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Biomedical subjects

F Hoffmann

Publications and source records attributed to F Hoffmann.

At least 37 records · Page 2Linked to original sources
PubMed2000

Simple technique for simultaneous on-line estimation of biomass and acetate from base consumption and conductivity measurements in high-cell density cultures of Escherichia coli.

In high-cell density cultures of Escherichia coli, the amount of ammonia required to maintain a constant pH was an effective on-line measure of biomass. When acetic acid formation occurred, biomass estimates were corrected by additional measurements of the culture conductivity. In the absence of acetic acid excretion, the culture conductivity decreased approximately linearly during the fed-batch phase of the high-cell density cultivation. Upward deviation of the culture conductivity from this trend was proportional to the acetate concentration in the medium. Thus, simultaneous determination of the acetic acid concentration and correction of biomass estimates from ammonia consumption were possible by conductivity measurements.

Acetic Acid↗
PubMed2000

An alternative approach to deal with geometric uncertainties in computer analysis of two-dimensional electrophoresis gels.

With the growing importance of proteomics in biomedical and pharmaceutical sciences a need has emerged for computing tools that are capable of digitally visualizing and analyzing protein spot patterns within two-dimensional electrophoresis (2-DE) gel. Matching programs need to meet requirements such as interlaboratory comparison and the comparison of samples from different origins. For such research purposes, we have developed the CAROL system that implements new algorithms for spot detection and matching, which enable researchers to take a different approach to protein spot identification and comparison. The present short communication discusses how the system deals with uncertain geometric spot information that arises from streaks and complex spot regions and how this can be amplified for the matching procedure.

Algorithms↗
PubMed2000

The effect of corticosteroid and cyclosporin A on murine corneal allograft rejection.

BACKGROUND: The immunomodulatory T-helper type 1 (Th1) cytokine interferon-gamma (IFN-gamma) was measured in serum and cornea to ascertain its general contribution to corneal graft rejection and to establish a rational basis for the decision for or against systemic therapy. METHODS: Eight groups of differently treated BALB/c (H-2d) mice received a C3H (H-2 k) corneal graft. There was one saline-treated control group and two groups that received intramuscular cyclosporin A (CsA) for 14 or 40. Three groups received systemic or topical, systemic plus topical corticosteroid treatment, which was combined with CsA in two further groups. To measure the IFN-gamma level by enzyme-linked immunosorbent assay (ELISA), blood was taken by heart puncture and corneae were excised at the limbus. RESULTS: Five days of systemic corticosteroid and 14 days of CsA had no significant effect on graft survival. A 40-day CsA treatment and a 40-day combined corticosteroid treatment significantly prolonged graft survival. An 80-day topical corticosteroid treatment produced additional prolongation. IFN-gamma could not be detected (limit of detection 25 pg/ml) in any of the serum samples, while significantly increased amounts of IFN-gamma were detected in the supernatants of the corneal tissue 13 or 14 days after allogeneic but not syngeneic corneal graft, corresponding to 9.5 pg, 5.1 pg and 1.8 pg per cornea. CONCLUSION: The detection of Th1 cytokines in the cornea but not the serum of mice at the time of allograft rejection is in accordance with the finding of long-lasting dose-dependent immunosuppression of topical steroids and the inefficacy of short-term systemic CsA and corticosteroids.

Animals↗
PubMed2000

Ballistic transfer of minimalistic immunologically defined expression constructs for IL4 and CTLA4 into the corneal epithelium in mice after orthotopic corneal allograft transplantation.

BACKGROUND: Experiments were performed to determine whether corneal epithelium transfected with minimalistic immunologically defined expression constructs for the extracellular fragment of CTLA4 and for interleukin-4 (IL-4) or interleukin-10 (IL-10) is able to modulate an allospecific immune response after orthotopic corneal grafting in mice. METHODS: Six groups of BALB/c (H-2d) mice received a C3H (H-2k) corneal graft and dexamethasone eye drops until day 11. Five groups of BALB/c mice had gold particles delivered into the corneal epithelium by Gene Gun on day 10 after transplantation. In four groups, minimalistic immunologically defined gene expression (MIDGE) vectors were delivered into the corneal epithelium by ballistic transfer. The levels of expressed IL-4 and IL-10 were determined by an enzyme-linked immunosorbent assay (ELISA) in shock-frozen homogenized corneas. The expression kinetics of Gene-Gun-transfected corneas were determined by measuring luciferase in lysed whole corneas at different time intervals. RESULTS: Luciferase expression was detectable during the first 5 days following transfection. ELISA was used to determine IL-4 and IL-10 expression in corneal tissue 36 h after transfection. Ballistic IL-4 and CTLA4 gene transfer significantly prolonged corneal graft survival in comparison with the gold-treated control group and the IL-10-treated group. CONCLUSION: The beneficial effect of IL-4 and CTLA4, but not IL-10 gene transfer into the corneal epithelium by MIDGE vectors was demonstrated for the first time in corneal transplantation.

Abatacept↗
PubMed2000

Limited heme synthesis in porphobilinogen deaminase-deficient mice impairs transcriptional activation of specific cytochrome P450 genes by phenobarbital.

Heme is not only a very important prosthetic group that modulates the structure and activity of heme proteins but also a regulatory molecule that controls metabolic pathways and the biosynthesis of various proteins. However, investigation into heme regulatory effects in higher vertebrates has been hampered by the lack of a suitable animal model. A knockout mouse with targeted disruption of porphobilinogen deaminase, the third enzyme of the heme pathway, has been generated in our laboratory and used in the present study as an in vivo model of heme deficiency to explore diverse heme regulatory properties. In this model with a defined heme disturbance, we observed a superinductive response of delta-aminolevulinate synthase, the first enzyme in heme synthesis, after phenobarbital treatment. We also found that limited heme is associated with decreased induction of cytochrome P450 by phenobarbital as a consequence of impaired gene transcription. This inhibitory effect is isoenzyme-specific, being significant for cyp2a5. The activity and mRNA level of this particular cytochrome P450 are significantly lower in the phenobarbital-induced porphobilinogen deaminase-deficient mice (55% and 43%, respectively), but its expression can be restored to normal values when exogenous heme is administered. Other heme proteins, namely neuronal nitric oxide synthase and soluble guanylate cyclase, function normally in mice with limited heme. Our results demonstrate that the expression of various heme proteins is differentially regulated in conditions of reduced heme availability. Moreover, our findings emphasize the importance of heme protein function in the genesis of pathophysiological manifestations in acute intermittent porphyria.

Animals↗
PubMed2000

PRK and LASIK--their potential risk of cataractogenesis: lipid peroxidation changes in the aqueous humor and crystalline lens of rabbits.

PURPOSE: There are insufficient data on the possible cataractogenic side effects of excimer laser corneal surgery. Higher malondialdehyde (MDA) levels could indicate oxidative events related to the cataractogenic process. We therefore examined MDA levels after refractive laser surgery. METHODS: Six white Russian rabbits received laser in situ keratomileusis (LASIK) (Schwind keratome) in the right eye and a 250-microm-deep microkeratome cut (Schwind microkeratome) in the left eye. Six others underwent photorefractive keratectomy (PRK) in the right eye; the left eye remained untreated. The 180 mJ/cm2 fluence applied at a rate of 10 Hz with an optical zone diameter of 5 mm in all rabbits (438 pulses) resulted in an estimated central photoablation depth of 116 microm. Two weeks later, lenses and aqueous were taken immediately after death. MDA was detected in aqueous and homogenate of lenses after reacting with thiobarbituric acid (TBA). MDA bound to TBA (MDA-TBA) was specifically analyzed by high-performance liquid chromatography (HPLC) (excitation, 525 nm; emission, 551 nm) using phosphate-buffered methanol as eluent. RESULTS: No significant laser-induced MDA alteration was found in either the aqueous or the lens. The microkeratome group, however, had two to three times higher MDA levels in the lenses than the control group (p = 0.12) or the PRK (p = 0.03) group. CONCLUSION: Elevation of MDA in the lens of the microkeratome group indicates that LASIK, but not PRK, may be a risk factor in cataractogenesis. The increased MDA levels in the LASIK group are probably caused by the microkeratome incision rather than the secondary radiation of the excimer laser. Postoperative inflammation may explain the surprising results.

Animals↗
PubMed2000

Comparison of ritonavir plus saquinavir- and nelfinavir plus saquinavir-containing regimens as salvage therapy in children with human immunodeficiency type 1 infection.

BACKGROUND: In this retrospective study we compared the antiretroviral effect of regimens consisting of simultaneous administration of two protease inhibitors (PI) with at least one nucleoside reverse transcriptase inhibitor on plasma viral load (VL) and CD4 cell count in HIV-infected children intensively pretreated with nucleoside reverse transcriptase inhibitors and PIs. METHODS: Eleven HIV-infected children were changed to antiretroviral combination regimens including two PIs and followed for a median time of 24 weeks. Group A comprised six patients who were given ritonavir + saquinavir (SQV) and Group B consists of five patients who were changed to nelfinavir + SQV. Patients were treated with these combinations with 2 PIs because of treatment failure (increasing viral load) of prior PI therapy or clinical signs of disease progression. OUTCOME MEASURES: Serial determinations of plasma viral load (Amplicor, Roche) and CD4 cells were performed every 4 to 8 weeks. The detection limit of the Amplicor-reverse transcriptase-PCR assay was 50 copies/ml (1.7 log10). RESULTS: In Group A the median VL reduction was 1.1 log10 after 3 months and 1.4 log10 after 6 months. In Group B median VL decreased 0.1 and 0.2 log10 after 3 and 6 months. In both groups during the study period none of the patients reached undetectable VL. The relative changes of CD4 cells above baseline in Group A showed a median increase of 7% after 3 months and 23% after 6 months. In Group B after 3 months CD4 cells did not increase, and after 6 months the median relative increase was only 7%. Both combination therapies were well tolerated, not necessitating any drug interruption during study period. CONCLUSIONS: In children with intensive prior antiretroviral treatment, a salvage therapy including two PIs demonstrated antiretroviral efficacy in some patients. In this study the reduction of the VL as well as the increase of CD4 cells was more pronounced with ritonavir + SQV than with nelfinavir + SQV. With both combinations complete suppression of HIV replication was not achieved. Therefore the long term effect of these combinations may be limited by the emergence of resistant HIV strains.

Adolescent↗
PubMed2000

[In Process Citation]

Although most subacromial decompressions are performed||| arthroscopically, rotator cuff repair is still performed using an open or||| mini-open procedure. Arthroscopic techniques have improved in the last decade,||| however, so that rotator cuff repair can also be performed arthroscopically.||| The potential complications of open repair are thus reduced and the superior||| functional results of cuff repair in comparison to debridement alone are||| maintained. The proposed advantages of the arthroscopic method are that it||| provides access to the glenohumeral joint for inspection and treatment of||| intra-articular lesions. The skin incisions are smaller, detachment of the||| deltoid muscle is not necessary, and there is less soft tissue dissection. By||| inspecting the bursal and articular side of the ruptured cuff, it is possible||| to measure the size of the tear and assess the quality of the tendon and||| whether it can be repaired. We present our arthroscopic technique of rotator||| cuff repair using bioabsorbable suture anchors and demonstrate our 1- to||| 6-years results with various suture anchors.

Journal Article↗
PubMed2000

[Arthroscopic rotator cuff reconstruction].

Although most subacromial decompressions are performed arthroscopically, rotator cuff repair is still performed using an open or mini-open procedure. Arthroscopic techniques have improved in the last decade, however, so that rotator cuff repair can also be performed arthroscopically. The potential complications of open repair are thus reduced and the superior functional results of cuff repair in comparison to débridement alone are maintained. The proposed advantages of the arthroscopic method are that it provides access to the glenohumeral joint for inspection and treatment of intra-articular lesions. The skin incisions are smaller, detachment of the deltoid muscle is not necessary, and there is less soft tissue dissection. By inspecting the bursal and articular side of the ruptured cuff, it is possible to measure the size of the tear and assess the quality of the tendon and whether it can be repaired. We present our arthroscopic technique of rotator cuff repair using bioabsorbable suture anchors and demonstrate our 1- to 6-years results with various suture anchors.

Aged↗
PubMed1999

Distinct mechanisms target stress and extracellular signal-activated kinase 1 and Jun N-terminal kinase during infection of macrophages with Salmonella.

The interaction between bacteria and macrophages is central to the outcome of Salmonella infections. Salmonella can escape killing by these phagocytes and survive and multiply within them, giving rise to chronic infections. Cytokines produced by infected macrophages are involved in the early gastrointestinal pathology of the infection as well as in the induction and maintenance of the immune response against the invaders. Jun N-terminal kinases (JNK) are activated by inflammatory stimuli and play a role in cytokine production. We have investigated the signaling routes leading to JNK activation in Salmonella-infected macrophages and have discovered that they differ radically from the mechanisms operating in epithelial cells. In particular, activation of the JNK kinase stress and extracellular-activated kinase 1 (SEK1) and of JNK in macrophages occurs independently of actin rearrangements and of the GTPases Cdc42 and Rac, essential mediators in other cells. Activation of JNK is effected by a novel pathway comprising tyrosine kinase(s), phosphoinositide 3-kinase and, likely, atypical protein kinase C zeta. SEK1 is stimulated by a distinct mechanism involving phosphatidylcholine-phospholipase C and acidic sphingomyelinase. Dominant-negative SEK1 can block JNK activation by LPS, but not by Salmonella. These data demonstrate that SEK1 and JNK are activated independently in Salmonella-infected macrophages and offer experimental support for the concept that incoming signals can direct the selective coupling of downstream pathways to elicit highly specific responses. Inhibitors of stress kinase pathways are receiving increasing attention as potential anti-inflammatory drugs. The precise reconstruction of stimulus-specific pathways will be instrumental in predicting/evaluating the effects of the inhibitors on a given pathological condition.

Animals↗
PubMed1999

Preliminary experiences with triple therapy including nelfinavir and two reverse transcriptase inhibitors in previously untreated HIV-infected children.

OBJECTIVE: In an intent-to-treat study increase in CD4 cell count, reduction of viral load, clinical benefit and adverse reactions were examined in HIV-infected previously treatment-naive children taking triple therapy. METHODS: sixteen HIV-infected children in category A or B on antiretroviral triple therapy were followed-up for a period of 12 months. In group I eight patients received zidovudine, lamivudine and nelfinavir; in group II eight patients received stavudine, didanosine and nelfinavir. Viral load and CD4 cell count were measured every 4-8 weeks. Plasma nelfinavir levels were assessed once in all patients at baseline and monitored in patients with increasing viral load. RESULTS: No significant differences were observed between treatment groups in terms of CD4 cell counts and viral load. A median viral load reduction of 2.8 log10 (range, 1.4-4.2 log10) was achieved over a period of 12 months in both groups. Viral load < 500 copies/ml was found in 69% of patients and viral load < 50 copies/ml in 44% of patients after 12 months. Median CD4 cell count increased from 656 x 10(6) to 850 x 10(6) cells/l after 3 months and was maintained at 813 x 10(6) cells/l after 12 months of treatment. Main side-effects were diarrhoea, rash and hyperlipidaemia. Except for application problems, both regimens were well tolerated. Appropriate formula and individual counselling must be performed during the first weeks of treatment in order to achieve good compliance in paediatric patients. CONCLUSION: Triple antiretroviral therapy shows a stronger and more sustained reduction of viral load in HIV-infected children compared with studies combining two nucleoside analogues.

Anti-HIV Agents↗
PubMed1999

Heat-inactivation of plasmid-encoded CI857 repressor induces gene expression from Ind- lambda prophage in recombinant Escherichia coli.

We have observed significant cell lysis upon temperature up-shift of recombinant Escherichia coli cultures harboring CI857-repressed lambda-based expression vectors. This event, that becomes evident about 30-40 min after the heat shock, takes place when using the lambda promoter system in Ind- lysogenic strains, but not in others commonly employed for recombinant gene expression. These results strongly suggest that the thermosensitive CI857 repressor, encoded by the expression vector, competes with CI Ind- molecules for binding to the prophage operator region, allowing for expression of lytic genes from the integrated Ind- viral genome upon temperature up-shift. Transcription of viral lytic genes does not include unspecific expression of a reporter sulA::lacZ gene fusion carried in the prophage genome. These results prompt, however, to carefully evaluate the limitations of expression systems based on pL/pR-CI857 in bacterial strains modified through lambda Ind- gene transfer vehicles.

Bacteriolysis↗
PubMed1999

Mammalian immunoassays for predicting the toxicity of malathion in a laboratory fish model.

This study describes the use of a panel of immune assays, originally developed by the National Toxicology Program for assessing xenobiotic-induced immunotoxicity in mice, to quantify the effects of sublethal malathion exposure on the immune responses of fish. For this study, Japanese medaka (Oryzias latipes) were exposed subchronically to the organophosphate pesticide malathion in a series of two experiments. In the first set of studies, fish were exposed for 7 or 14 d to untreated well water (i.e., controls) or to waterborne malathion at 0.2 or 0.8 mg/L. Following exposure, fish from each group were sacrificed and their kidneys (primary organ of leukopoiesis in fish and equivalent to mammalian bone marrow) were used to provide cells for assessing any malathion-induced effects upon nonspecific and acquired immune defense mechanisms. Effects upon humoral-mediated immunity were determined by enumerating antibody plaque-forming cell (PFC) numbers from a subset of fish exposed to malathion for 14 d and then injected intraperitoneally (ip) with sheep erythrocytes (sRBC). Results of these studies demonstrated that while malathion exposure had no significant effect upon hematocrit/leukocrit values or upon mitogen-stimulated T-cell lymphoproliferation, PFC numbers in the kidney of exposed fish were significantly reduced (compared to control fish) in a dose-dependent manner. In addition, total recoverable kidney cell numbers and viability, as well as superoxide anion production by kidney phagocytes, were reduced slightly (compared to control values) in fish exposed for 14 d to the highest malathion concentration tested. In the second set of experiments, medaka exposed for up to 21 d to either 0.1 or 0.3 mg malathion/L were challenged ip with an LD50 dose of the bacterial fish pathogen Yersinia ruckeri. Results from these infectivity studies demonstrated that exposure to either malathion concentration, for 14 or 21 d reduced host resistance against Yersinia infection. Taken together, these findings demonstrate the applicability of mammalian immune assays for predicting malathion-induced immunosuppression in a teleost fish, as well as the potential utility of a small laboratory fish to serve as an alternate model for mammals in immunotoxicological studies.

Animals↗
PubMed1999

Evaluation of anterior knee joint instability with the Rolimeter. A test in comparison with manual assessment and measuring with the KT-1000 arthrometer.

We report on a comparative measurement of anterior knee joint laxity on 30 healthy test subjects and 30 patients with anterior knee joint instability using a new knee testing device (Rolimeter) and the KT- 1000 arthrometer compared to manual assessment of the anterior tibial translation in 30 degrees flexion (Lachman's test). We wanted to establish the reliability of the Rolimeter device compared to manual assessment and to the KT- 1000 arthrometer. The statistical evaluation by means of an analysis of variance (ANOVA) at a significance level of 5% showed no significant difference in the exactitude of measurement between the Rolimeter and the KT-1000 arthrometer, but altogether a significant difference between both instrumental methods compared with manual assessment. Thus the Rolimeter provides an economic, exact and simply operating device for quantifying anterior knee joint instability.

Adolescent↗
PubMed1999

Secretion-dependent proteolysis of heterologous protein by recombinant Escherichia coli is connected to an increased activity of the energy-generating dissimilatory pathway.

The synthesis of a proteolytically unstable protein, originally designed for periplasmic export in recombinant Escherichia coli BL21(DE3), a strain naturally deficient for the ATP-dependent protease Lon (or La) and the outer membrane protease OmpT, is associated with a severe growth inhibition. This inhibition is not observed in BL21(DE3) synthesizing a closely related but proteolytically stable protein that is sequestered into inclusion bodies. It is shown that the growth inhibition is mainly caused by a slower cell division rate and a reduced growth yield and not by a general loss of cell division competence. Cells proceed with their normal growth characteristics when exposed again to conditions that do not sustain the expression of the heterologous gene. The performance of cells synthesizing either the stable or the degraded protein was also studied in high cell density cultures by employing a new method to calculate the actual specific growth rate, the biomass yield coefficient, and the dissimilated fraction of the carbon substrate in real-time. It is shown that the growth inhibition of cells synthesizing the proteolytically degraded protein is connected to an increased dissimilation of the carbon substrate resulting in a concomitant reduction of the growth rate and the biomass yield coefficient with respect to the carbon source. It is postulated that the increased dissimilation of the carbon substrate by lon-deficient Bl21(DE3) cells synthesizing the proteolytically unstable protein may result from a higher energy demand required for the in vivo degradation of this protein by ATP-dependent proteases different from the protease Lon.

ATP-Dependent Proteases↗
PubMed1998

[Discrimination between pain-induced head movement disturbances after whiplash injuries and their simulation].

Neck pain after whiplash injury of the cervical spine often induces typical changes in head motion patterns (amplitude, velocity). These changes of kinematics may help to recognize malingerers. We investigated the hypothesis that malingerers are not able to reproduce their simulated head movement disturbances three times. The kinematics of head movements of 23 patients with neck pain after whiplash injury and of 22 healthy subjects trying to act as malingerers were compared. The healthy subjects were informed about the symptomatology of whiplash injury and were asked to simulate painful head movements. Two different kinds of head movements were registered and analyzed by Cervicomotography: (1) the slow free axial head rotation (yaw) and (2) the axial head rotation (yaw) tracking a moving visual target. Each experimental condition was presented three times, expecting the malingerers not to be able to produce as well as to reproduce the same head movement disturbances again and again. In patients, as a consequence of their distinct pain patterns, we expected less variance between the test repetitions. The statistical analysis showed significant differences of the calculated kinematic parameters between both groups and the inability of healthy subjects to simulate and to reproduce convincingly distinct pain patterns.

English Abstract↗
PubMed1998

[Rise in intraocular tension in microkeratome sections (LASIK) and with the GTS trephine system for keratoplasty].

UNLABELLED: Microkeratome systems are being increasingly applied in lamellar corneal surgery (e.g., LASIK). The results of the few studies on intraocular pressure changes during the microkeratome cut vary widely. In this study, we examined the intraocular pressure pattern (IOP) in relation to the initial pressure. METHODS: We performed lamellar corneal cuts on freshly enucleated porcine bulbs with three different microkeratome systems and different setting for the initial pressure (10, 20 and 30 mm Hg). The bulbs were cannulated, and the IOPs were recorded online with a two-chamber measuring system. In addition, we examined the GTS trephine system applied for corneal transplantation. RESULTS: It became obvious that there were significant differences between systems (significance level, P = 0.05). With an initial pressure of 10 mm Hg the measured values of the Schwind system are significantly lower than with the Polytech system, and these values are again significantly lower than with the Chiron microkeratome. With 20 mm Hg the Chiron system shows significantly higher values than both other systems. With 30 mm Hg initial pressure, the pressure values with the Schwind system and with the Chiron microkeratome are significantly higher than with the Polytech system. Thus with all microkeratome systems the middle and maximum pressure values rise in correlation with the initial pressure levels. This effect was not seen with the trephine system. With the same initial pressure, the standard deviation of the measured data of different mikrokeratomes was low (range 3.1-9.0 mm Hg). CONCLUSION: The pressure values shown are higher than the data published by the manufacturers. There is current discussion as to whether these pressure values are dangerous (e.g. bleeding) or not. The pressure values reached intraocularly during the microkeratome cut depend on the system and also on the present initial intraocular pressure values. Only with the same initial pressure can reproducible applanation and cutting conditions be obtained, which guarantee stable quality of the cut.

Animals↗