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F Niessen

Publications and source records attributed to F Niessen.

18 recordsLinked to original sources
PubMed2002

[The development of visual function].

Development of vision mainly takes place during the first year of life. Visual function cannot be restricted to the measurement of visual acuity. Indeed it is a plural function including functions of environment exploration, relative appreciation of objects, control of body position and movements organization, acquisition of knowledge and communication. From an analytical point of view visual function comprises sensorial (such as visual acuity), cognitive (cerebral processing of sensorial information) and oculomotor elements. Synthetically it may be seen as a neuro-visual loop organized around the eye, by turns sensor (vision) and effector (look). This neurovisual loop representation is of interest as it allows better recognition and analysis of the neurovisual pathologies encountered in children with cerebral injuries, especially former premature infants.

Child↗
PubMed2001

Orbitally induced oscillations in the East Antarctic ice sheet at the Oligocene/Miocene boundary.

Between 34 and 15 million years (Myr) ago, when planetary temperatures were 3-4 degrees C warmer than at present and atmospheric CO2 concentrations were twice as high as today, the Antarctic ice sheets may have been unstable. Oxygen isotope records from deep-sea sediment cores suggest that during this time fluctuations in global temperatures and high-latitude continental ice volumes were influenced by orbital cycles. But it has hitherto not been possible to calibrate the inferred changes in ice volume with direct evidence for oscillations of the Antarctic ice sheets. Here we present sediment data from shallow marine cores in the western Ross Sea that exhibit well dated cyclic variations, and which link the extent of the East Antarctic ice sheet directly to orbital cycles during the Oligocene/Miocene transition (24.1-23.7 Myr ago). Three rapidly deposited glacimarine sequences are constrained to a period of less than 450 kyr by our age model, suggesting that orbital influences at the frequencies of obliquity (40 kyr) and eccentricity (125 kyr) controlled the oscillations of the ice margin at that time. An erosional hiatus covering 250 kyr provides direct evidence for a major episode of global cooling and ice-sheet expansion about 23.7 Myr ago, which had previously been inferred from oxygen isotope data (Mi1 event).

Journal Article↗
PubMed2000

Effect of CO(2) pneumoperitoneum on early cellular markers of retinal ischemia in rabbits with alpha-chymotrypsin-induced glaucoma.

BACKGROUND: Increased intraperitoneal pressure in the head-down position is associated with a significant increase in intraocular pressure (IOP) in rabbits with alpha-chymotrypsin-induced glaucoma. Also, the retinal cells are weakened by the induction of increased IOP, and/or glaucoma, even when IOP is controlled by adequate therapy; therefore, these cells need to be protected from any additional aggression. Actin and vimentin are proteins of the retinal cell cytoskeleton that react readily in response to retinal injuries, including ischemia and glaucoma. Early changes in these cytoskeleton proteins determine the morphological changes observed after retinal damage. Therefore, we set out to investigate intracytoplasmic changes in vimentin and actin after a 4-h CO(2) pneumoperitoneum in the head-down position in rabbits with alpha-chymotrypsin-induced glaucoma. METHODS: Twenty-one rabbits with alpha-chymotrypsin-induced glaucoma in one eye received general anesthesia for 4 h in the head-down position and were randomly allocated to have (a) no pneumoperitoneum, (b) a 10 mmHg CO(2) pneumoperitoneum, or (c) a 20 mmHg CO(2) pneumoperitoneum. At the end of the trial, both the right glaucomatous and the left control eyes were enucleated and investigated immunocytochemically for alterations in vimentin and actin, and morphologically for retinal layer disorganization. RESULTS: Except for the preexisting morphological changes induced by glaucoma, both the control and the glaucomatous eyes in all rabbits appeared normal in terms of retinal layer organization and the distribution of intracellular vimentin and actin whatever the intraperitoneal pressure level applied. CONCLUSION: In rabbits with alpha-chymotrypsin-induced glaucoma, a 4-h CO(2) pneumoperitoneum of </=20 mmHg in the head-down position did not induce either retinal layer disorganization or alteration of actin or vimentin.

Actins↗
PubMed1999

Cytomegalovirus retinitis in advanced HIV-infected patients treated with protease inhibitors: incidence and outcome over 2 years.

We prospectively studied the incidence of cytomegalovirus (CMV) retinitis in 93 patients treated with highly active antiretroviral therapy (HAART) containing a protease inhibitor (PI), during a median follow-up period of 24 months. The median initial CD4+ count was 22 cells/microl (range, 1-311 cells/microl), and the median plasma HIV viral load was 5.1 log10 copies/ml (range, 2.4-6.4 log10 copies/ml). The fundus was examined monthly in patients with a history of CMV retinitis or an initial CD4+ count <50 cells/microl and every 3 months in the other patients. Of patients with previously controlled CMV retinitis, 1 of 7 relapsed. In addition, 6 of 59 patients with a CD4+ count <50 cells/microl and no history of CMV retinitis before starting PI therapy developed CMV retinitis. Of them, 3 had at least one relapse during follow-up. CD4+ counts were <40 cells/microl at the time of primary or recurrent CMV retinitis, except in two cases (147 cells/microl and 203 cells/microl). In conclusion, the incidence of CMV retinitis was 0.091 per patient-year among study subjects with advanced HIV infection who were receiving HAART (95% confidence interval [CI], 0.037-0.145). The time to progression of CMV retinitis (mean, 215 days; 95% CI, 113-317 days) was longer than reported before widespread use of PIs.

AIDS-Related Opportunistic Infections↗
PubMed1998

No beneficial effects of taurine application on oxygen free radical production after hemorrhagic shock in rats.

Oxygen free radical generation contributes to the reinfusion damage after hemorrhagic shock. Taurine has been proposed to have radical scavenging properties under certain experimental conditions. Therefore the present study was undertaken to investigate if taurine would be able to attenuate adverse effects of shock/resuscitation in male rats (fasted over night). Under pentobarbital anesthesia, hemorrhagic shock (HS) was induced for 1 h by bleeding of the animal [mean arterial blood pressure (MAP) = 40 mm Hg] followed by shed blood reinfusion and another 1 h period of resuscitation. Rats were divided into two groups: Treated rats (n = 6) were injected with taurine (40 mg/kg body mass) prior to withdrawal of shed blood; untreated rats (n = 9) received respective volumes of a normal saline solution. In untreated animals, free radical induced lipid peroxidation was documented by an increase of malondialdehyde (MDA) in the systemic circulation (nmol/ml; HPLC measurement) from 1.06 +/- 0.08 during normotension (NT) to 1.35+/- 0.18** 1 h after resuscitation (RS). Accordingly, plasma levels of alanine aminotransferase (ALT) (11 +/- 2; 35 +/- 12; 94 +/- 44 U/l, NT; HS; RS) and ammonia (120 +/- 39; 532 +/- 161; 224 +/- 101 micrograms/dl) changed significantly during the experimental protocol. Hepatic ATPase-content as an indicator of energetic status of the liver fell from 4.8 +/- 0.83 to 0.56 +/- 0.27 after HS and recovered to only 2.7 +/- 1.6 mumol/g after RS. Leukocyte infiltration of the liver was followed by tissue levels of myeloperoxidase (MPO) which did not change during HS, but rose during RS (37.9 +/- 18.5; 38.6 +/- 16.4; 77.5 +/- 24; arbitrary units), documenting an inflammatory reaction after HS. Taurine treated rats showed levels of MDA not different from untreated rats after RS; also no differences were observed concerning enzyme concentrations and ammonia levels. The liver tissue levels of ATP and MPO revealed no differences between the two groups during the various periods of the experiment. Liver tissue perfusion, as measured by Laser Doppler flowmetry, also did not show significant differences between both groups. MAP was significantly higher in the taurine-treated rats during the first 40 min of resuscitation. It is concluded that even a relatively high dose of taurine failed to attenuate the impact of oxygen free radicals and did not improve the recovery of the rats during the early resuscitation period.

Alanine Transaminase↗
PubMed1998

[Incidence and evaluation of viral retinitis in patients infected with the HIV virus and treated with HIV protease inhibitors].

BACKGROUND: Since the beginning of the use of HIV-Protease Inhibitors (PI) to treat HIV-infected patients, a decrease of the incidence of extraocular opportunistic infections has been observed. We studied the incidence of CMV-retinitis in patients treated with a highly active antitetroviral therapy (HAART) containing PI over a mean follow-up of 12 months. METHODS: Ninety-three HIV-infected patients treated with HAART containing PI were included. The mean initial CD4+ cell-count was 54/microliter (median: 22/microliter), and the mean plasma HIV-load was 5.46 log 10 RNA-copies/ml. Fundus examination was performed each month in case of a previously treated and controlled CMV-retinitis or if initial CD4 cells were below 50/microliter. In other patients, fundus examination was performed every 3 months. The mean follow-up was 362 days. RESULTS: Among the 7 patients with a previously treated and controlled CMV-retinitis, one experienced a progression during the study (after 163 days of PI). Among the 59 patients with CD4 cells below 50/microliter and without previous CMV-retinitis before the beginning of PI, 5 experienced a CMV-retinitis (mean delay after the onset of HAART: 141 days), including 2 with relapse. When retinitis occurred, CD4 cells were below 32/microliter except in one case (147/microliter). CONCLUSIONS: Compared to previously published reports, this study showed an increase of the time to progression of previously treated and controlled CMV-retinitis in patients treated with PI. Considering deeply immunocompromised patients (less than 50 CD4-cells/microliter), the risk of suffering from CMV-retinitis was 8.5% after 12 months of PI treatment. Longer follow-up remains necessary to confirm these results.

AIDS-Related Opportunistic Infections↗
PubMed1996

No evidence for a protective effect of ascorbic acid on free radical generation and liver injury after hemorrhagic shock in rats.

Oxygen free radicals have been shown to be implicated in ischemic tissue injury, and free radical-induced reactions may also play an important role in the pathophysiology of circulatory shock. The present study was designed to investigate the potential use of ascorbic acid as an exogenous antioxidant on the liver's recovery from hemorrhagic shock in situ. Rats (fasted overnight) were subjected to 60 min of hemorrhagic shock (HS) (mean arterial pressure = 40 mmHg) under pentobarbital anesthesia, followed by retransfusion of the shed blood. One-half of the animals (n = 6) were injected with 10 mg/kg of ascorbic acid prior to induction of shock, while untreated animals (n = 6) received the same volume of saline solution. in untreated animals, systemic plasma levels of malondialdehyde rose from 1.07 +/- .08 during normotension (NT) to 1.36 +/- .18* 60 min after resuscitation (RS), documenting oxygen free radical-induced lipid peroxidation. Accordingly, plasma levels of alanine aminotransferase (16.5 +/- 2.5; 34.9 +/- 12.3*; 105.8 +/- 68.7* U/L; NT/HS/RS) and ammonia (127 +/- 40; 532 +/- 160*; 304 +/- 244* micrograms/dL) rose significantly during the experiment. Hepatic ATP content of the liver fell from 4.8 +/- .83 to .56 +/- .27* after HS and recovered partially to 2.7 +/- 1.6* mumol/g after RS. Leukocyte infiltration in the liver, indicated by tissue levels of myeloperoxidase, remained constant during HS but rose during RS (37.9 +/- 18.5; 38.6 +/- 16.4; 81.4 +/- 30.7*, arbitrary units), thus documenting an inflammatory reaction after HS. In the ascorbic acid group, plasma levels of malondialdehyde were comparable to those of untreated animals after RS, as were enzyme concentrations and ammonia. No differences were observed with regard to the tissue concentrations of ATP or myeloperoxidase. Mean arterial blood pressure as well as liver tissue perfusion, as measured by Laser Doppler flowmetry, did not show significant differences between the groups. It was concluded that, although an effect of oxygen free radicals on liver tissue could be found during and after HS, treatment with ascorbic acid alone, in our model, failed to ameliorate the recovery of the animals upon resuscitation (values are mean +/- SD; *, p < .05 vs. NT; one-way ANOVA).

Alanine Transaminase↗
PubMed1996

Intra-ocular pressure changes during gynaecological laparoscopy.

Laparoscopic surgery carried out under general anaesthesia is associated with physiological changes, which also determine changes in intra-ocular pressure. We measured intra-ocular pressure at each phase of gynaecological laparoscopy, carried out under propofol-alfentanil-isoflurane general anaesthesia, in young women of ASA 1 status, with no pre-existing eye disease. Measurements were made with a Perkins applanation tonometer. Mean arterial pressure and end-tidal CO2 tension were kept constant throughout the study. Intra-ocular pressure decreased significantly after induction of anaesthesia, remained unchanged after a pneumoperitoneum of up to an intraperitoneal pressure of 15 mmHg had been created, increased significantly with head down tilt, but did not increase significantly above pre-induction values. Adequate depth of anaesthesia compensated for the intra-ocular pressure increase caused by head down position. Plateau airway pressure, considered as reflecting intrathoracic pressure, increased with intraperitoneal pressure elevation. However, such changes did not correlate with intra-ocular pressure changes.

Adult↗
PubMed1989

[Radiation-induced maculopathies].

About two clinical cases with maculopathy resulting from irradiation with so low dosage as to have been previously considered harmless in most of the literature. The authors suggest that early photocoagulation laser treatment as a mean of preserving a good visual prognosis for these eyes.

Adolescent↗