Biomedical subjects

M Nowak

Publications and source records attributed to M Nowak.

At least 19 recordsLinked to original sources

PubMed2006

Baseline survey of sun-protection knowledge, practices and policy in early childhood settings in Queensland, Australia.

Excessive exposure to sunlight during early childhood increases the risk of developing skin cancer. Self-administered questionnaires exploring sun-protection knowledge, practices and policy were mailed to the directors/coordinators/senior teachers of all known early childhood services in Queensland, Australia, in 2002 (n = 1383; 56.5% response). Most (73.7%) services had a written sun-protection policy (SPP). However, 40.6% of pre-schools and kindergartens had not developed a written SPP. Most directors had moderate knowledge about sun-protection (median score: 7/12 [IQR 6, 8]), but few understood the UV index, the sun-protection factor rating for sunscreens or the association between childhood sun-exposure, mole development and melanoma. Pre-school teachers had lower knowledge scores than directors of long day care centers and other services (P = 0.0005). Staff members reportedly wore sun-protective hats, clothing and sunglasses more often than children. However, sunscreen use was higher among children than staff. Directors' knowledge scores predicted reported hat, clothing, sunscreen and shade utilization among children. Remoteness impacted negatively on director's knowledge (P = 0.043) and written SPP development (P = 0.0005). Higher composite sun-protection scores were reported for children and staff from services with written sun-protection policies. SPP development and increased sun-protection knowledge of directors may improve reported sun-protective behaviors of children and staff of early childhood services.

Adolescent↗

PubMed2006

[Perioperative echocardiography: basic principles].

Over the past decades, echocardiography has undergone a continuous evolution in technology that has promoted its clinical application and acceptance throughout perioperative medicine. These technological advances include improvements in transducer development that permit superior imaging quality and a wider selection of probes for epicardial, epiaortic, and surface echocardiography which can also be used in conjunction with multiplane transesophageal echocardiography. Moreover, the addition of Doppler technology and digital acquisition has secured the role of echocardiography as a valuable and relatively noninvasive diagnostic tool for the assessment of cardiovascular disease and hemodynamic monitoring throughout the perioperative period. Therefore, it has become increasingly important for perioperative physicians to understand the basic principles and underlying fundamental concepts pertaining to the technology and physics of echocardiography, as well as its inherent limitations. The current review outlines the modes and applications of different echocardiographic techniques used in perioperative echocardiography including M-mode, two-dimensional echocardiography, and Doppler assessment of blood flow. In addition, the limitations of these techniques and typical artifacts associated with the perioperative use of echocardiography are described.

Artifacts↗

PubMed2006

Effect of an exercise training program on endothelial dysfunction in diabetic and non-diabetic patients with severe chronic heart failure.

BACKGROUND: Endothelial dysfunction is found both in patients with chronic heart failure and in patients with insulin-treated type 2 diabetes mellitus. This endothelial dysfunction leads to a significant reduction in endothelium-derived vasodilation. Physical exercise can have a positive effect on endothelial dysfunction in patients with coronary artery disease, chronic heart failure and diabetes mellitus. It is not clear, however, whether an exercise program influences endothelial function in diabetics with chronic heart failure. Our study was thus aimed at investigating whether a special exercise program would affect endothelial function. Comparisons were made with insulin-treated type 2 diabetics and with non-diabetics suffering from chronic heart failure. METHODS: 42 patients with severe chronic heart failure (LVEF < or = 30%), insulin-dependent diabetics (n=20, mean age 67+/-6 yrs, 16 male, 4 female), non-diabetics (n=22, mean age 68+/-10 yrs, 20 male, 2 female) participated in a 4-week exercise program consisting of ergometer and special muscle strength training. Before (T1) and at the end (T2) of the training program endothelium-dependent and endothelium-independent vasodilatory capacity were assessed by brachial artery diameter measurement. RESULTS: At the end of the training program, there were no significant results within the two groups. The endothelium-dependent vasodilation changed between T1 and T2 as follows: In the diabetic group, the endothelium-dependent vasodilation at T1 and T2 was 5.1+/-3.6 and 4.9+/-2.5%, respectively. For the non-diabetics, the endothelium-dependent vasodilation was 6.8+/-4.5 and 7.6+/-4.0% at T1 and T2, respectively. The endothelium-independent vasodilation in the diabetics was 10.5+/-5.6 at T1 and dropped to 8.7+/-4.1% at T2. The results for the non-diabetics were 13.2+/-5.8 and 12.3+/-6.3% at T1 and T2, respectively. The LVEF in the diabetics was 24.2+/-3.4% at T1, increasing to 27.8+/-5.8% at T2. In the non-diabetics, the LVEF was 22.9+/-3.8 at T1 vs. 28.6+/-6.9% at T2. In the groups of diabetics, the maximum oxygen uptake (VO2-max) was 10.3+/-3.9 at T1 vs. 11.4+/-2.8 ml/kg/min at T2 and in the group of non-diabetics 10.0+/-3.1 vs. 13.5+/-5.0 ml/kg/min. No correlations were found between the change in endothelium-dependent vasodilation and the increase in oxygen uptake. CONCLUSION: In our study, a program of physical exercise had no influence on endothelium-dependent or endothelium-independent vasodilation in insulin-treated type 2 diabetics or in non-diabetics with considerably reduced ejection fraction. In both groups, however, an exercise-related influence on medical parameters and physical performance could be observed.

Aged↗

PubMed2006

Immunohistochemical identification method of tumour cells in the S phase of mitotic cycle and its usefulness in diagnostics of mammary gland adenocarcinomas in bitches.

The studies aimed at identification of neoplastic cells at the S phase of mitotic cycle in mammary gland adenocarcinomas of bitches. The material was sampled from bitches of various races, aging 6 to 12 years, in which the mammary gland tumours developed spontaneously. The tumours were verified histopathologically and, then, immunohistochemical reactions were performed in order to detect cells which had incorporated BrdU (bromodeoxyuridine), contained Ki-67 or PCNA antigen. The histological preparations were photographed and obtained pictures were subjected to computer-assisted image analysis using Axiophot microscope (Carl Zeiss) coupled to a computer and the Multi-ScaneBase V 8.08 software, working under Windows. Fifty percent of sections from mammary gland adenocarcinomas demonstrated BrdU labelling index of 4-5%, 40% of 1-3%, while in the remaining 10% of examined tumours no BrdU incorporation could be demonstrated. No evident relationship could be detected between the presence of BrdU incorporation and Ki-67 or PCNA antigen presence but a significant correlation was demonstrated between the expression of Ki-67 and PCNA.

Adenocarcinoma↗

PubMed2005

Changes in lipid metabolism in women with age-related macular degeneration.

Age-related macular degeneration (AMD) is one of the leading causes of visual loss among people aged 65 and older. At present the origin of AMD still remains unknown. The objective was to evaluate the chosen lipid and lipoprotein concentrations in blood of patients with AMD. Sixty women aged 55-71 (mean age 65.1+/-5.7) were treated in the outpatient ophthalmological clinic for more than two years because of AMD. We evaluated total serum cholesterol (TCH), triglycerides (TG), HDL-cholesterol (HDL), LDL-cholesterol (LDL), lipoprotein (a) (Lp(a)), apolipoprotein AI (Apo AI) and apolipoprotein B (Apo B) by direct spectrophotometry (Human and Randox standard kits, USA). We found a significant increase of TCH, LDL and TG (224.36+/-41.67 mg/dl, 159.02+/-39.66 mg/dl and 120.92+/-42.64 mg/dl), and a significant decrease of HDL (38.68+/-6.36 mg/dl) in the AMD patients when compared with the control group. We have not found a significant difference in the average TG level between the studied groups. The concentration of Apo B was markedly increased (164.66+/-46.46 mg/dl) and Apo AI concentration was markedly decreased (128.9+/-17.01 mg/dl) in the AMD patients when compared with the control group. There was no significant difference in the concentration of the Lp(a) between the two groups. The results of our present study could point to the fact that changes in the lipid metabolism could be one of the very important risk factors involved in the pathogenesis of AMD.

Aged↗

PubMed2005

Perp is required for tissue-specific cell survival during zebrafish development.

The tumor suppressor p53 has two alternative effects, causing either cell cycle arrest or apoptosis. These different effects are supposed to be mediated by the transcriptional activation of different target genes. perp, encoding a transmembrane protein of the Pmp22 family, is a transcriptional p53 target exclusively upregulated in apoptotic cells. However, its role during normal development had remained largely unclear. Here, we report the isolation and characterization of a zebrafish perp homolog. Upon overexpression in early zebrafish embryos, perp induces apoptosis. In addition, it contributes to p53-dependent and UV-induced cell death. However, during normal zebrafish development, perp displays a p53-independent and spatially restricted expression in specific cell types and tissues. Antisense-mediated loss of Perp function leads to increased apoptosis in perp-expressing cells of the developing skin and notochord. We conclude that, in contrast to its proapoptotic function in stressed cells, Perp plays an antiapoptotic role during normal zebrafish development to regulate tissue-specific cell survival.

Animals↗

PubMed2005

TGF-beta1 mRNA expression in liver biopsy specimens and TGF-beta1 serum levels in patients with chronic hepatitis C before and after antiviral therapy.

BACKGROUND AND OBJECTIVE: Transforming growth factor (TGF)-beta1 is the best-characterized profibrogenic cytokine. TGF-beta1 increases the production of extracellular matrix proteins and their receptors and inhibits the synthesis of matrix degrading proteolytic enzymes. We undertook this study to simultaneously evaluate the effect of interferon alpha 2b plus ribavirin therapy on TGF-beta1 daily serum levels and on mRNA TGF-beta1 expression in liver biopsy specimens from 60 patients with chronic hepatitis C. METHODS: Serum levels of TGF-beta1 were measured by ELISA. The levels of the RNAs in liver biopsy specimens were measured by quantitative reverse transcriptase polymerase chain reaction. After treatment, patients were divided into two groups: 34 responders [undetectable hepatitis C virus (HCV)-RNA, normal ALT levels, decrease in histology activity index compared with pretreatment liver biopsy] and 26 non-responders (detectable HCV-RNA, elevated ALT levels, no decrease in the histology activity index). RESULTS AND DISCUSSION: In patients with hepatitis C, the 'responders' to the antiviral treatment showed significant decreases in both mean daily serum TGF-beta1 levels and mRNA TGF-beta1 expression in the liver biopsy specimens. The 'non-responders' serum TGF-beta1 concentrations did not change significantly, but the mRNA TGF-beta1 expression did. CONCLUSION: Both serum TGF-beta1 concentration and mRNA TGF-beta1 expression in liver biopsy specimens may be useful as prognostic markers in patients with hepatitis C undergoing antiviral therapy.

Adult↗

PubMed2005

Studies on nucleolar organiser regions (AgNors) in selected spontaneous and transplantable animal tumors.

Behaviour of argyrophilic nucleolus organising regions (AgNOR) was estimated in various types of spontaneous and transplantable tumors in animals. The studies were performed on spontaneous epithelial and mesenchymal tumors, malignant and non-malignant, as well as transplantable tumors: Morris hepatoma, mammary gland carcinoma and Yoshid sarcoma. The examinations were made on paraffin sections, using silver-staining method according to Ploton et al. Quantitative assessment was made with computer-aided microscopic image analysis system Multi-Scan Base V.8 for Windows, coupled with Carl Zeiss microscope. It was demonstrated that AgNOR index reflects malignancy of the tumor, since it increases clearly in cancers and sarcomas, both spontaneous and transplantable. The highest AgNOR index--0.13--was noted in the group of spontaneous tumors in epithelial malignant tumors, and in the group of transplantable tumors in mesenchymal tumors (Yoshid sarcoma) it was 0.15. Classification of the studied spontaneous and transplantable tumors into groups of the same histogenesis, though phenotypically different, was aimed at demonstration of the increasing tendency of AgNOR index.

Animals↗

PubMed2005

Trends in the incidence of the free wall cardiac rupture in acute myocardial infarction. observational study: experience of a single center.

PURPOSE: Free wall cardiac rupture (CR) is one of the most common cause of in-hospital death in acute myocardial infarction (AMI). The early diagnosis of CR and selection of the patients predisposed to CR become an important clinical tool. AIM: assessing the occurrence of CR in patients with AMI, to determine the factors which could help to identify the patients threatened with CR. MATERIAL AND METHODS: 2320 consecutive patients with AMI. CR was proved by autopsy or by echocardiography performed during cardio-pulmonary resuscitation (CPR). RESULTS: In-hospital mortality was 11% (254 patients). 50 patients (2%) died from CR. CR was the cause of 20% of total in-hospital death. Patients with CR were older than survivors (72 vs 60 years, p<0.0001). Women prevailed in CR group: (62% in CR group vs 27% in the survivors, p<0.01). 29% of patients were treated with thrombolytics (Th+). Out of 58 patients from Th (+) group who died, 17 (29.31%) died because of CR. CR occurred in 33 (16.8%) patients out of 196 died in Th (-) group. In the logistic regression analysis only age and sex remained as predictors of CR. 16 patients died from CR during first 24 h from admission (ECR). In 34 patients CR occurred >24 h (LCR). In ECR group were no prevalence of women, while in LCR women constituted 68%. In ECR group all but one patient had no previous history of MI (p=0.06). Frequency of thrombolythic therapy was equal. CONCLUSIONS: Advanced age patients, particularly women with first AMI are at risk of CR. Decision of thrombolytic treatment in this group of patients must be very cautious.

Acute Disease↗

PubMed2004

Serum adiponectin in women with polycystic ovarian syndrome and its relation to clinical, metabolic and endocrine parameters.

UNLABELLED: Several studies have demonstrated that low levels of serum adiponectin are present in obesity, insulin resistance, hypertension and hyperlipidemias. The aim of our study was to determine whether serum adiponectin level is different between patients with polycystic ovarian syndrome (PCOS) and control subjects. We also investigated relationships between various cardiovascular risk factors, levels of serum adiponectin and other hormones, such as androstendione, testosterone, estradiol, DHEAS, sex hormone binding globulin (SHBG), and leptin. We also analysed the correlation between serum adiponectin and free androgen index. Ninety-one women with clinical diagnosed PCOS and 53 healthy control subjects, carefully matched by body mass index (BMI) and age, were enrolled in the study. The fasting blood samples were obtained and all participants underwent an oral 75 g glucose tolerance test. The prevalences of impaired glucose tolerance (IGT), hypertension and hypertriglyceridemia were higher in the PCOS group. PCOS women had increased androgen concentrations and higher free androgen index and decreased level of serum SHBG. Lower serum adiponectin concentrations were observed among cases than in controls (median 13.7 microg/ml vs 17.8 microg/ml, p<0.001) despite being matched by BMI. In the PCOS group adiponectin levels correlated significantly with: BMI (r=-0.32, p=0.002), waist circumference (r=-0.32, p=0.003), waist-to-hip ratio (WHR, r=-0.38, p=0.001), triglycerides (r=-0.31, p=0.007), SHBG (r=0.30, p=0.003) and free androgen index (r=-0.29, p=0.02). In contrast, the adiponectin level does not appear to be related to total testosterone, DHEAS and leptin levels. The adiponectin and SHBG levels were found to be decreased in PCOS women with IGT compared to PCOS women with normal glucose tolerance, but after adjustment by BMI or WHR, the differences were no longer statistically significant. To exclude a possible confounding effect due to a higher prevalence of IGT in the PCOS group, this comparison was repeated for the subgroup of 58 PCOS women and 48 control women after excluding those with IGT. Neither adiponectin nor SHBG were significantly different between those subgroups. Multiple regression analysis revealed that serum adiponectin concentrations were best predicted by WHR, free androgen index and presence of IGT when all patients were considered. In PCOS subjects, the only independent predictor of adiponectin concentrations was glucose tolerance status. CONCLUSIONS: Lower adiponectin levels were observed in PCOS group than in control women, and these differences were probably due to higher prevalence of IGT in these cases.

Adiponectin↗

PubMed2004

Immunocytochemical identification of neoplastic cell clone in phase S of cell cycle in transplantable rat tumors.

Wistar and Buffalo rats of both sexes, aged 4 months, were divided into three groups: I which was given an intramuscular injection of 3 x 10(6) cells of Morris hepatoma (Buffalo males), II--subcutaneous injection of 3 x 10(4) cells of mammary gland carcinoma (Wistar females), III--intraperitoneal injection of 3 x 10(4) cells of Yoshid sarcoma (Wistar males). The animals were killed: in group I--19, group II--13 and in group III--6 days after tumor transplantation. Twenty four hours before euthanasia the rats were given 5-brome-2'-deoxyuridine (BRd-U) at a dose of 50 mg/kg body mass. The control group consisted of animals with tumour. They were not treated with BRd-U. Immunocytochemical reaction was performed on the sections of tumors, using monoclonal anti-BRd-U clone BU-33, Sigma. Computer measurements of tumor cells were carried out. There was a high similarity in morphological parameters between two kinds of cancer, and clear differences between them and Yoshid sarcoma. The main difference was noted in a twofold increase in the quantity of synthesised DNA in the nuclei of sarcoma cells. Immunocytochemical identification of tumor cells in phase S of the cell cycle with the use of monoclonal anti-BRd-U antibody is a precise and quick method of estimation of their proliferative potential.

Animals↗

PubMed2004

Circadian rhythm of androstendione and free testosterone in asthmatic women with postmenopausal hormone therapy.

OBJECTIVE: of this study was to assess daily rhythm of androstendione (delta4alpha) and free testosterone (FT) levels in postmenopausal asthmatic women before and after hormonal replacement therapy and the influence of inhaled glucocorticosteroids (GC). METHODS: 54 asthmatic and 20 healthy postmenopausal women (aged 48-59) before and after 6 months of estrogen plus progestin therapy (EPT) were studied. Hormone concentrations in serum (delta4alpha and FT) were assessed with the use of RIA method. Statistical analysis of the circadian rhythm was performed with the use of cosinor test according to Halberg et al RESULTS: Cosinor analysis of delta4alpha and FT secretion during the day showed existence of daily rhythm in three studied groups before as well as after postmenopausal hormone therapy (HT). A statistically significant decrease of circadian concentrations of delta4alpha and FT in groups of patients treated with GC was observed. Changes in amplitude of delta4alpha and FT rhythm between studied groups were not observed. However, displacement of rhythm acrophase of studied hormones in asthmatic women in comparison to control group before and after HT was shown. No significant differences in circadian values of delta4alpha and FT concentrations before HT use compared to values after HT were shown. CONCLUSIONS: Postmenopausal asthmatic women show diminished circadian concentrations of androstendione and free testosterone in serum caused among other things by inhalative GC. Postmenopausal hormone therapy did not influence any changes in function of studied endocrine organs.

Administration, Inhalation↗

PubMed2003

Conformational constraints on side chains in protein residues increase their information content.

Like all other complex biological systems, proteins exhibit properties not seen in free amino acids (i.e., emergent properties). The present investigation arose from the deduction that proteins should offer a good model to approach the reverse phenomenon, namely top-down constraints experienced by protein residues compared to free amino acids. The crystalline structure of profilin Ib, a contractile protein of Acanthamoeba castellanii, was chosen as the object of study and submitted to 2-ns molecular dynamics simulation. The results revealed strong conformational constraints on the side chain of residues compared to the respective free amino acids. A Shannon entropy (SE) analysis of the conformational behavior of the side chains showed in most cases a strong decrease in the SE of the chi1 and chi2 dihedral angles compared to free amino acids. This is equivalent to stating that conformational constraints on the side chain of residues increase their information content and hence recognition specificity compared to free amino acids. In other words, the vastly increased information content of a protein relative to its free monomers is embedded not only in the tertiary structure of the backbone, but also in the conformational behavior of the side chains. The postulated implication is that both backbone and side chains, by virtue of being conformationally constrained, contribute to the recognition specificity of the protein toward other macromolecules and ligands.

Computer Simulation↗

PubMed2003

Changes in blood antioxidants and several lipid peroxidation products in women with age-related macular degeneration.

PURPOSE: The aim of this study was to evaluate the ferric reducing ability of plasma (FRAP), selected enzymatic and non-enzymatic components of the antioxidative system, and the intensity of peroxidative processes in the blood of patients with age-related macular degeneration (AMD). METHODS: In the peripheral blood, we evaluated FRAP; concentrations of vitamins C, A, and E; and of thiols. We assayed the activity of enzymatic components of the antioxidative system-superoxide dismutase, catalase, ceruloplasmin and the concentration of reduced glutathione as an indicator of glutathione peroxidase activity. In order to determine the intensity of lipid peroxidation, we measured the concentrations of malondialdehyde and hydroxyalkenales (MDA-HNA) and conjugated diens (CD). RESULTS: We found a significant increase in FRAP in patients with AMD compared with the control group. The average concentrations of vitamins A and C were low and vitamins E and GSH were significantly higher in AMD than in the control group. The activity of almost all the antioxidative enzymes was high. We found a significant increase in MDA-HNA but no difference in CD. CONCLUSIONS: The significantly higher concentration of lipid peroxidation products in patients with AMD indicates an important pathogenic role of oxido-reduction disturbance. The high FRAP concentration may be one of the protective mechanisms in oxidation stress. The adaptive increase of the antioxidant barrier mostly involves the enzymatic components.

Aged↗

PubMed2003

The relationship between bone metabolism, melatonin and other hormones in sham-operated and pinealectomized rats.

OBJECTIVE: The influence of pinealectomy and long-term melatonin (MEL) administration on circadian oscillations of selected biochemical markers of bone metabolism [serum alkaline phosphatase (ALP) activity, carboxyterminal propeptide type I procollagen (PICP) and carboxyterminal telopeptide type I collagen (ICTP) concentrations as well as urinary excretion of hydroxyproline (HYP) and Ca] and possible involvement of circadian secretion of IGF-I, parathyroid, thyroid, adrenal cortex and gonads function in this mechanism was evaluated. METHODS: Studies were performed in 192 adult male Wistar rats weighing 145 +/- 9 g which were subjected to pinealectomy or sham operation. In half of the animals from each group MEL (Sigma, USA) in a dose of 50 mg/100 g b.w. was administered intraperitonealy (daily between 17.00 and 18.00 h for a 4-week period). Material for studies (blood and urine) was collected every 3 hours during a day. Hormones, PICP and ICTP concentrations were determined with the use of RIA methods. whereas ALP, HYP and Ca values - spectrophotormetrically. RESULTS: The study has shown that pinealectomy had an inducing, while exogenous MEL a suppressing effect upon the level of investigated biochemical markers of bone metabolism. Furthermore, substantial changes in the values of amplitude and phase of their circadian oscillations were shown. Distinct, dependent on the time of day disturbances in circadian fluctuations of PICP, ICTP, HYP and Ca showing generally negative correlation with changes in endogenous MEL concentrations and positive with IGF-I and corticosterone (B) levels were found. In addition, changes in circadian oscillations of ALP and PICP correlated negatively with daily oscillations of calciotropic hormones and B. However, ICTP, HYP and Ca concentrations correlated positively with circadian fluctuations of B and FT3 (the latter only in sham operated rats receiving MEL). CONCLUSIONS: This study showed that both pinealectomy and long-term MEL administration influence the circadian rhythm of bone metabolism and that an important role in the mechanism of this dependence is played by the changes of endogenous MEL levels. Secondary changes in circadian oscillations of calciotropic hormones, IGF-I and corticosterone concentrations, caused by pinealectomy and long-term MEL administration result in altered bone metabolism rhythm.

Alkaline Phosphatase↗

PubMed2002

[Epulis in a newborn. histogenetic comparison with a granular cell tumor in adults].

The congenital granular cell tumor is a rare lesion of newborns located on the alveolar ridge with a marked predilection for female infants. Histologically these tumors are characterized by large eosinophilic granular cells, similar to granular cell tumors in adults which are often seen as Abrikossoff tumors. Immunohistochemical studies revealed the different histogenesis and evolution of both these tumor entities. We report on a female newborn infant with a congenital epulis of the left anterior maxillary alveolar ridge. This case demonstrates a rare congenital tumor of newborns and reveals the histogenetic differences to granular cell tumors in adults.

Adult↗

PubMed2002

[Psychogenic paralysis in childhood and adolescence].

OBJECTIVES: This article presents the characteristics of psychogenic paralysis in children and adolescents. The overview covers the changes in its diagnostic classification from ICD-6 to ICD-10. METHODS: Characteristics of this diagnostic entity are presented and epidemiological data discussed on the basis of clinical studies from the literature. Among the dissociative disorders in children and adolescents, psychogenic paralysis shows a characteristic distribution according to sex and age. Furthermore the literature indicates a better prognosis for patients with this symptomatology than for children and adolescents with pseudoseizures and psychogenic vision disorders. RESULTS: Iatrogenic invasive diagnostic and therapeutic procedures, somatic injuries, infections and a model for the symptoms play an important role in the pathogenesis of gait disorders.

Adolescent↗

PubMed2002

Egg yolk platelet proteins from Xenopus laevis are amyloidogenic.

The association of amphibian (Xenopus laevis) egg yolk platelet proteins, represented predominantly by lipovitellin, was studied as a model of the formation of amyloid deposits. Two kinds of molecular organization formed by this protein material - native and heat-denatured - were found to exhibit amyloid properties although they differ significantly in structural organization. The first consisted in protein molecules arranged in the natural, physiological, net-like platelet organization, with a tendency to orient uni-directionally. The second was obtained by the gradual removal of Congo red from lipovitellin denatured by heating in an excess of dye. This procedure produced the twisted fibrillar organization of molecules typical for amyloids, represented predominantly by end-to-end associated major polypeptide chains of lipovitellin. Both native and denatured structural forms bind Congo red and produce a green birefringence effect, confirming the near parallel alignment of the complexed Congo red molecules. However, a dye(1,4-bis(1-amino-4-sulfonaphtyl-2-azo)phenylene) closely related to Congo red but with a very weak self-assembling tendency appeared inactive when the spectral shift was studied in a cross-polarization system, indicating in this way that dye supramolecularity is an extra factor which may determine binding to amyloid proteins and specific spectral effects.

Amyloid↗