidases that are constituents of a defence mechanism in dicotyledonous plants. 34% sequence identity was even found with mammalian and bacterial beta-glucosidases of the BGA family. Avenacosidase extends the occurrence of this family of beta-glucosidases to monocotyledonous plants.

The amino acid sequence previously attributed to a protein kinase or a TCP1-related molecular chaperone and co-purified with phytochrome is a beta-glucosidase

A 60 kDa protein (P60) co-purified with phytochrome was identified as avenacosidase, a beta-glucosidase which is part of the defense system of Avena sativa. An antiserum raised against P60 was used to isolate a cDNA clone coding for the complete amino acid sequence of P60. The cDNA-derived amino acid sequence contained the partial sequences described before for a protein kinase [(1989) Planta 178, 199-206] and for a TCP1-related molecular chaperone [(1993) Nature 363, 644-647] co-purified with phytochrome. We conclude that these activities were related to minor contaminants and that only sequences of avenacosidase had been obtained.

Natural inhibitors of germination and growth, VII synthesis of ribulosebisphosphate carboxylase in darkness and its inhibition by coumarin

Cress (Lepidium sativum) seeds were germinated in darkness. Seedlings were investigated for soluble proteins by SDS-PAGE. Two proteins were identified by microsequencing: the small subunit of ribulosebisphosphate carboxylase (SSU) and the alpha subunit of the storage protein cruciferin. Net synthesis of small and large subunits of ribulosebisphosphate carboxylase (SSU and LSU) was investigated by Western blot. Net synthesis of both subunits was inhibited by coumarin. To the contrary, net synthesis of cruciferin was increased by coumarin. With specific cDNA probes, we determined steady state levels of the corresponding mRNAs (rbcS mRNA for SSU, rbcL mRNA for LSU). Both mRNAs can be detected in dry seeds; their amount increases during germination in the dark. Incubation with coumarin inhibits this increase. Inhibition of development by coumarin on the level of transcription is discussed.

Gonosomal mosaicism in myotonic dystrophy patients: involvement of mitotic events in (CTG)n repeat variation and selection against extreme expansion in sperm

Myotonic dystrophy (DM) is caused by abnormal expansion of a polymorphic (CTG)n repeat, located in the DM protein kinase gene. We determined the (CTG)n repeat lengths in a broad range of tissue DNAs from patients with mild, classical, or congenital manifestation of DM. Differences in the repeat length were seen in somatic tissues from single DM individuals and twins. Repeats appeared to expand to a similar extent in tissues originating from the same embryonal origin. In most male patients carrying intermediate- or small-sized expansions in blood, the repeat lengths covered a markedly wider range in sperm. In contrast, male patients with large allele expansions in blood (> 700 CTGs) had similar or smaller repeats in sperm, when detectable. Sperm alleles with > 1,000 CTGs were not seen. We conclude that DM patients can be considered gonosomal mosaics, i.e., combined somatic and germ-line tissue mosaics. Most remarkably, we observed multiple cases where the length distributions of intermediate- or small-sized alleles in fathers' sperm were significantly different from that in their offspring's blood. Our combined findings indicate that intergenerational length changes in the unstable CTG repeat are most likely to occur during early embryonic mitotic divisions in both somatic and germ-line tissue formation. Both the initial CTG length, the overall number of cell divisions involved in tissue formation, and perhaps a specific selection process in spermatogenesis may influence the dynamics of this process. A model explaining mitotic instability and sex-dependent segregation phenomena in DM manifestation is discussed.

Characteristics of intergenerational contractions of the CTG repeat in myotonic dystrophy

In myotonic dystrophy (DM), the size of a CTG repeat in the DM kinase gene generally increases in successive generations with clinical evidence of anticipation. However, there have also been cases with an intergenerational contraction of the repeat. We examined 1,489 DM parent-offspring pairs, of which 95 (6.4%) showed such contractions in peripheral blood leukocytes (PBL). In 56 of the 95 pairs, clinical data allowed an analysis of their anticipation status. It is surprising that anticipation occurred in 27 (48%) of these 56 pairs, while none clearly showed a later onset of DM in the symptomatic offspring. The contraction occurred in 76 (10%) of 753 paternal transmissions and in 19 (3%) of 736 maternal transmissions. Anticipation was observed more frequently in maternal (85%) than in paternal (37%) transmissions (P < .001). The parental repeat size correlated with the size of intergenerational contraction (r2 = .50, P << .001), and the slope of linear regression was steeper in paternal (-.62) than in maternal (-.30) transmissions (P << .001). Sixteen DM parents had multiple DM offspring with the CTG repeat contractions. This frequency was higher than the frequency expected from the probability of the repeat contractions (6.4%) and the size of DM sib population (1.54 DM offspring per DM parent, in 968 DM parents). We conclude that (1) intergenerational contractions of the CTG repeat in leukocyte DNA frequently accompanies apparent anticipation, especially when DM is maternally transmitted, and (2) the paternal origin of the repeat and the presence of the repeat contraction in a sibling increase the probability of the CTG repeat contraction.

Promotion of preneoplastic foci in rat liver with 2,3,7,8-tetrachlorodibenzo-p-dioxin, 1,2,3,4,6,7,8-heptachlorodibenzo-p-dioxin and a defined mixture of 49 polychlorinated dibenzo-p-dioxins

In a two-stage initiation-promotion experiment the hypothesis was investigated that 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) equivalents (TE), calculated from data of CYP1A induction in hepatocytes in primary culture, or international TCDD equivalents (ITE) are useful for evaluating the tumor-promoting potency of 1,2,3,4,6,7,8-heptachlorodibenzo-p-dioxin (HpCDD) and of a defined mixture (M2) of 49 polychlorinated dibenzo-p-dioxins (PCDDs) in comparison with TCDD. Therefore, female Wistar rats were treated with an initiating dose of N-nitrosomorpholine, and subsequently received daily doses of 2, 20 and 200 ng TCDD/kg or equivalent doses of HpCDD or M2, based on TE values. After a promotion phase of 13 weeks, hepatic PCDD levels, CYP1A activity and the relative hepatic volume of adenosinetriphosphatase-negative or glutathione S-transferase P-positive preneoplastic foci were determined. After logarithmic transformation, linear PCDD level-response relationships were obtained for induction of CYP1A activity with TCDD, HpCDD or M2. Based on TE values, inducing potencies of both HpCDD and M2 were over-estimated at higher doses, whereas induction was approximately equivalent at the lowest dose. The best fit of PCDD level-response relationships of relative hepatic volumes of preneoplastic lesions was achieved using a four-parameter logistic model. Significantly different functions were calculated for promotion with TCDD or HpCDD. It is concluded that (i) different PCDD level-response relationships exist for the induction of hepatic CYP1A activity and the promotion of preneoplastic liver foci, and (ii) that TE or ITE factors provide only a rough estimate of the tumor-promoting potency of a PCDD mixture but may overestimate the risk from exposure to higher-chlorinated 2,3,7,8-substituted congeners such as HpCDD.