Bacterial bioluminescence: Spectral study of the emitters in the in vitro reaction

Transient fluorescent species are observed in the bioluminescent reactions of three reduced flavin mononucleotides with aliphatic aldehydes and oxygen, catalyzed by bacterial luciferase. In each case the fluorescence spectral distribution is similar to that of the bioluminescence but is readily distinguishable from it on the basis of a significantly greater signal strength. The corrected bioluminescence maxima using Beneckea harveyi luciferase are 479 nm (iso-FMNH(2)), 490 nm (FMNH(2)), and 560 nm (2-thio-FMNH(2)). In an ethanol glass at 77 K, 2-thioriboflavin is fluorescent (varphi(F) = 0.03, lambda(max) = 562 nm). These results are interpreted by a sensitized chemiluminescence mechanism in which the flavins bound to luciferase act as acceptors of excitation energy. For 2-thio-FMNH(2), this acceptor species appears to be the oxidized 2-thio-FMN on the basis of the spectral evidence, whereas for the other flavins, some form of reduced species is a more likely candidate.

Intravenous thrombolysis in patients with stroke attributable to small artery occlusion

BACKGROUND

Intravenous thrombolysis (IVT) for stroke seems to be beneficial independent of the underlying etiology. Recent observations raised concern that IVT might cause harm in patients with strokes attributable to small artery occlusion (SAO).

OBJECTIVE

The safety of IVT in SAO-patients is addressed in this study.

METHODS

We used the Swiss IVT databank to compare outcome and complications of IVT-treated SAO-patients with IVT-treated patients with other etiologies (non-SAO-patients). Main outcome and complication measures were independence (modified Rankin scale <or=2) at 3 months, intracranial hemorrhage (ICH), and recurrent ischaemic stroke.

RESULTS

Sixty-five (6.2%) of 1048 IVT-treated patients had SAO. Amongst SAO-patients, 1.5% (1/65) patients died, compared to 11.2% (110/983) in the non-SAO-group (P = 0.014). SAO-patients reached independence more often than non-SAO-patients (75.4% versus 58.9%; OR 2.14 (95% CI 1.20-3.81; P = 0.001). This association became insignificant after adjustment for age, gender, and stroke severity (OR 1.41 95% CI 0.713-2.788; P = 0.32). Glucose level and (to some degree) stroke severity but not age predicted 3-month-independence in IVT-treated SAO-patients. ICHs (all/symptomatic) were similar in SAO- (12.3%/4.6%) and non-SAO-patients (13.4%/5.3%; P > 0.8). Fatal ICH occurred in 3.3% of the non-SAO-patients but none amongst SAO-patients. Ischaemic stroke within 3 months after IVT reoccurred in 1.5% of SAO-patients and in 2.3% of non-SAO-patients (P = 0.68).

CONCLUSION

IVT-treated SAO-patients died less often and reached independence more often than IVT-treated non-SAO-patients. However, the variable 'SAO' was a dependent rather than an independent outcome predictor. The absence of an excess in ICH indicates that IVT seems not to be harmful in SAO-patients.

The risk of a second diagnostic window with 4th generation HIV assays: Two cases

BACKGROUND

Despite the improved sensitivity of the 4th generation combined antigen/antibody HIV assays, detection of HIV in the early phase of an infection may still be ineffective.

OBJECTIVES

Description of two cases that highlight the existence of the "second diagnostic window phase" observed with commonly used sensitive 4th generation HIV assays.

STUDY DESIGN

Samples were screened with different 4th generation HIV assays. HIV infection was confirmed with an HIV I/II antibody assay, a HIV-1 p24 antigen assay, the INNO-LIA HIV I/II Score Line immunoassay and HIV-1 PCR.

RESULTS

In both investigated cases, the limitations of the 4th generation HIV assays within the second diagnostic window were apparent.

CONCLUSIONS

The overall sensitivity of the commercial 4th generation HIV assays is currently higher than the 3rd generation HIV assays. Nevertheless, the rare occurrence of a second diagnostic window with 4th generation HIV assays strongly suggests that the following up testing algorithms need to be adjusted accordingly.

Dynamical structures in binary media of potassium-driven neurons

According to the conventional approach neural ensembles are modeled with fixed ionic concentrations in the extracellular environment. However, in some cases the extracellular concentration of potassium ions cannot be regarded as constant. Such cases represent specific chemical pathway for neurons to interact and can influence strongly the behavior of single neurons and of large ensembles. The released chemical agent diffuses in the external medium and lowers thresholds of individual excitable units. We address this problem by studying simplified excitable units given by a modified FitzHugh-Nagumo dynamics. In our model the neurons interact only chemically via the released and diffusing potassium in the surrounding nonactive medium and are permanently affected by noise. First, we study the dynamics of a single excitable unit embedded in the extracellular matter. That leads to a number of noise-induced effects such as self-modulation of firing rate in an individual neuron. After the consideration of two coupled neurons we consider the spatially extended situation. By holding parameters of the neuron fixed, various patterns appear ranging from spirals and traveling waves to oscillons and inverted structures depending on the parameters of the medium.

Assessment of cold induced alterations in catecholamine turnover of lean and glutamate-treated obese rats

Excretion of norepinephrine (NE) and vanillylmandelic acid (VMA) in urine as well as NE-turnover in tissues from lean and glutamate-treated obese rats were determined in warm and cold environment. NE-and VMA-excretion in urine was elevated by cold exposure, indicating an activation of the sympathetic nervous system in animals of both groups. Organspecific NE-turnover responds with higher sensitivity to cold in obese rats but without complete compensation in brown adipose tissue. Urinary NE- and VMA- excretion as well as NE-turnover in organs confirmed that cold exposure activates the sympathetic nervous system. Measurement of NE-turnover in tissues gives organspecific information regarding alterations in sympathetic activity during cold exposure, whereas excretion of NE and VMA in urine is a summarizing measure for the whole body turnover only.

Effects of selenium and iodine deficiency on type I, type II and type III iodothyronine deiodinases and circulating thyroid hormones in the rat

The effects of nutritional selenium (Se) deficiency over a period of three generations and of a combined selenium and iodine deficiency on hepatic and cerebrocortical iodothyronine deiodinases and on circulating thyroid hormone levels were examined in the rat. Se deficiency strongly decreased hepatic type I iodothyronine 5'- and 5-deiodinase to 6-13% of that in controls. Iodine depletion had only a marginal decreasing effect on the type I activity. Cerebrocortical type II 5'-deiodinase was decreased in Se-deficient, iodine-replete rats. Its 5-6-fold elevation in iodine-deficient rats was not reversed by additional selenium deficiency. Cortex type III 5-deiodinase was modestly decreased in all groups with insufficient trace element supply. Long-term Se deficiency has only limited effects on serum T4 and T3 levels. Two months of iodine deficiency decreased serum T4 to less than 10% of that in controls, but did not significantly affect serum T3 levels. The strong decrease of hepatic outer- and inner-ring deiodination of T4 in Se deficiency obviously reflects the reduced tissue concentration of the type I deiodinase which was recently identified as a selenoenzyme. The maintenance of increased cerebrocortical type II deiodinase in iodine-depleted animals irrespective of adequate or deficient selenium supply suggests that the type II isoenzyme does not contain selenium in its catalytic site. Further studies are necessary to clarify whether the weak, but repeatedly confirmed decrease of cortex type III deiodinase is the direct effect of Se deficiency or the indirect consequence of the multilevel change in thyroid hormone metabolism.(ABSTRACT TRUNCATED AT 250 WORDS)

In vivo assessment of insulin binding in different organs of growing and adult glutamate-induced obese rats

Injection of Na-L-glutamate into neonate Wistar-rats (2 mg/g body mass s.c.; day 1-5 of life) induces hypothalamic lesions, which are followed by hypoplastic-hypertrophic obesity despite normophagia. In contrast to other animal models of obesity, these rats develop obesity under peripheral normoinsulinemic conditions. However, beginning at an age of 2 months (growing rats), peripheral insulin concentration rises gradually and at an age of 6 months (adults rats) hyperinsulinemia becomes manifest. Surprisingly, adult rats show normoglycemia, pointing to alterations in insulin sensitivity. In continuation to previous work, insulin binding of different organs of growing and adult rats was investigated using the in vivo radioreceptor assay described by Whitcomb et al. in 1985. In contrast to in vitro methods, this assay works under real metabolic and hormonal conditions in plasma of lean and obese rats. Insulin binding of liver, pancreas, adrenals, stomach, duodenum, spleen, and heart muscles was found to be not statistically different between lean and obese rats of both age groups. Thus, liver insulin binding was 6323 +/- 458 pg/g wet organ in growing, and 7586 +/- 959 pg/g in adult lean rats. Corresponding values for obese rats were 5755 +/- 445 pg/g and 7830 +/- 526 pg/g, respectively. Organ specific down regulation of insulin binding in obese rats was not detected, suggesting unalterated insulin sensitivity. It is concluded that hyperinsulinemia of adult glutamate-induced obese rats cannot be explained by diminished insulin binding and reduced organ specific insulin clearance.

Factor XI deficiency in animal models

The blood coagulation system forms fibrin to limit blood loss from sites of injury, but also contributes to occlusive diseases such as deep vein thrombosis, myocardial infarction, and stroke. In the current model of a coagulation balance, normal hemostasis and thrombosis represent two sides of the same coin; however, data from coagulation factor XI-deficient animal models have challenged this dogma. Gene targeting of factor XI, a serine protease of the intrinsic pathway of coagulation, severely impairs arterial thrombus formation but is not associated with excessive bleeding. Mechanistically, factor XI may be activated by factor XII following contact activation or by thrombin in a feedback activation loop. This review focuses on the role of factor XI, and its deficiency states as novel target for prevention of thrombosis with low bleeding risk in animal models.

High-dose methotrexate combined with procarbazine and CCNU for primary CNS lymphoma in the elderly: results of a prospective pilot and phase II study

BACKGROUND

To improve survival of elderly patients with primary central nervous system lymphoma (PCNSL), we conducted a phase II study with high-dose methotrexate (MTX) combined with procarbazine and CCNU. To reduce neurotoxicity, whole-brain irradiation was reserved for patients not responding to chemotherapy.

PATIENTS AND METHODS

High-dose MTX was applied on days 1, 15, and 30, procarbazine on days 1-10, and CCNU on day 1. Study treatment comprised up to three 45-day cycles. There was no lower limit of Karnofsky performance status (KPS).

RESULTS

Thirty patients with PCNSL (n = 29) or primary ocular lymphoma (n = 1) were included (median age 70 years, range 57-79 years). The median initial KPS was 60% (range 30%-90%). Best documented response in 27 assessable patients were 12 of 27 (44.4%) complete remissions, 7 of 27 (25.9%) partial remissions, and 8 of 27 (29.6%) disease progressions. Two patients died of probable treatment-related causes. With a median follow-up of 78 months (range 34-105), the 5-year overall survival is 33%. Eight of 30 patients (26.7%) are currently alive and well, six without signs of leukoencephalopathy.

CONCLUSION

The combination of high-dose MTX with procarbazine and CCNU is feasible and effective and results in a low rate of leukoencephalopathy. Comorbidity and toxicity remain of concern when treating PCNSL in elderly patients.

Functional electrical stimulation assisted cycling of patients with subacute stroke: kinetic and kinematic analysis

BACKGROUND

Cycling is a safe and functionally effective exercise for patients with early post-stroke and poor balance. Such exercise is considered even more effective when functional electrical stimulation is added. Our principal aim was to determine the biomechanically quantifiable parameters of cycling that can be improved in patients with subacute hemiparesis by incorporating functional electrical stimulation. These parameters were defined as objective goals that can be achieved in clinical applications. A secondary aim was to determine whether they could be used to identify subjects who would benefit from such therapy.

METHODS

Using a tricycle testbed, we tested 39 subacute (mean 10.9 weeks post-stroke (SD 5.9)), hemiplegic subjects. During isometric measurements we recorded volitional and electrically evoked crank torques, the latter at maximal tolerable intensity. During ergometric measurements, volitional pedaling was alternated with combined pedaling (volitional supported by stimulation), performed at 30-s intervals. Power, smoothness, and symmetry of cycling were evaluated.

FINDINGS

Twenty-six percent of the subjects significantly improved the smoothness of their cycling with functional electrical stimulation. Only 8% and 10% significantly increased their power and symmetry, respectively. The improvement in smoothness significantly correlated with the capability of the individual to generate electrical torque (Spearman's rank correlation coefficient=0.66 at P=0.001).

INTERPRETATION

The smoothness of cycling was the most sensitive parameter improved by functional electrical stimulation. This improvement depended on the amount of torque evoked, and the torque achieved, in turn, correlated with the tolerated intensity of stimulation.