Seasonal molecular timekeeping within the rat circadian clock

In temperate zones duration of daylight, i.e. photoperiod, changes with the seasons. The changing photoperiod affects animal as well as human physiology. All mammals exhibit circadian rhythms and a circadian clock controlling the rhythms is located in the suprachiasmatic nucleus (SCN) of the hypothalamus. The SCN consists of two parts differing morphologically and functionally, namely of the ventrolateral (VL) and the dorsomedial (DM). Many aspects of SCN-driven rhythmicity are affected by the photoperiod. The aim of the present overview is to summarize data about the effect of the photoperiod on the molecular timekeeping mechanism in the rat SCN, especially the effect on core clock genes, clock-controlled genes and clock-related genes expression. The summarized data indicate that the photoperiod affects i) clock-driven rhythm in photoinduction of c-fos gene and its protein product within the VL SCN, ii) clock-driven spontaneous rhythms in clock-controlled, i.e. arginine-vasopressin, and in clock-related, i.e. c-fos, gene expression within the DM SCN, and iii) the core clockwork mechanism within the rat SCN. Hence, the whole central timekeeping mechanism within the rat circadian clock measures not only the daytime but also the time of the year, i.e. the actual season.     

UV Rays, the prooxidant/antioxidant imbalance in the cornea and oxidative eye damage

In this minireview, the factors involved in the development of corneal injury due to an increased amount of UVB rays are summarized. Experimental studies have shown that an increased number of UVB rays leads to a profound decrease in corneal antioxidants (high molecular weight, antioxidant enzymes as well as low molecular weight, mainly ascorbic acid) so that a prooxidant/antioxidant imbalance appears. The decrease of corneal antioxidant protective mechanisms results in oxidative injury of the cornea and causes damage of the inner parts of the eye by UVB rays and by reactive oxygen species generated by them.     

LVV-hemorphin-7 lowers blood pressure in spontaneously hypertensive rats: radiotelemetry study

Cardiovascular effects of LVV-hemorphin-7, a member of the family of fragments from beta-chain of human or bovine hemoglobin, were studied in conscious spontaneously hypertensive (SHR) and Wistar-Kyoto (WKY) rats by radiotelemetry. Intraperitoneal injection of hemorphin in a dose of 100 microg/kg significantly decreased blood pressure in SHR, whereas negligible effect was seen in normotensive WKY rats. Blood pressure changes were accompanied by reduction of heart rate. In conclusion, a direct effect of LVV-hemorphin-7 on blood pressure was demonstrated in SHR. These biologically active peptides could be involved in blood pressure regulation especially in hypertensive rats, but the precise mechanism should be elucidated.     

Selectins and monocyte chemotactic peptide as the markers of atherosclerosis activity

The role of adhesive selectin molecules in the process of atherogenesis is an open question. These molecules are known as markers of atherosclerosis activity, however, only some biological mechanisms are known up to now. In this study we examined the levels of soluble forms of E-, P-selectin and monocyte chemotactic protein (MCP-1) in the process of extracorporeal cholesterol elimination by LDL-apheresis. We measured the levels of sE-, sP-selectin and MCP-1 in the plasma before and after LDL-apheresis and in the washout solution from immunoabsorption columns Lipopak. Eighty measurements were performed repeatedly in 6 patients with severe familial hypercholesterolemia (FH) on long-term LDL-apheresis treatment. Before the procedure P-selectin levels were 204+/-179 ng/ml, E-selectin 32.1+/-33.7 ng/ml, MCP-1 323.8+/-121 pg/l, whereas after the procedure we found P-selectin levels 131.6+/-34 ng/ml, E-selectin 33.1+/-51 ng/ml, and MCP-1 200.4+/-15 pg/l. Levels of P-selectin were increased in the blood of patients with FH in spite of long-term intensive extracorporeal LDL-elimination, documenting thus the activity of atherosclerosis. The levels of P-selectin and MCP-1 decreased significantly after the hypolidemic procedure and could be used as another marker showing the effectivity of the extracorporeal LDL-cholesterol elimination (immediately after the procedure), and, after further verification, may serve as a marker for controlling the therapy efficacy.     

Cough, expiration and aspiration reflexes following kainic acid lesions to the pontine respiratory group in anesthetized cats

The importance of neurons in the pontine respiratory group for the generation of cough, expiration, and aspiration reflexes was studied on non-decerebrate spontaneously breathing cats under pentobarbitone anesthesia. The dysfunction of neurons in the pontine respiratory group produced by bilateral microinjection of kainic acid (neurotoxin) regularly abolished the cough reflexes evoked by mechanical stimulation of both the tracheobronchial and the laryngopharyngeal mucous membranes and the expiration reflex mechanically induced from the glottis. The aspiration reflex elicited by similar stimulation of the nasopharyngeal region persisted in 73% of tests, however, with a reduced intensity compared to the pre-lesion conditions. The pontine respiratory group seems to be an important source of the facilitatory inputs to the brainstem circuitries that mediate cough, expiration, and aspiration reflexes. Our results indicate the significant role of pons in the multilevel organization of brainstem networks in central integration of the aforementioned reflexes.     

Anti-GAD-positive patients with type 1 diabetes mellitus have higher prevalence of autoimmune thyroiditis than anti-GAD-negative patients with type 1 and type 2 diabetes mellitus

The aim of our study was to evaluate antibodies against thyroglobulin (anti-TG) and thyroid peroxidase (anti-TPO) - markers of autoimmune thyroiditis - in several groups of adult patients with type 1 and type 2 diabetes mellitus (DM). We were particularly interested whether the presence of thyroid antibodies is related to the positivity of glutamic acid decarboxylase antibodies (anti-GAD). We found elevated anti-GAD in 46 % (97/210) patients with type 1 DM. All patients with type 2 diabetes were anti-GAD-negative. At least one thyroid antibody (anti-TG and/or anti-TPO) was found in 30 % (62/210) patients with type 1 DM and 27 % (22/83) type 2 diabetes patients. The patients with type 1 DM were further grouped according to their anti-GAD status. The anti-GAD-positive patients had a higher prevalence of anti-TG antibodies than the anti-GAD-negative patients (25 % vs. 12 %, p=0.03) as well as anti-TPO antibodies (32 % vs. 12 %, p<0.001). At least one thyroid antibody was detected in 39 % (38/97) of anti-GAD-positive but only in 21 % (24/113) of anti-GAD-negative patients with type 1 DM (p=0.006). No significant difference in the frequency of thyroid antibodies was found between anti-GAD-negative patients with type 1 and type 2 DM (21 % vs. 27 %, p=0.4). The groups with or without thyroid antibodies in both type 1 and type 2 diabetic patients did not differ in actual age, the age at diabetes onset, duration of diabetes, body mass index or HbA1c level. Patients with elevated thyroid antibodies had significantly higher levels of TSH than those without thyroid antibodies (1.86 vs. 3.22 mIU/l, p=0.04 in type 1 DM; 2.06 vs. 4.89 mIU/l, p=0.003 in type 2 DM). We conclude that there is a higher frequency of thyroid-specific antibodies in anti-GAD-positive adult patients with type 1 DM than in anti-GAD-negative patients or in patients with type 2 DM. Patients with or without thyroid antibodies do not differ in age, DM onset and duration, BMI or HbA1c. Thyroid antibodies-positive patients have higher levels of thyroid stimulating hormone (TSH).     

Lipid-induced filamentous growth in Ustilago maydis

The phytopathogenic fungus Ustilago maydis is obligately dependent on infection of maize to complete the sexual phase of its life cycle. Mating interactions between haploid, budding cells establish an infectious filamentous cell type that invades the host, induces large tumours and eventually forms large masses of black spores. The ability to switch from budding to filamentous growth is therefore critical for infection and completion of the life cycle, although the signals that influence the transition have not been identified from the host or the environment. We have found that growth in the presence of lipids promotes a filamentous phenotype that resembles the infectious cell type found in planta. In addition, the ability of the fungus to respond to lipids is dependent on both the cAMP signalling pathway and a Ras/MAPK pathway; these pathways are known to regulate mating, filamentous growth and pathogenesis in U. maydis. Overall, these results lead us to hypothesize that lipids may represent one of the signals that promote and maintain the filamentous growth of the fungus in the host environment.     

Specificity of IgG and IgE antibodies against plant and insect glycoprotein glycans determined with artificial glycoforms of human transferrin

Cross-reactive carbohydrate determinants of plants are essentially a mixture of N-glycans containing beta1,2-xylose and core alpha1,3-fucose, the latter also found in insect glycoproteins. To determine the relative contributions of these two sugar residues to antibody binding, we prepared an array of glycomodified forms of human apo-transferrin. Using core-alpha1, 3-fucosyltransferase (EC 2.4.1.214) and beta1,2-xylosyltransferase (EC 2.4.2.38) recombinantly expressed in Pichia pastoris and suitable glycosidases, glycoforms containing either only fucose (MMF), only xylose (MMX), both (MMXF), or neither (MM) linked to the common pentasaccharide core were generated. Additional glycoforms were obtained by enzymatic removal of the alpha1,3-linked mannosyl residue. These transferrin glycoforms served to define the binding specificity of antibodies in western blot, ELISA, and inhibition ELISA. Rabbit anti-horseradish peroxidase serum bound to both the fucosylated (MMF) and the xylosylated (MMX) glycoforms. Inhibition studies indicated two independent highly specific populations reacting with either of the two epitopes. In contrast, the monoclonal antibody YZ1/2.23 appears to recognize a larger structure including both the fucosyl and the xylosyl residue. The mannose-deficient glycoform was a poorer inhibitor for both antibodies. Terminal GlcNAc residues prevented antibody binding. Rabbit anti-bee venom serum reacted with fucosylated forms (MMF and MMXF) only. Experiments with sera from allergic patients suggest that glycomodified human transferrin, especially the MMXF glycoform, is a suitable reagent for the detection of antibodies against cross-reactive carbohydrate determinants. Within the panel studied, several sera contained high levels of fucose-reactive IgE but only a few sera showed any binding to MMX-transferrin.     

Changes in glycosidase activities during galactoglucomannan oligosaccharide inhibition of auxin induced growth

The inhibition of 2,4-D-induced elongation growth by galactoglucomannan oligosaccharides (GGMOs) in pea stem segments (Pisum sativum L. cv. Tyrkys) after 18 h of incubation results in changes of extracellular, intracellular and cell wall glycosidase activities (beta-D-glucosidase, beta-D-mannosidase, beta-D-galactosidase, beta-D-xylosidase, alpha-D-galactosidase, and alpha-L-arabinosidase). GGMOs lowered the glycosidase activities in the extracellular fraction, while in the cell wall fractions their activities were markedly increased. The intracellular enzyme alpha-d-galactosidase increased while the beta-d-galactosidase decreased in activity in response to the GGMO treatment. Extracellular enzymes showed low values of activities in comparison with intracellular and cell wall glycosidases. It is evident that GGMOs can alter auxin induced elongation and glycosidase activities in different compartments of the cell, however, the mode and site of their action remains unclear.