Stability of Drug Additives in Peritoneal Dialysis Solutions in a New Container

Objective

To evaluate the stability of gentamicin, tobramycin, netilmycin, vancomycin, cefazolin, unfractionated heparin, and low molecular weight heparin when added to four different peritoneal dialysis (PD) solutions [Extraneal (Baxter Healthcare, Castlebar, Ireland); Physioneal, Nutrineal, and Dianeal (Baxter Healthcare, Grosotto, Italy)] in new, non-PVC Clear-Flex containers.

Measurements

Gentamicin, tobramycin, netilmycin, vancomycin, cefazolin, unfractionated heparin, and low molecular weight heparin were injected into separate bags of PD solution. Samples were withdrawn at predefined sampling times and the concentration of each drug was analyzed using high-performance liquid chromatography (for gentamicin, tobramycin, vancomycin, and cefazolin), or bioassay (for netilmycin, gentamicin, and tobramycin in Nutrineal), or coagulation methods (heparins).

Results

Netilmycin, vancomycin, cefazolin, and heparin in Physioneal, Nutrineal, Extraneal, and Dianeal were stable for at least 24 hours at 25°C and for an additional 4 hours at 37°C. Gentamicin in Nutrineal, Extraneal, and Dianeal was stable for at least 24 hours at 25°C and for an additional 4 hours at 37°C; gentamicin in Physioneal was stable for less than 24 hours at 25°C. Tobramycin in Nutrineal and Extraneal was stable for at least 24 hours at 25°C and for an additional 4 hours at 37°C; tobramycin in Physioneal and Dianeal was stable for less than 24 hours at 25°C.

Compatibility of Insulin over 24 Hours in Standard and Bicarbonate-Based Peritoneal Dialysis Solutions Contained in Bags Made of Different Materials

Background

The purpose of this study was to evaluate potency changes in insulin in different solutions and bag materials used for peritoneal dialysis (PD). One of the PD solutions (Physioneal) tested is available in two different solution containers, PVC and Clear-Flex. Four insulin concentrations (4 IU/L, 10 IU/L, 20 IU/L, and 40 IU/L) were evaluated. This range of concentrations was defined in accordance with standard medical practice. All PD solutions made by Baxter, Castlebar, Ireland.

Methods

Insulin determination was performed by immunoassay (ELISA).

Results

In Dianeal, more than 90% of the initial dose of insulin remained available up to 24 hours for all concentrations tested. In Physioneal, for the higher concentrations tested (10 IU/L, 20 IU/L, and 40 IU/L), more than 90% of the initial dose of insulin remained available up to 6 hours, and more than 80% up to 24 hours. For the lowest concentration of insulin tested in Physioneal (4 IU/L), more than 90% of the initial dose of insulin remained available up to 3 hours, and more than 70% up to 24 hours. Also for the lowest concentration of insulin, recovery correlated with the pH of the tested solutions. This effect became apparent over the storage time.

Conclusions

The data show that insulin adsorption is less than 10% during the first 3 hours for every PD solution tested. Insulin recovery tends to be stable or to decrease slightly over time for the lower insulin concentrations tested. The results for insulin recovery show a correlation with insulin concentration and with pH for the lowest insulin dose tested. From a solution–container interaction perspective, Clear-Flex is an equivalent alternative to standard PVC material.

Compatibility of insulin over 24 hours in standard and bicarbonate-based peritoneal dialysis solutions contained in bags made of different materials

BACKGROUND

The purpose of this study was to evaluate potency changes in insulin in different solutions and bag materials used for peritoneal dialysis (PD). One of the PD solutions (Physioneal) tested is available in two different solution containers, PVC and Clear-Flex. Four insulin concentrations (4 IU/L, 10 IU/L, 20 IU/L, and 40 IU/L) were evaluated. This range of concentrations was defined in accordance with standard medical practice. All PD solutions made by Baxter, Castlebar, Ireland.

METHODS

Insulin determination was performed by immunoassay (ELISA).

RESULTS

In Dianeal, more than 90% of the initial dose of insulin remained available up to 24 hours for all concentrations tested. In Physioneal, for the higher concentrations tested (10 IU/L, 20 IU/L, and 40 IU/L), more than 90% of the initial dose of insulin remained available up to 6 hours, and more than 80% up to 24 hours. For the Lowest concentration of insulin tested in Physioneal (4 IU/L), more than 90% of the initial dose of insulin remained available up to 3 hours, and more than 70% up to 24 hours. Also for the lowest concentration of insulin, recovery correlated with the pH of the tested solutions. This effect became apparent over the storage time.

CONCLUSIONS

The data show that insulin adsorption is less than 10% during the first 3 hours for every PD solution tested. Insulin recovery tends to be stable or to decrease slightly over time for the lower insulin concentrations tested. The results for insulin recovery show a correlation with insulin concentration and with pH for the lowest insulin dose tested. From a solution-container interaction perspective, Clear-Flex is an equivalent alternative to standard PVC material.

Thrombolyse der A. basilaris: Ergebnisse im Saarland über einen Zeitraum von 5 Jahren

Acute thrombosis of the basilar artery has a fatal outcome if left untreated. The relatively good prognosis with intra-arterial thrombolysis makes it the therapy of choice for acute basilar thrombosis. In the Saarland stroke registry, we analyzed 47 patients with angiographically proven basilar artery thrombosis within the last 5 years. We observed a better outcome in patients with good income, with recanalization, and a short time between onset of symptoms and start of thrombolysis. The complications, such as intracerebral bleedings, occurred only in the group treated with rt-PA. Intra-arterial thrombolysis with urokinase or rt-PA is a relatively safe therapy, but should be performed in neuroradiological centers. With progressing symptoms the therapeutic window can be stretched up to 12 h, but coma lasting for more than 4 h is related to a bad outcome.

Stability of drug additives in peritoneal dialysis solutions in a new container

OBJECTIVE

To evaluate the stability of gentamicin, tobramycin, netilmycin, vancomycin, cefazolin, unfractionated heparin, and low molecular weight heparin when added to four different peritoneal dialysis (PD) solutions [Extraneal (Baxter Healthcare, Castlebar, Ireland); Physioneal, Nutrineal, and Dianeal (Baxter Healthcare, Grosotto, Italy)] in new, non-PVC Clear-Flex containers.

MEASUREMENTS

Gentamicin, tobramycin, netilmycin, vancomycin, cefazolin, unfractionated heparin, and low molecular weight heparin were injected into separate bags of PD solution. Samples were withdrawn at predefined sampling times and the concentration of each drug was analyzed using high-performance liquid chromatography (for gentamicin, tobramycin, vancomycin, and cefazolin), or bioassay (for netilmycin, gentamicin, and tobramycin in Nutrineal), or coagulation methods (heparins).

RESULTS

Netilmycin, vancomycin, cefazolin, and heparin in Physioneal, Nutrineal, Extraneal, and Dianeal were stable for at least 24 hours at 25 degrees C and for an additional 4 hours at 37 degrees C. Gentamicin in Nutrineal, Extraneal, and Dianeal was stable for at least 24 hours at 25 degrees C and for an additional 4 hours at 37 degrees C; gentamicin in Physioneal was stable for less than 24 hours at 25 degrees C. Tobramycin in Nutrineal and Extraneal was stable for at least 24 hours at 25 degrees C and for an additional 4 hours at 37 degrees C; tobramycin in Physioneal and Dianeal was stable for less than 24 hours at 25 degrees C.

[Mono- or bilateral abducens paralysis as the initial symptom of sinus vein thrombosis]

BACKGROUND

Sinus vein thrombosis is a rare intracerebral complication of mastoiditis. We report on the clinical ophthalmologic symptomatology of this secondary illness.

PATIENTS AND METHODS

HISTORY

two young female patients, aged 14 and 3.5 years, presented at our pediatric ophthalmology section due to diplopia. Both girls had suffered 1-2 weeks earlier from otitis media, which had been treated with antibiotics. Other neurological symptoms were not reported.

CLINICAL COURSE

Best corrected visual acuity was 20/20 OD/OS in both patients. Ocular alignment revealed a bilateral abduction deficit in the 14-year-old girl and a monolateral abduction deficit of the right eye in the younger patient. Ophthalmoscopic examination evidenced bilateral papilledema in both patients. Magnetic resonance tomography and magnetic resonance angiography showed mastoiditis and thrombosis of the sigmoid and transverse sinuses.

THERAPY

Following mastoidectomy, high-dose antibiotic therapy, and full-dose heparin therapy, rapid improvement occurred.

CONCLUSIONS

Thrombosis of the sigmoid sinus following mastoiditis is a rare but severe complication of middle ear inflammation. Immediate surgical and antibiotic therapy is necessary. Symptoms can possibly occur even when the primary focus seems to resolve.

[Embolization of dural carotid cavernous sinus fistulas via the sylvian vein in 2 patients]

BACKGROUND

Dural carotid sinus cavernous fistulas account for about 12% of intracranial arteriovenous fistulas. These dynamic shunts are dilemmas not only for the clinical diagnosis but also for the management of ocular complications and in the application of diagnostic and therapeutic techniques. The traditional therapy is transarterial embolisation by an interventional neuroradiologist. We report on the management of two fistulas where the classical therapeutic methods were not possible or failed.

PATIENTS AND METHODS

Two patients underwent an osteoplastic pterional craniotomy with cannulation of a vein of the sylvian fissure and controlled embolisation of the fistula with polyvinyl alcohol particles.

RESULTS

Successful closure of both arteriovenous shunts was achieved on angiography with normalisation of clinical symptoms. As a severe complication one patient suffered from a stroke after the postoperative angiography.

CONCLUSIONS

Arteriovenous fistulas not approachable by traditional therapeutic methods, can be embolised effectively via a superficial vein of the sylvian fissure. This surgical route should only be considered if other therapeutic ways fail or seem impossible.

[Hereditary occlusive cerebroretinal vasculopathy in two sisters]

BACKGROUND

Retinal microvascular abnormalities associated with multiorgan disease may be observed in a number of systemic illnesses and syndromes.

PATIENTS

Two sisters with identical signs of a hereditary cerebroretinal vasculopathy (occlusive retinal angiopathy--cerebral vasculopathy--microcephalus) were treated at the University Hospital of Saarland.

COURSE

Photocoagulation for treatment of neovascular complications secondary to retinal ischemia was performed. In one eye a vitrectomy became necessary because of persistent vitreal hemorrhage. One sister died because of non treatable intracranial hypertension at the age of 22 years.

CONCLUSIONS

Interdisciplinary work-up is important in patients with cerebroretinal disease. Neuropathologic evaluation including brain biopsy and neuroimaging plus ophthalmoscopy and pedriatic findings lead to the diagnosis of this rare hereditary, in this case most likely autosomal recessive condition. Photocoagulation may limit neovascular complications secondary to retinal ischemia. A specific form of treatment has, however, not yet been found.

[Surgical transvenous embolization of spontaneous carotid cavernous sinus fistulas in two patients]

BACKGROUND

Arteriovenous communications in which blood flows from meningeal branches of the internal and external carotid arteries into the venous circulation around and in the cavernous sinus are termed spontaneous (dural) carotid sinus cavernous fistulas. Due to their mostly low shunt volume they are rarely life threatening, but without treatment they may cause severe ocular complications like episcleral secondary glaucoma, central vein occlusion or exudative retinal detachment. Traditional therapy is the transarterial approach by an interventional neuroradiologist. If such an approach is not possible or unsuccessful a transvenous route has to be considered.

PATIENTS AND METHODS

Two patients underwent anterior orbitotomy via sub brow incision or infraciliary incision with cannulation of the superior ophthalmic vein or the inferior ophthalmic vein and embolization of the cavernous sinus with platinum coils.

RESULTS

Successful closure was achieved on angiography and normalisation of clinical symptoms after a short period of progressive venous congestion.

CONCLUSIONS

For arteriovenous fistulas that cannot be embolized arterially the surgical transvenous orbital route may work as a method of second choice. When performed by an interdisciplinary team (orbital surgeon, interventionell neuroradiologist) it is a technically straightforward, effective and promising approach.

Short-term CT and MR changes in brain tumors following 125I interstitial irradiation

PURPOSE

The study was undertaken to assess characteristic short-term CT and MR changes in brain tumors following 125I interstitial irradiation.

METHOD

Sixteen patients were included who had both CT and MR control examinations at regular intervals over a period of 18 months following treatment. Two groups were distinguished: low grade tumors (11 cases) and high grade malignancies (5 patients). 125I seeds were used as temporary implants. The cumulative dose was 50-60 Gy.

RESULTS

In some patients of both groups, a low attenuation spheric structure with a contrast-medium-enhanced ring and a diameter of 6-8 mm was observed. There was no edema around the structure, which represents a zone of tissue necrosis at the site of the temporary 125I implant. Tumors in both groups were completely destroyed, some decreased in size, and others were unchanged. Pseudotumor necrosis with accompanying edema occurred in two patients with low grade astrocytoma, the diameter of which was > 4 cm.

CONCLUSION

The behavior of cerebral tumors and their appearance on CT and MR images after interstitial irradiation seem to be variable. Decrease in tumor size may take place at different intervals after therapy. Brachytherapy of tumors with a diameter of > 4 cm may produce space-occupying radionecrosis.

The radiation exposure of the patient from stable-xenon computed tomography

For stable-xenon computed tomography (CT), an X-ray examination for measurement of cerebral blood circulation in the brain, the radiation exposure of the patient was determined in order to estimate the risk of inducing cancer. Organ doses of brain, eyelenses, thyroid and gonads have been calculated using the measured air kerma free-in-air on the axis of rotation and organ-specific conversion factors calculated with the Monte Carlo method. Dose measurements with TLD-100 rods using a humanoid Alderson phantom were carried out for verification of the calculated organ doses. In the case of brain partially located in the region of primary radiation a mean organ dose of 39 mSv was calculated. The dose measurements showed dose equivalents between 6 and 68 mSv in different regions of the brain and consequently an inhomogeneous dose distribution. From an estimation of the radiation-induced risk using the effective dose of 1.6 mSv it follows that one additional fatal cancer per 12,500 stable-xenon CT examinations has to be expected. The organ doses of eyelenses and thyroid located in the region of scattered radiation are so low that biological effects are hardly to be expected. The calculated dose equivalents of 6.5 mSv and 0.5 mSv, respectively, are in good agreement with measurements. The organ dose of gonads amounted to less than 0.07 mSv.

Real-time ultrasound imaging of cerebral lesions during "target point" stereotactic procedures through a burr hole. Technical note

Stereotactic burr-hole procedures like biopsies of brain tumours based on CT scan or MRI and angiographic data have so far usually been carried out without real-time ultrasound image control. Intra-operative real-time ultrasound imaging was carried out during twelve target-point stereotactic procedures via a single standard burr-hole using a new slender ultrasound transducer with a diameter of 8 mm. The technical parameters of the transducer are: frequency range of 5 < - > 3.5 MHZ, phased array sector scan, 90 degree sector. The transducer has a bayonet-like configuration and can be sterilized. Sufficient quality of the images was achieved in these twelve cases with different pathological entities such as malformation cysts (3 cases), gliomas (7 cases), one metastasis and one intracerebellar haemorrhage. Moreover, co-ordinate values may be calculated from the ultrasound images generated peroperatively, allowing the surgeon to choose additional targets. Colour flow mapping provides the visualization of vascular structures. For the beginner stereotaxy may be easier to learn using ultrasound real-time imaging.

Assessment of cerebral vasomotor reactivity by transcranial Doppler ultrasound and breath-holding. A comparison with acetazolamide as vasodilatory stimulus

BACKGROUND AND PURPOSE

Evaluating cerebrovascular vasomotor reactivity seems to be of prognostic relevance for patients with occlusive internal carotid artery disease. To evaluate its clinical usefulness, the recently introduced breath-holding maneuver as a carbon dioxide-dependent vasodilatory stimulus was compared with the acetazolamide challenge by means of transcranial Doppler ultrasound and stable xenon-enhanced computed tomography.

METHODS

In a total of 134 middle cerebral arteries of 74 patients (mean +/- SD age, 62 +/- 9 years) with unilateral or bilateral occlusive carotid artery disease, vasomotor reactivity was estimated by the increase of middle cerebral artery mean blood velocity by transcranial Doppler ultrasound, comparing the breath-holding maneuver and 1 g IV acetazolamide as vasodilatory stimuli. The carotid artery findings were classified as normal, stenosis of 50% to < 70%, 70% to < 90%, 90% to 99%, and occlusion. Eighteen of the 74 patients additionally underwent stable xenon-enhanced computed tomography to calculate the increase of mean cortical regional cerebral blood flow in the middle cerebral artery territory after acetazolamide stimulation.

RESULTS

The percentage of mean regional cerebral blood flow changes (n = 36 hemispheres) correlated best with the absolute mean blood velocity changes while breath-holding (P = .007, r = .4332). The absolute mean regional cerebral blood flow changes correlated best with the percentage of mean blood velocity changes after acetazolamide stimulation (P = .004, r = .4580). On all 134 middle cerebral arteries, both vasodilatory stimuli correlated highly significantly (P < .0001) when comparing increases in absolute (r = .5448) or relative (r = .3516) mean blood velocity. Both stimulation techniques similarly indicated significantly reduced vasomotor reactivity with increasing degree of internal carotid artery lesions (P < or = .01). However, the acetazolamide challenge differentiated more accurately between the various groups of internal carotid artery findings.

CONCLUSIONS

The assessment of vasomotor reactivity by transcranial Doppler ultrasound correlates with cerebral blood flow changes even when different vasodilatory stimuli are used. In cooperative patients the breath-holding maneuver as vasodilatory stimulus seems clinically useful for a first estimation of cerebral vasomotor reactivity.

Chromatid aberration dose responses and dispersal in human G2 lymphocytes treated with bleomycin: comparison with equivalent X-irradiation reveals formation of a novel class of heavily damaged cells

We describe the dose responses and dispersal of chromatid (ct) aberrations in human peripheral blood lymphocytes, treated with a 5-min pulse of bleomycin (BLM) in doses ranging from 0.78 to 200 micrograms/ml during the G2 phase of the cell cycle. Damage was assessed in cells fixed at the time of peak damage 1 h after treatment. Both ct breaks and the percentages of damaged cells rose according to log BLM dose above 6.3 micrograms/ml only. Below this dose all endpoints exhibited flat responses suggestive of thresholding. A dose of 100 micrograms/ml produced similar amounts and distribution of ct breakage per cell (B/c) as a previously studied X-ray dose of 0.8 Gy, permitting future direct cytogenetic comparisons between clastogens. Within the scorable range (0-29 B/c) the dispersal of ct breakage after BLM treatment resembled that after equivalent X-irradiation; but BLM treatment alone resulted in the formation of heavily damaged cells (HDC) defined as with > or = 30 B/c, representing a cytogenetic endpoint of DNA damage reminiscent of apoptosis. At the dose producing equivalent chromatid breakage, BLM produced 7.4 times fewer exchanges than X-rays in G2.

Structure of the Acetobacter methanolicus MB 129 capsular polysaccharide, and of oligosaccharides resulting from degradation by bacteriophage Acm7

The capsular polysaccharide of Acetobacter methanolicus MB 129 consists of D-Glc, D-Gal, L-Rha, and L-glyceric acid in the molar ratios 1:1:1:0.3. Periodate oxidation, methylation analysis, solvolysis with HF, and detailed 1H and 13C NMR analysis resulted in the structure of the repeating unit shown below. [formula: see text] Bacteriophage Acm7-associated end-alpha-L-rhamnopyranoside hydrolase depolymerizes the CPS even in the presence of the O-acyl group, to give the respective hexa-, nona-, and dodeca-saccharides.

Treatment of mycoplasma contamination in a large panel of cell cultures

Mycoplasmal contamination remains a significant impediment to the culture of eukaryotic cells. For certain cultures, attempts to eliminate the infection are feasible alternatives to the normally recommended disposal of the contaminated culture. Here, three antibiotic regimens for mycoplasmal decontamination were compared in a large panel of naturally infected cultures: a 1-wk treatment with the fluoroquinolone mycoplasma removal agent (MRA), a 2-wk treatment with the fluoroquinolone ciprofloxacin, and three rounds of a sequential 1-wk treatment with BM-Cyclin containing tiamulin and minocyclin. These antibiotic treatments had a high efficiency of permanent cure: MRA 69%, ciprofloxacin 75%, BM-Cyclin 87%. Resistance to mycoplasma eradication was observed in some cell cultures: BM-Cyclin 0%, MRA 20%, ciprofloxacin 20%. Nearly all resistant contaminants that could be identified belonged to the species Mycoplasma arginini and M. orale. Detrimental effects of the antibiotics were seen in the form of culture death caused by cytotoxicity (in 5 to 13% of the cultures). Alterations of the cellular phenotypic features or selective clonal outgrowth might represent further untoward side effects of exposure to these antibiotics. Overall, antibiotic decontamination of mycoplasmas is an efficient, inexpensive, reliable, and simple method: 150/200 (75%) chronically and heavily contaminated cultures were cured and 50/200 (25%) cultures could not be cleansed and were either lost or remained infected. It is concluded that eukaryotic cell cultures containing mycoplasmas are amenable to antibiotic treatment and that a cure rate of three-quarters is a reasonable expectation.

Structure of the capsular polysaccharide and the O-side-chain of the lipopolysaccharide from Acetobacter methanolicus MB 70, and of oligosaccharides resulting from their degradation by the bacteriophage Acm6

Acetobacter methanolicus MB 70 was shown to be related to the type strain of this species MB 58/4 (IMET 10945) having the same galactan-->2)-beta-D-Gal f-(1-->3)-beta-D-Gal p-(1-->as the capsular polysaccharide (CPS) and the O-side-chain of the lipopolysaccharide (LPS). Additionally, a glucan built up of the disaccharide repeating unit-->6)-alpha-D-Glc p-(1-->2)-alpha-D-Glc p-(1-->was identified in strain MB 70. In the CPS, the polymers were present in the ratio approximately 1:1, whereas the glucan preponderated in the LPS. Bacteriophage Acm6 specific to A. methanolicus MB 70 hydrolysed selectively the glucan component of both CPS and LPS. Structural elucidation of the resulting oligosaccharides led to the identification of the phage-associated depolymerase as an endo-alpha-(1-->6)-D-glucopyranoside hydrolase.

Modulated surgery in the management of ruptured intracranial aneurysm in poor grade patients

The treatment of subarachnoid haemorrhage caused by aneurysm in comatose patients with or without midbrain symptoms is a matter of controversy. The question is, which comatose patients will profit from aneurysm surgery and which will not? In a retrospective study, 573 patients were examined between 1986 and 1992. Of these, 116 were in poor condition (Hunt and Hess Grade IV or V). The following management protocol was used: after computer tomography, a decision was made whether intensive medical treatment was performed or not. The reason for not operating was essentially the severity of the cerebral haemorrhage and poor or absent intracranial filling on angiography. Extracerebral causes were renal failure, sepsis, liver cirrhosis and pulmonary embolism. The direct early aneurysm operation was performed in the clinical deterioration phase in patients with space-occupying haematomas. In dilatation of the ventricle system, external drainage was initially positioned, in the case of bilateral haematocephalus, two-sided drainage was positioned, then intensive medical treatment and angiography were performed. The aneurysm operation was then ruled out if there was no clinical improvement. Aneurysm operation was performed on 57 of the 116 patients; 13 died, 32 showed a good and 12 a poor or fair outcome. 15 patients had mid-brain syndrome, and 5 of them died. Based on our experience, we draw the following conclusion: the Hunt and Hess scale alone is not a sufficient basis for decision taking. Some of the comatose patients, even in mid-brain syndrome, profit from an early operation.(ABSTRACT TRUNCATED AT 250 WORDS)

[Single photon emission tomography (SPECT). Cerebral function diagnosis for the clinical routine. Indications and radiotracers]

Nuclear medicine techniques have been powerful tools in neurology since their introduction. Computed tomography, magnetic resonance imaging and newer techniques, i.e. MR spectroscopy and angiography, sonography, Doppler sonography and EEG mapping with squid elements have overtaken most earlier nuclear medicine techniques for neurological diagnosis. Positron emission tomography is the gold standard for in vivo research in neurophysiology and pathology. The introduction of SPECT and the development of such tracers as 99mTc-HMPAO (99mTc-d,l-hexamethylpropylenaminoxim) and, more recently, 123I-iomazenil and 123I-IBZM (123I-3-iodo-6-methoxybenzamide) allowed closer examination of the perfusion of the brain and neuroreceptor density mapping in more than the few institutions that can afford PET and the production of special tracers marked with a positron emitting nucleus. Nuclear medicine's future will be based on neuroreceptor density mapping, as further tracers will become commercially available and no other technique can probably show such low concentrations of the receptors. Probably MR techniques will be used for brain's perfusion measurement in future. For examination of a limited cerebral region xenon-enhanced CT is an alternative to perfusion measurements with HMPAO, or a very interesting supplement. Of the old techniques in nuclear medicine, examination of the liquor dynamics is still feasible and well supplemented by SPECT.

Substrate-analogue-induced changes in the nickel-EPR spectrum of active methyl-coenzyme-M reductase from Methanobacterium thermoautotrophicum

Methyl-coenzyme-M reductase (MCR) catalyzes the formation of methane from methyl-coenzyme M [2-(methylthio)ethanesulfonate] and 7-mercaptoheptanoylthreonine phosphate in methanogenic archaea. The enzyme contains the nickel porphinoid coenzyme F430 as a prosthetic group. In the active, reduced (red) state, the enzyme displays two characteristic EPR signals, MCR-red1 and MCR-red2, probably derived from Ni(I). In the presence of the substrate methyl-coenzyme M, the rhombic MCR-red2 signal is quantitatively converted to the axial MCR-red1 signal. We report here on the effects of inhibitory substrate analogues on the EPR spectrum of the enzyme. 3-Bromopropanesulfonate (BrPrSO3), which is the most potent inhibitor of MCR known to date (apparent Ki = 0.05 microM), converted the EPR signals MCR-red1 and MCR-red2 to a novel axial Ni(I) signal designated MCR-BrPrSO3. 3-Fluoropropanesulfonate (apparent Ki < 50 microM) and 3-iodopropanesulfonate (apparent Ki < 1 microM) induced a signal identical to that induced by BrPrSO3 without affecting the line shape, despite the fact that the fluorine, bromine and iodine isotopes employed have nuclear spins of I = 1/2, I = 3/2 and I = 5/2, respectively. This finding suggests that MCR-BrPrSO3 is not the result of a close halogen-Ni(I) interaction. 7-Bromoheptanoylthreonine phosphate (BrHpoThrP) (apparent Ki = 5 microM), which is an inhibitory substrate analogue of 7-mercaptoheptanoylthreonine phosphate, converted the signals MCR-red1 and MCR-red2 to a novel axial Ni(I) signal, MCR-BrHpoThrP, similar but not identical to MCR-BrPrSO3. The results indicate that inhibition of MCR by the halogenated substrate analogues investigated above is not via oxidation of Ni(I)F430. The different MCR EPR signals are assigned to different enzyme/substrate and enzyme/inhibitor complexes.

Treatment of mycoplasma-contaminated continuous cell lines with mycoplasma removal agent (MRA)

Thirty-nine continuous adherent or suspension cell lines were treated with a quinolone antibiotic, Mycoplasma Removal Agent (MRA), for the elimination of chronic mycoplasma contamination. In preliminary experiments MRA did not show any cytostatic or cytotoxic effects on mycoplasma-free cell cultures in concentrations up to ten-fold the concentration used for mycoplasma eradication. Twenty-eight cell lines (72%) were effectively cleansed of the mycoplasma contaminants by MRA treatment. The persistent removal of the mycoplasma infection was monitored by three mycoplasma detection assays. In seven cell lines (18%) the mycoplasmas were resistant to treatment with MRA. The resistant species was mainly M. arginini followed by M. orale and A. laidlawii; however, other cell lines harboring these species were cured. Four cell lines (10%) which prior to treatment presented with decreased viability and poor or no cell growth were lost during or shortly after the exposure to the antibiotic. If an antibiotic elimination is attempted it is imperative to closely examine the effectiveness of treatment and possible eukaryotic cytotoxicity. The treated mycoplasma-free cells may also no longer express the original features as a result of treatment or the absence of mycoplasma.

Sensitivity and specificity of five different mycoplasma detection assays

The sensitivity and specificity of five different mycoplasma detection tests were evaluated in comparison with the classical microbiological culture assay on agar plates as the reference method: direct fluorochrome DNA staining (direct DAPI), DNA staining of an indicator cell line (indirect DAPI), RNA hybridization with a cDNA specific for ribosomal mycoplasmal RNA, an enzyme-linked immunosorbent assay (ELISA) with mycoplasma-specific antibodies, and a biochemical cytotoxicity assay (6-MPDR). A large panel of continuous cell lines (20 adherent and 233 suspension cell lines, most of the latter were human leukemia-lymphoma cell lines) were analyzed for infection with mycoplasma. The results of the comparative analysis for sensitivity and specificity of the various tests were as follows: 100% and 100% for the indirect DAPI, 100% and 98% for the RNA hybridization assay, 87% and 94% for the direct DAPI, 72% and 100% for the ELISA, 75% and 90% for the biochemical 6-MPDR assay. Each of these approaches has both advantages and disadvantages with regard to cost, time, reliability, specificity, and sensitivity. The best compromise for routine mycoplasma testing is a combination of several techniques (e.g. direct culture on agar, RNA hybridization, and direct or indirect DAPI).

Methyl-coenzyme-M reductase from Methanobacterium thermoautotrophicum (strain Marburg). Purity, activity and novel inhibitors

Methyl-coenzyme-M reductase from Methanobacterium thermoautotrophicum (strain Marburg) was purified to a stage where, besides the alpha, beta and gamma subunits, no additional polypeptides were detectable in the preparation. Under appropriate conditions the enzyme was found to catalyze the reduction of methyl-CoM with 7-mercaptoheptanoylthreonine phosphate (H-S-HTP) to CH4 at a specific rate of 2.5 mumol.min-1.mg protein-1. This finding contradicts a recent report that methyl-CoM reductase is only active when some contaminating proteins are present. The two polypeptides encoded by the open reading frames ORF1 and ORF2 of the methyl-CoM reductase transcription unit did not co-purify with the alpha, beta and gamma subunits. They were neither required nor did they stimulate the activity under the assay conditions. 3-Bromopropanesulfonate (apparent Ki = 0.05 microM) and 2-azidoethanesulfonate (apparent Ki = 1 microM) were found to be two new competitive inhibitors of methyl-CoM reductase. Both inhibitors were considerably more effective than the "classical" 2-bromoethanesulfonate (apparent Ki = 4 microM).