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Biomedical subjects

L Schaefer

Publications and source records attributed to L Schaefer.

At least 37 records · Page 2Linked to original sources
PubMed1994

A YAC-based binning strategy facilitating the rapid assembly of cosmid contigs: 1.6 Mb of overlapping cosmids in Xp22.

We have applied a yeast artificial chromosome (YAC)-based cosmid isolation and binning strategy to convert a YAC contig in Xp22 into 1.6 Mb of overlapping cosmids. This strategy is based on the screening of a high-density arrayed X chromosome-specific cosmid library with large YAC-derived restriction fragments and entire YAC probes. Cosmids selected in this way were gridded on dot blots and further mapped into bins defined by the overlap intervals of the YACs and YAC fragments. This rapid binning of cosmids simplified the subsequent assembly of cosmid contigs by restriction fingerprint hybridization. In total, we identified 139 cosmids spanning the entire 1.6 Mb region with a minimal overlap set of 53 clones. These cosmids were assigned to 17 bins and 9 contigs. One of the contigs is 665 kb in length and is one of the largest uninterrupted cosmid contigs in humans reported to date. The gaps between the contigs are minor and, together, they represent less than 7% of the region covered. Two previously identified genes are contained in these cosmids, the gene for amelogenin (AMG) and the recently isolated putative chloride channel gene CICN4. In addition, two disease loci have been mapped to this region: X-linked ocular albinism type 1 (OA1) and the microphthalmia with linear skin defects (MLS) syndrome. The assembly of the cosmid maps allowed us to determine the size of the deletion intervals for these two loci, which were estimated to be 110 kb for OA1 and 570 kb for MLS.(ABSTRACT TRUNCATED AT 250 WORDS)

Albinism, Ocular↗
PubMed1994

Urinary excretion of cathepsin B and cystatins as parameters of tubular damage.

The urinary excretion of the lysosomal hydrolases cathepsin B and beta-N-acetylglucosaminidase (beta-NAG) was compared with the tubular activities of these enzymes in remnant kidneys 16 weeks after subtotal nephrectomy (5/6 NX) or unilateral nephrectomy (UNX), as well as in kidneys from diabetic rats. In addition, the urinary excretion of the low-molecular weight protein cystatins, inhibitors of lysosomal cathepsins, was also followed in these animals. The urinary excretion of cathepsin B and beta-NAG was significantly enhanced in all three models of renal disease. The highest excretion rates for these enzymes were found in diabetic animals (cathepsin B: 4-fold; beta-NAG: more than a 10-fold increase over respective controls). In terms of tubular enzyme activities, tissue activities of both hydrolases were reduced in the remnant kidney after 5/6 NX, while in UNX and diabetes only cathepsin B activity was decreased. The urinary excretion of cystatins was enhanced in all three animal models, particularly in 5/6 nephrectomized rats, where a 40-fold increment over control animals was observed. Taken together, these findings indicate that there was severe tubular damage in the remnant kidney after 5/6 NX (reduced tubular enzyme activities, enzymuria and severely compromised tubular protein reabsorption). Furthermore, considerable enzymuria and disturbed protein reabsorption in early diabetes suggest tubular dysfunction before signs of glomerular damage become evident.

Acetylglucosaminidase↗
PubMed1994

Anaphylactoid reactions during hemodialysis.

Taken together, with the wide-spread use of ACE-inhibitors within the dialysis population, a novel type of hypersensitivity reaction has been recognized, which may occur not only during hemodialysis but also during other forms of extracorporeal therapy. From the data available today, it seems that such reactions are triggered by negatively charged biomaterials which are capable to activate factor XII, leading among others to the generation of bradykinin. Normally this kinin is rapidly degraded by the serine proteinase kininase II. Thus, in the absence of ACE inhibitors plasma bradykinin levels increase only moderately during dialysis with AN69 membranes and clinically most patients are free of symptoms. However, once kininase II, which is identical with converting enzyme, is blocked by ACE inhibitors, plasma levels may increase more than 100-fold and patients will suffer from severe anaphylaxis. Based on our present knowledge, the consequences for clinical medicine are straightforward. It is mandatory to avoid the combination of negatively charged membranes or other biomaterials with ACE inhibitor therapy. As there are many different membranes available, this should be no unsurmountable problem in the setting of clinical hemodialysis.

Anaphylaxis↗
PubMed1994

Effectiveness and safety of recombinant human erythropoietin (r-HuEPO) in the treatment of anemia of chronic renal failure in non dialysis patients. European Multicentre Study Group.

Seventy-five non-dialized patients with chronic renal failure (CRF) and severe renal anemia were enrolled in a study, receiving r-HuEPO subcutaneously thrice weekly for 6 months. In 64 patients (85%) 7 weeks of treatment with a weekly dose of 158 U/kg were required to achieve Hb concentrations within the target range of 10 to 12 g/dl. Of the 11 patients (15%) who failed to achieve the target Hb range, none were considered to be non-responders as they were excluded for unrelated reasons prior to week 16 (8 cases), or were iron deficient (2 cases), or had bleeding complications (1 patient). Maintaining the Hb concentration at a level of 10.5 g/dl required a mean r-HuEPO dose of 92 U/kg per week. Adverse events were generally mild or moderate. The most commonly reported were hypertension (8%), viral infection/including flu-like syndrome (7%), nausea (7%), and dizziness (5%). Statistically significant increases in mean creatinine concentrations observed after 12 and 24 weeks were most likely due to the progression of renal disease. These results confirm that 50 U/kg of r-HuEPO given 3 times per week subcutaneous provide a safe and effective therapy for anemic predialysis patients.

Adolescent↗
PubMed1993

A high resolution deletion map of human chromosome Xp22.

We have developed a 32-interval deletion panel for human chromosome Xp22 spanning about 30 megabases of genomic DNA. DNA samples from 50 patients with chromosomal rearrangements involving Xp22 were tested with 60 markers using a polymerase chain reaction strategy. The ensuing deletion map allowed us to confirm and refine the order of previously isolated and newly developed markers. Our mapping panel will provide the framework for mapping new sequences, for orienting chromosome walks in the region and for projects aimed at isolating genes responsible for diseases mapping to Xp22.

Base Sequence↗
PubMed1993

The genes for X-linked ocular albinism (OA1) and microphthalmia with linear skin defects (MLS): cloning and characterization of the critical regions.

We have used cell lines from patients with deletions and translocations involving the Xp22 region to map the genes for two X-linked disorders, ocular albinism type 1 (OA1) and microphthalmia with linear skin defects (MLS). Using existing and newly isolated DNA markers, the map position within Xp22 of key patient breakpoints, defining the boundaries of the genomic regions involved in these disorders (the critical regions), has been precisely determined. A 2.6 Mb yeast artificial chromosome (YAC) contig, spanning the critical regions for these two disorders, was assembled. Detailed long-range restriction analysis of the contig established the sizes of the critical regions to be 200 kb for OA1 and 800 - 925 kb for MLS. Ten potential CpG-islands, representing candidate sites for genes, have been mapped within the 2.6 Mb region. Our data should greatly facilitate efforts aimed at cloning the genes for these developmental defects.

Albinism, Ocular↗
PubMed1993

Role of bradykinin in anaphylactoid reactions during hemodialysis with AN69 dialyzers.

In vitro experiments have related anaphylactoid reactions in patients treated with angiotensin-converting enzyme (ACE) inhibitors during dialysis with AN69 membranes to excessive bradykinin generation using this negatively charged dialysis membrane. In the present clinical trial plasma bradykinin levels were followed during the early phase of dialysis in 10 patients, not being treated with ACE inhibitors, using AN69, cuprophane, and polysulfone membranes. Bradykinin was measured after extraction by radioimmunoassay. During this study one episode of anaphylaxis occurred during dialysis with the AN69 membrane. Blood samples were collected during the first 5 min of the adverse reaction and showed a more than 100-fold increase in the venous effluent of the AN69 dialyzer (baseline 40 +/- 3 vs. 4,900 +/- 130 fmol/ml after 5 min). Even though none of the patients received ACE inhibitors, there were 4 more asymptomatic individuals who displayed a more than two-fold increase in their plasma bradykinin concentrations in the venous effluent of the AN69 dialyzer. When these patients were treated either with cuprophane or with polysulfone dialyzers, no significant bradykinin formation was detected, nor were there any adverse events. Taken together, these findings show that anaphylactoid reactions with the AN69 membrane are due to excessive bradykinin generation which even may occur in the absence of ACE inhibitors.

Acrylic Resins↗
PubMed1992

Effect of beta 2-microglobulin on immunoglobulin production.

Chronic renal failure patients display high serum levels of beta 2-microglobulin (beta 2-M) and a pronounced defect in immunoglobulin production. In this light, the present study was conducted to investigate whether beta 2-M might influence the rate of antibody synthesis. Peripheral blood mononuclear cells (PBMC) from healthy subjects were cultured in the presence of beta 2-M (80 mg/l) for 7 days. Immunoglobulin concentrations were measured by ELISA-techniques in culture supernatants. Basal IgM levels were 390 +/- 10 ng/ml and increased to 940 +/- 216 ng/ml in the presence of beta 2-M. After PWM stimulation, IgM concentrations were 2654 +/- 614 ng/ml without and 3750 +/- 914 ng/ml with beta 2-M. IgG and IgA production by PBMCs was not influenced by beta 2-M in the culture medium. Likewise, the generation of beta 2-M by PBMCs was unchanged in the presence of exogenous beta 2-M in the medium. In terms of clinical relevance, serum beta 2-M levels of 28 uremic patients were correlated with capacity of their PBMCs for immunoglobulin production in vitro. However, there was no apparent correlation between beta 2-M serum levels and immunoglobulin synthesis in vitro. Taken together, beta 2-M seems to have a stimulatory effect on IgM synthesis in vitro. Whether this has some clinical meaning in patients with chronic renal failure remains to be investigated.

Adult↗
PubMed1992

Effect of dietary protein on glomerular proteinase activities.

Recent studies suggest that proteolytic enzymes are involved in the degradation of extracellular matrix components of the renal glomerulus. In the present study, the effects of feeding 3 different protein diets on glomerular cysteine proteinase and metalloproteinase activities to healthy rats for 6 weeks were examined. The diets contained 5, 20, or 60% casein and were made isocaloric by starch. On sacrifice, the glomeruli were isolated by differential sieving. Proteolytic activities were measured using fluorogenic substrates and were expressed per glomerular DNA content. Body weight was virtually unchanged by the amount of protein ingested, whereas kidney weight was closely correlated with dietary protein content (5%: 1,625 +/- 324; 20%: 2,110 +/- 326; 60%: 2,705 +/- 910 mg). Activity of cathepsin B, the most abundant cysteine proteinase in the glomerulus, decreased with protein loading (5%: 1,498 +/- 110; 20%: 1,321 +/- 82; 60%: 914 +/- 84 pmol/min/micrograms DNA). The same pattern emerged with cathepsin L (5%: 869 +/- 71; 20%: 846 +/- 70; 60%: 517 +/- 83 pmol/min/micrograms DNA) and cathepsin H (5%: 498 +/- 45; 20%: 478 +/- 55; 60%: 330 +/- 39 pmol/min/micrograms DNA). The differences between the 20 and 60% groups were statistically significant for all 3 cathepsins measured. The intraglomerular activity of the metalloproteinase collagenase declined significantly with the amount of protein ingested (5%: 233 +/- 14; 20%: 189 +/- 13; 60%: 137 +/- 11 microU/micrograms DNA). Gelatinase activity also fell as protein intake increased (5%: 183 +/- 18; 20%: 115 +/- 10; 60%: 94 +/- 11 F/micrograms DNA).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Role of glomerular proteinases in the evolution of glomerulosclerosis.

Recent studies suggest that proteolytic enzymes located within the glomerulus are involved in the degradation of extracellular matrix components. In the present investigation glomerular proteinase activities were followed in a variety of non-immune-mediated renal diseases as well as during different dietary manipulations. Azocaseinolysis was significantly reduced in the obese Zucker rat compared with lean littermates (pH 5.4:8.9 +/- 0.4 vs 11.4 +/- 0.7; pH 7.4:5.8 +/- 0.7 vs 9.3 +/- 0.6 arb. U/mg protein). When the glomerular proteolytic capacity was measured in old rats, again a significant decline in proteolysis was observed (pH 5.4:9.8 +/- 0.8 vs 17.7 +/- 0.8; pH 7.4:6.4 +/- 0.7 vs 11.7 +/- 0.5 arb. U/mg protein). In Goldblatt hypertensive rats the unclipped kidney, which is exposed to high blood pressure, revealed lower glomerular azocaseinolytic activity compared with the contralateral clipped kidney (pH 5.4:8.1 +/- 0.4 vs 12.9 +/- 0.5 arb. U/mg protein). In parallel, the cathepsin B content was also diminished in glomeruli from kidneys exposed to hypertension. When proteinases were followed in glomeruli from intact kidneys of rats fed protein-modified diets (fraction of casein 0.05, 0.20 or 0.60) a significant fall in the activities of cysteine proteinases, e.g. cathepsin B (casein 0.05:1,498 +/- 110 vs casein 0.60:914 +/- 84 microU/micrograms DNA), as well as metalloproteinases, e.g. collagenase (casein 0.05:233 +/- 14 vs casein 0.60:137 +/- 11 microU/micrograms DNA), occurred. These data indicate that in both early and late stages of glomerulosclerosis, proteolytic activities within the glomerulus tend to be reduced, which could allow extracellular matrix accumulation. Moreover, changes in dietary protein intake resulted in profound alterations of glomerular proteinases.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1990

Perception of unilateral weightbearing during unilateral and bilateral upright stance.

To compare the effect of stance (unilateral vs bilateral) and of weightbearing target (25%, 50%, 75%) on error in weightbearing perception, two groups, unilateral and bilateral, of 30 comparable subjects were tested. Weightbearing was measured while subjects stood on digital scales; bilateral stance was accomplished using two scales, and unilateral stance was accomplished using a walker and a single scale. The subject's error in perceiving weightbearing at each target level was assessed by taking the absolute value of the target percent weightbearing minus the mean actual percent weightbearing. The mean errors at the 25, 50 and 75% targets were 6.5, 3.2, 17.6% for the unilateral group and 3.1, 1.4, 3.8% for the bilateral group. A two-way analysis of variance indicated the magnitude of error differed between groups and target levels, with a greater over-all error displayed by the unilateral weightbearing group. Our results suggest that adults are less accurate in judging weightbearing while standing on one, rather than on two, lower extremities. Clinicians should not expect patients to follow accurately instructions to weightbear at a specific percentage of full weight, particularly when using an assistive device to adjust weightbearing.

Adult↗
PubMed1988

Evaluation of Abbott CMV-M enzyme immunoassay for detection of cytomegalovirus immunoglobulin M antibody.

The Abbott CMV-M enzyme immunoassay (EIA) for the qualitative determination of immunoglobulin M (IgM) antibody to cytomegalovirus in human serum was compared with the indirect fluorescent-antibody (IFA) test on 338 human serum specimens. Discordant specimens were evaluated by IFA following isolation of IgM fractions. Discordant specimens remaining after IFA testing were evaluated by an IgM-specific EIA (CYTOMEGELISA M; M.A. Bioproducts). After resolution of discordant specimens, the CMV-M EIA was 94.7% sensitive and 99.1% specific.

Antibodies, Viral↗
PubMed1988

Ability of TESTPACK ROTAVIRUS enzyme immunoassay to diagnose rotavirus gastroenteritis.

TESTPACK ROTAVIRUS, a simple 10-min enzyme immunoassay, was compared with electron microscopy and Pathfinder enzyme immunoassay on feces from 172 patients of various ages with gastroenteritis. The percent sensitivities and specificities before blocking with antiserum were as follows: TESTPACK, 100% sensitivity and 99% specificity; Pathfinder, 95% sensitivity and 98% specificity. After blocking, the sensitivity and specificity, respectively, were 100% and 100% for TESTPACK and 95% and 99% for Pathfinder. TESTPACK ROTAVIRUS was more sensitive, but not significantly, than Pathfinder (P greater than 0.1) and the direct electron microscopy technique (P greater than 0.1).

Feces↗
PubMed1980

[Percutaneous antegrade pyelography with a fine needle].

In 15 patients the percutaneous antegrade pyelography with thin needle was performed for the clarification of a mute kidney and a urinary stasis kidney. The two groups of diseases could not be clarified by means of the methods of the conventional urography. The retrograde pyelography was intentionally given up. By means of the percutaneous antegrade pyelography we could clarify a mute kidney in 8 cases and in 4 cases a urinary stasis kidney. In 3 cases with mute kidney we did not succeed in the demonstration of the renal calyces. No complications appeared. In strong indication the percutaneous antegrade pyelography is an evident diagnostic measure by great security, little stress for the patient and little cost. Despite modern investigation methods including sonography and computer tomography is referred to the fields of application of the percutaneous antegrade pyelography.

Biopsy, Needle↗