Search PubMed⌕ Search

Biomedical subjects

S Wolf

Publications and source records attributed to S Wolf.

At least 199 records · Page 11Linked to original sources
PubMed1994

Perifoveal microcirculation with non-insulin-dependent diabetes mellitus.

Fluorescein angiograms were performed to evaluate perifoveal capillary blood velocities (v), capillary density (perifoveal intercapillary areas: PIA) and the foveal avascular zone (FAZ) by means of the scanning laser technique (SLO-101 Rodenstock). The angiograms were digitally stored and the data quantified off-line with an image analyzing system (IBAS). In the present study 46 patients with non-insulin-dependent diabetes mellitus (NIDDM) were examined and their data compared with that of 31 healthy volunteers. The perifoveal capillary flow velocity of the NIDDM subjects (v = 2.33 +/- 0.36 mm/s) was significantly (P < 0.01) decreased as compared to healthy subjects (v = 2.86 +/- 0.41 mm/s). The perifoveal intercapillary areas in the foveal avascular zone were significantly increased in patients with NIDDM (PIA = 10029 +/- 3402 microns2; FAZ = 0.415 +/- 0.272 mm2) as compared with healthy subjects (PIA = 3965 +/- 467 microns2; FAZ = 0.221 +/- 0.071 mm2). These data suggest the possibility that a decrease in perifoveal capillary blood velocities in combination with decreased capillary density (enlarged PIA) and an enlargement of the foveal avascular zone may occur in patients with NIDDM. The determination of these parameters could help in monitoring the progress of diabetic retinopathy and diabetic maculopathy.

Adult↗
PubMed1994

A universal spine tester for in vitro experiments with muscle force simulation.

We report a new apparatus to determine the quasistatic, three-dimensional, load-displacement characteristics of spines including muscle forces. The loading frame can be adapted to mono- and polysegmental specimens from the lumbar or cervical spine as well as to entire spines. Three force and three moment components can be applied in either direction individually or in combination with no constraint on the resulting motion; the loads can be applied at user-chosen rates of application and release with continuous recording of displacements, so as to study either creep or relaxation. The loads and displacement-measuring devices are computer-controlled. Thus, this testing device provides a tool for many kinds of stability tests and for basic research of spine biomechanics. A first experiment shows that the application of muscle forces significantly affects the load-deformation characteristics and intradiscal pressure.

Biomechanical Phenomena↗
PubMed1994

Physiological perturbation of ocular and cerebral blood flow as measured by scanning laser ophthalmoscopy and color Doppler imaging.

Retinal blood flow regulation in health remains poorly described. We hypothesized that retinal perfusion is controlled to provide constant O2 delivery to that tissue, and that changes in retinal blood flow in response to chemical stimuli parallel changes in carotid and retrobulbar perfusion. Accordingly, in 11 young adults with normal eye examinations, we measured retinal blood flow indices (via scanning laser ophthalmoscopy [SLO] during fluorescein angiography) and carotid, ophthalmic, and central retinal arterial blood flow indices (via Doppler imaging [CDI]) under control, hypoxic (alveolar PO2 = 55 +/- 3 mmHg) and hyperoxic (alveolar PO2 = 655 +/- 18 mmHg) conditions. The three conditions were counterbalanced in order and isocapnia was maintained in each. Retinal arterial mean dye velocity and arteriovenous passage time, as measured by SLO, were slowed by hyperoxia and accelerated by hypoxia, in rough proportion to the changes in arterial O2 content (+/- 10%; p < 0.05). In the seven subjects in which relative measurements of retinal arterial diameters were obtained, neither hypoxia nor hyperoxia significantly altered vessel diameter. At the same time, mean retinal capillary transit velocity was independent of PO2, suggesting that, in health, retinal capillaries may be recruited as PO2 falls. O2-induced changes in carotid, ophthalmic, or central retinal arterial blood flow velocities (via CDI) were not found, though a wide coefficient of variation (30% for CDI vs. 14% for SLO) may have contributed to this failure. We conclude that, under isocapnic conditions, retinal perfusion may be regulated to provide constant O2 delivery.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Measurement of retinal hemodynamics with scanning laser ophthalmoscopy: reference values and variation.

High resolution video fluorescein angiography using scanning laser ophthalmoscopy allows the assessment of retinal macro- and microcirculation. Data on the retinal macrocirculation were obtained from 221 healthy subjects. The data were derived from estimations of the arm-retina time, the arteriovenous passage time and mean arterial dye velocity, characterizing the passage of fluorescein to the eye, the mean arterial plasma velocity, and the arteriovenous passage through the entire vascular bed of one segment. Additionally, the transit of hypofluorescent segments in the capillary macular network were measured in 90 healthy subjects. These parameters provide a wide range of information for understanding the physiology of healthy and diseased eyes. Fundamental for all interpretations is the knowledge of the physiological variations. In the present study the inter- and intraindividual variability of retinal hemodynamics in healthy volunteers were assessed. The interindividual variation was 23.8% for the arm-retina time, 20.7% for the arteriovenous passage time, 23.7% for the mean arterial dye velocity, and 14.2% for the capillary flow velocity; the coefficient for variation, characterizing the intraindividual variation, was 26.6%, 15.6%, 16.7%, and 7.9%, respectively. The knowledge of the inter- and intraindividual variation of retinal blood flow indices allows for a priori power estimations for pathophysiologic and pharmacological studies.

Adult↗
PubMed1994

Community social change and mortality.

This paper first reviews the types of explanations that have been used in analyzing unequal distribution in coronary heart disease among different groups and changes in prevalence over time. The explanations have mostly focused on the individual: individual behaviors, personalities, stressors, or social ties. It is suggested here that a shift in focus to community-level characteristics may also aid in understanding changes in mortality. Data are presented from Roseto, PA--a town that became known in the 1960's for its strong Italian traditions and very low mortality from myocardial infarction and that subsequently experienced a sharp rise in mortality--and from the adjacent comparison town of Bangor. Data collected over several decades--in some cases as far back as 1925--on marriages, population composition, organizational memberships, voting patterns, and social class indicators suggest that important community changes that accelerated significantly in the 1960's coincided with and may help to explain Roseto's loss of protection from coronary heart disease deaths after 1965.

Coronary Disease↗
PubMed1994

Retinal blood velocities during carbogen breathing using scanning laser ophthalmoscopy.

Hyperoxic-hypercapnic gas mixture ('carbogen': 6% CO2-94% O2) is widely used clinically. Its influence on retinal perfusion remains unclear, since past work suggests that high O2 may reduce and high CO2 may increase retinal blood flow. To examine the changes in retinal blood velocity during 'hyperoxic-hypercapnic' gax mixture breathing, we quantified retinal blood velocity indices. Twenty-eight healthy subjects were studied using scanning laser video fluorescein angiograms at baseline and after gas inhalation. Retinal arteriovenous passage time and mean arterial dye velocity were measured by means of a digital image processing system. Arterial diameter measurements showed no change (4%) during carbogen breathing. Increased arterial Pco2 and Po2 resulted in small but statistically significant increases in systolic and diastolic blood pressure and heart rate (each c. 8%, p < 0.05), and a dramatic increase in mean dye velocity (27%, p < 0.01), with parallel reduction in arteriovenous passage time (40%, p < 0.01). The substantial acceleration of retinal dye velocity and transit under combined hyperoxia and hypercapnia strongly suggests that this clinically standard gas mixture may indeed improve oxygenation without reducing retinal perfusion.

Adult↗
PubMed1994

Quantification of retinal capillary density and flow velocity in patients with essential hypertension.

Arterial hypertension is known to be an important risk factor for cerebral and cardiovascular disease. Previous studies in rats have demonstrated that changes in both capillary density and vessel diameter may contribute to increased vascular resistance in hypertension. In vivo studies of human subjects with essential hypertension revealed a reduction in the number of arterioles in the skin and conjunctiva; no other in vivo data are available from other tissues. By means of a new imaging technique, capillary density and capillary blood flow velocity can now be assessed in the human retina. We undertook the present investigation to determine whether patients with essential hypertension and only minor clinical retinal vascular alterations have decreased retinal capillary density and altered capillary flow velocity. Seventeen hypertensive patients with only minor retinal vascular alterations and 17 healthy volunteers matched for age were selected. All study participants underwent ophthalmologic examination and fluorescein angiographic studies by means of scanning laser ophthalmoscopy. Capillary density and capillary blood flow velocity in the perifoveal network were evaluated from the angiograms. The retinal microcirculation in the perifoveal capillary network of hypertensive patients showed significant alterations. Both the capillary density and capillary flow velocities were significantly reduced compared with the control group. For the first time alterations of capillary blood flow and capillary density in a vascular network very similar to that of the brain have been demonstrated in hypertensive patients in vivo. Further studies with this technique may help identify patients at high risk for cerebrovascular diseases.

Adult↗
PubMed1994

[Effect of hemodilution on retinal hemodynamics in retinal branch vein occlusion].

The aim of hemodilution therapy in branch retinal vein occlusion is to lower the hematocrit (HCT) and plasma viscosity and thus to ameliorate perfusion of the affected areas. In this study we compared the influence of hemodilution therapy on the retinal hemodynamics of affected areas with unaffected areas. Thirty patients with branch vein occlusion (duration of symptoms less than 14 days) aged 40-84 years (mean 63 +/- 11 years) were examined. All patients received iso- (HCT > or = 42%) or hypervolemic (HCT < 42%) hemodilution with hydroxyethyl-starch (MW 200,000/0.5 10%, HAES-steril) for 10 days. Retinal hemodynamics were quantified by means of video fluorescein angiography assessing arteriovenous passage time (AVP) of the affected and unaffected branches. Hemodilution resulted in a significant decrease in hematocrit, plasma viscosity and erythrocyte aggregation. The arteriovenous passage time of the affected area improved significantly (before therapy 4.91 +/- 2.2 s, after therapy 3.9 +/- 1.6 s). The unaffected branch showed no significant change in the arteriovenous passage time (1.85 +/- 0.7 s before and 1.79 +/- 0.7 s after therapy). The decrease in AVP in the affected branch indicates ameliorated perfusion in the affected branch area without changing the retinal hemodynamics in unaffected areas.

Adult↗
PubMed1994

Indocyanine green video angiography in patients with age-related maculopathy-related retinal pigment epithelial detachments.

Previous studies have stressed the benefit of laser photocoagulation for patients with age-related macular degeneration (AMD) and well-defined subretinal neovascularization (SRN). However, such lesions account for only 30% of cases with exudative age-related maculopathy. Especially in patients with retinal pigment epithelial detachment (PED), SRN is usually occult. This study was performed to reveal the role of digital indocyanine green (ICG) video angiography in the diagnosis of SRN in patients with PED. A total of 34 patients with AMD-associated retinal PED participated in the current study and underwent fluorescein and ICG angiography using scanning laser ophthalmoscopy. In these patients fluorescein angiography revealed no distinct SRN, whereas in 21 eyes (62%) ICG angiography showed well-demarcated choroidal neovascularization. The present study demonstrates that SRN can be detected in more than 50% of patients with PED by means of ICG video angiography. Therefore, ICG video angiography improves the detection of SRN in patients with AMD-associated PED.

Aged↗
PubMed1994

Higher KT/V urea associated with greater protein catabolic rate and dietary protein intake in children treated with CCPD compared to CAPD. Mid-European Pediatric CPD Study Group (MPCS).

Being more suitable to children's lifestyle habits, continuous cycling peritoneal dialysis (CCPD) is becoming the treatment modality of first choice in the pediatric CPD population. In order to establish whether these regimens, prescribed on an empirical basis, provide an equally effective dialysis as does standard continuous ambulatory peritoneal dialysis (CAPD), we performed a cross-sectional analysis of dialysate and residual renal small molecule clearances in 85 children aged 3 months to 20 years, who were treated in 16 pediatric dialysis centers. Forty-three children were on CAPD and 42 were on CCPD. The two patient groups did not differ in age, body size, duration of dialysis, underlying disease distribution, or residual renal function. The CAPD patients achieved an average daily drain volume of 159 +/- 40 mL/kg body weight, as compared to 208 +/- 95 mL/kg in the CCPD group (p < 0.005). Average serum creatinine and BUN values were similar in both groups. While the (total) creatinine clearance did not differ, the KT/V urea was significantly higher in the patients treated with CCPD (0.35 +/- 0.12 vs 0.28 +/- 0.13, p < 0.05). The estimated protein catabolic rate (PCR) was significantly higher in the CCPD group (1.39 +/- 0.6 g/kg d) than in the CAPD patients (1.08 +/- 0.48 g/kg d, p < 0.05). Three-day dietary histories, available in 20 patients, showed a similar difference in dietary protein intake between CCPD and CAPD patients. We conclude that CCPD treatment regimens, at the dose currently prescribed in Mid-European pediatric dialysis centers, provide a higher clearance of urea and, possibly, other small molecules.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1994

[Follow-up of arteriosclerosis-induced anterior ischemic optic neuropathy].

In 22 patients with acute arteriosclerotic anterior ischemic optic neuropathy (AION), examinations were conducted before the start of therapy and between 1 and 3 years later. In the acute stage of the disease the patients were treated with hemodilution for 10 days. The visual acuity improved from 0.2 to 0.4 (median). Compared with the visual acuity before therapy, at the follow-up 1-3 years later visual acuity had improved by 3 lines or more in 11 patients, remained stationary in 9 patients (+/- 1 line), and worsened in 2 patients by 3 lines or more. The visual fields (Goldmann) improved in 8 patients, did not change in 10 patients and worsened in 4 patients. After 1-3 years, 14 patients (64%) showed a sectorial pallor and 8 patients (36%) a diffuse pallor of the optic disc. Videofluorescein angiography revealed hypofluorescent discs in all patients. No difference in arm-retina time (ART) was found between the acute phase (13.0 +/- 3.3 s) and the examination 1-3 years later (13.1 +/- 2.2 s). ART was within normal limits in all patients. The arteriovenous passage time (AVP) dropped significantly, from 2.36 (+/- 0.81) s in the acute phase to 1.91 (+/- 0.56) s 1-3 years later. However, the AVP still did not fall to normal levels (1.45 +/- 0.40 s). Slowed retinal hemodynamics (AVP) with normal ART at the same time suggests a disturbance in microcirculation still present 1-3 years after the acute phase of AION. The rheological parameters (hematocrit, plasma viscosity, erythrocyte aggregation index) did not show any change between examinations.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1994

Retinal hemodynamics after pars plana vitrectomy with silicone oil tamponade.

Pars plana vitrectomy with silicone-oil tamponade is frequently performed in cases of complicated retinal detachment. Because of the lower specific gravity and the lower surface tension of silicone oil in comparison with the aqueous phase of the vitreous, an influence on the blood flow in the retinal vessels would be expected. However, not only the silicone oil but also the operative trauma and a buckling procedure may have an influence on the retinal blood flow. To examine this question we measured the arteriovenous passage time in the silicone-oil-filled eye and in the contralateral eye in 14 cases using a laser scan ophthalmoscope at 3-5 days after surgery. The arteriovenous passage time is a parameter for the retinal microicirculation. In all cases we found a prolonged arteriovenous passage time in the silicone-oil-filled eye in comparison with the contralateral eye (mean value +/- SD, 2.5 +/- 0.8 vs 1.25 +/- 0.25 s; P < 0.01). The prolongation of arteriovenous passage times observed in silicone-oil-filled eyes indicates that the microcirculation is worsened at least during the early postoperative period.

Adult↗
PubMed1993

Ubiquitin found in the archaebacterium Thermoplasma acidophilum.

Systematic N-terminal sequencing of the low molecular weight proteins from Thermoplasma acidophilum separated by two-dimensional poly-acrylamide gel electrophoresis led to the discovery of a polypeptide with an apparent M(r) of 4.5 kDa identical as its first 18 amino acid residues to human ubiquitin. The occurrence of ubiquitin and proteasomes in an archaebacterium strongly suggests that ATP-ubiquitin-dependent proteolysis is a cellular function that developed early in evolution.

Amino Acid Sequence↗
PubMed1993

Interleukin 12 is required for the T-lymphocyte-independent induction of interferon gamma by an intracellular parasite and induces resistance in T-cell-deficient hosts.

Immunity against the intracellular protozoan Toxoplasma gondii is highly dependent on interferon gamma (IFN-gamma). We have previously shown that, in addition to T lymphocytes, natural killer (NK) cells can be stimulated by the parasite to produce this cytokine by a reaction requiring adherent accessory cells and tumor necrosis factor alpha. We now demonstrate that a recently characterized cytokine, interleukin 12 (IL-12), is also necessary for parasite-induced IFN-gamma synthesis by NK cells. Anti-IL-12 antibodies completely inhibited T. gondii or bacterial endotoxin-stimulated IFN-gamma production by NK-enriched spleen cells from severe combined immunodeficient mice. Moreover, potent NK cytokine responses were induced by the combination of IL-12 and tumor necrosis factor alpha. In addition, adherent spleen cells from scid/scid mice or thyoglycollate-elicited macrophages from BALB/c animals produced high levels of both IL-12 (p40) and tumor necrosis factor alpha mRNAs when exposed to either live tachyzoites, parasite extracts, or endotoxin, confirming that these cytokines are produced by accessory cells. Finally, in vivo studies showed that treatment with recombinant IL-12 results in prolonged survival of scid mice after infection with T. gondii by means of a response dependent on both IFN-gamma and NK cells. Together the data argue that IL-12 is required for the T-cell-independent triggering of NK cells by intracellular parasites and that the cytokine may be useful for inducing this protective pathway in immunodeficient hosts.

Animals↗
PubMed1993

Job factors, radiation and cancer mortality at Oak Ridge National Laboratory: follow-up through 1984.

A previous study of mortality among white men hired at Oak Ridge National Laboratory between 1943 and 1972 (n = 8,318) revealed an association between low-dose external penetrating ionizing radiation and cancer mortality in follow-up through 1984. The association was not observed in follow-up through 1977. This report considers the role of possible selection and confounding factors not previously studied. Control for hire during the World War II era and employment duration of less than 1 year had little effect on the radiation risk estimates. Risks associated with length of time spent in 15 job categories were considered as proxies for the effects of other occupational carcinogens. Adjustment for employment duration in each job category one at a time produced only small changes in the radiation risk estimate. Adjustment for potential exposures to beryllium, lead, and mercury also had little effect on the radiation risk estimates. These analyses suggest that selection factors and potential for chemical exposure do not account for the previously noted association of external radiation dose with cancer mortality. However, power to detect effects of chemical exposures is limited by a lack of individual exposure measures.

Confounding Factors, Epidemiologic↗