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Biomedical subjects

S Schmidt

Publications and source records attributed to S Schmidt.

At least 253 records · Page 14Linked to original sources
PubMed1997

Association between a delta opioid receptor gene polymorphism and heroin dependence in man.

Two allelic variants of the delta opioid receptor gene, distinguished by a single base exchange T to C in codon 307 of the translated region, were detected in humans. The amino acid sequence was thereby not changed. The resulting C and T alleles combined to give the three genotypes CC, CT and TT. Allele C was more frequent in a sample of 103 German Caucasian heroin addicts (53.4%) than in a control group (39.1%, n = 115). The proportion of CC homozygotes was much greater among the drug-dependent subjects (26.2%) than in controls (9.6%). Although the reasons for this association remain to be explained, our results argue for a participation of the delta type of opioid receptors in the pathophysiology of heroin dependence.

Alleles↗
PubMed1997

Long-term food restriction down-regulates the density of serotonin transporters in the rat frontal cortex.

The influence of feeding rats only half the amount of their normal daily intake of a complete rat chow on the affinity and the density of serotonin (5-HT) transporters was measured in membrane preparations of the frontal cortex and the midbrain by a [3H]paroxetine binding assay. In young rats (10 weeks), a significant reduction of about 30% of the Bmax values of [3H]paroxetine binding occurred in the frontal cortex after 1 and 2 weeks of restricted food intake. No starvation-induced decline of the density of 5-HT transporters was seen in the midbrain. When older rats (50 weeks) were subjected to the same 50% reduction of daily food intake for 2 weeks, no such down-regulation of the density of cortical 5-HT transporters was observed. The affinity of the 5-HT transporters, as indicated by the unchanged Kd values of [3H]paroxetine binding, was not affected by semistarvation in both regions and at both ages. The observed decline of [3H]paroxetine binding sites in the frontal cortex of young adult rats is the first demonstration of long-term regulatory phenomena of brain 5-HT transporters triggered by a physiologic stimulus.

Aging↗
PubMed1997

The Spg1p GTPase is an essential, dosage-dependent inducer of septum formation in Schizosaccharomyces pombe.

The spg1 gene (septum-promoting GTPase) was cloned as a multicopy suppressor of a dominant-negative mutant of the Cdc7p kinase. It encodes a small GTPase of the Ras superfamily. spg1 is an essential gene. Null or heat-sensitive alleles do not make a division septum, but growth, S-phase, and mitosis continue in the absence of cell division, producing elongated, multinucleate cells. Increased expression of Spg1p induces septum formation in G2, S-phase, and pre-Start G1-arrested cells. This requires the activity of Cdc7p kinase, but not p34(cdc2). Increased expression of Cdc7p bypasses the requirement for Spg1p. Spg1p and Cdc7p can be coimmunoprecipitated from cell extracts, and interact in the two-hybrid system. These data indicate that Spg1p is a key element in controlling the onset of septum formation in Schizosaccharomyces pombe, and that it acts through the Cdc7p kinase.

Amino Acid Sequence↗
PubMed1997

Interaction of protein kinase C zeta with ZIP, a novel protein kinase C-binding protein.

The atypical protein kinase C (PKC) member PKC-zeta has been implicated in several signal transduction pathways regulating differentiation, proliferation or apoptosis of mammalian cells. We report here the identification of a cytoplasmic and membrane-associated protein that we name zeta-interacting protein (ZIP) and that interacts with the regulatory domain of PKC-zeta but not classic PKCs. The structural motifs in ZIP include a recently defined ZZ zinc finger as a potential protein binding module, two PEST sequences and a novel putative protein binding motif with the consensus sequence YXDEDX5SDEE/D. ZIP binds to the pseudosubstrate region in the regulatory domain of PKC-zeta and is phosphorylated by PKC-zeta in vitro. ZIP dimerizes via the same region that promotes binding to PKC-zeta suggesting a competitive situation between ZIP:ZIP and ZIP:PKC-zeta complexes. In the absence of PKC-zeta proper subcellular localization of ZIP is impaired and we show that intracellular targeting of ZIP is dependent on a balanced interaction with PKC-zeta. Taking into account the recent isolation of ZIP by others in different contexts we propose that ZIP may function as a scaffold protein linking PKC-zeta to protein tyrosine kinases and cytokine receptors.

Alanine↗
PubMed1997

Biologic properties of a bispecific single-chain antibody directed against 17-1A (EpCAM) and CD3: tumor cell-dependent T cell stimulation and cytotoxic activity.

Anti-CD3 x anti-tumor-bispecific Abs have been used to redirect cytotoxic T cells to tumor cells in an MHC-unrestricted fashion and to induce their rejection in vivo. We have recently described a recombinant bispecific single-chain Ab that combines four different V regions of two Abs, anti-17-1A and anti-CD3, on one polypeptide chain. It folds correctly to a 60-kDa globular protein and is secreted in fully functional form by a high producer Chinese hamster ovary cell line. In this work, we report that its remarkable cytotoxicity against 17-1A+ tumor cells is exerted via T cells without an apparent engagement of a detectable costimulatory pathway. T cells are activated only by the bispecific Ab when coincubated with 17-1A+ target cells. In a chromium release assay, CD8+ T cells reach maximal tumor cell cytotoxicity within 4 h, while CD4+ T cells need about 20 h to reach similar levels of cytotoxicity. Addition of costimulatory CD28 Abs did not lead to a further increase in cytotoxicity. Its remarkable stability at 37 degrees in serum, the ease of production, and purification by affinity chromatography via polyhistidine tail make this smaller version of a bispecific Ab a promising candidate for a therapeutic trial in patients with solid tumor. Because adjuvant therapy with an intact, much less cytotoxic IgG2a Ab against the 17-1A target had already increased the 7-yr survival of colorectal cancer patients by 30%, the presented small bispecific construct lacking the immunogenic murine Fc region as well as autochthonous T lymphocyte stimulatory activity warrants a therapeutic trial in patients with minimal residual 17-1A+ cancer.

Animals↗
PubMed1997

[Reactive thymus dysplasia following therapy for ACTH-producing tumors].

UNLABELLED: Surgical or conservative treatment of ACTH-producing tumors results in acute drop of the previously excessively high cortisol levels. The following associated pathophysiological changes also occur in the organism's recovery from stress, such as trauma, operation or chemotherapy of tumors. Both cases result in a regeneration of the immune system, which might even be exalted. The corresponding radiographic feature is the "rebound" enlargement of the thymus occurring about six months after remission of hypercortisolism. Histological examination reveals benign thymus hyperplasia. Especially in cases of still unknown primary tumor the appearance of this anterior mediastinal mass can lead to misdiagnosis. We present the cases of two patients with diffuse thymic hyperplasia following surgical and medical correction of hypercortisolism. One patient suffered from classic Cushing's disease responding to transsphenoidal resection of an ACTH-secreting pituitary microadenoma. Six months later CT of the chest incidentally demonstrated an anterior mediastinal mass known as thymic hyperplasia. The second patient presented with an ectopic, still unkown source of ACTH-production. Six months after medical correction of hypercortisolism CT of the thorax showed an enlargement of the anterior mediastinum. Thymectomy was performed in order to exclude thymus carcinoid. Histological examination revealed benign thymus hyperplasia with negative immunostaining. CONCLUSION: Radiologists and clinicians should be familiar with the pathophysiological changes resulting from precipitously dropping cortisol levels in order to prevent diagnostic errors and unnecessary operations.

Adrenocortical Hyperfunction↗
PubMed1997

Cost-effectiveness of treating nicotine dependence: the Mayo Clinic experience.

OBJECTIVE: To estimate the cost-effectiveness of treating nicotine dependence, expressed as cost per net year of life gained by smoking cessation. DESIGN: A cost-effectiveness analysis was conducted of a cohort of consecutive adult patients treated for nicotine dependence from April 1988 through December 1992 at the Mayo Clinic Nicotine Dependence Center (NDC). MATERIAL AND METHODS: The study cohort consisted of 5,544 patients (50.8% female; mean age, 47.8 years) with a mean baseline smoking rate of 25.4 cigarettes per day. After an initial consultation, a nonphysician counselor developed an individual nicotine dependence treatment plan, which could include follow-up counseling, nicotine replacement therapy (patches or gum), group therapy, or an inpatient program. A relapse-prevention program included telephone calls and a series of letters to the patient. We computed the years of life gained for each person specific to age, gender, smoking rate at entry, and 6-month smoking status by using published mortality rates for current and former cigarette smokers. The 6-month smoking status was assumed to be applicable at 1 year. For subsequent determinations, we modeled by computer simulation the year-by-year (to age 100) smoking status by using published relapse and late cessation rates. Coupled with treatment costs, this information allowed the expression of cost per net year of life gained by stopping smoking. Net years of life gained, discounted 0, 3, and 5%, were computed with use of cessation and relapse rates expected for patients not seen in the NDC. Treatment costs were based on 1993 rates for the intervention services but did not include any tobacco product cost savings associated with smoking cessation. RESULTS: The 1-year smoking-cessation rate was 22.2%. With all NDC patients included, the estimated net years of life gained, with use of a 5% rate of discount for benefits, was 0.058, and the corresponding cost was $6,828 per net year of life gained. CONCLUSION: In comparison with the cost-effectiveness of other medical services, the cost of $6,828 per net year of life gained by treatment of nicotine dependence is relatively inexpensive. Such cost-outcome data are important as economic considerations are applied for optimal allocation of limited health-care resources. Nonphysician health-care professionals can assume a key role in the provision of cost-effective nicotine dependence intervention.

Adult↗
PubMed1997

Lithium versus carbamazepine in the maintenance treatment of bipolar disorders--a randomised study.

In a randomised multicentre study, the prophylactic efficacy of lithium and carbamazepine was compared in 144 patients with bipolar disorder (74 vs. 70 patients; observation period: 2.5 years; lithium serum level: 0.63 +/- 0.12 mmol/l, carbamazepine dose: 621 +/- 186 mg/day). Hospitalisations, recurrences, need of psychotropic comedication and adverse effects prompting discontinuation were defined as treatment failures. Survival analyses regarding hospitalisations and recurrences showed no statistically significant differences between both drugs. Results were distinctly in favour of lithium, considering recurrences combined with comedication (P = 0.041) and/or adverse effects (P = 0.007). Whereas adverse effects prompting discontinuation were more frequent under carbamazepine (9 vs. 4, ns), lithium patients reported more often slight/moderate side effects (61% vs. 21% after 2.5 years; P = 0.0006). In completers, recurrences occurred in 28% (lithium) vs. 47% (carbamazepine) of the patients (P = 0.06). Lithium seems to be superior to carbamazepine in maintenance treatment of bipolar disorder, in particular when applying broader outcome criteria including psychotropic comedication and severe side effects.

Adult↗
PubMed1997

The microbial degradation of halogenated diaryl ethers.

The structurally related polyhalogenated diaryl ethers such as diphenyl ethers (DEs), dibenzofurans (DFs), and dibenzo-p-dioxins (DDs) are regarded, due to their physicochemical and toxicological properties, as a class of compounds giving reason for serious environmental concern. While the nonhalogenated basic structures are biodegradable under aerobic conditions, there is the need for rather specialized strains to mineralize the halogenated derivatives. Certain halogenated metabolites might cause serious problems such as having inhibitory effects upon the degradation. Anaerobic methanogenic consortia do have the ability to almost completely dehalogenate even polyhalogenated congeners. It has been shown that certain fungi are capable of transforming chlorinated DFs and DDs by the activity of nonspecific enzymes such as lignin-peroxidases.

Journal Article↗
PubMed1997

Nephropathy of type II diabetes: evidence for hereditary factors?

Family studies point to an important genetic element in the genesis of diabetic nephropathy, but it is not known whether renal abnormalities are present prior to the onset of diabetes. To address this issue we examined all consecutive patients suffering from type II diabetes with a duration of more than 10 years who attended a diabetes outpatient clinic. Ninety-four patients had nephropathy, 307 did not. All offspring who were phenotypically normal (no hypertension, normal oral glucose tolerance, non-smoking) and agreed to participate were examined, 26 from nephropathic and 30 from non-nephropathic diabetic parents. They were compared with 30 offspring matched for age, gender and BMI from non-diabetic parents as controls. We measured urinary albumin excretion under baseline conditions and at several time points after ingestion of 300 g cooked beef and submaximal treadmill exercise, respectively. In addition, casual blood pressure, ambulatory blood pressure, urinary albumin and urinary alpha-1-microglobulin were measured. Primary renal disease was excluded by clinical examination. Under baseline conditions, median urinary albumin excretion rate (AER; microgram/min) was significantly (P < 0.005) higher in offspring of nephropathic type II diabetic patients (7.8; range 1.04 to 19.5) than in the offspring of non-nephropathic type II diabetic patients (4.8; 0.36 to 17.5) and controls (4.4; 0.16 to 18.4). Submaximal treadmill exercise caused a greater proportional increase of AER in offspring of nephropathic type II diabetics (median 16-fold) than in offspring of non-nephropathic diabetic patients (6.3-fold) or controls (4.8-fold). In offspring of nephropathic diabetic patients casual and particularly ambulatory systolic blood pressures were significantly higher, but AER was not correlated with blood pressure. In summary, higher values, albeit within the normal range, for baseline and postexercise albuminuria were noted in phenotypically normal offspring of parents with type II diabetes and nephropathy. The observation suggests that changes in transglomerular albumin traffic are demonstrable prior to the onset of diabetes and diabetic nephropathy in subjects with a potential genetic predisposition to these conditions.

Adult↗
PubMed1997

Circadian variations in blood pressure and heart rate in diabetes prone and resistant rat strains compared with spontaneously hypertensive rats.

Circadian blood pressure (BP), heart rate (HR) and motor activity (MA) of nondiabetic (nd) and spontaneously diabetic (d) BB/OK rats were compared with that of spontaneously hypertensive rats (SHR). In addition a diabetes-resistant and non-hypertensive rat strain (LEW.1W) was monitored for the same parameters. Systolic and diastolic BP (SBP, DBP), HR and MA were measured telemetrically. In d BB rats, the 24 h mean value of SBP (132 +/- 0.15 mm-Hg) was significantly increased compared to nd BB rats (125 +/- 0.18 mmHg). No differences were found in DBP between d and nd BB rats (93 +/- 0.13 v.s. 94 +/- 0.15 mmHg). Both, d and nd BB rats were significantly different in SBP and DBP to that of SHR (155 +/- 0.19 and 110 +/- mmHg). Nondiabetic BB rats did not significantly differ from LEW.1W rats in SBP and DBP (125 vs. 123 mmHg and 94 vs. 94 mmHg). The heart rate was lowest in diabetic BB rats compared with all other strains. Compared to nd BB the diabetic rats had an altered daily rhythm in BP. The results demonstrate that the diabetic BB rats develop circadian variations in BP and HR similar to those observed in hypertensive rats.

Animals↗
PubMed1997

Functional alterations in the rat kidney induced either by diabetes or high protein diet.

The aim of this study was to compare the effect of long-term diabetes with that of a long-term high protein diet in vivo on the kidney function and in vitro on cellular parameters of isolated glomeruli of BB rats. Four groups of rats were investigated: Group 1 = normoglycaemic (N) rats > 250 days old; group 2 = age-matched diabetic (D) rats with a diabetes duration of more than 150 days; group 3 = BB rats which were fed a protein diet of 8% (low protein = LP) and group 4 = rats which received a high protein (HP) diet (32%) for more than 80 weeks. From 24-h-urine samples albumin, urea, creatinine and electrolyte excretion were estimated. At the end of the study the total kidney weight was determined and glomeruli were isolated for in vitro experiments. Hyperglycaemic and HP fed rats were characterised by a significantly increased excretion of albumin, urea and different electrolytes compared to normoglycaemic or LP fed animals. Creatinine excretion was neither affected by hyperglycaemia nor HP diet. HP and D caused a significant increase in total kidney weight when compared to the LP and N group, respectively (N: 1.79 +/- 0.08; D: 2.33 +/- 0.09; LP: 2.26 +/- 0.18; HP: 3.28 +/- 0.46 g; p < 0.05). The increased kidney weight of diabetic and HP rats correlated well with a significant enhanced DNA content of isolated glomeruli (N: 3.41 +/- 0.15; D: 4.45 +/- 0.19; LP: 4.18 +/- 0.35; HP: 6.40 +/- 0.62 micrograms/1000 glomeruli; p < 0.02). In addition, glomeruli obtained from either D or HP fed BB rats incorporated significantly more 3H-thymidine into their DNA indicating an elevated rate of DNA synthesis. The results demonstrate that HP diet caused markedly altered kidney function and induced cellular changes of glomeruli which are interpreted as enhanced proliferative processes. These alterations are comparable to those associated with diabetes mellitus. An unbalanced high protein diet represents a considerable risk factor for the development of functional and structural impairments of the kidney and should absolutely be avoided in patients suffering from diseases which are known to be associated with kidney alterations.

Albuminuria↗
PubMed1997

Lineage study of degenerating photoreceptor cells in the rd mouse retina.

PURPOSE: A retroviral marker was used to label daughter cells arising from individual neuroblasts in the rd mouse retina, in order to investigate the hypothesis that a clonal relationship exists among degenerating photoreceptor cells. METHODS: On the day of birth, a single injection of retrovirus with a lac Z (beta-galactosidase) reporter construct was injected into the retina in the vicinity of the subretinal space. Descendants of single neuroblasts were identified histochemically by examining the retinas at P14 (postnatal day 14). Light and electron microscopic studies were used to identify the retrovirally-induced marker beta-galactosidase using Bluo-gal dye. Double-labeling of degenerating cone cells was accomplished by taking 100 microns vibratome sections of retrovirally-injected eyes and using either FITC-PNA or HRP-PNA to visualize clusters of degenerating cones as well as Bluo-gal labeled clones of photoreceptor cells on the same tissue section. RESULTS: A relatively large number of clones of primarily photoreceptor cells were observed in the peripheral retinas of both normal and rd mice. In a few cases in the rd, photoreceptor cells in a given clone consisted of both PNA- and Bluo-gal-labeled cells as well as of only Bluo-gal-labeled cells. CONCLUSION: These results suggest that during the period of intense cell death in the rd retina, a single dying photoreceptor cell can be surrounded by photoreceptors (either rods or cones) from the same clone that appear morphologically normal without evidence of degeneration.

Animals↗
PubMed1997

Multiple sclerosis: comparison of the human T-cell response to S100 beta and myelin basic protein reveals parallels to rat experimental autoimmune panencephalitis.

The adoptive transfer of autoreactive S100 beta-specific T cells induces experimental autoimmune panencephalomyelitis and uveoretinitis in the Lewis rat, mimicking the distribution of lesions seen in a subset of patients with multiple sclerosis. We studied the frequency and functional properties of the human T-cell response to S100 beta in eight patients (two relapsing-remitting multiple sclerosis, one chronic-progressive multiple sclerosis, two with multiple sclerosis and uveitis, two neuromyelitis optica, one panuveitis) and in seven healthy individuals, using bovine S100 beta for T-cell stimulation. Both in patients and controls, the frequency of S100 beta-specific T-cell responses was half of that obtained for myelin basic protein (MBP), and only 10% of that obtained using purified protein derivative (PPD). The stimulation indices obtained in response to S100 beta were also less than half those obtained with either MBP or PPD. However, four long-term S100 beta-specific T-cell lines were established and studied in more detail. The four T-cell lines all exhibited a CD4+, CD8-, T-cell receptor alpha beta + surface phenotype and secreted tumour necrosis factor-alpha, interferon-gamma, interleukin-10 and interleukin-4 upon antigenic stimulation, but they were heterogenous with respect to T-cell receptor usage; two T-cell lines expressed V beta 2, one V beta 6.7 and one V beta 13. Antigen-specificity was confirmed using bovine S100 beta beta and alpha beta-isoforms, as well as a recombinant rat S100 beta preparation. The response to S100 beta was shown to the HLA-(human leukocyte antigen-) DR-restricted for two of the S100 beta-specific T-cell lines. Human S100 beta-specific T-cell lines were cytotoxic, although to a lesser extent than MBP-specific T-cell lines derived from the same donors. The phenotypic and functional properties of human S100 beta-specific T-cell lines raise the possibility that these T cells are pathogenic, as they are in the rat. The low frequency and proliferative index of S100 beta-specific, as opposed to MBP-specific T-cell responses suggests that the T-cell response to this widely expressed calcium-binding protein is under more efficient regulatory control.

Adult↗
PubMed1997

Excess of DD homozygotes in haemodialysed patients with type II diabetes. The Diabetic Nephropathy Study Group.

The role of the insertion/deletion polymorphism of the angiotensin-converting enzyme (ACE) gene in the genesis of diabetic nephropathy has been controversial. It has recently been proposed that progression occurs more rapidly in individuals with diabetic and non-diabetic renal disease who are homozygous for the D allele. We studied 658 patients with type II diabetes, 347 without diabetic nephropathy and 311 with various stages of diabetic nephropathy, and determined the I/D polymorphism of the ACE gene. Patients at the extremes of renal risk, i.e. normotensive patients without antihypertensive treatment and without nephropathy (n = 144), vs patients on dialysis (n = 61), differed with respect to genotype (DD 36.8% vs 57.4%; P = 0.007) and allele frequencies (D 0.59 vs 0.76; P < 0.001). In contrast, patients with and without presumed nephropathy as assessed by albuminuria did not differ with respect to DD genotype. In conclusion, in this study, which was limited by sample size, patients with the highest renal risk more frequently had the DD genotype. This would be compatible with a greater risk of (or rate of) progression to end-stage renal failure.

Adult↗
PubMed1997

A polymorphism in the gene for the angiotensin II type 1 receptor is not associated with hypertension.

BACKGROUND: A mutation in the gene for the angiotensin II type 1 (AT1) receptor (A1166C) has been reported to be associated with primary hypertension. OBJECTIVE: To determine whether this observation could be confirmed with a different population sample. DESIGN: We examined 414 individuals with primary hypertension and 172 normotensive controls. METHODS: The mutation in the gene for the AT1 receptor was detected using restriction polymerase chain reaction. CONCLUSIONS: We detected no association of the AT1 receptor polymorphism with hypertension, but a trend towards a decreased prevalence of the 1166C allele among hypertensive patients with a late age at diagnosis (> or = 50 years) was observed.

Adult↗
PubMed1997

Genetics of the renin-angiotensin system and renal disease: a progress report.

The genes of the renin-angiotensin system and their relation to renal diseases are of great interest. The number of studies examining the role of polymorphism in these genes in development or progression of renal diseases has increased nearly logarithmically, but results remain conflicting. Evidence is increasing that progression of renal disease is more rapid in DD-homozygotes of the angiotensin-converting enzyme gene polymorphism, but other relationships have not been solidly established.

Angiotensinogen↗