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Biomedical subjects

T Schroeder

Publications and source records attributed to T Schroeder.

At least 109 records · Page 6Linked to original sources
PubMed1989

Congenital hypertrophy of the retinal pigment epithelium in familial adenomatous polyposis.

One hundred fifty-three members of 56 kindreds with familial adenomatous polyposis (FAP) underwent funduscopic examination for congenital hypertrophy of the retinal pigment epithelium (CHRPE). All patients underwent wide-angle fundus photography to document lesions, proctosigmoidoscopy to document polyps, and examination for extracolonic manifestations. Ninety-seven patients were diagnosed as having FAP and 56 patients were offspring of FAP patients and thus at 50% risk of inheriting the disease. In two thirds of the kindreds, CHRPE could be used as a congenital phenotypic marker to predict the presence or development of polyps. In these kindreds, all patients with diagnosed FAP and 39% of the patients at risk had at least four CHRPE lesions. In one third of the kindreds, CHRPE could not be used as a predictive congenital marker, and in these kindreds all patients had zero to three total lesions of CHRPE. The presence of CHRPE did not correlate with any other extracolonic manifestations. In kindreds without any other extracolonic manifestations, CHRPE can still be present and can be used as a predictive congenital phenotypic marker.

Adenomatous Polyposis Coli↗
PubMed1989

Real time B-mode mapping of the greater saphenous vein.

Real time ultrasound mapping of the greater saphenous vein (GSV) was performed in 30 consecutive patients admitted for in situ femoro-crural revascularisation. The overall accuracy in predicting the adequacy of the GSV for in situ bypass was 90%. The predictive value of finding the vein usable was 96%, whereas the predictive value of judging the vein inadequate was 50%. The scanning procedure provided morphologic information about the GSVs, including size, tributaries, varicosities, and double segments, which may prevent unnecessary dissection and may further shorten the duration of surgery. In our opinion the technique is sufficiently accurate to replace phlebography for the routine preoperative assessment of GSV in patients considered for in situ bypass. Veins judged inadequate at scanning, however, should be further evaluated.

Adult↗
PubMed1989

Haemodynamic evaluation of carotid artery disease.

Cerebral ischaemia in the region of an internal carotid artery (ICA) stenosis may be caused by embolism or cerebral hypoperfusion. A severe ICA stenosis may be well compensated by collateral blood supply, however, in some patients the capacity of the collateral blood supply is insufficient. Studies evaluating therapeutic modalities or natural history of carotid artery disease should therefore include a test capable of assessing cerebral haemodynamics. However, most studies, invasive as well as non-invasive, have focused on the ability of the test to diagnose the ICA lesions itself, rather than the haemodynamic changes induced by the stenosis. This paper reviews non-invasive methods for haemodynamic evaluation of carotid artery disease. Haemodynamic evaluation of ICA stenoses may be performed accurately by different techniques. Analysis of Doppler waveforms obtained distal to the ICA lesion and CBF reactivity tests may identify patients with severe reduction in ICA perfusion pressure. Periorbital Doppler examination and OPG identifies ICA lesions causing minor pressure gradients, however, they are unable to discriminate between minor and moderate to severe pressure reduction. Transcranial Doppler examination may prove to be useful in haemodynamic assessment of ICA stenoses, but, this remains to be evaluated. Presently, in addition to direct evaluation of the carotid arteries, we use a combination of periorbital Doppler examination and analysis of distal ICA waveforms. In cases of an ICA stenosis and orthograde flow any severe pressure reduction may be ruled out. In cases of inverted flow, analysis of distal ICA waveforms may identify patients with severe reduction in ICA perfusion pressure.

Brain Ischemia↗
PubMed1989

Cerebral blood flow during submaximal and maximal dynamic exercise in humans.

Cerebral blood flow (CBF) in humans was measured at rest and during dynamic exercise on a cycle ergometer corresponding to 56% (range 27-85) of maximal O2 uptake (VO2max). Exercise bouts were performed by 16 male and female subjects, lasted 15 min each, and were carried out in a semisupine position. CBF (133Xe clearance) was expressed as the initial slope index (ISI) and as the first compartment flow (F1). CBF at rest [ISI, 58 (range 45-73); F1, 76 (range 55-98) ml.100 g-1.min-1] increased during exercise [ISI to 79 (57-94) and F1 to 118 (75-164) ml.100 g-1.min-1, P less than 0.01]. CBF did not differ significantly between work loads from 32 (24-33) to 86% (74-96) of VO2max (n = 10). During exercise, mean arterial pressure increased from 84 (60-100) to 101 (78-124) Torr (P less than 0.01) and PCO2 remained unchanged [5.1 (4.6-5.6) vs. 5.4 (4.4-6.3) kPa, n = 6]. These results demonstrate a median increase of 31% (0-87) in CBF by ISI and a median increase of 58% (0-133) in CBF by F1 during dynamic exercise in humans.

Adult↗
PubMed1989

Cerebral blood flow and liver function in patients with encephalopathy due to acute and chronic liver diseases.

The purpose of the present investigation was to study changes in cerebral blood flow (CBF) in hepatic encephalopathy, to ascertain whether this was related to the changes in liver function and whether these changes gave any prognostic information. CBF, determined by the intravenous xenon-133 method, and liver functions, assessed by the prothrombin index, bilirubin concentration, and the galactose elimination capacity, were studied in patients with acute fulminant liver failure and in patients with encephalopathy due to chronic liver diseases--that is, cirrhosis of various etiologies. The CBF range in healthy young subjects (age, 23-42 years) was 44-61 ml/100 g/min; in patients with grade I + II encephalopathy (mean +/- SEM) it was 32.8 +/- 3.6 ml/100 g/min in acute (n = 4; age, 28 +/- 8 years) and 37.0 +/- 3.3 ml/100 g/min in chronic liver patients (n = 10; age, 51 +/- 2 years). In grade III + IV encephalopathy it was 28.7 +/- 3.8 ml/100 g/min in acute (n = 8; age, 28 +/- 3 years) and 32.9 +/- 3.7 ml/100 g/min in chronic patients (n = 12; age, 49 +/- 3 years). CBF did not correlate with the liver function and was of no prognostic value. The liver function was markedly reduced in all the patients, without any differences between patients with acute or chronic liver diseases or the different degrees of hepatic encephalopathy. In conclusion, a marked reduction of the CBF was seen in hepatic encephalopathy, irrespective of the etiology of the disease.

Adult↗
PubMed1989

[Femoro-crural in situ bypass].

During a period of 21 months from April 1986, 108 in situ femoro-crural bypass procedures were performed. The indication for surgery was in all cases a limb threatening ischemia. Always the technique described by Leather et al. was used. All the patients had obstructive disease of the crural arteries, thus the distal anastomosis was performed in a single crural or pedal artery for 102, and for 40 at the level of the ankle or foot. 97 per cent of the patients were discharged from the hospital with a salved limb, the one year patency was 76 per cent and one year limb survival 90 per cent. In our hands the in situ technique has shown much better results than the reversed vein technique.

Adult↗
PubMed1989

Study on the peroral absorption of the endekapeptide cyclosporine A.

The beagle dog was found to be a suitable model for pharmacokinetic and bioavailability studies of cyclosporine A (CsA). All pharmacokinetic parameters studied were in the same order of magnitude as those found in man. Three CsA peroral formulations in the form of capsules were compared with a commercially available P.O. solution (to be diluted for administration) and a solution for intravenous administration. Of the three experimental capsule formulations, one based on a microemulsion resulted in an extent of absolute and relative bioavailability not different from that of the available P.O. solution. The advantage, however, is that it is a capsule preparation, ready to swallow, and does not need any manipulation by the patient to dilute the solution. The other two capsule preparations, based on a Gelucire gel with sorption promoters and a microemulsion containing Azone, resulted in a lesser bioavailability than the solution.

Administration, Oral↗
PubMed1988

Determination of lysozyme content in eggs and egg products using SDS-gel electrophoresis.

Lysozyme can be separated commercially from other egg components and is used as a natural, antibiotically active protein. A method for the detection of de-lysozymed egg products using SDS-polyacrylamide gel electrophoresis (PAGE) is described. The method can also be used for lysozyme quantification. Lysozyme concentrations in egg products are tentatively assigned to three classes, based on the lysozyme contents found in intact eggs. The results obtained from a series of egg products on the market allow two groups to be distinguished. The first group has values for average lysozyme content, standard deviation and total protein content very close to the values found for intact eggs, and the second group clearly shows a lower lysozyme content but a total protein content comparable with intact eggs.

Animals↗
PubMed1988

Pad-weighing test performed with standardized bladder volume.

The result of the one-hour pad-weighing test proposed by the International Continence Society has been demonstrated to depend on the urine load during the test. To increase reproducibility of the pad-weighing test by minimizing the influence of variation in urine load the test was done with a standardized bladder volume (50% of the cystometric bladder capacity). Twenty-five female patients with stress or mixed incontinence underwent two separate tests. Test-retest results were highly correlated (r = 0.97, p less than 0.001). Nonetheless, analysis of test-retest differences revealed a variation up to +/- 24 g between two tests. It is concluded that this setup (i.e., standardized bladder volume) of the one-hour pad-weighing test allows for a more reliable assessment of urinary incontinence for quantitative purposes.

False Negative Reactions↗
PubMed1988

Changes in Doppler waveforms can predict pressure reduction across internal carotid artery stenoses.

Cerebral ischemia can result from either embolism or be due to hemodynamic failure. The purpose of this study was to evaluate whether Doppler waveforms, obtained distal to an internal carotid artery (ICA) stenosis, could predict the degree of hemodynamic compromise in terms of reduction in cerebral perfusion pressure. Forty-nine patients were examined consecutively with ultrasound Doppler prior to carotid endarterectomy. Pulsatility index (PI), pulse rise-time (RT), and systolic width (SW) were related to angiographic degree of stenosis and the ratio of distal ICA blood pressure to common carotid artery (CCA) blood pressure (ICA/CCA pressure ratio). The latter was determined during surgery. All three waveform parameters were significantly correlated with the ICA/CCA pressure ratio when calculated from the mean frequency curve (p less than 0.001). A reduction in ICA pressure of 20% could be predicted with an accuracy of 90-95%. Correlating the waveform parameters with arteriography was less convincing, reaching the level of statistical significance for PI only. ICA Doppler waveforms, obtained as distal in the neck as possible can accurately predict the degree of hemodynamic compromise. It is recommended as a simple adjunct to routine Doppler evaluation of carotid stenoses.

Angiography↗
PubMed1988

Haemodynamic evaluation of the cerebral circulation by periorbital Doppler examination and cerebral blood flow (CBF) measurement in carotid artery disease.

To assess the haemodynamic significance of an internal carotid artery (ICA) stenosis, angiography or direct ultrasound examination should be supplemented by indirect physiologic testing of the collateral circulation. Among the tests proposed, we used the periorbital flow direction, assessed by Doppler technique, and cerebral blood flow reactivity to vasodilation, by i.v. xenon-133 technique, in 35 patients before carotid endarterectomy. The results were related to the actual perfusion pressures, measured during surgery in the distal ICA. All 15 patients with normal orthograde periorbital flow had normal cerebral blood flow (CBF) vasoreactivity and no, or only minor, reduction in ICA perfusion pressure. Of the 20 patients with inverted flow, 12 had normal and 8 had abnormal CBF reactivity. These 8 patients proved to have significantly lower cerebral perfusion pressures, as compared with the remaining 12 patients with inverted periorbital flow (p less than 0.001), who in turn had lower perfusion pressures than the 15 patients with orthograde flow (p less than 0.005). Based on these results, we suggest periorbital Doppler examination as a haemodynamic adjunct to direct ICA visualization. A normal orthograde flow will most certainly rule out any severe pressure reduction. By measuring CBF at rest and following vasodilation in cases with inverted flow, most patients with severe reduction in cerebral perfusion pressure may be identified.

Adult↗
PubMed1988

Middle cerebral artery occlusion in presence of low perfusion pressure increases infarct size in rats.

A model was set up in order to evaluate the importance of hemispheric perfusion pressure when the middle cerebral artery (MCA) is occluded in anaesthetized rats. In 6 animals the internal carotid artery (ICA) was occluded prior to ipsilateral MCA occlusion; in 17 animals the MCA only was occluded; 6 animals underwent the same preparation, but the vessels were left unoccluded. Four days after surgery the infarct volume was measured with a computerized image analyser. The infarcted areas were significantly larger in the ICA + MCA occluded group compared with the MCA occluded group (p less than 0.005), which in turn had larger infarcts than the sham-operated animals (p less than 0.001). These results indicate that patients with hypoperfusion, due to severe ICA stenosis and impaired collateral blood supply, are at higher risk of developing major stroke, when embolism into a cerebral artery occurs, as compared to patients with no, or only minor, reduction in hemispheric perfusion pressure.

Animals↗
PubMed1988

The synergistic effect of low-dose cyclosporine and fluocinolone acetonide on the survival of rat allogeneic skin grafts.

Both CsA and topical FA can prolong the survival of skin allografts under the proper conditions. This study was performed to determine if there is a synergistic effect between these two compounds. Buf (RT1b) rat split-thickness skin grafts were transplanted onto the backs of Lew (RT1l) rats. The MST for the control group was 9.89 +/- 0.35 days. In rats given oral CsA, 2.5 or 5 mg/kg, daily from the second day of grafting, the MST was 16.0 +/- 1.9 and 13.6 +/- 0.4 days (blood CsA levels were 166 +/- 20 and 640 +/- 32 ng/ml at the time of rejection, respectively. Topical FA applied daily beginning 72 hr after grafting resulted in a MST of 24.1 +/- 3.6 days. When both topical FA and 5 mg/kg oral CsA were used, the allograft survival time was more than 100 days in 4 of 7 animals. When oral CsA 2.5 mg/kg was combined with topical CsA and FA, the allograft rejection was delayed until 50 days postgrafting in four of six animals. The synergistic effects of oral CsA and topical FA is significant, and thus allows for the use of a subtherapeutic dosage of each compound and provides a potentially safe means for prolonging skin allograft survival.

Animals↗
PubMed1988

Hemodynamic significance of internal carotid artery disease.

Neurologic symptoms in the region of an internal carotid artery stenosis are considered to be embolic in most instances. Only in a subgroup has carotid occlusive disease with impairment of the collateral supply, caused a state of hemodynamic failure with marked reduction of perfusion pressure. Though unproven, it is reasonable to assume that without surgical intervention, the risk is higher than average for patients with hemodynamic failure. Equally, should there be any postoperative improvement of cerebral blood flow or neurologic deficits, it should be looked for in this group. Thus, it is necessary to distinguish those with low perfusion pressure from the population of patients with carotid artery disease. Preoperative clinical evaluation and direct visualization of the carotid bifurcation should be supplemented by indirect physiological tests which allow assessment of collateral perfusion. Examination of periorbital flow direction or oculoplethysmography could be used as a screening procedure. Negative tests most certainly rule out any severe pressure gradient across the stenosis, irrespective of the luminal reduction. A positive result, on the other hand, should be further quantified since most indirect tests become positive at relatively small pressure gradients. Studies of cerebral blood flow at rest and during cerebral vasodilation makes it possible to identify patients with severe reduction of cerebral perfusion pressure. Such hemodynamic failure of one hemisphere may be identified in most cases by a conventional non-invasive xenon-133 technique and stationary detectors. Smaller focal regions of hypoperfusion may be identified by computer emission tomography, either by the detection of single-photon emission or by paired detection of annihilation photons. Endarterectomy does improve cerebral hemodynamics in terms of increased flow through the reconstructed vessel and elimination of pressure gradients. The cerebral blood flow, though remains unchanged in the majority of patients, at least when measured at baseline. Only in those patients with a reduction in perfusion pressure can a significant improvement in baseline flow occur. Flow reserve determined by cerebral vasodilation, however, will improve in most patients with hemodynamic failure. In addition, some patients in the low-pressure group develop marked, but temporary, hyperperfusion after reconstruction of very high grade carotid stenosis. This is considered a result of chronic low perfusion pressure with subsequent loss of autoregulation, and autoregulatory control is first regained after some days.(ABSTRACT TRUNCATED AT 400 WORDS)

Angiography↗
PubMed1988

Pulsed multigated Doppler ultrasonography in the diagnosis of carotid artery disease.

To evaluate the accuracy of a pulsed multigated Doppler system, 128 carotid arteries were examined. The spectral broadening index was calculated from the power spectrum of a small sample volume located in the center of the stream according to the flow profile and was related to the degree of stenosis as determined by contrast angiography. Even minor wall irregularities seen on the angiogram were classified as disease. The ability of the system to discriminate between normal and diseased vessels reached a sensitivity of 94% and a specificity of 91%. Classification of greater than 50% or less than 50% stenosis could be performed with a sensitivity of 90% and a specificity of 85%. Pulsed multigated Doppler ultrasonography allows identification of even minor degrees of stenosis of the carotid artery and provides an alternative to duplex scanning. Furthermore, the blood flow profile provided by a multigated Doppler system may add valuable information concerning blood flow characteristics not obtainable by single-gated systems.

Adult↗