Biomedical subjects

G Koliakos

Publications and source records attributed to G Koliakos.

29 records · Page 2Linked to original sources

PubMed1995

Detection of a high molecular weight heparin binding acidic growth factor in human placenta.

A heparin binding fibroblast growth factor with a molecular weight of approximately 45 kDa has been detected in human placenta. The protein was extracted from placenta and purified by a combination of ammonium sulfate precipitation, DE-52 anion exchange chromatography, G100 gel exclusion and heparin sepharose affinity chromatography. The molecule was shown to be monomeric after treatment with beta-mercaptoethanol, and had an acidic isoelectric point. The properties of the polypeptide described in this paper (45 kDa, Pi 4-5, monomeric, heparin binding fibroblast growth factor), suggest that it may represent an as yet undescribed growth factor.

Female↗

PubMed1994

Rat liver endoplasmic reticulum protein kinases.

1. Rat liver microsomal membranes were studied for the presence of protein kinases. Microsomal proteins solubilized with Triton X-100 were analyzed by means of ion exchange chromatography. 2. Protein kinase activity was detected in the column fractions using specific assays for cAMP-dependent protein kinase, cGMP-dependent protein kinase, protein kinase C, Ca2+/calmodulin-dependent protein kinase and casein kinases. 3. Fractions with protein kinase activity were further analyzed by SDS-polyacrylamide gel electrophoresis. 4. The results indicate that cAMP-dependent protein kinase type I and II, casein kinases I and II, protein kinase C proenzymes I and II and Ca2+/calmodulin kinase II are associated with the membranes of endoplasmic reticulum (ER).

Animals↗

PubMed1992

Effect of pyridoxine deficiency on immunological phenomena.

Measurements of serine hydroxymethyltransferase (SHMT) in resting lymphocyte cultures showed that the level of activity of this enzyme was very low. Under the influence of mitogenic stimuli serine hydroxymethyl-transferase activity was induced 5-20-fold. Addition in the cultures of 4-deoxypyridoxine, a potent antagonist of vitamin B6 coenzymes, concurrently with the mitogen, inhibits the induction of serine hydroxymethyltransferase. Thus deoxypyridoxine exerts its effects not only at the level of the enzyme itself by antagonizing the coenzyme but also at the level of its biosynthesis. Synchronous addition of vitamin B6 with deoxypyridoxine effectively reverses the inhibitory effects. The T helper cells of the lymphocyte culture are very sensitive to deoxypyridoxine action in contrast to T suppressor cells. The effect of phytohaemagglutinin or concanavalin A on the production of interleukin-1b, interleukin-2 and interleukin-2 receptors is profoundly affected by deoxypyridoxine. These results give a deeper insight of the mechanisms by which pyridoxine deficiency causes significant reduction of humoral and cellular immune responses to antigenic stimuli. On the basis of the data of this report a detailed illustration of the events that follow the T cell activation is presented. From this investigation the enzyme serine hydroxymethyltransferase emerges as a key element in the processes of immune responses and cell proliferation. Based on this finding we advance the following two propositions for possible future medical application: (i) combination of deoxypyridoxine with immunosuppressive drugs in case of immunosuppressive therapy or organ transplantation. (ii) the enzyme presents an excellent target for chemotherapy and therefore development of special agents directed against its apoprotein may prove to be a very valuable medical tool.

Antibody Formation↗

PubMed1989

Total body haematocrit iron kinetics and erythrocyte life span in pigeons (Columba livia).

1. The mean pigeon erythrocyte life span was found to be 17-25 days by Cr51-labeled erythrocytes and 21 +/- 3.4 days by iron kinetics. 2. Total red blood cell volume has been calculated by Cr51-labeled erythrocytes while total plasma volume was determined both by a dye method and iron kinetic data. From these results total blood volume and total body haematocrit were found to be 0.090 +/- 0.002 ml/g body wt and 36 +/- 4.3%, respectively. 3. Venous haematocrit, haemoglobin concentration, erythrocyte count, mean corpuscular haemoglobin concentration, plasma iron and red blood cell iron have also been measured. 4. A significant difference between total body and venous haematocrit and a short mean red blood cell life span, due to ageing and to random destruction of erythrocytes were shown. 5. The above observations are compared with analogous available data for human beings and their physiological significance is discussed.

Animals↗

PubMed1989

A new glucose 6-phosphate dehydrogenase variant (G6PD Thessaloniki) in a patient with idiopathic myelofibrosis.

A new deficient glucose 6-phosphate dehydrogenase (G6PD) variant, G6PD Thessaloniki, which was found in the red blood cells of a 70-year-old woman who had idiopathic myelofibrosis, is described. G6PD Thessaloniki had a low Michaelis constant (Km) for G6P (20 microM), high Km for NADP (10.1 microM), normal pH optimum, reduced heat stability, decreased electrophoretic mobility (96-98% of the normal), increased 2-deoxy-G6P and decreased galactose 6-phosphate utilization. Several other enzymatic activities measured in the patient's red blood cells were normal. Studies of red blood cell survival and glucose utilization gave evidence of haemolysis caused by defective glucose utilization by the pentose phosphate pathway. The only son of the patient had normal G6PD in his red blood cells. In an attempt to investigate the origin of G6PD Thessaloniki, heat stability tests of G6PD extracted from the patient's skin have been performed.

Aged↗

PubMed1988

C3 complement types in northern Greece.

The C3 complement types were studied in 463 patients with thyroid diseases and in 211 controls. There were no significant differences with respect to gene or phenotype frequencies between patient groups and controls. In the total sample, the gene frequencies are similar to those found in other European populations.

Adult↗

PubMedDate not supplied

Leptin levels in maternal and cord serum: relationship with fetal development and placental weight.

OBJECTIVE: To test the hypothesis that the circulating levels of leptin in the maternal and cord serum correlate with the birthweight of the newborns and with the weight of the placenta. METHODS: In a population of 85 women from northern Greece who gave birth to an equal number of full-term infants, we calculated the concentration of leptin in the maternal serum as well as in the cord serum, right after delivery, by using an immunoradiometric assay. The correlation between these values, the maternal BMI before pregnancy and at the time of delivery, the neonatal BMI, Ponderal Index, and the placental weight was studied. RESULTS: Mean maternal leptin showed a statistically significant difference from mean cord serum leptin (14.7 and 7.07 ng/ml, respectively) and was positively correlated to the maternal BMI at the time of delivery (r = 0.3, P = 0.016), but not to neonatal BMI. A positive correlation between the mean cord serum leptin and the BMI of the neonates (r = 0.26, P = 0.031 ) was found. There was no correlation between the maternal BMI at the time of delivery and the neonatal BMI. Similarly, no correlation could be established between the placental weight and the levels of leptin in the maternal or in the cord serum but a positive correlation between placental weight, neonatal BMI and weight, and mothers' BMI was observed. Finally, although a noteworthy difference between the mean leptin levels of neonates of two different sexes was observed (male 5.9 ng/ml, female 7.8 ng/ml), that difference never reached a statistically significant level. CONCLUSIONS: The maternal leptin level could not be used as a reliable marker of fetal growth but a positive correlation between cord serum leptin and fetus growth is suggested.

Adult↗

PubMedDate not supplied

Resistin levels are normal in hypothyroidism and remain unchanged after attainment of euthyroidism: relationship with insulin levels and anthropometric parameters.

The aim of this controlled prospective study was to investigate resistin levels in hypothyroidism before and after restoration of euthyroidism and correlate the results with body weight (BW), body fat (BF), waist circumference (WC), body mass index (BMI) and serum insulin levels. Fifty-three hypothyroid patients with Hashimoto's disease (6 males, 47 females) and 30 controls matched for age, BMI and BF were investigated. Anthropometric parameters, resistin and insulin levels were measured. All patients were started on levothyroxine treatment and 4 to 5 months after initiation of treatment the investigations were repeated. Hypothyroid patients exhibited normal resistin values, which were no different from controls (mean+/-SD 7.4+/-4.0 vs 5.1+/-3.5 ng/ml, p=0.063). Normalization of circulating thyroid hormone levels produced no significant change in resistin levels (7.4+/-4.0 vs 6.8+/-4.2 ng/ml, p=ns) and post-treatment resistin levels did not differ from euthyroid controls. Furthermore, no gender difference was demonstrated in resistin levels either before (6.4+/-3.7 for males vs 7.6+/-4.1 ng/ml for females, p=ns) or after therapy (7.9+/-4.3 vs 6.7+/-4.3 ng/ml, for males and females respectively, p=ns), nor was there a difference in resistin levels in either sex induced by treatment of hypothyroidism (6.4+/-3.7 vs 7.9+/-4.3 ng/ml for males, p=ns, and 7.6+/-4.1 vs 6.7+/-4.3 ng/ml for females, p=ns). However, a small but significant difference in resistin levels was found between female patients and female controls (7.6+/-4.1 vs 5.0+/-4.0 ng/ml, p=0.047). Insulin levels and homeostasis model assessment insulin resistance (HOMA-IR) index did not differ before and after treatment in hypothyroid patients (13.0+/-10.2 vs 12.6+/-11.8 microU/ml, 22.7+/-1.4 vs 21.8+/-1.3, respectively, p=ns for both) or between patients and controls. In conclusion, our results demonstrate that resistin levels are normal in hypothyroidism and remain within normal range after attainment of euthyroidism. Resistin is not associated with serum insulin and HOMA-IR index, as well as BMI, BF, WC and BW.

Adolescent↗

PubMedDate not supplied

Growth hormone, insulin growth factor-1, and igf binding protein-3 axis relationship with bone mineral density among healthy men.

The aim of this study was to investigate serum levels of growth hormone (GH), insulin growth factor-I (IGF-I), and insulin growth factor binding protein-3 (IGFBP-3) in 363 healthy caucasian men with and without decreased bone density, who had never experienced fractures. Mean age was 51+/-8.7 years. Height and weight were measured and BMI was calculated using the formula weight (kg)/height (m(2)). Bone mineral density (BMD) was assessed: in 4 skeletal sites (lumbar spine [LS], femoral neck [FN], Ward's triangle [WT], and trochanter [T]) using dual-energy X-ray absorpsiometry (DEXA). After an overnight fasting, blood samples were taken at 8:00 a.m. Serum concentrations of GH, IGF-I, and IGFBP-3 were measured using the immunofunctional (GH) and IRMA (IGF-I and IGFBP-3) methods. The BMD at the 4 skeletal sites is expressed as mean value+/-SD in g/cm(2) and T score. Forty-four men (11%) had bone mineral density (BMD)<-2.5 SD (T score). Mean GH, IGF-I, and IGFBP-3 levels were 0.2+/-0.1, 186.1+/-177.3, and 4990+/-1460 ng/mL, respectively. There were no significant differences between men with normal BMD and men with reduced BMD concerning GH, IGF-I, and IGFBP-3 measurements. In normal men (319), mean GH, IGF-I, and IGFBP-3 levels were 0.4+/-0.1, 192+/-87, and 4960+/-1530 ng/mL, respectively. In the subgroup with reduced BMD (44), mean GH, IGF-I and IGFBP-3 levels were 0.2+/-0.1, 179+/-72 and 5230+/-1270 ng/mL, respectively. An age-dependent attenuation of GH, IGF-I, and IGFBP-3 levels was also found. No correlation was revealed between BMD and GH in the 4 skeletal sites tested. On the contrary, a positive correlation was established between BMD and IGF-I levels in 3 skeletal sites (LS, FN, T). The same was true between BMD and IGFBP-3 in 2 skeletal sites (LS, FN). In conclusion, 11% of Greek healthy males had decreased bone density. No fractures were demonstrated in any individuals. No significant differences were found between men with normal and reduced BMD, with regards to serum GH, IGF-I, and IGFBP-3, although these levels decreased with age. No correlation was found between BMD and GH levels in the 4 skeletal sites. A positive correlation was found between BMD and IGF-I levels in 3 skeletal sites and IGFBP-3 in 2 skeletal sites.

Absorptiometry, Photon↗

PubMedDate not supplied

Stability of serum TSH concentration after non refrigerated storage.

BACKGROUND: The ignorance of how sensitive serum samples for defined assays may be, can lead to overprotecting measures. This attitude not only increases cost and labor in everyday routine but may be responsible for not evaluating series of measurements if performed in serum samples not well stored. METHODS: Thyrotropin (TSH) concentration in serum was tested in three pooled samples drawn from various patients, before and after four days storage at freezing (-15 degrees C), low (4 degrees C), and room temperature (18-22 degrees C). TSH concentration was measured in each part, in 22 replicates using a commercial assay. RESULTS: The variation of the measured values due to the storage conditions was less than 10%, not exceeding the accepted between assay variation. CONCLUSIONS: For the estimation of TSH concentration, patient serum samples may be stored up to four days at 4 degrees C or even at room temperature without significant loss of measurement accuracy.

Biochemical Phenomena↗

PubMedDate not supplied

Serum leptin values in relation to bone density and growth hormone-insulin like growth factors axis in healthy men.

A novel action of leptin on bone formation has recently been described in animals. However, in humans, studies provide data, that, are less conclusive. So far, few studies investigated the leptin-bone density association in males. Moreover, it has been suggested that GH, IGF-1 and IGFBP-3 may be major players in the hormonal or paracrine pathways that regulate bone cell metabolism. Also, leptin has been shown to modulate the GH/IGF pathway. The aim of this study was to clarify further this issue by investigating (a) the influence of serum levels of leptin, GH, IGF-1 and IGFBP-3 on bone mass in various skeletal sites and, (b), the relationship between leptin and the GH/IGF axis. 363 healthy individuals were investigated. BMD and serum leptin, GH, IGF-1 and IGFBP-3 serum levels were assessed. Our results indicate that 11% of healthy males had bone density with T scores </=2.5 SD. No significant differences were found between men with normal and those with reduced BMD with regards to serum leptin, GH, IGF-1 and IGFBP-3 levels. A positive correlation was found between BMD and leptin levels in FN and T, and a negative one between leptin and IGF-1 levels. Further studies are needed before we reach final conclusions.

Adult↗