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Biomedical subjects

M Polak

Publications and source records attributed to M Polak.

At least 73 records · Page 4Linked to original sources
PubMed2000

Parallel man-machine training in development of EEG-based cursor control.

A new parallel man-machine training approach to brain-computer interface (BCI) succeeded through a unique application of machine learning methods. The BCI system could train users to control an animated cursor on the computer screen by voluntary electroencephalogram (EEG) modulation. Our BCI system requires only two to four electrodes, and has a relatively short training time for both the user and the machine. Moving the cursor in one dimension, our subjects were able to hit 100% of randomly selected targets, while in two dimensions, accuracies of approximately 63% and 76% was achieved with our two subjects.

Biofeedback, Psychology↗
PubMed2000

Intestinal and pancreatic metaplasia at the esophagogastric junction in patients without Barrett's esophagus.

OBJECTIVES: A distinctive type of columnar epithelium with intestinal metaplasia is considered diagnostic for Barrett's esophagus. The neoplastic potential of pancreatic metaplasia at the esophagogastric junction is unknown. The aims of the present study were: 1) to characterize both forms of metaplasia at the esophagogastric junction, and to estimate their prevalence; 2) to investigate c-erbB-2 expression and K-ras mutations in pancreatic metaplasia; and 3) to study the relationship between metaplasia, inflammatory changes in the cardiac mucosa, and presence of H. pylori. METHODS: A total of 76 esophagogastrectomy specimens of patients with a normally located squamocolumnar junction, were investigated immunohistochemically. K-ras mutations were evaluated using PCR. RESULTS: Intestinal metaplasia in the cardia was found in 12% of patients: six complete-type, and three incomplete-type. Pancreatic metaplasia was demonstrated in 14% of patients, and neither c-erbB-2 expression nor K-ras mutations were found. Intestinal and pancreatic metaplasia were associated with mucosal inflammation. In contrast to generalized gastritis, isolated "carditis" was not associated with H. pylori infection. CONCLUSIONS: When intestinal metaplasia occurs in a biopsy from the esophagogastric junction, it is not necessarily a marker for Barrett's esophagus. No indication was found that pancreatic metaplasia has neoplastic potential. Both forms of metaplasia reflect mucosal inflammation. Carditis may be a distinct inflammatory condition of the gastric mucosa that is not related to H. pylori infection.

Adenocarcinoma↗
PubMed2000

Arterial mechanical changes in children with familial hypercholesterolemia.

Atherosclerosis is preceded by a phase of changes in the arterial wall that could have functional consequences even before the appearance of atheromatous changes. We hypothesized that early alterations of the mechanical properties of the arterial wall could precede clinical and echographic modifications. We used an automatic, computerized, ultrasonic procedure to evaluate geometric and mechanical characteristics of the common carotid artery (CCA) in normotensive children with primary familial class IIA hypercholesterolemia (FH; n=30; mean+/-SD age, 11+/-2 years old; mean+/-SD systolic/diastolic blood pressure, 109+/-9/55+/-7 mm Hg). These subjects were compared with age-matched, nonobese control subjects (n=27; 11+/-3 years old; 112+/-10/55+/-7 mm Hg). Noninvasive ultrasonic measurements were performed by the same investigator to measure the CCA luminal systolic and diastolic diameters and intima-media thickness (IMT). The cross-sectional compliance, cross-sectional distensibility, and the incremental elastic modulus of the CCA wall were then calculated. Finally, we assessed the degree of reactive hyperemia in the brachial artery produced after distal cuff occlusion and release. The changes in brachial arterial diameter in response to reactive hyperemia (endothelium-dependent dilation) and to glyceryltrinitrate (endothelium-independent dilation) were then measured. In patients with FH, we observed a significant reduction of systodiastolic variations in diameter (by 20%, P:<0.001) without a significant difference in IMT. Cross-sectional compliance and cross-sectional distensibility were significantly reduced in FH subjects (by 15%, P:<0.05 and 19%, P:<0.01, respectively). In parallel, the incremental elastic modulus was significantly increased (by 27%, P:<0.01) in children with FH. No correlation was evident between the carotid incremental modulus and either IMT or plasma low density lipoprotein cholesterol level. There was no difference in diameter of the brachial artery at rest in control and FH subjects (3.0+/-0.5 versus 3.0+/-0.4 mm). The reactive hyperemia and glyceryltrinitrate dilation were also similar in the 2 groups. However, the flow-mediated dilation of the brachial artery was smaller in the FH subjects (4.2+/-2.9%) than in controls (9.0+/-3.1%, P:<0.001). In FH, endothelium-dependent dilation was negatively correlated with the plasma low density lipoprotein cholesterol level (P:<0.04). These results indicate that increased stiffness of the CCA wall in children with FH is independent of blood pressure and could be related to endothelial dysfunction. Thus, alterations in CCA wall mechanics could be early and easily measurable markers of atheromatous changes in the arterial wall.

Biomechanical Phenomena↗
PubMed2000

Refinement of the 6q chromosomal region implicated in transient neonatal diabetes.

Transient neonatal diabetes mellitus (TNDM) is estimated to occur in approximately 1 in 500,000 births and represents 50-60% of cases of neonatal diabetes. The pattern of inheritance of TNDM and its association with chromosome 6 uniparental disomy is consistent with the presence on chromosome 6 of an imprinted gene involved in pancreatic beta-cell development. Systematic screening for chromosome 6 abnormalities in nine families with 13 individuals affected by TNDM revealed paternal isodisomy of chromosome 6 in one child and paternally derived trisomy of the chromosomal region 6q in six children from three unrelated families. To delineate more accurately the region suspected of harboring the gene of interest, precise mapping of the duplicated area was performed in children exhibiting partial 6q trisomy by using microsatellite markers. The smallest region of duplication observed in our patients was flanked by markers D6S308 and D6S1010, which are separated by <1 cM. These findings confirm that TNDM may result from the overexpression of a gene located on chromosome 6q that is exclusively expressed from the paternal allele at least during some periods of life and further refine the localization of this gene.

Aneuploidy↗
PubMed2000

Early pattern of differentiation in the human pancreas.

In the early human embryonic/fetal pancreas, we studied 1) the ontogenetic pattern of the endocrine cells and the evolution of the endocrine mass, and 2) the morphogenetic pattern of development and, more precisely, the complex relationship of the epithelial mass with the surrounding mesenchyme. We studied 15 pancreases between 7 and 11 weeks of development (WD) by double immunohistochemistry. Epithelial cells in these pancreatic anlage were detected by cytokeratin staining, and differentiated endocrine cells were detected by insulin, glucagon, somatostatin, and pancreatic polypeptide staining. Proliferation was quantified using a nuclear marker, the Ki-67 antibody. At this early stage, the pancreas is made up of an epithelial mass composed of central ducts intermingled with a loose mesenchyme and peripheral ducts surrounded by a dense peripancreatic mesenchyme. Hormone-containing cells appear in the epithelium at 8 WD. Newly differentiated endocrine cells coexpress insulin, glucagon, and somatostatin; endocrine differentiation starts within the central ducts of the epithelial mass, at a distance from the dense peripancreatic surrounding mesenchyme. The fraction of the primitive endocrine cells undergoing proliferation is low (5% of the insulin cells at 8 WD, 3% at 11 WD), which is in favor of massive differentiation as the major mechanism for increasing endocrine mass. By contrast, the nonendocrine epithelial cells have a higher rate of proliferation; the epithelial cells in contact with the dense peripancreatic surrounding mesenchyme show more proliferation activity than those within the central part of the epithelial mass (at 11 WD, labeling index: periphery 65% vs. center 15%, P < 0.001). In conclusion, the patterns of endocrine differentiation and epithelial proliferation observed within the human pancreas early in development suggest that the mesenchyme plays a role in these phenomena.

Cell Division↗
PubMed2000

[Isolated sphenoiditis treated with endoscopic surgery in a child].

Isolated sphenoiditis in childhood is a rare entity which is often very difficult to diagnose with conventional techniques. The authors present a case of sphenoiditis in nine years old boy, where chronic rhinitis and persistent cephalqia where the main symptoms. The diagnosis was made on the base of computed tomography and nasal endoscopy. Because of lack of effect after pharmacological treatment the child was submitted to endoscopic surgery--sphenoethmoidectomy, which resulted it total recovery. The diagnosis, indications to computed tomography of paranasal sinuses in children, options of both conservative and surgical treatment and possible complications of the diseases are discussed.

Child↗
PubMed1999

Rectal epithelial apoptosis in familial adenomatous polyposis patients treated with sulindac.

BACKGROUND: Sulindac regresses colorectal adenomas in patients with familial adenomatous polyposis (FAP), although the mechanism of polyp regression is unclear. AIMS: To determine whether differences occur in alteration of rectal epithelial apoptotic index and expression of apoptosis related proteins in FAP patients treated with sulindac compared with placebo. PATIENTS: Twenty one FAP patients; 12 had not undergone colectomy. METHODS: Patients with FAP were treated with sulindac 150 mg orally twice a day for three months (n=10) or placebo (n=11). Colorectal polyp number was determined and biopsies of the normal rectal mucosa were performed before and after three months of treatment. Response to treatment and alteration of the apoptotic ratio (index in base of crypt divided by index in surface epithelium) were evaluated. Bcl-2, bax, p21/WAF-1, and p53 proteins were assessed semiquantitatively by immunohistochemistry. RESULTS: Significant decreases in polyp number and in the apoptotic ratio were seen in patients treated with sulindac compared with controls. The mean percentage change in polyp number from baseline was -46% in the sulindac group and +13% in the placebo group (p=0.005). Mean percentage change in the apoptotic ratio was -8% and +25% in the sulindac and placebo treated patients, respectively (p=0.004). No differences in expression or compartmentalisation of apoptosis related proteins were noted between treatment groups. CONCLUSIONS: Sulindac regression of colorectal adenomas is accompanied by alteration of the rectal epithelial apoptotic ratio with relative increase in apoptosis in surface cells compared with the deeper crypt. The utility of the apoptotic ratio as an intermediate biomarker for colorectal tumorigenesis deserves further study.

Adenomatous Polyposis Coli↗
PubMed1999

Sera from children with type 1 diabetes mellitus react against a new group of antigens composed of lysophospholipids.

Several autoantibodies related to Type 1 diabetes mellitus and their corresponding autoantigens have been previously identified. While peptide antigens are more widely recognized, lipid antigens like sulfatides and gangliosides are also known epitopes for the diabetic humoral immune response. Islet cell antibodies (ICA) in Type 1 diabetes are heterogeneous immunoglobulins directed against selected antigens in the islets of Langerhans. Moreover, ICA may be the best predictive marker of disease in family members of patients with Type 1 diabetes. The aims of this study were: (1) to purify lipids from porcine pancreas that contain ICA epitopes; (2) to characterize these lipid antigens, and (3) to use the purified lipids in an assay to detect antibodies in patients with Type 1 diabetes. A unique family of 4 lysophospholipids, 1 fully characterized as lysophosphatidylmyoinositol, partially inhibited ICA staining, and therefore, were considered to be candidate antigens for an ICA immunoassay. Using a dot blot immunoassay, we detected antibodies directed against these phospholipids in 28 out of 46 (61%) diabetic sera, while detecting only 1 false positive out of 28 nondiabetic sera (3.6%; p < 0.0001 comparing diabetic vs. nondiabetic serum). Therefore, lysophospholipid immunoassay positivity is present in sera of Type 1 diabetic patients. Furthermore, we detected 15 out of 23 ICA-negative diabetic sera (65.2%), showing that our phospholipid immunoassay does not correlate with ICA positivity.

Autoantibodies↗
PubMed1999

Short needles (8 mm) reduce the risk of intramuscular injections in children with type 1 diabetes.

OBJECTIVE: To study whether 8-mm needles can reduce the frequency of intramuscular injections in diabetic children. RESEARCH DESIGN AND METHODS: We conducted a prospective crossover study in 50 children whose BMI was < or = 60th percentile to compare two lengths of needles (12.7 and 8 mm) regarding the occurrence of intramuscular injections as assessed by ultrasonography. RESULTS: The frequency of intramuscular injections was 86% with the 12.7-mm needles and 38% with the 8-mm needles. The frequency of intramuscular injections was significantly reduced when using the 8-mm needles in the arms (P < 0.01) and thighs (P < 0.001). The efficiency of 8-mm needles, as defined by an intramuscular injection with a 12.7-mm needle and a subcutaneous injection with an 8-mm needle, was found for half of the children who injected in the arm and for two-thirds of the children who injected in the thigh. The subcutaneous tissue (SQT) thickness measured by ultrasonography with a skinfold was significantly higher (9.8 +/- 2.2 mm) in the group in which the 8-mm needles were efficient than in the group in which they were not efficient (6.8 +/- 2.1 mm, P < 0.0001). The efficiency of the 8-mm needle was not related to age, sex, BMI, percentile of BMI, injection device, or injection site. The sensibility and specificity of SQT thickness in predicting the efficiency of the 8-mm needles were both 79%. CONCLUSIONS: Needles that are 8 mm long significantly reduce the risk of intramuscular insulin injection in slim or normal-weight (BMI < or = 60th percentile) diabetic children and adolescents.

Adolescent↗
PubMed1999

Theophylline intoxication mimicking diabetic ketoacidosis in a child.

A 5-year-old boy presented with abdominal pain, nausea and vomiting of blood. Twelve hours after admission, "diabetic ketoacidosis" was diagnosed on the basis of elevated glycaemia, glycosuria, ketonuria and a low bicarbonate blood level, which led to treatment with fluids and regular insulin infusion. Over a 36-hour period, insulin was progressively decreased and finally stopped because of the rapid fall and normalization of blood glucose concentration. Drug poisoning was suspected on the basis of persistent tachycardia in the absence of other signs of dehydration. Salicylate intoxication was excluded, and theophylline was finally incriminated. This compound, used by adults in the child's home, had caused accidental theophylline poisoning, mimicking diabetic ketoacidosis. Pre-diabetic immune markers were repeatedly negative, and no diabetes has developed after four years of follow-up. Thus, the transient increase in blood glucose was not related to a pre-diabetic status. A diagnosis of masked theophylline poisoning should be considered in similar situations involving a rapid decrease of insulin requirements.

Adult↗
PubMed1998

Parasite-induced risk of mortality elevates reproductive effort in male Drosophila.

A trade-off between sex and somatic maintenance is fundamental to life-history theory. Tests of this trade-off usually emphasize deleterious consequences of increased reproduction on life span. Here we show the reverse effect, that reductions in the expected life span elevate sexual activity. Experimentally parasitized male Drosophila nigrospiracula lived shorter lives, but before dying, they courted females significantly more than unparasitized controls. This greater courtship resulted in increased mating speed, and potentially greater reproductive success than parasitized males would have achieved otherwise. The results show that an environmental reduction in life span increases reproductive effort, and support the hypothesis of a trade-off between these key life-history traits.

Animals↗
PubMed1998

A mating plug and male mate choice in Drosophila hibisci Bock.

The functional significance of mating plugs and their relation to male mating behaviour in insects are obscure. In Drosophila hibisci, we describe a firm, gelatinous, mating plug that fills the entire uterus at copulation, and evaluate two nonmutually exclusive hypotheses for the plug's function: (1) retention of sperm near the openings of the sperm storage organs and (2) inhibition of further matings. Unlike full-sized plugs, smaller plugs produced by previously mated males failed to retain sperm at the anterior end of the uterus, indicating that full-sized plugs prevent sperm backflow away from female storage organs. Sexually mature males failed to copulate with previously mated, young females, suggesting that the plug may also deter rival matings. In newly emerged females, the plug remains within the uterus for up to 4 days after copulation, but in mature females, the plug and ejaculate are expelled whenever the next mature oocyte descends into the uterus from the common oviduct, which may be soon after copulation. Males remained in copula significantly longer with mature females, perhaps to compensate for this greater likelihood of ejaculate expulsion. Males showed a mating preference for young virgins over older virgin and nonvirgin females. This unusual mating preference may confer fertility benefits made available through the effectiveness of the plug in reducing sperm competition. Copyright 1998 The Association for the Study of Animal Behaviour.

Journal Article↗
PubMed1998

[Activating mutations of the TSH receptor: a synthesis highlighting certain pediatric aspects].

Mutations of the TSH receptor gene cause constitutive activation of the TSH receptor responsible for cases of familial hereditary hyperthyroidism (germline mutations), cases of sporadic congenital hyperthyroidism (de novo mutations), and thyroid hyperfunctioning autonomous adenomas (somatic mutations). The discovery of these mutations not only clarifies the pathogenesis of some forms of thyroid autonomy, such as cases of persistent neonatal hyperthyroidism without maternal thyroid autoimmunity, but also contributes to a better understanding of the structure-function relationships of the TSH receptor.

Adenoma↗
PubMed1998

Hyperthyroidism in early infancy: pathogenesis, clinical features and diagnosis with a focus on neonatal hyperthyroidism.

Neonatal hyperthyroidism has mostly been described in the context of maternal Graves' disease. It has been estimated that about 0.2% of pregnant women have Graves' disease; however only 1% of the children born to these women are described as having hyperthyroidism. In most of the cases, the disease is due to maternal antibodies transferred from the mother into the fetal compartment, which stimulate the fetal thyroid by binding to the thyrotropin (TSH) receptor. In this form of neonatal hyperthyroidism, thyrotoxicosis disappears with the clearance of the maternal antibodies and usually signs disappear during the first 4 months of life. Rare forms of persistent, nonimmune neonatal hyperthyroidism are explained by molecular abnormalities of the TSH receptor. Prematurity is frequent, as well as hypotrophia. Tachycardia, goiter, hyperexcitability, poor weight gain, hepatomegaly and/or splenomegaly, stare and/or eyelid retraction are among the most frequent neonatal thyrotoxicosis clinical signs. Diagnosis is based on the determination of the blood level of thyroxine (T4), triiodothyronine (T3), and TSH. Even if these levels are normal in the cord blood, tests should be repeated 3 to 10 days later to detect possible delayed appearance of the disorder. These parameters should be interpreted according to the age of the neonate. To confirm the immune nature of this hyperthyroidism, thyroid-stimulating immunoglobulins (TSI) should be determined. The TSI determination is crucial in identifying nonimmune causes of neonatal hyperthyroidism: in this neonatal hyperthyroidism, TSI are not detected, either by radioreceptor assay and/or by functional assay, and molecular studies are needed to identify the mutation. Mutation of the TSH receptor leading to its constitutive activation and to neonatal hyperthyroidism have been described. Germline mutations are found in hereditary hyperthyroidism; de novo germline mutations can cause sporadic congenital hyperthyroidism.

Autoantibodies↗
PubMed1998

Confirmatory typing results of the National Polish Bone Marrow Donors Registry.

Preliminary analysis of HLA class I typing of 618 individuals (patients and healthy members of 153 families) referred to the National Polish Bone Marrow Donors Registry (NPBMDR) for a donor search revealed that the number of undetected locus A and B antigens was more frequent than it was reported in a large scale population study in Poland (0.28 vs 0.076, p=0.000). This was associated with a lack of typing of family members for 51 out of 153 patients. 171 individuals primary typed (140 by serology and 31 by DNA typing) in 6 different Polish institutions were retyped in our laboratory with the use of PCR-SSO or PCR-SSP techniques. The results were discrepant in 50 cases (29%) including 19 patients and 31 family members. In 46% one DR specificity was missing, false typing of one or two specificities was evident in 46% and 14% of erroneous typing, respectively. The highest rate of errors was found in DRw52 group of specificities with the most difficult DR13 (32% of all false typing and 67% of errors within DRw52 group).

Bone Marrow↗