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Biomedical subjects

E Ritz

Publications and source records attributed to E Ritz.

At least 865 records · Page 48Linked to original sources
PubMed1980

Developmental potentialities and surface antigens of mouse teratocarcinoma x lymphoid cell hybrids.

Hybrids between PCC4-aza 1 teratocarcinoma cells and either thymus cells (PcT and RPcT hybrids) or Lc lymphocytic leukemia cells (PcLc hybrids) are carcinoma cells and when injected into hosts they produce tumors which are teratocarcinomas. PcT and RPcT hybrids) or Lc lymphocytic leukemia cells (PcLc hybrids) are carcinoma cells and when injected into hosts they produce tumors which are teratocarcinomas. PcT and RPcT hybrid tumors are well differentiated and include a large variety of somatic tissues. In most PcLc tumors, neuroectoderm differentiation is predomonant. Like the PCC4 parental cells, PcT, RPcT, and PcLc hybrids carry F9 embryonic antigens and do not express perceptible amounts of H-2 alloantigens. Nonexpression of the H-2d haplotype of the thymus cell parent in PcT hybrids is not due to the loss of chromosome 17 which carried the major histocompatibility complex.

Animals↗
PubMed1980

Is there a renal phosphorus leak in recurrent renal stone formers with absorptive hypercalciuria?

In ten male hypophosphataemic hypercalciuric recurrent renal stone formers with absorptive hypercalciuria and ten male normophosphataemic normocalciuric control persons, fasting plasma and urine chemistry was studied throughout the day under basal conditions and following an oral phosphorus load. After overnight fasting, plasma phosphorus and TMP/GFR were lower and urinary calcium higher in patients than in controls. Both in patients and controls, plasma phosphorus rose throughout the morning hours. In the afternoon, plasma phosphorus was almost equal in patients and controls. The circadian rise of plasma phosphorus despite no increase of urinary phosphorus argues against the presence of a fixed renal tubular phosphorus leak in absorptive hypercalciuria, at least in the fasting state. Patients differed from controls not only with respect to urinary calcium, but also with respect to fasting absolute and fractional urinary excretion of sodium and chloride. Increased fractional urinary sodium was found both in normotensive and hypertensive patients. Since tubular reabsorption of phosphorus and the setting of fasting plasma phosphorus depend, among other factors, on tubular handling of sodium, the finding may be relevant for the genesis of transient fasting hypophosphataemia in absorptive hypercalciuria.

Adult↗
PubMed1980

Hyperlipoproteinemia in renal insufficiency.

In uremic patients, hyperlipoproteinemia is common, but its role as a risk factor in atherogenesis remains controversial. The main abnormality appears to be diminished catabolism of lipoproteins in the face of unchanged or low hepatic synthesis. The relation of diminished catabolism to reduced postheparinlipolytic activity and selective deficiency of hepatic triglyceride lipase remains to be established. Hyperlipoproteinemia in uremic patients, most commonly of the type IV variety, responds to dietary methods (reduction of carbohydrate content, increase in P/S ratio) or pharmacological intervention. Guidelines for therapy remain controversial in view of the uncertainty about the pathogenic role of hyperlipoproteinemia in atherogenesis.

Animals↗
PubMed1980

Hemofiltration and plasma dopamine beta-hydroxylase activity.

Plasma dopamine beta-hydroxylase (DBH) activity was studied in control patients (n = 70), in patients on maintenance hemodialysis (n = 79) and in patients on maintenance hemofiltration (n = 19). DBH activity was significantly lower in patients on hemodialysis (32.4 +/- 20.6 IU) and hemofiltration (32.8 +/- 29.7 IU) than in control individuals (50.0 +/- 29.3 IU). Sequential measurements of DBH in patients on maintenance hemofiltration failed to show a fall of plasma DBH with time. 7 patients were studied during one session of hemodialysis and one session of hemofiltration. External fluid balance was identical. The change of DBH during hemodialysis and hemofiltration was not significantly different. Such rise of DBH as occurs may entirely be accounted for by hemoconcentration.

Adult↗
PubMed1980

Vocational rehabilitation in dialyzed patients. A cross-sectional study.

The physicians in charge of 15 German hemodialysis units furnished data on 713 dialysis patients. Data relating to the vocational status were examined for 612 patients aged 60 years or below. It was found that the current working status varies with psychological and social factors. The data show that the vocational status is importantly influenced by the premorbid profession, the level of schooling and by the conditions of the local labor market. With the exception of severe complications or secondary diseases, no relation existed between the somatic state and the current working status. As assessed by the physicians in charge, most dialysis patients were able to work part time, but unable to work full time. Lack of facilities for, or financial disincentives against, part time employment are felt to be the single most important obstacle to vocational rehabilitation of dialysis patients.

Cross-Sectional Studies↗
PubMed1980

Does parathyroid hormone play a role in lipid metabolism?

PTH activates hormone-sensitive lipolysis in adipose tissue by an adenylate cyclase mechanism. Effects on lipoprotein synthesis and catabolism are conceivable, but have not been studied in detail so far. Information on serum lipids in primary and secondary hyperparathyroidism is conflicting. Some authors find an increase of serum lipids upon administration of PTH and in patients with primary hyperparathyroidism, while others find a decrease of serum cholesterol and serum triglycerides which reverts to normal upon parathyroidectomy in patients with primary hyperparathyroidism. In experimental models of uremia, PTH clearly plays a permissive role for the development of uremic hyperlipemia. In PTX uremic animals, hyperlipoproteinemia is less marked than in PT-intact uremic animals, but serum lipids are still higher in PTX uremic animals than in nonuremic PT-intact animals. This would indicate that hyperlipemia is caused by PTH-independent mechanisms but is intensified by the presence of secondary hyperparathyroidism. The role of PTH in the hyperlipoproteinemia of uremic patients has not been clarified so far.

Adenylyl Cyclases↗
PubMed1980

The effect of 1,25 (OH)2D3 on bone mineralization: ultrastructural studies in patients with renal osteodystrophy.

The acute effects (15-50 days) of 1,25(OH)2D3 (0.5-2 microgram/day) on the histological, fluorescence-microscopical and ultrastructural appearance of mineralizing osteoid in iliac crest spongiosa were studied in 6 uremic patients on maintenance hemodialysis. While there was a marked decrease on endosteal fibrosis and osteoclast counts, volumetric and surface densities of osteoid continued to stay elevated during the observation period. The number of osteoid seams with tetracycline double label increased in 4/6 patients but no such seams appeared in 2 patients who had shown only nonlabeled seams with diffuse staining of osteoid prior to therapy. In studies with transmission electron microscopy, the interface between non-mineralized osteoid and mineralized bone was irregularly outlined and broad. In contrast to normals, coarse mineral deposits were widely scattered in the nonmineralized osteoid. The mineral deposits had two different appearances, presumable depending on the plane of section relative to the direction of collagen fiber bundles: patches of microcristalline deposits encircling perpendicularly cut non-mineralized collagen bundles and needle- or plate-shaped crystals following the striation pattern of collagen fibers. The findings point to close interaction between the pattern of mineral deposition and collagen texture. The latter was highly irregular (woven) in all uremic patients. Mineral deposits were in part normal and in part highly abnormal in texture, the latter particularly in sites with irregular collagen texture. Upon therapy, no consistent change of the ultrastructure of the mineralizing osteoid/bone interface was observed by transmission or scanning and electron microscopy.

Adult↗
PubMed1980

Abnormal bone histology in idiopathic hypercalciuria.

Bone histology was evaluated in iliac creast biopsies of 15 patients with idiopathic hypercalciuria of the hyperabsorptive type and recurrent calcium oxalate stone formation. The biopsies were studied using quantitative histomorphometric analysis of undecalcified sections and fluorescent microscopy after double tetracycline labeling. Uring calcium and cAMP excretion were measured under basal conditions and after oral administration of calcium phosphate. Absorptive hypercalciuria was defined as a urinary excretion of calcium of more than 15 meq/24 h and/or a urinary ratio of Ca to Cr of more than 0.2, with a fall in the Ca to Cr ratio of more than 40% after the administration of oral cellulose phosphate. Osteoclastic bone resorption was normal or low in all patients and did not show any recognizable correlation with urinary calcium or urinary cAMP. All but one of the patients showed an increase in the fraction of inactive osteoid. Total osteoid was increased in 60% of the patients. Osteoblastic activity was significantly lower in the patient than in the control subjects. The fraction of mineralizing osteoid seams (i.e. seams with a tetracycline double labeling pattern), was diminished in all patients and the mean rate of apposition of bone matrix was decreased. These findings point to a diminished amount of bone matrix produced by individual osteoblasts and to a delay or cessation of terminal (secondary) mineralization of osteoid seams.

Adult↗
PubMed1980

Perforation of the nasal septum in patients with renal failure.

Spontaneous perforation of the nasal septum was observed in 8 out of 104 patients (74 on maintenance hemodialysis; 30 after cadaveric renal transplantation). All patients showed a round or oval defect of the non-osseous septum, which was accompanied by marked atrophic rhinitis. Epistaxis was common in uremic patients in general and was also present in 5 patients with septal perforation, but otherwise the defect was hardly associated with any symptoms. Various factors may play a role in the pathogenesis of this lesion; local trauma from nasal catheters postoperatively; impaired mucosa cell proliferation; disturbed innervation of the vessels in the nasal septum due to polyneuropathy of the autonomous nervous system; ischemia secondary to arteriolar narrowing.

Adolescent↗
PubMed1980

Inhibition of Na+,K+-stimulated ATPase in the cochlea of the guinea pig. A potential cause of disturbed inner ear function in terminal renal failure.

The frequent occurrence of sensorineural hearing loss in patients with chronic renal insufficiency prompted us to study the influence of chronic renal failure upon Na+,K+-ATPase in the inner ear of guinea pigs. Na+,K+-activated ATPase was defined as the ouabain-sensitive part of total ATPase, the activity of which was obtained in the presence of sodium, potassium and magnesium. A significant reduction of Na+,K+-activated ATPase was found in the inner ear of uremic animals. Such inhibition could be demonstrated as early as 12 hours after subtotal nephrectomy. An inverse correlation was found between serum creatinine levels and Na+,K+-activated ATPase. A similar inhibition of Na+,K+-activated ATPase in uremia is also found in other tissues (erythrocytes, renal tubules, intestinal mucosal cells, sarcolemma). Na+,K+-ATPase in the cochlea plays a key role in the maintenance of cochlear cationic gradients. It is suggested that inhibition of this enzyme system may contribute to the inner ear dysfunction in uremia.

Animals↗
PubMed1980

Acute flank pain in dialysed patients. Demonstration of hydronephrosis by computer tomography.

Repeated episodes of acute renal flank pain were observed in a uremic patient on maintenance hemodialysis. Computer tomography during the acute attack repeatedly showed unilateral hydronephrosis which always subsided after passage of stones. X-ray failed to visualize the non-radioopaque stones and sonography was non-contributory. The stones consisted of organic matrix and contained protein material. The present observation documents that computer tomography is valuable in establishing the diagnosis of acute ureteral obstruction resulting from non-radioopaque renal stones in dialysed patients with contracted kidneys.

Adult↗
PubMed1980

Azotemic osteodystrophy - indications for intervention.

Because the pathogenetic mechanisms leading to azotemic osteodystrophy are incompletely understood, prophylactic and therapeutic intervention must necessarily be less than satisfactory. There is no proof that prophylactic measures, e.g. phosphate binders and vitamin D (metabolites) are beneficial in incipient renal failure but measures to prevent secondary hyperparathyroidism appear reasonable. In advanced renal failure, oral phosphate binders, administration of calcium salts and vitamin D (metabolites) are effective in returning serum chemistry towards normal, but considerably less effective in restoring normal bone histology. Hemodialysis, using adequate calcium concentrations in the dialysate, permits one to normalize predialytic calcium and phosphorus levels, and maintain calcium balance in the majority of patients. Hemodialysis does not, however, prevent hyperparathyroidism and the various types of metabolic bone disease. Symptomatic azotemic osteodystrophy increases in frequency and severity with increasing duration of dialysis. While osteitis fibrosa responds favorably to vitamin D and several vitamin D metabolites, osteomalacia is considerably less responsive. It remains unknown whether this is due to low bone turnover, absence of some crucial unknown vitamin D metabolite, or involvement of non-vitamin D-related factors. Parathyroidectomy for uncontrollable hyperparathyroidism is required only in a minority of patients.

Bone Diseases↗
PubMed1980

Nitrogen metabolism and growth in experimental uremia.

Growth in length, weight gain and gain of body nitrogen were compared in rats with stable long-term uremia (U) resulting from subtotal two-stage nephrectomy with irradiation of residual parenchyma, in sham-operated pair-fed control rats (PFC) and in ad libitum fed control rats (LC). Growth in length and weight gain were considerably lower in U than in LC rats, reflecting mainly diminished intake of food in uremia. However, they were also significantly lower in U than in PFC despite identical intake of food, pointing to a specific adverse effect of uremia on growth. Whole body dry matter, whole body nitrogen and weight of a reference muscle (triceps surae) were significantly lower in U than in PFC animals, showing that dietary nitrogen and/or energy are less efficiently utilized for protein synthesis in U animals. Diminished net nitrogen retention was paralleled by increased urinary nitrogen loss (excretion of urea, alpha-amino nitrogen, protein, and creatinine). Within the precision of the method used, no significant difference of oxygen consumption between U and PFC animals could be demonstrated. The plasma amino acid pattern was deranged and the tyrosine/phenylalanine ratio was decreased despite no change in hepatic phenylalanine hydroxylase. The findings document increased nitrogen and/or energy cost of growth in rats with stable chronic uremia; this finding agrees with previous observations of disturbed protein metabolism and hypercatabolism in experimental uremia.

Amino Acids↗
PubMed1980

Acquired renal cysts in uremic patients--in vivo demonstration by computed tomography.

The development of renal cysts appears to be a common feature of terminal renal failure in patients with diffuse renal parenchymal disease. In the present investigation, the kidneys of 13 patients with terminal renal failure but not receiving dialysis, of 14 patients on maintenance hemodialysis and of 4 patients after renal transplantation (patients' own kidneys) were studied by computed tomography. Cystic lesions in the contracted renal parenchyma could be demonstrated by computed tomography in 7/13 non-dialyzed patients with terminal renal failure, in 11/14 patients on maintenance hemodialysis as well as in 3/4 transplanted patients (patients' own kidneys). Both solitary cysts (10/21 patients) and multiple cysts (11/21 patients) were observed. The size varied from 0.5 cm (barely detectable) to 3 cm in diameter. Such cysts could also be demonstrated at autopsy. Possible clinical complications include spontaneous retroperitoneal hemorrhage, macrohematuria, matrix stone formation and formation of benign or malignant papilloma. The present study shows that computed tomography allows the detection of acquired renal cysts in uremic patients in vivo. The cysts appear prior to dialysis, seem to increase in frequency during dialysis and do not disappear after transplantation. The lesions can be distinguished from multicystic or polycystic disease.

Adult↗
PubMed1979

[Vitamin D metabolism in kidney insufficiency: disorders of an endocrine regulatory zone].

The vitamin metabolite 25(OH)D is transformed into the active secosterole 1.25(OH)2D3 in the proximal tubular epithelium of the kidney. This transformation is disturbed in patients with renal insufficiency. However, this review shows that presumably not all vitamin D dependent disturbances in patients with renal insufficiency are explicable merely as the consequence of reduced renal synthesis of 1.25(OH)2D3 secondary to nephronal loss. In incipient renal failure, vitamin D dependent functions (calcemic action of PTH, intestinal absorption of Ca) are disturbed. Yet, circulating 1.25(OH)2D3 levels are slightly elevated. This finding is compatible with an inadequate response of the renal 1-alpha-hydroxylase system to activating stimuli (hyperparathyroidism, hypocalcemia, fasting hypophosphatemia) and/or end-organ resistance to the action of 1.25(OH)2D3. Osteomalacia in renal insufficiency cannot entirely be explained as the consequence of a reduction of the serum-concentration of any of the known vitamin D metabolites [25(OH)D3; 1.25(OH)2D3; 24.25(OH)2D3]. The relatively poor response of osteomalacia of uremic patients to the administration of 1.25(OH)2D3 leads to the question of whether other vitamin D metabolites or non-vitamin D related factors are important in its genesis. Critical information is lacking with respect to 1.25(OH)2D3 receptors, post receptor events and interaction between vitamin D metabolites and PTH in bone cells of such patients. A specific action of 1.25(OH)2D3 on longitudinal growth of uremic children has been described. However, several clinical and experimental studies failed to provide evidence of normalization of growth by 1.25(OH)2D3 and failed to show differences in this respect between vitamin D and 1.25(OH)2D3. Currently, it remains undecided whether vitamin D metabolites affect PTH secretion, and if so which vitamin D metabolite is involved. Clarification of this problem is of paramount importance for the therapeutic suppression of the parathyroids of uremic patients. Vitamin D metabolites play an important role in some organ functions unrelated to homeostasis of Ca-Pi-metabolism (e.g. muscle, testis, pancreas, etc). The loss of such function is of potential importance in the genesis of the uremic syndrome and its imcomplete reversal by hemodialysis.

Absorption↗