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S Wolf

Publications and source records attributed to S Wolf.

At least 217 records · Page 12Linked to original sources
PubMed1993

Red-green color discrimination in peripheral vision.

Color discrimination thresholds were measured for four colors from the red-green portion of the visible spectrum. Thresholds were measured for a stimulus field 1.5 deg in diameter in the fovea and at three locations on the nasal retina (eccentricities of 5, 20 and 40 deg). Outside the fovea threshold increased exponentially with eccentricity and the slope of the function was similar for all four standard colors. Peripheral thresholds were adequately described by an equation developed for foveal red-green thresholds by Boynton and Kambe [(1980) Color Research and Applications, 5, 13-23] and also by a modified form of this equation containing a rod term. Differences between foveal and peripheral thresholds were characterized by changes in two coefficients in the equations. The CIELUV color difference equation also provided a reasonably good description of peripheral thresholds.

Adult↗
PubMed1993

Plasmodesmata: the intercellular organelles of green plants.

Cytokinesis in higher plants results in the incomplete separation of daughter cells, due to the formation of special plasma-membrane-lined cytoplasmic bridges, called plasmodesmata. Within the green algae, these structures coordinate biochemical and physiological processes by facilitating the cell-to-cell diffusion of simple metabolites and ions. Until recently, most plant biologists thought that plasmodesmata perform a similar function in higher plants. However, it is now known that the more structurally advanced plasmodesmata of higher plants can also traffic macromolecules, including proteins and nucleic acids. These findings give new insights into how green plants evolved the ability to orchestrate their developmental and physiological processes in a supracellular rather than a multicellular manner.

Journal Article↗
PubMed1993

Retinal hemodynamics using scanning laser ophthalmoscopy and hemorheology in chronic open-angle glaucoma.

PURPOSE: Recent studies suggest that elevated intraocular pressure is not the only causative factor for the development of visual field loss and optic nerve damage in glaucomatous eyes. The authors determine whether retinal hemodynamics or blood fluidity are alternated in eyes of patients with open-angle glaucoma compared with those of age- and sex-matched healthy subjects. METHOD: High-quality video fluorescein angiograms were obtained from single eyes of 51 patients with chronic open-angle glaucoma. From these angiograms, the arm-retina time, mean dye velocity, and arteriovenous passage time were quantified. The data from patients were compared with those of an age- and sex-matched group of healthy subjects. RESULTS: In patients with chronic open-angle glaucoma, an 11% reduction of the mean dye velocity (P < 0.05) and a 41% prolongation of the arteriovenous passage time (P < 0.01) was observed relative to the values obtained among the control subjects. Among hematocrit values, plasma viscosity, and erythrocyte aggregation, only plasma viscosity showed a significant increase (4%; P < 0.01) in patients with chronic open-angle glaucoma. CONCLUSION: These results indicate that a pronounced circulatory deficit exists within the retinal vasculature of glaucomatous eyes, which may coexist with, but cannot be fully attributed to, an increase in plasma viscosity.

Adult↗
PubMed1993

Emergency physician workload: a time study.

STUDY HYPOTHESIS: Physician service time varies with patient service category, length of stay, and intensity of service. DESIGN: Prospective time study of emergency physician services. Physicians recorded the beginning and ending times of each service episode offered to a patient (whether at the bedside or occurring elsewhere in the department). Each episode was defined as an "interaction," with the total service time offered to a patient being the sum of all interactions for that patient. Length of stay was the time interval from when the patient registered in the emergency department to when the patient was released. Intensity of service was calculated as service time divided by length of stay. SETTING: University-affiliated community teaching hospital. TYPE OF PARTICIPANTS: One thousand three hundred forty-seven ED patients were entered into the study for nonselected (514), walk-in (637), observation (52), laceration repair (102), or critical care (42) services. Six of 12 physicians in the group staffing the ED participated in the study. Patient data were entered onto study cards when the service was offered. Patients were entered into the study consecutively except when the physician became too busy to see one patient at a time and accurately enter time data; such interruptions occurred for 18% of the patients. RESULTS: Physician service time for nonselected service patients (24.2 minutes per patient; 95% CI, 23.1-25.3) was consistent with ACEP's findings for nonselected services offered by emergency physicians (22 minutes per patient). Physician service time did not vary significantly from the standard for laceration repair patients (25.0 minutes per patient; 95% CI, 22.6-27.4) but did vary significantly from the standard for walk-in (9.8 minutes per patient; 95% CI, 9.3-10.3; P < .05), observation (55.6 minutes per patient; 95% CI, 50.7-60.5; P < .05), and critical care patients (31.9 minutes per patient; 95% CI, 26.2-37.6; P < .05). Walk-in and laceration repair patients had a single physician-patient interaction (1.3 per patient and 1.1 per patient, respectively), consistent with a discrete service offered during episodic care. Observation and critical care patients had multiple physician-patient interactions (6.3 per patient and 2.6 per patient, respectively) over an extended period, which is consistent with additional services being offered during their period of observation/holding. CONCLUSION: Case mix of patient services affects emergency physician workload and should be considered in planning departmental staffing needs.

Connecticut↗
PubMed1993

Lacunar infarcts and white matter attenuation. Ophthalmologic and microcirculatory aspects of the pathophysiology.

BACKGROUND AND PURPOSE: By means of neurological and ophthalmologic examinations we considered whether there is a microcirculatory disorder not related to hypertension and diabetes in patients with lacunar infarcts and whether there are microcirculatory differences in patients with lacunar infarcts compared with those with white matter attenuation. METHODS: Eighty neurological patients with a lacunar infarct underwent computed tomography and, based on the results, were prospectively assigned to subgroups as follows: (1) patients without changes; (2) patients with white matter attenuation but without lacunar infarcts; (3) patients with lacunar infarcts alone; and (4) patients with both lacunar infarcts and white matter attenuation. Clinical and ophthalmologic parameters were monitored. The retinal microcirculation was studied by videofluorescence angiography. These neurological patients were compared with control ophthalmologic patients matched for age, sex, hypertensive and diabetic ocular fundus changes, and smoking habits. RESULTS: On average, the 80 patients with lacunar infarcts had a significantly (P = .0001) slower arteriovenous passage time (2.6 +/- 0.7 seconds) than the ophthalmologic control subjects (1.6 +/- 0.6 seconds). Arteriovenous dye passage time through the retinal microcirculation was nearly normal (2.2 +/- 0.8 seconds) in patients with white matter attenuation alone, but was significantly prolonged in patients with lacunar infarcts (2.9 +/- 0.8 seconds, P = .00085) or both white matter attenuation and lacunar infarcts (2.8 +/- 0.4 seconds, P = .008). CONCLUSIONS: Patients with lacunar infarcts are characterized by an additional disorder of retinal microcirculation independent of arterial hypertension and diabetes. Our data suggested that white matter attenuation and lacunar infarcts may be phenomena with only weak interdependence.

Aged↗
PubMed1993

[Hemodilution therapy in patients with acute anterior ischemic optic neuropathy].

A prospective study was performed in 22 patients with an anterior ischaemic optic neuropathy (AION). All patients underwent iso- (Hct > or = 42%) or hypervolemic (Hct < 42%) haemodilution for 10 days with daily infusion of 250 ml hydroxyethyl starch (MW 200,000/0.5, 10% HAES-sterile) in combination with pentoxifylline (p.o.: 1200 mg/day; i.v.: 300 mg/day; Trental). Only patients with recent AION (less than 2 weeks' duration of symptoms) were considered for the prospective trial. Clinical, haemodynamic (arterio-venous passage time) and rheological (haematocrit, plasma viscosity, erythrocyte aggregation) data of all patients were recorded before therapy and after 10 days. An improvement of central vision by 2 or more lines was seen in 7 patients after 10 days. Initially the arterio-venous passage time was significantly prolonged in patients (2.42 +/- 0.7 s) with AION compared with healthy volunteers (1.45 +/- 0.4 s). After the 10-day trial arterio-venous passage time was significantly shorter than baseline values. In addition, the initially elevated plasma viscosity (1.33 +/- 0.1 mPa) was significantly lowered by haemodilution therapy.

Aged↗
PubMed1993

[Retinal hemodynamics in patients with arterial hypertension].

Arterial hypertension is a risk factor for the development of retinal, cerebral and renal microangiopathy. Therefore, a prospective study was started to investigate the progression of retinal microangiopathy in hypertensive patients. Initially, 254 patients were examined in a cross-sectional study. Following an ophthalmological examination, retinal hemodynamics were quantified by means of video-fluorescence angiography. Moreover, blood fluidity (hematocrit, plasma viscosity and erythrocyte aggregation) was analyzed. The severity of the retinal changes was defined according to the Neubauer classification. One hundred (40%) patients showed retinal changes corresponding to stage I; 133 (52%) were classified as stage II. Hypertensive retinopathy (stage III and IV) was encountered in 20 (8%) patients. Arm-retina time was significant prolonged among the hypertensive patients compared with a control group. Arteriovenous passage time showed no significant differences between hypertensive patients and reference values. Plasma viscosity was significantly increased in hypertensive patients and showed a significant increase with progression of the retinal changes. Hematocrit and erythrocyte aggregation were normal among the patients studied. The present findings show an alteration in blood fluidity among hypertensive patients, whereas retinal microcirculation showed no significant disturbances. Follow-up studies are planned to assess the development of retinal microcirculatory changes among hypertensive patients.

Adult↗
PubMed1993

Hypothyroidism.

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Diagnosis, Differential↗
PubMed1992

The conus medullaris: time of ascendence to normal level.

This study was intended to determine the level of the conus medullaris in normal babies. We examined 114 healthy infants using high resolution ultrasound which identified the spinal cord and the tip of the conus medullaris. This method provided a good analysis of the level of the conus medullaris so that we could assess the rate of ascent to L1/2. The range of the conus level for all children was at TH12/L1 interspace to L4.78% of babies aged between the 30th and 39th postmenstrual week had the tip of the conus medullaris between L2 and L4.84% of babies aged between the 40th and 63rd postmenstrual week had their conus level between TH12/L1 and L1/2 interspace. In one girl aged 53 weeks the tip was found at L4. Ultrasound is a reliable method to observe the development of the conus level in young infants and to identify a tethered cord.

Female↗
PubMed1992

[Retinal circulation and current blood glucose value in diabetic retinopathy].

In 42 type II diabetic patients with nonproliferative diabetic retinopathy the arm-retina time (ART) and arteriovenous passage time (AVP) were measured by means of videofluorescein angiography. Glycosylated hemoglobin (HbAlc) as a parameter of longterm diabetic control and the blood glucose level were determined. The ART in the diabetics was similar to the ART of normals and the AVP was significantly prolonged. HbAlc level ranged between 5.6 and 12.2% (8.6 +/- 1.7%) and the blood glucose level between 4.5 and 22.9 mmol/l (11.4 +/- 4.5 mmol/l). Significant correlations were found between AVP and blood glucose (r = 0.37) and between AVP and HbAlc (r = 0.49). No correlation was found neither between ART and blood glucose nor between ART and HbAlc. A multiple stepwise regression analysis shows that of both investigated parameters HbAlc is the predicting variable for AVP. These results show that in diabetic patients the retinal blood flow is more influenced by the longterm diabetic control than by the blood glucose level at the time of examination.

Aged↗
PubMed1992

Preservation of hearing in bilateral acoustic neurinomas by deliberate partial resection.

With the aim of preserving hearing, 20 acoustic neurinomas in 17 patients with neurofibromatosis 2 were intentionally submitted to an incomplete (80%) tumour removal. In 12 cases this was an operation on the last hearing ear with total deafness of the contralateral ear. If an auditus existed in both ears the better hearing ear was selected for the primary intervention. Early audiological controls evidenced residual hearing in 19 of the 20 cases operated on by the enlarged middle fossa approach, which was utilized inspite of the tumour diameters being between 1 and 6 cm in the cerebello-pontine angle. The oncologic and functional follow-up over 1 to 7 years showed different patterns of slow progression of hearing loss and of persistent auditory function over 2 to 7 years. Facial nerve function was excellent in 16 of the 18 controlled cases. Continued CT or MRT imaging revealed no signaling in 2 cases, constant tumour sizes in 10 cases and slow progression in 3 cases. With regard to the importance of an auditory communication in the younger adult, the described treatment modality appears to be the first choice method.

Adult↗
PubMed1992

Secondary plasmodesmata are specific sites of localization of the tobacco mosaic virus movement protein in transgenic tobacco plants.

Expression of the tobacco mosaic virus 30-kD movement protein (TMV MP) gene in tobacco plants increases the plasmodesmatal size exclusion limit (SEL) 10-fold between mesophyll cells in mature leaves. In the present study, we examined the structure of plasmodesmata as a function of leaf development. In young leaves of 30-kD TMV MP transgenic (line 274) and vector control (line 306) plants, almost all plasmodesmata were primary in nature. In both plant lines, secondary plasmodesmata were formed, in a basipetal pattern, as the leaves underwent expansion growth. Ultrastructural and immunolabeling studies demonstrated that in line 274 the TMV MP accumulated predominantly in secondary plasmodesmata of nonvascular tissues and was associated with a filamentous material. A developmental progression was detected in terms of the presence of TMV MP; all secondary plasmodesmata in the tip of the fourth leaf contained TMV MP in association with the filamentous material. Dye-coupling experiments demonstrated that the TMV MP-induced increase in plasmodesmatal SEL could be routinely detected in the tip of the fourth leaf, but was restricted to mesophyll and bundle sheath cells. These findings are discussed with respect to the structure and function of plasmodesmata, particularly those aspects related to virus movement.

Cytoplasm↗
PubMed1992

[Movement correction of digital sequence angiographies of the retina].

Retinal hemodynamics can be quantified from videoangiographic image sequences by digital image processing. Intensity changes of dye dilution curves provide dynamics parameters of the local retinal blood flow. The measuring points of dye dilution curves have to be fixed on identical image contents in each image of a complete image sequence. To obtain measurements for every pixel on the retinal surface a motion-compensated image sequence is required. A new method adapted to the compensation of eye motion and movement artifacts in Scanning Laser Ophthalmoscopy in long image sequences (300-500 images) is presented in this paper. To inhibit error propagation of time sequential motion estimation, the eye movement is divided into two dynamic movements components. The method presented permits compensation for eye motion in retinal fluorescein angiographic sequences. Owing to the short calculation times, this algorithm can be used in clinical routine.

Artifacts↗