COVID-19 and macular edema: a necessarily blindness?

Graefe's Archive for Clinical and Experimental Ophthalmology -     

Differential role for the striatum and cerebellum in response to novel movements using a motor learning paradigm.

The aim of this pilot study was to examine the role of the striatum and cerebellum in the adaptation to a novel movement within a sequence of practiced movements using a motor learning paradigm. The performance of patients in the early or advanced stages of Parkinson's disease (PD) and of patients with damage to the cerebellum (CE) was compared, respectively to a group of aged and young matched controls on an adapted version of the Mirror-Tracing Test. In this task, subjects were required to trace a series of complex figures in two conditions: (1) a Practiced condition, in which the figures were composed of the juxtaposition of three simple designs that were extensively practiced before; and (2) a Mixed condition in which triads were created by replacing the last simple figure of the triads in the Practiced condition by a new simple figure that had never been traced individually before. Results showed that all clinical groups were slower than controls at tracing the Practiced triads. Most interestingly, however, only patients in the advanced stages of PD showed increased completion time to trace the triads in the Mixed condition. This suggests that a bilateral striatal dysfunction affects the ability to adapt to a novel motion within a sequence of practiced movements. Although exploratory, these results support a functional dissociation between the striatum and cerebellum in acquiring visuomotor skilled behaviors.     

Therapeutic Consequences of Variation in Intraarterial Pressure Measurements After Iliac Angioplasty

Purpose: To assess the accuracy of intraarterial measurement of transstenotic pressure gradients for the detection of hemodynamically suboptimal iliac angioplasty. Methods: In 14 patients, referred for diagnostic angiography, mean pressure gradients in the aorta and iliac artery were obtained twice, using a double-sensor pressure catheter. Additional iliac measurements were performed during pharmacologically induced flow augmentation. Repeatability was assessed by calculation of the mean difference plus standard deviation (MD ± SD) and repeatability coefficient (2 × SD). These results were extrapolated to 137 iliac angioplasty procedures with secondary stenting where there was a residual pressure gradient > 10 mmHg. Results: MD ± SD for repeated measurements at rest and during flow augmentation were 0 ± 2 mmHg and 1 ± 3 mmHg, respectively. Repeatability coefficients were 3 and 6 mmHg. Mean pressure gradients after hemodynamically insufficient angioplasty were 8 ± 7 mmHg at rest and 17 ± 5 mmHg following vasodilatation. Inaccurate pressure recordings may have led to inappropriate stent placement in less than 2.5%, and inappropriate denial of stent placement in less than 5% of the lesions. Conclusion: Variability of intraarterial pressure measurements has little consequence in the detection of hemodynamically significant stenosis after angioplasty. Received: 0/00/00/Accepted: 0/00/00     

Dioxin treatment of rats results in increased in vitro induction of sister chromatid exchanges by alpha-naphthoflavone: an animal model for human exposure to halogenated aromatics

Recent reports have shown that alpha-naphthoflavone (alpha-NF) in vivo enhances the sister chromatid exchange (SCE) frequency in lymphocytes from human populations exposed to cigarette smoke or polychlorinated biphenyls and dibenzofurans. In this study, female Sprague-Dawley rats (9-11 weeks old) were administered a single oral dose of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and killed 6 days after treatment. Blood cultures were established with or without alpha-NF. The baseline and alpha-NF-induced SCE frequencies were assessed in lymphocytes after a 72-hr culture period. No effect on the SCE baseline frequency (cultures without alpha-NF) was detected in rats exposed to 0-30 micrograms TCDD/kg. However, the SCE frequencies from cultures incubated in the presence of alpha-NF were significantly higher in lymphocytes from rats treated with TCDD. Moreover, delta SCE values (SCE alpha-NF minus SCE baseline) were significantly higher in lymphocytes from rats treated with TCDD than in controls. A dose-dependent increase in delta SCE values was observed between 0 and 3 micrograms TCDD/kg, followed by a plateau at higher doses. This induction pattern closely resembled the induction of the liver microsomal aryl hydrocarbon hydroxylase activity by TCDD. In contrast to TCDD, phenobarbital treatment of rats (75 mg/kg/day) had no effect on alpha-NF-induced SCE frequencies in lymphocytes. Liver microsomes from TCDD-treated rats metabolized alpha-NF at a rate much faster than that of control microsomes. These studies indicate that TCDD-exposed rats provide a useful model to investigate the mechanism of enhanced in vitro induction of SCE frequency in lymphocytes from humans exposed to toxic halogenated aromatics or cigarette smoke.     

Bioreductive activation of quinones: A mixed blessing

Quinones can be metabolized by various routes: substitution or reductive addition with nucleophilic compounds (mainly glutathione and protein thiol groups), one-electron reduction (mainly by NADPH: cytochrome P-450 reductase) and two-electron reduction (by D,T-diaphorase). During reduction semiquinone radicals and hydroquinones are formed, which can transfer electrons to molecular oxygen, resulting in the formation of reactive oxygen intermediates and back-formation of the parent quinone (redox cycling). Reaction of semiquinones and reactive oxygen intermediates with DNA and other macromolecules can lead to acute cytotoxicity and/or to mutagenicity and carcinogenicity. The enhanced DNA-alkylating properties of certain hydroquinones are exploited in the bioreductive alkylating quinones. Acute cytotoxicity of quinones appears to be related to glutathione depletion and to interaction with mitochondria and subsequent disturbance of cellular energy homoeostasis and calcium homoeostasis. These effects can to a certain extent be predicted from the electron-withdrawing and electron-donating effects of the substituents on the quinone nucleus of the molecule. Prediction of cytostatic potential remains much more complicated, because reduction of the quinones and the reactivity of the reduction products with DNA are modulated by the prevailing oxygen tension and by the prevalence of reducing enzymes in tumour cells.This article is based on a lecture given at the 16th LOF Symposium, 27 October 1989, Utrecht, the Netherlands.     

Hypophyseal Non-Hodgkin's Lymphoma presenting with clinical panhypopituitarism successfully treated with chemotherapy

Summary A patient is described with a testicular Non-Hodgkin's Lymphoma (NHL) presenting with panhypopituitarism caused by a hypophyseal localization. A⁶⁷Gallium scintigraphy showed avid uptake in the hypophyseal region. Obviously⁶⁷Gallium could reach the tumor, by the intravenous route, which was the reason to treat the patient with intravenous chemotherapy. A complete remission was induced, which seems to be lasting (+ 25 months). As far as we know this is the first report of panhypopituitarism caused by a hypophyseal NHL in the hypophysis and successfully treated by intravenous chemotherapy.     

Evolutionary aspects of “chloroplast-like” trnN and trnH expression in higher-plant mitochondria

Two identical “chloroplast-like” tRNA^Asn genes, trnN1 and trnN2, have been identified in the potato (Solanum tuberosum) mitochondrial genome. The flanking sequences of trnN1 are unrelated to the corresponding authentic potato chloroplast regions, whilst those of trnN2 are very similar to the chloroplast sequences. The trnN1 copy is present in the mitochondrial genome of various plants whereas the second copy, trnN2, is absent from all the other plant genomes studied so far. Interestingly, both trnN copies are expressed in potato mitochondria. Sequences flanking the chloroplast-like tRNA^His gene (trnH), present as a single copy in the potato mitochondrial DNA, are unrelated to the corresponding chloroplast sequences, whereas chloroplast-derived sequences have been maintained in the vicinity of the maize chloroplast-like mitochondrial trnH gene. However, both the potato and the maize trnH are expressed in mitochondria. Received: 10 April / 1 August 1997     

Neuropathy associated with “benign” anti-myelin-associated glycoprotein IgM gammopathy: Clinical,immunological, neurophysiological pathological findings and response to treatment in 33 cases

We studied 33 patients presenting with a peripheral neuropathy associated with non-malignant anti-myelin-associated glycoprotein (MAG) IgM monoclonal gammopathy (MG) in an attempt to delineate their clinical, immunological, electrophysiological and pathological characteristics; we also reviewed our experience concerning long-term follow-up and therapy. Peripheral neuropathy associated with non-malignant anti-MAG IgM MG was observed mostly in males (sex ratio 7.2), and mean age at onset was 67 years (range 46–81). A predominantly sensory pattern was noted in more than 80% of cases, although some patients were affected by a predominantly motor peripheral neuropathy. Although disease progression was slow in most cases, 45% of patients suffered severe disability, and in 2 cases, the patient's death appeared to stem directly from the neuropathy. The electrophysiological findings were indicative of a demyelinating process in 90% of cases, and electron microscopic examination of nerve biopsy specimens demonstrated widening of the myelin lamellae in more than 95% of cases. Most of our patients showed a disappointing response to steroids and chemotherapy or plasma exchanges. Intravenous immune globulin, evaluated in 17 patients, had a transient, mostly subjective effect in 35% and led to a clear-cut improvement in 24% of cases. We did not observe any correlation between the severity of the clinical picture and the anti-sulphoglucuronyl paragloboside antibody titre; in individual cases, clinical improvement occurred without lowering of IgM levels. Although the severity and the rate of progression may greatly vary from patient to patient, the combination of clinical, electrophysiological and pathological features delineates a characteristic pattern in peripheral neuropathy associated with non-malignant anti-MAG IgM MG.