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Biomedical subjects

L Ziegler

Publications and source records attributed to L Ziegler.

At least 19 recordsLinked to original sources
PubMed2000

Stereodeficient subjects demonstrate non-linear stereopsis.

There appear to be two modes of stereoscopic processing: a conventional linear operation that is dependent on correspondence between local luminance components in the two eyes' views, and a non-linear or second-order processing mode. This second mode may use disparity information provided by particular 'non-Fourier' features of the stimulus such as the contrast envelope. Preliminary results suggest that people who fail standard clinical stereotests are able to extract non-linear disparity information from Gabor stimuli [McColl & Mitchell, 1998. Vision Research, 38, 1889-1900]. Here we evaluate the status of the non-linear mechanism in such individuals by using two types of contrast enveloped stimuli, namely random line and Gabor micropatterns, in a task that requires near/far depth judgements [Ziegler & Hess, 1999. Vision Research, 39, 1491-1507]. Although our sample was small, three of our four subjects who had performed poorly on at least one standard clinical test of stereopsis could perform the task, as well as one 'stereoblind' subject who had failed all four standard clinical tests. The overall results suggest that individuals with stereoanomalies show a diversity of deficits, but some nevertheless can see depth using 'non-linear' mechanisms.

Amblyopia↗
PubMed1996

Culture of human vascular endothelial cells on an RGD-containing synthetic peptide attached to a starch-coated polystyrene surface: comparison with fibronectin-coated tissue grade polystyrene.

A synthetic peptide, Gly-Arg-Gly-Asp-Ser-Pro-Lys (GRGDSPK), which includes the cell-adhesive region of fibronectin, Arg-Gly-Asp (RGD), was covalently bound to a dialdehyde starch (DAS) coating on a polymer surface by reductive amination. The GRGDSPK/DAS-coated surface was characterized by atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). AFM and SEM revealed a uniform, roughened, textured surface, much more so than standard polymer or adhesive protein-coated polymer surfaces. XPS showed that GRGDSPK binding to DAS occurred in dose-dependent fashion in the 0-200 micrograms ml-1 GRGDSPK concentration range, with a plateau happening in the 200-400 micrograms ml-1 range. AFM revealed a uniform peptide layer on the DAS surface with a maximum separation distance of 50 nm between peptides. Angle-dependent XPS showed that the peptide is present in nearly constant amounts to at least 10 nm depth of the DAS coating. The attachment, spreading and growth properties of anchorage-dependent human umbilical vein endothelial cells (EC) on the GRGDSPK/DAS-coated polystyrene surface were compared with a standard fibronectin-coated polystyrene surface. EC adhesion, spreading and growth properties were similar for cells plated on polystyrene surfaces coated with fibronectin (5 micrograms cm-2) and GRGDSPK (25-50 micrograms ml-1)/DAS. In contrast, EC adhesion, spreading and growth performance significantly increased for cells plated on GRGDSPK (100-200 micrograms ml-1)/DAS compared with the fibronectin-coated surface. These findings support the conclusion that the GRGDSPK/DAS-coated surface can be substituted for an adhesive protein-coated surface in the culture of anchorage-dependent cells.

Amino Acid Sequence↗
PubMed1996

The resistance of the Wistar/Furth rat strain to steroid hypertension.

We have previously reported that the Wistar/Furth (W/Fu) rat strain is resistant to mineralocorticoid hypertension. In the current study, we have examined renal mRNA levels for mineralocorticoid receptor (MR), glucocorticoid receptor (GR), renin and Na+, K(+)-ATPase in response to treatment with mineralocorticoids. Uninephrectomized male Wistar (WI) and W/Fu rats were treated with aldosterone or deoxycorticosterone acetate (DOCA) and were given 1% NaCl to drink. Rats were sacrificed after 1, 3 or 7 days of treatment. Renal MR and ATPase mRNA levels were significantly reduced in aldosterone and DOCA-treated WI rats (e.g. MR was 30% on day 3 and ATPase was 50% of control on day 7 of aldosterone treatment). Unexpectedly, GR mRNA levels paralleled the changes in MR. In W/Fu rats the level of message was either unchanged or only moderately altered by this treatment. In vivo administration of the MR antagonist RU28318 or the GR antagonist RU38486 to WI rats for 4 days reduced renal mRNA levels for both subunits of ATPase. In the W/Fu rat, this treatment resulted in no change in the alpha subunit and an increase in the beta subunit of ATPase. In preliminary studies, we have determined that the W/Fu rat is also resistant to dexamethasone-induced hypertension. These studies suggest that altered MR- and GR-mediated mechanisms may contribute to the resistance of the W/Fu rat strain to steroid-induced hypertension.

Adenosine Triphosphatases↗
PubMed1992

[MR angiography in neuropediatric problems: the technic and the clinical results].

31 children aged between 6 months and 14 years with various neurovascular abnormalities were examined by MR angiography in a prospective study. In order to test the sensitivity and specificity of the MR results, these were compared in 8 cases with the findings of digital subtraction angiography or conventional angiography. In 24 patients arterial MR angiography was performed; in 17 these showed anomalies or abnormalities of the intracranial vascular system. In 7 patients venous MR angiography was performed and demonstrated the presence of sinus thrombosis in 6 of these. Comparison between MR angiography and DSA showed agreement in 7 cases; in one patient the degree of a stenosis was exaggerated by MR. The results of this study indicate that arterial and venous MR is of great value as an additional study in paediatric neurovascular problems.

Angiography, Digital Subtraction↗
PubMed1992

[Pre- and postoperative NMR tomographic studies in avascular femur head necrosis].

46 patients with avascular necrosis of the femoral head were examined by T2- and T1-weighted MR before and after infusion of Gd-DTPA. Both sides were involved in 12 cases. The classification was done according to Ficat. In early stages and in postoperative studies a correlation of signal intensity after infusion of Gd-DTPA and clinical symptoms was found. Hyperintensity of the avascular area or of the implanted material was assumed to be vascularised or vital components in 4 cases of Ficat I and in 15 postoperative studies. Contrariwise, we found in 5 patients with severe postoperative symptoms, low signal intensity areas due to avascular regions.

Contrast Media↗
PubMed1990

[Destructive bladder mole--follow-up by human chorionic gonadotropin (HCG), ultrasound and digital subtraction angiography (DSA)].

A case report of a mola destruens is presented including the clinical monitoring and the therapeutical conclusions. Control parameters were the HCG, ultrasound and DSA. The DSA in a new and improved technique, provided helpful information during a critical phase of the disease, when changing from mono- to polychemotherapy was necessary. Furthermore, the excellent vascular mapping enables planning of radiological interventions. In case of tumour bleeding hysterectomy can be avoided by embolisation. There may thus be more time for conservative treatment by chemotherapy.

Adult↗
PubMed1990

[Arthrographic imaging of ganglions of the hand].

In the genesis of ganglions synovial herniation is discussed with an existence of a valve mechanism which prevents the synovial fluid from returning into the joint space. Arthrography of the wrist was performed in 34 patients with suspicion of ganglions on the dorsal and volar aspect of the wrist. By injection of contrast medium in 6 cases directly into the ganglion no connection with the carpal joint cavity was seen. On the contrary, wrist arthrography with examination of the midcarpal and radiocarpal joint showed regularly a communication by a torturous narrow duct between the midcarpal joint and the dorsal ganglion and the radiocarpal joint and the volar ganglion. Other pathologic findings were seen, like tears of the scapholunate ligament and of the triangular fibrocartilage. The consequences for surgical therapy and conclusions for the aetiology of the ganglions are shown.

Adolescent↗
PubMed1990

[Echinococcus cysticus--rare differential diagnosis of a splenic cyst].

Splenic involvement in hydatid disease is uncommon, representing less than 2% of all human organ manifestations by echinococcus cysticus. We report on the rare case of an isolate splenic infection. The case history and the clinical findings were compatible with a traumatic cyst. Ultrasound, CT and MR findings are discussed.

Cysts↗
PubMed1989

[The importance of 111-indium marked leukocyte scintigraphy in inflammatory intracranial processes].

111-indium-labelled leukocyte scintigraphy used for testing inflammatory intracranial lesion delimitation in differential diagnosis, shows reliable results in 80% of the cases, whereas 10% demonstrate false-positive as well as false-negative results. Loss of time is caused by the 24 h waiting period for measurement, and because of supply problems. Due to these drawbacks, this method is of only limited help to the neurosurgeon in quickly finding safe pointers for determining the time of operation if inflammatory intracranial lesions are suspected. Hence, this method requires to be improved upon, or a new one should be developed.

Adult↗
PubMed1985

The effect of nitroglycerin ointment on the external ocular structures of rabbits.

The toxicity of three different transdermal nitroglycerin ointments on the external ocular structures of New Zealand White rabbits was investigated. Using a randomized, double-blind protocol, both eyes of four rabbits in each of four treatment groups received 3.75 mg of either Nitrol Ointment, Nitrong Ointment, Nitro-bid Ointment, or Lacri-lube Ointment twice a day for 21 days. The eyelids, palpebral and bulbar conjunctiva, cornea, anterior chamber, and iris were evaluated by slit lamp. Pupillary size was noted and intraocular pressure was measured with an applanation tonometer. All parameters were evaluated pretreatment and two hours after the last dose on treatment days 1, 8, 15, and 22. On days 8 and 15, all four treatment groups had evidence of mild conjunctival injection; however, only the three nitroglycerin groups had mild conjunctival chemosis. At day 22, all four treatment groups had no statistically significant evidence of toxicity to the eyelid, conjunctiva, and iris. Only Nitrong Ointment produced any corneal toxicity, a mild diffuse punctate keratopathy statistically significant only on day 22. In addition, the four treatment groups showed no change in pupil size and intraocular pressure. Transdermal nitroglycerin preparations were well tolerated by the external ocular structures of rabbits. Additional animal studies to evaluate the dosage and frequency effects on tolerance and intraocular pressure are indicated.

Animals↗