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Biomedical subjects

M Klein

Publications and source records attributed to M Klein.

At least 163 records · Page 9Linked to original sources
PubMed1999

Preconditioning of donor livers with prostaglandin I2 before retrieval decreases hepatocellular ischemia-reperfusion injury.

BACKGROUND: Prostaglandins have been shown to protect against a variety of liver insults, including ischemia-reperfusion injury. Decreased graft injury and improved survival have been demonstrated in animal studies of liver transplantation after donor pretreatment with prostaglandin before organ retrieval. This potential clinical application has not been examined in human subjects. PATIENTS AND METHODS: One hundred and six liver donors were randomly assigned to receive either prostaglandin I2 (epoprostenol, 500 microg intravenous bolus) immediately before cold perfusion or no drug as control. Donor and recipient characteristics were recorded, and liver function tests were monitored after transplant to assess the effect of epoprostenol on graft injury. RESULTS: Donor pretreatment with epoprostenol significantly improved the rapidity and homogeneity of graft reperfusion. Epoprostenol pretreatment also significantly reduced peak values of transaminases after transplantation: serum glutamic-pyruvic transaminase, control (851+/-121 international units [IU]/L) and epoprostenol (463+/-78 IU/L); serum glutamic-oxalaacetic transaminase, control (870+/-127 IU/L) and epoprostenol (463+/-78 IU/L); serum glutamate dehydrogenase, control (458+/-95 IU/L) and epoprostenol (170+/-30 IU/L); P<0.01 for all, by t test. Serum levels of bilirubin and alkaline phospatase were not significantly altered by donor pretreatment with epoprostenol. CONCLUSIONS: Reduction of ischemia-reperfusion injury by administration of epoprostenol before graft retrieval may have important applications in liver transplantation. Further studies are required to establish the mechanism of this effect and to define its precise role in clinical practice.

Adolescent↗
PubMed1999

Identification of a splice variant of neutrophil collagenase (MMP-8).

We have identified a splice variant of human neutrophil collagenase (MMP-8) transcript (MMP-8alt) that has a 91 bp insertion between codons for amino acid residues 34 and 35 of MMP-8 cDNA. This splice variant encodes an open reading frame for a 444 residue protein, lacking a secretory signal sequence. Our data suggested that, as opposed to the original MMP-8, the translation product of MMP-8alt is not a secreted protein; nevertheless, it is enzymatically active. Further studies aimed at identifying the physiological substrates of MMP-8alt protein may lead to uncover novel roles it plays in cellular physiology.

Alternative Splicing↗
PubMed1999

Combining DNA and protein vaccines for early life immunization against respiratory syncytial virus in mice.

Early life responses to respiratory syncytial virus (RSV)-F DNA and RSV-F protein immunization were studied in murine models of neonatal immunization. RSV-F DNA induced similar antibody (Ab) responses, antigen-specific IFN-gamma production and cytotoxic T lymphocyte (CTL) responses in 1-week-old and adult BALB / c mice. In contrast, RSV-F protein induced much higher IL-5 responses in early life. Both vaccines elicited Ab and CTL responses in spite of maternal Ab, but with distinctive kinetics. Sequential RSV-F DNA priming / protein boosting primed 1-week-old mice for RSV-F-specific CTL responses, reduced IL-5 production and enhanced Ab responses. In contrast, IL-5 exceeded IFN-gamma responses when young mice were primed with protein and boosted with DNA. Last, when protein and DNA immunization were combined, a single vaccine dose induced early Ab responses, preferential IL-5 responses but strong CTL responses. Sequential or combined DNA / protein immunization thus represent interesting strategies for early life immunization.

Animals↗
PubMed1999

[Prosthetic management of tumor-induced nasal defects].

Reconstructive plastic surgery is not always possible or advisable for nasal defects following tumor resections. Facial prostheses offer an alternative therapy. Since 1991, 37 patients with nasal defects after tumor surgery were treated in the Berlin Center of Facial Prostheses: 28 received "soft" silicone facial prostheses and 9 "solid" polymethylmetacrylate facial prostheses. In 35 patients protheses were bone-anchored: Brånemark implants were used in 12 patients and an Epitec frame construction in 23 patients. Glue-on prostheses were applied to only two patients. No intraoperative complications occurred at implant insertion. During following visits only minor inflammations were observed around implants and were treated locally. The implant success rate was 78% for the Brånemark implants (89.7% in non-radiated areas and 50% in radiated areas) and 100% in radiated and non-radiated areas for the Epitec system. Our investigation shows that given the right indication, the bone-anchored facial prosthesis is safe, cosmetically acceptable, uncomplicated and not stressful for the patient.

Aged↗
PubMed1999

[Bilateral rehabilitation with an implant-anchored orbital prosthesis].

From the aesthetic point of view, a patient can be completely rehabilitated after the loss of an eye with the insertion of an artificial eye made of glass. If the delicate structures of the eyelids have been severely damaged, however, or if the eye socket does not provide adequate retention for an eye prosthesis, rehabilitation becomes more difficult, and sometimes cannot be achieved with a cosmetically satisfactory result. In such cases, a facial prosthesis offers an alternative solution. Stable retention can be ensured with craniofacial implants. Single-sided rehabilitation by this method is quite common, but bilateral treatment is a rarity. We report on the prosthetic rehabilitation of a patient after exenteration on both sides due to retinoblastomas.

Adult↗
PubMed1999

The role of p21ras in pancreatic neoplasia and chronic pancreatitis.

K-ras mutations have been detected in both ductal cell carcinoma and intraductal papillary mucinous tumor (IPMT) of pancreas. The frequency of this mutation in ductal cell carcinoma is high, whereas in IPMT, it is variable. It has been suggested that the relatively high frequency of this mutation in ductal cell carcinomas compared with IPMT may account for the differences in biological behavior between these tumor types. More recently, the significance of K-ras mutations in pancreatic tissue has been questioned with the demonstration of this mutation in nonneoplastic pancreata. The current study aims to estimate the relative frequency and evaluate the biological significance of K-ras gene mutations in these neoplasms by performing polymerase chain reaction (PCR) assays of microdissected areas of IPMT, ductal cell carcinomas, and resected chronic pancreatitis. The study also investigates whether alterations of p21ras occur in K-ras mutation-negative cases by using immunohistochemical staining for K-, N- and H-ras. K-ras codon 12 mutations were found almost as frequently in IPMT (71%) as in ductal cell carcinomas (78%). They were also associated with the earliest morphological lesion, flat mucinous change. This mutation also was detected in 42% of cases of chronic pancreatitis. Expression of p21ras was found to correlate closely with K-ras mutation status in IPMT and ductal cell carcinoma. Negative staining for pan-ras, H-ras, and N-ras in cases with wild-type K-ras genes suggests that alternative routes of ras gene alteration are not operative in IPMT or ductal carcinoma. The findings suggest that K-ras activation is frequently associated with both IPMT and ductal cell carcinoma. Its high prevalence in nonneoplastic pancreata suggests that it is also associated with self-limited morphological lesions of the pancreas that do not progress to malignancy.

Aged↗
PubMed1999

Immunological properties of plaque purified strains of live attenuated respiratory syncytial virus (RSV) for human vaccine.

Respiratory syncytial virus (RSV) causes severe lower respiratory tract disease in infants, young children, and the elderly. Efforts to develop satisfactory live or inactivated vaccines have not yet been proven successful. Our research focuses on the development of four purified live attenuated RSV sub-type A human vaccine clones. Temperature sensitive (ts) and attenuated purified clones of either cold-adapted (ca) RSV or high-passage (hp) RSV were administered intra-nasally (i.n.) to BALB/c mice and tested for immunogenicity. All four clones produced significant anti-RSV F IgG2a and IgG1 titres in the sera of mice, RSV-specific neutralizing titres higher than those produced by their wild-type progenitor viruses, cytotoxic T-lymphocyte (CTL) activity, and total protection against wild-type (wt) viral challenge. These purified vaccine candidates await testing in humans to determine which contain the required balance between immunogenicity and attenuation.

Aged↗
PubMed1999

Determinants of pathogenicity of echovirus 9 in men: significance of a functional RGD-motif.

In this study, we investigated nine independent echovirus 9 isolates obtained from sick children in 1995. It is discovered that these isolates differ in respect to their pathogenicity for newborn mice indicating that the degree of human pathogenicity of an echovirus 9 variant does not necessarily correlate with mouse pathogenicity. Nevertheless, all virus variants are found to code for an RGD-motif within their VP1 protein. Hence, the RGD-motif and its highly conserved flanking regions are the conditio sine qua non, but, as expected, not sufficient for the mouse-pathogenic character.

Amino Acid Sequence↗
PubMed1999

Potato StubSNF1 interacts with StubGAL83: a plant protein kinase complex with yeast and mammalian counterparts.

StubSNF1 is a potato cDNA that encodes a protein kinase similar to the yeast SNF1 gene involved in transcriptional regulation of glucose-repressible genes. The yeast SNF1 functions in a complex with GAL83/SIP1/SIP2 and SNF4 proteins. We have used StubSNF1 as bait in a yeast two-hybrid system to screen for potato cDNAs encoding proteins that bind to StubSNF1. Three overlapping cDNAs, two different in size, were isolated. DNA sequence analysis revealed that they were orthologues of the yeast GAL83/SIP1/SIP2 genes and their mammalian counterparts, AMPK beta-subunits. The direct interaction between the potato proteins StubGAL83 and StubSNF1 was shown by an in vitro binding assay. Southern and Northern hybridisations revealed that StubGAL83 exists in a low copy number in the potato genome and is highly (but organ-specifically) expressed in potato. In contrast, StubSNF1 possesses low transcript levels in each organ, except in flowers where high amounts of StubSNF1 mRNA could be detected. We demonstrate here that StubGAL83 can also interact with yeast SNF4 in a yeast two-hybrid system suggesting that plant SNF1 kinases may function in complexes similar to those detected in yeast and mammals.

Amino Acid Sequence↗
PubMed1999

Regulation of the murine NMDA-receptor-subunit NR2C promoter by Sp1 and fushi tarazu factor1 (FTZ-F1) homologues.

We have cloned the 5'-region of the murine N-methyl-d-aspartate (NMDA) receptor channel subunit NR2C (GluRepsilon3) gene and characterized the cis- and trans-activating regulatory elements responsible for its tissue specific activity. By using a native epsilon3-promoter/lacZ-construct & various 5'-deletion constructs, we compared beta-galactosidase expression in non-neuronal NIH3T3 cells and in neuronal epsilon3-gene-expressing HT-4 cells and show that large parts of the epsilon3 promoter are responsible for the repression of the epsilon3 gene in non-neuronal cells. Deletion of exon 1 sequences led to an enhancement of epsilon3 transcription, suggesting a role of the 5'-untranslated region in epsilon3 gene regulation. Sequence analysis of the promoter region revealed potential binding sites for the transcription factor Sp1, the murine fushi tarazu factor1 (FTZ-F1) homologues, embryonic LTR binding proteins (ELP1,2,3) and steroidogenic factor (SF-1), as well as for the chicken ovalbumin upstream promoter transcription-factor (COUP-TF). Electrophoretic mobility shift assays confirmed specific binding of Sp1, SF-1 and COUP-TFI. Whereas point mutation studies indicate that, in neuronal HT-4 cells, Sp1 is apparently not critically involved in basal epsilon3 gene transcription, SF1 is a positive regulator. This was evident from a selective enhancement of epsilon3-promoter-driven reporter gene expression upon cotransfection of an SF1-expression vector, which was reverted by deletion and point mutation of the SF1 binding site.

3T3 Cells↗
PubMed1999

Deficient activation and different expression of transforming growth factor-beta isoforms in active proliferative diabetic retinopathy and neovascular eye disease.

An increased expression and secretion of angiogenic growth factors was proposed to occur in proliferative diabetic retinopathy and other neovascularizing retinal diseases. However, a loss of anti-angiogenic factors also might promote retinal neovascularization. Therefore we investigated the active and latent vitreous levels of the subtypes of the endothelial anti-mitogen transforming growth factor-beta in vitreous of 58 patients. Four groups of patients were compared: Controls without retinal hypoxia, patients with quiescent and active proliferative diabetic retinopathy (PDR), and patients with severe retinal hypoxia resulting in rubeosis iridis. Whereas the amount of total TGF-beta in the four groups did not differ significantly, latent TGF-beta isoform expression showed complex alterations in ocular vitreous. Levels of active TGF-beta of patients with active PDR (79.5 +/- 28 pg/ml; n = 8) were decreased to 20% of the control levels (378 +/- 55 pg/ml; n = 12; p = 0.0005) and 25% of the mean concentration in quiescent PDR (346 +/- 64 pg/ml; n = 9; p = 0.0021). Levels in rubeosis (52 +/- 10 pg/ml; n = 10) did not differ significantly from those found in active PDR but were decreased to 15% of those in patients with quiescent PDR (p = 0.0004). Furthermore a highly significant inverse correlation between active TGF-beta and alpha2-antiplasmin, a liver produced inhibitor of the activation of TGF-beta by plasmin was noted (r = -0.59; n = 28; p = 0.001). We conclude that deficient activation of TGF-beta occurs in active proliferative diabetic retinopathy and in hypoxic angiogenesis most likely as a consequence of a blood retina barrier breakdown and influx of alpha2-antiplasmin from serum. The disinhibition of endothelial cell proliferation may be a central component in the process of neovascularization.

Aged↗
PubMed1999

Early and late results after thymectomy in myasthenia gravis: a retrospective study [correction of analysis].

BACKGROUND: This study aims to evaluate the early and late outcome of patients treated by surgery for myasthenia gravis and the diagnostic value of the Besinger Score, which is based on a correlation of severity of symptoms with specific antibodies to acetylcholine receptors, in the follow-up investigation after surgical therapy. METHODS: Between June 1984 and April 1992 thoracotomy was performed in 51 myasthenia gravis cases at our department. The retrospective analysis considered patients with (n = 13) or without thymoma (n = 38). The Besinger score was used to describe the severity of disease preoperatively and up to 5 years postoperatively. RESULTS: The Besinger score fell continually post surgery. Changes in relative serum concentrations of antibodies were similar to the Besinger score. Five years after thymectomy complete remission was diagnosed in 40% of the patients. The required dosage of pyridostigmine had fallen by two thirds after 5 years. Patients with follicular hyperplasia had significantly higher remission rates than those with thymoma. CONCLUSIONS: Surgery for myasthenia gravis is successful. The Besinger score well quantifies the severity of the disease.

Adolescent↗
PubMed1999

[Rehabilitation with bone anchored facial prostheses].

BACKGROUND: Rehabilitation of orbita defects with loss of eyelids is difficult to achieve with plastic surgery. Here defect coverage with a facial prosthesis shows good results. PATIENTS AND METHODS: 105 patients with orbita defects were treated since 1991 with bone anchored facial prostheses. Preoperatively we measured the bone availability with computed tomography. We inserted Brånemark-titanium implants (Fa. Nobel Biocare), with a two-stage procedure. After a period of at least three months we exposed implants and connected the supraconstruction. Then our anaplastologist produced the facial prosthesis, either a "soft" facial prosthesis of silicone or a "solid" prosthesis of polymethylmetacrylate (PMMA). Not later than every three months patients came to recall. RESULTS: For all patients we found enough bone for implantation. The implants were screwed into the lateral bony orbital margin. There were no intraoperative complications accompanying implant insertion. For 96 patients we chose the silicone material; for nine patients we did produce the facial prosthesis of PMMA. In about 10.5% of the implants we had to remove subcutaneous tissue in local anesthesia because of recurrent periimplantary inflammations. Three years after insertion 95.8% of the implants were still firmly anchored in the bone. CONCLUSIONS: Performed by the experienced specialist the prosthetic treatment of orbita defects with a bone anchored facial prosthesis is a cosmetically satisfactory procedure with good long-term outcome. While modern plastic materials can replace the lost tissue with deceptively natural results, the implants guarantee firm secure retention of the facial prosthesis.

Adolescent↗
PubMed1999

Whole body protein turnover of growing rats in response to different dietary proteins--soy protein or casein.

Whole body protein turnover was studied in growing rats fed restrictively on isoenergetic (GE 17.6 MJ/kg DM) and isonitrogenous (104 g CP/kg DM) diets based on soy protein isolate or casein supplemented with D,L-methionine. During each of the three separate experiments six male Fischer rats per group were housed individually in metabolic cages at 24 degrees C. Prefeeding of both dietary groups up to similar body weights at the start of the main experimental periods (105-134 g) lasted up to 16 d for casein-fed rats and up to 30 d for the soy protein-fed rats. Following the energy and nitrogen balance periods whole-body protein synthesis was estimated by the end-product method using a single tracer dose of a mixture of 15N-labelled amino acids. Fractional protein accretion rate [% of the protein pool accreted per day] was significantly lower in soy protein-rats than in casein-fed rats in all three experiments whereas fractional synthesis rate was not significantly lower. Therefore, protein breakdown subsequently calculated as the difference between synthesis and accretion showed a tendency towards higher values in this group. In soy protein-fed rats also a tendency towards higher excretion of 3-methylhistidine as a marker of myofibrillar protein breakdown was observed. It is concluded that increase in lean tissue growth resulting from improved protein quality is brought about by changes of both rates, by small increase of protein synthesis and by reduced rate of body protein breakdown.

Animals↗
PubMed1999

Degradation of a short-lived glycoprotein from the lumen of the endoplasmic reticulum: the role of N-linked glycans and the unfolded protein response.

We are studying endoplasmic reticulum-associated degradation (ERAD) with the use of a truncated variant of the type I ER transmembrane glycoprotein ribophorin I (RI). The mutant protein, RI(332), containing only the N-terminal 332 amino acids of the luminal domain of RI, has been shown to interact with calnexin and to be a substrate for the ubiquitin-proteasome pathway. When RI(332) was expressed in HeLa cells, it was degraded with biphasic kinetics; an initial, slow phase of approximately 45 min was followed by a second phase of threefold accelerated degradation. On the other hand, the kinetics of degradation of a form of RI(332) in which the single used N-glycosylation consensus site had been removed (RI(332)-Thr) was monophasic and rapid, implying a role of the N-linked glycan in the first proteolytic phase. RI(332) degradation was enhanced when the binding of glycoproteins to calnexin was prevented. Moreover, the truncated glycoprotein interacted with calnexin preferentially during the first proteolytic phase, which strongly suggests that binding of RI(332) to the lectin-like protein may result in the slow, initial phase of degradation. Additionally, mannose trimming appears to be required for efficient proteolysis of RI(332). After treatment of cells with the inhibitor of N-glycosylation, tunicamycin, destruction of the truncated RI variants was severely inhibited; likewise, in cells preincubated with the calcium ionophore A23187, both RI(332) and RI(332)-Thr were stabilized, despite the presence or absence of the N-linked glycan. On the other hand, both drugs are known to trigger the unfolded protein response (UPR), resulting in the induction of BiP and other ER-resident proteins. Indeed, only in drug-treated cells could an interaction between BiP and RI(332) and RI(332)-Thr be detected. Induction of BiP was also evident after overexpression of murine Ire1, an ER transmembrane kinase known to play a central role in the UPR pathway; at the same time, stabilization of RI(332) was observed. Together, these results suggest that binding of the substrate proteins to UPR-induced chaperones affects their half lives.

Calcimycin↗
PubMed1999

The impact of early clinical training in medical education: a multi-institutional assessment.

With funding from The Robert Wood Johnson Foundation's Generalist Physician Initiative, Dartmouth Medical School (DMS), New York Medical College (NYMC), and Virginia Commonwealth University School of Medicine (VCU-SOM) adopted early community-based training models for longitudinal clinical experiences. These schools developed different evaluation strategies to assess these models. This paper describes each program, the method used to evaluate an aspect of the program, lessons learned about early clinical teaching and learning, and challenges encountered. Each program used cross-sectional evaluation, and the analysis methods included descriptive statistics, chi-square, t-tests, analysis of variance, and generalized linear models. Dartmouth determined that the type of preceptor does not greatly influence the development of clinical skills, although case-specific differences were discovered. NYMC learned that students taught clinical skills in community-based settings performed as well as or better than their peers who received early patient experience on hospital wards. Virginia Commonwealth discovered that community experiences contributed positively to students' education, critical thinking, and problem-solving skills. Students value early clinical experiences and make important achievements in clinical skills and knowledge development, although logistic challenges exist in conducting these courses. Evaluations are critical to ensure competency, and faculty development must be linked to the evaluation process.

Curriculum↗
PubMed1999

Promoting institutional change to encourage primary care: experiences at New York Medical College and East Carolina University School of Medicine.

New York Medical College and East Carolina University School of Medicine significantly changed their curricula and organizational structures in response to The Robert Wood Johnson Foundation's Generalist Physician Initiative (GPI). Seven common elements essential to successful institutional change were retrospectively identified at these two markedly different schools. They are (1) using national priorities to promote need for change, (2) establishing internal and external financial support, (3) developing a planning process and organizational structure to effect change, (4) devising an ongoing evaluation strategy, (5) sustaining positive attitudes toward primary care, (6) integrating community-based physicians, and (7) sustaining interest in the GPI. Within this framework, the authors present the GPI objectives at both schools, discuss examples of methods for institutional change and describe successes, failures, and lessons learned. The authors conclude that both schools have significantly increased the number of students choosing primary care careers and note the general perception of improvement in the quality of primary care educational programs, student recruitment, departmental collaboration, and faculty development opportunities. Although these changes have not yet been fully institutionalized, the similarities of the processes described may be of value to others addressing similar issues.

Attitude of Health Personnel↗