Search PubMed⌕ Search

Biomedical subjects

M Wehrmann

Publications and source records attributed to M Wehrmann.

At least 73 records · Page 4Linked to original sources
PubMed1992

Holmium:YAG laser angioplasty. Experimental ablation of vascular tissue via flexible ring catheters.

This experimental study was designed to define the potential value of a mid-infrared holmium laser in the free running mode for angioplasty. Immediately after removal, fresh normal and diseased human cadaveric arteries were irradiated under saline with a Ho:YAG laser (wavelength 2.13 microns). The laser was pulsed at 3 Hz, 250 microseconds pulse width and fluences of 10 to 40 J/cm2. The laser beam was coupled to ring catheters with multiple low-OH quartz fibers. The tip of the delivery device was held in direct contact with the vessel surface with the laser beam oriented perpendicularly. Ablation of atherosclerotic plaque was accomplished at an ablation threshold of 10 J/cm2. The ablation rate was 2.1 to 8.3 microns/pulse. Removal of calcified plaque was only partially effective. There were marked thermal effects with vacuolizations extending up to 1505 +/- 178 microns into the adjacent tissue. Laser light at the mid-infrared wavelength of 2.13 microns is supposed to be attractive as it is readily absorbed in water and can easily be transmitted through optical fibers. However, Q-switching seems to be essential to minimize thermal side effects and to make effective ablation of calcium possible.

Angioplasty, Laser↗
PubMed1992

The consequences for renal function of widening of the interstitium and changes in the tubular epithelium of the renal cortex and outer medulla in various renal diseases.

The following parameters were measured in 63 renal biopsy specimens, most of which exhibited mesangioproliferative glomerulonephritis: the relative area of the interstitium and the area of the capillaries in the cortex and outer stripe of the outer medulla, and the area of the epithelium of the proximal tubules and of the ascending limbs of Henle's loop. The percentage of hyalinized glomeruli was also determined. Investigation of correlations between these values and parameters of renal function revealed the following: 1) The serum creatinine concentration increases and the endogenous creatinine clearance decreases significantly as the interstitium of both the cortex and the outer stripe of the outer medulla increases in width. 2) The urine osmolality decreases significantly as the epithelial areas of the proximal tubules and ascending limbs of Henle's loop decrease, and as the serum creatinine concentration rises and the areas of the interstitium increase. 3) No significant correlation exists between the percentage of hyalinized glomeruli and the urine osmolality. 4) The total area of the intertubular capillaries in the cortex decreases significantly as the interstitium in this area increases in width and as the serum creatinine concentration increases. 5) Compensatory hypertrophy of individual nephrons, as proposed by Bricker's hypothesis, was found only where more than 90% of the glomeruli were hyalinized.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Smooth muscle cell proliferation and restenosis after stand alone coronary excimer laser angioplasty.

It has been shown that coronary excimer laser angioplasty can remove atherosclerotic intracoronary tissue. Stand alone coronary excimer laser angioplasty was successfully performed in a 53 year old white man with 90% stenosis of the left anterior descending coronary artery and exertional angina (Canadian Cardiovascular Society class III). The lesion was reduced to a 30% residual stenosis with use of a 1.2 mm and subsequently a 1.8 mm diameter laser catheter. Early follow-up angiography 24 h later revealed persistent patency and unchanged lesion diameter of the target vessel. The patient was free of symptoms during the 2 month follow-up period, but died suddenly while playing in a tennis tournament 63 days after the procedure. Postmortem histologic examination revealed 80% restenosis at the lesion site without plaque disruption or thrombosis. Specific staining of the histologic specimen for smooth muscle cells using alpha-actin revealed significant smooth muscle cell proliferation at the site of coronary excimer laser angioplasty. However, most of the vessel narrowing appeared to be due to underlying fibrotic plaque as a result of insufficient tissue ablation. This was probably related to the size of the currently available catheters, which are too small to create a large channel.

Angioplasty, Laser↗
PubMed1991

Potential use of holmium lasers for angioplasty: evaluation of a new solid-state laser for ablation of atherosclerotic plaque.

Tissue effects of the mid-IR Holmium laser (emitting at a wave-length of 2130 nm) were evaluated. This wavelength is attractive because it combines high water absorption and easy transmission through standard optical fibres. The laser was pulsed with pulse durations in the range of 100 microseconds and repetition rates between 2 and 6 Hertz. For all experiments a repetition rate of 2 Hertz was used. The laser beam was coupled into waterfree quartz fibers with core diameters of 200 and 800 microns with an efficiency of 70 and 80%, respectively. Ablation of atherosclerotic plaque has been performed at an ablation threshold of 10J/cm2 for the 800 microns and 40J/cm2 for the 200 microns fibre. Removal of calcified plaque was possible. Ablation efficiency increased in a non-linear fashion with increasing pulse energies. The ablation rate per pulse was approximately 2 mm at energy fluences of 1000J/cm2 for the 200 microns fibre and 1.25 mm at energy fluences of 70J/cm2 for the 800 microns fibre; a further increase in energy densities did not result in higher ablation rates. On macroscopic examination only very limited thermal injury was found in crater adjacent tissue structures. Crater edges were even and did not reveal signs of crater charring or debris in the crater lumen. However, the histologic specimens revealed zones of thermal damage extending 100 up to 1000 microns lateral into adjacent tissue. Thermal damage increased with increasing radiant exposures and depended on the medium used.

Angioplasty, Laser↗
PubMed1991

The pathogenesis of chronic renal failure in diabetic nephropathy. Investigation of 488 cases of diabetic glomerulosclerosis.

Investigation of renal biopsy specimens from 488 patients with diabetic glomerulosclerosis (DGS) of varying severity revealed the following: 1) The severity of DGS increases with the duration of the diabetes. 2) As the severity of DGS increases, it is complicated with increasing frequency by exudative changes, which correspond in detail to hyperperfusion lesions described in the literature. 3) As the severity of DGS increases, the severity of arteriolosclerosis and the incidence of nephrotic syndrome increase significantly. 4) The 5- and 10-year renal survival rates are highest for those diabetic patients in whom the tubules and renal cortical interstitium are of normal appearance. These survival rates are diminished if any of the following are present at the time of biopsy: a) interstitial fibrosis; b) hyperperfusion lesions; c) nephrotic syndrome; d) elevation of the serum creatinine concentration to more than 1.3 mg%. 5) No significant correlation was found between renal survival rate and age, sex, or type of diabetes. 6) The inflammation of the renal interstitium seen in diabetes does not differ from that seen in chronic glomerulonephritis. Monocytes, macrophages, T lymphocytes, fibroblasts and fibrocytes play the major role in this inflammation. This inflammatory process is considered to represent not pyelonephritis, but rather an auto-immune process. In other words, it is proposed that the diabetic kidney fails not only as a result of non-specific glomerular lesions (hyperperfusion lesions) but also because of non-specific tubulointerstitial changes, whereas diabetic glomerulosclerosis alone does not lead to chronic renal failure.

Adult↗
PubMed1991

[Macro- and microscopic changes in the atherosclerotic arterial wall caused by high frequency current].

To investigate the effect of radiofrequency energy (600 kHz) on atherosclerotic tissue, high frequency current was applied on 160 specimens of human abdominal and iliac artery autopsies with various duration and energy density. All experiments were performed in air, saline, and blood. Application of 5 to 30 joule resulted in coagulation of the intima and the media. Time dependent a shrinking of the vessel wall did occur at energy rates above 30 joule. At higher energies vaporization was found. In blood coagulation at the catheter tip became evident at 30 joule and higher energies. Histologic cross sections showed distending of intimal layers at 25 joule, additional shrinking of medial layers at 50 joule, vacuoles at 75 joule and separation of intima layers from underlying layers at 200 joule. In vitro application of high frequency current on atherosclerotic tissue results in thermal effects only. The extent of these effects seems to be unpredictable because of the ever changing composition of the tissue, resulting in changes of energy delivery at the tip tissue interface. On calcified plaques an energy dependent contraction mainly of adjacent vessel wall could be seen. Because of the non-predictable effects and adverse side effects on adjacent normal vessel wall the method seems not to be useful for clinical application.

Aged↗
PubMed1990

The consequences of tubulo-interstitial changes for renal function in glomerulopathies. A morphometric and cytological analysis.

Morphometric investigation of the structures of the cortex in kidneys exhibiting various types of glomerulopathy revealed the following: 1. In various types of glomerulonephritis, diabetic glomerulosclerosis, and glomerular amyloidosis there are significant correlations between the severity of fibrosis of the renal cortical interstitium and tubular atrophy resulting from chronic interstitial inflammation, and the serum creatinine concentration, creatinine clearance, inulin clearance and PAH clearance. 2. As illustrated with the example of membranoproliferative glomerulonephritis type I, if glomerulopathy alone is present, there is no elevation of the serum creatinine concentration, even if the glomerular inflammatory changes are severe; neither are severe renal amyloidosis that is confined to the glomeruli and severe isolated diabetic glomerulosclerosis associated with elevation of the serum creatinine concentration. 3. There is a significant negative correlation between the severity of interstitial fibrosis resulting from chronic inflammation and the total number and cross-sectional area of the intertubular capillaries; i.e., the total cross-sectional area and number of capillaries per unit area decrease as the fibrosis of the cortical interstitium increases. 4. Cases of glomerulonephritis in which there is accompanying fibrosis of the renal cortical interstitium have a significantly worse long-term prognosis than those in which there is only severe glomerulitis. 5. Obliteration of the post-glomerular capillaries leads to an increase in the cross-sectional area of the glomerular capillary convolution, the morphological equivalent of an increase in intraglomerular pressure. 6. The cause of the disease of the renal cortical interstitium that may accompany the various types of glomerulonephritis is not known. It is considered possible, as a working hypothesis, that this inflammation represents a T-cell stimulated autoimmune process in which fibroblast proliferation occurs, leading to an increase in numbers of fibrocytes in the renal cortical interstitium and thus to increased production of collagen.

Creatinine↗
PubMed1990

[Excimer laser angioplasty. I. The tissue effects of a ring catheter system on peripheral arterial vessels].

We have carried out an experimental study using a new laser catheter on 28 cadaver femoral arteries in 14 subjects and on six aortas. This ring catheter system consists of 12 circular quartz fibres with a central lumen and allows the application of energies up to 20 mJ through a 7F flexible catheter in vivo. The laser emits ultraviolet light of a wave-length of 308 nm, in pulses of 60 ns and a frequency of 2-40 Hz. The energy within a single fibre is 5 J/cm2 and exceeds the intensity required to ablate calcifications. Histologically it has been shown that, depending on the type of tissue, 1 to 2.4 microns of tissue per pulse is removed. Experimentally, rate of progress in a calcified occlusive lesion in the femoral artery, using 20 Hz and energy transmission of 20 mJ, was 3 to 5 mm per minute. Perforation of vessel wall if the catheter tip was at right angles to it depended on the degree of atherosclerosis and was between nine and 116 seconds. Marginally, there was only minimal thermal damage.

Angioplasty, Balloon↗
PubMed1990

Blood findings in generalized mastocytosis: evidence of frequent simultaneous occurrence of myeloproliferative disorders.

Blood findings in 61 cases of generalized mastocytosis (GM) were evaluated. The cases were divided into two major variants: Systemic mastocytosis (SM; n = 34) with urticaria pigmentosa-like skin lesions, and malignant mastocytosis (MM; n = 27), without skin involvement. The following results were obtained: (1) Significant differences between MM and SM were found in the main haematological parameters (erythrocyte, platelet and leucocyte counts and haemoglobin level); normal values were found in 16 of the SM cases, but never in MM. (2) The main pathological findings were: in SM, anaemia (9/34) and leucocytosis (5/34); and in MM, leucocytosis (19/27), monocytosis (14/27), eosinophilia (12/27), bicytopenia (12/27, mostly anaemia with thrombocytopenia), basophilia (10/27) and isolated anaemia (7/27). (3) The major finding was a significant difference between MM and SM in the incidence of myeloproliferative disorders (MPD), myelodysplasia and mast cell leukaemia (MCL): these disorders occurred in 23 (92%) MM patients, but only in two (6%) SM patients (P less than 0.001). The four instances of MCL and two of myelodysplasia all occurred with MM. Of the 19 cases of MPD, six (SM, 1; MM, 5) were acute variants (acute myeloid and myelomonocytic leukaemias) and 13 (SM, 1; MM, 12) were chronic variants. No case of malignant lymphoma was noted. (4) The blood picture in 10 of 13 chronic MPD cases represented an atypical chronic myeloid leukaemia for which the preliminary descriptive term 'mastocytosis-associated MPD' is proposed. (5) A survey of 103 published cases (SM, 77; MM, 26) yielded similar findings, including a high incidence of MPD and MCL in MM. These findings add further weight to the argument for recognizing SM and MM as two separate entities.

Adult↗
PubMed1990

IgA nephritis: on the importance of morphological and clinical parameters in the long-term prognosis of 239 patients.

This study is concerned with the correlation between tubulointerstitial changes (interstitial fibrosis, acute renal failure, and interstitial fibrosis with acute renal failure), glomerular changes (focal and segmental lesions, hyperperfusion lesions), vascular changes, clinical data at the time of biopsy (serum creatinine concentration, creatinine clearance, hematuria, proteinuria, and hypertension) and first symptoms (hematuria, proteinuria and hypertension) and the kidney survival rate in 239 patients with IgA nephritis without nephrotic syndrome. The morphological and clinical parameters were subjected to multivariate analysis in order to examine their significance with regard to the prognosis. The interstitial fibrosis was proven to be the most important morphological parameter, and the most important clinical parameters were the serum creatinine concentration and the creatinine clearance.

Acute Kidney Injury↗
PubMed1990

[Massive hemorrhage from an "esophageal tumor": thoracic aortic aneurysm rupturing into the esophagus].

We report on an arteriosclerotic aneurysm of the descending aorta penetrating into the esophagus. On endoscopy it mimicked a bleeding esophageal tumour. The typical clinical course of aortoesophageal fistulas (AEF) exhibits Chiari's triad of midthoracic pain, sentinel arterial hemorrhage, usually hematomesis, and final exsanguination after a symptom-free interval. The various causes of AEF are discussed together with the respective diagnostic and therapeutic problems.

Aged↗
PubMed1990

Long-term prognosis of focal sclerosing glomerulonephritis. An analysis of 250 cases with particular regard to tubulointerstitial changes.

The following results were obtained in a long-term retrospective study including 250 patients with focal sclerosing glomerulonephritis: 1. The renal survival rate (RSR) was 90% at 5 years and 67% at 10 years, the average period of observation being 4.7 years. 2. Univariate analysis revealed that the following morphologic and clinical parameters are associated with an increased risk of terminal renal failure or death due to renal causes: a) Tubulointerstitial changes in the form of interstitial fibrosis, with or without acute renal failure; b) Advanced glomerular lesions; c) Advanced vascular alterations; d) Nephrotic syndrome present at the time of the biopsy; e) Elevated serum creatinine concentration at the time of the biopsy; f) Arterial hypertension at the time of the biopsy; g) Greater age at diagnosis; h) Male sex. 3. Multivariate survivorship analysis showed that tubulointerstitial changes and the presence of nephrotic syndrome at the time of biopsy are the only variables with significant independent predictive value for the outcome. Assessment of these factors thus allows the pathologist to make a relevant statement concerning the probable course and prognosis of the disease at the time of the diagnostic biopsy.

Adolescent↗
PubMed1990

[Experimental intracoronary Excimer laser angioplasty].

To determine the feasibility of intracoronary application of pulsed ultraviolet laser light 38 coronary arteries of 18 in situ hearts were treated with the bare fiber technique and a specially constructed catheter device. Eight hearts had no coronary artery disease, in 10 hearts coronary artery disease of one or more vessels could be documented angiographically. Total time of laser irradiation varied from 30-490 seconds. Radiation was performed until vessel wall perforation was documented. In all cases a reduction of the stenotic area was realized using the bare fiber technique. Due to a lack in the flexibility of the bare fiber only proximal lesions could be treated and the time of perforation could not be precisely predicted. Dissections were observed in six coronary arteries. The handling of the catheter device was comparable to the conventionally used balloon technique. Ablative treatment of distal vessel lesions was possible. Perforations did not occur. The histologic specimens documented smooth lumen margins not revealing thermal damage. It can be expected that the innovative catheter device will enhance the intracoronary use of pulsed laser light.

Angioplasty, Balloon, Coronary↗
PubMed1989

Squamous cell carcinoma of the gastric stump. A case report and review of the literature.

Adenosquamous and pure squamous cell carcinomas of the stomach are very rare. This report is apparently the first published case of pure squamous cell carcinoma of the gastric stump. It occurred in a 67-year-old patient 37 years after Billroth II resection. This case satisfied the criteria established in the literature for the diagnosis of gastric squamous cell carcinoma. A diagnosis of adenosquamous carcinoma was excluded by extensive histologic investigation of a large number of tissue samples--a total 122 sections from 25 blocks--that revealed neither glandular structures nor mucin. The tumor stroma contained an unusually large number of eosinophils. Immunohistochemically, the tumor cells reacted with a monoclonal antibody against keratin (KL1), but not with antibodies against neuroendocrine or endothelial markers, or alpha 1-antichymotrypsin. The tumor may possibly originate from ectopic squamous epithelium, squamous metaplasia of the gastric mucosa, or an undifferentiated mucosal stem cell. However, we excluded an endothelial origin (which has been proposed by other authors) on the basis of immunohistochemical findings.

Aged↗
PubMed1989

[Clinical pathology of the glomerulus--from phenomenon to entity. The mesangial lesion].

The numerous findings discussed lead to the following conclusions: 1. The mesangial lesions, which may take a wide range of different forms, can be classified into two groups according to whether an underlying immunological pathomechanism is involved. Those that result from such a pathomechanism represent various types of glomerulonephritis. 2. Amongst these immunologically-mediated glomerulonephritides mesangioproliferative glomerulonephritis (and, of this group, IgA nephritis) is the most common. Membranoproliferative glomerulonephritis is the most severe of these diseases. Either may be idiopathic or secondary, or may occur in association with systemic disease. 3. The number of macrophages in the mesangial lesions in glomerulonephritis correlates with the severity of the glomerulonephritis, the localization of the immune complex deposits and the degree of proteinuria. If the immune complex deposits extend out of the mesangium into the subendothelial space, the number of macrophages is higher, the structural changes are more marked, and proteinuria is more severe. 4. Various pathomechanisms and nosologic entities can lead to mesangial lesions of the type seen in mesangioproliferative glomerulonephritis or membranoproliferative glomerulonephritis. On the other hand, the same entity may be associated with mesangial lesions of different severity, and consequently the prognosis varies. Differential diagnosis of the mesangial lesions, which represent heterogeneous nosologic entities, requires the use of light microscopic, immunohistochemical, and electron microscopic techniques. Exact diagnosis is necessary because of the differences in prognosis. 5. The course and prognosis of mesangial lesions are determined by immunological and nonimmunological factors. Long-term studies have demonstrated that prognostically relevant information can already be gained at the time of biopsy by the assessment of certain morphological features (e.g., immunohistological findings, severity of glomerulonephritis, the presence of focal/segmental lesions) and clinical parameters (e.g., proteinuria, hematuria, hypertension, and serum creatinine concentration). The decisive predictor of an unfavorable prognosis is the presence of interstitial fibrosis.

Glomerular Mesangium↗