Diabetes mellitus as a general membrane disease and its consequences

The metabolic disturbances and their consequences in diabetes mellitus are well known more or less in details too. However, our knowledge on the diabetic disorders in membrane functions are limited. These damages are connected mostly with the disregulation of the membrane protein syntheses due to deficiency of insulin. In this review the impairments of the Na(+)-pump and the Ca(2+)-transport mechanisms as well as the insulin-dependent glucose transporter GLUT4 will be discussed in diabetes. The capacity of these transporters could be decreased even more than 50 percent in diabetes. This is the reason why using the same dose of cardioactive steroids as if in not diabetic subjects--can cause toxic alterations on the heart in diabetic patients. Insulin regulates not only the expression of some membrane proteins but it can initiate the translocation of the Na(+)-pump and GLUT4 from the intracellular membrane compartments to the plasma membrane in muscle, heart and adipose tissue. Therefore the uptake of K+ and glucose into these tissues will increase significantly under the acute influence of insulin. Untreated diabetic patients generally show hyperkalemia. Forceful treatment with insulin of these subjects often causes severe hypokalemia as a consequence of sudden translocation of the Na(+)-pump. Different Ca(2+)-transport systems are also impaired in diabetes. These changes may result significantly higher free Ca2+ concentration in the cytoplasma of cardiomyocytes. This is one of the most important reason for the Ca2+ overloading and ultimately for heart death. According to authors opinion, beside the dangerous metabolic disorders, general membrane damage and extended disturbances in membrane functions are also very characteristic for diabetes. The acknowledgement of these alterations are very important for the exact planning of the up to date treatment of diabetes.     

Input-dependent synaptic targeting of alpha(2)-subunit-containing GABA(A) receptors in synapses of hippocampal pyramidal cells of the rat

Pyramidal cells, expressing at least 14 subunits of the heteropentameric GABA(A) receptor, receive GABAergic input on their soma and proximal dendrites from basket cells, activating GABA(A) receptors and containing either parvalbumin or cholecystokinin and vasoactive intestinal polypeptide. The properties of GABA(A) receptors are determined by the subunit composition, and synaptic receptor content governs the effect of the presynaptic neuron. Using a quantitative electron microscopic immunogold technique, we tested whether the synapses formed by the two types of basket cell show a difference in the subunit composition of GABA(A) receptors. Terminals of one of the basket cells were identified by antibodies to parvalbumin. Synapses made by parvalbumin-negative terminals showed five times more immunoreactivity for the alpha(2) subunit than synapses made by parvalbumin-positive basket cells, whose synapses were frequently immunonegative. This difference is likely to be due to specific GABA(A) receptor alpha subunit composition, because neither synaptic size nor immunoreactivity for the beta(2/3) subunits, indicating total receptor content, was different in these two synapse populations. Synapses established by axo-axonic cells on axon initial segments showed an intermediate number of immunoparticles for the alpha(2) subunit compared to those made by basket cells but, due to their smaller size, the density of the alpha(2) subunit immunoreactivity was higher in synapses on the axon. Because the two basket cell types innervate the same domain of the pyramidal cell, the results indicate that pyramidal cells have mechanisms to target GABA(A) receptors, under presynaptic influence, preferentially to distinct synapses. The two basket cell types act via partially distinct GABA(A) receptor populations.     

Occupational stress in naval personnel

Introduction: Increased stress levels have been reported and it has been implicated for mental illness amongst service personnel. However no study has been reported among Indian naval sailors.     

Comparison of (S)-mephenytoin and proguanil oxidation in vitro: contribution of several CYP isoforms

AIMS: To compare the oxidative metabolism of (S)-mephenytoin and proguanil in vitro and to determine the involvement of various cytochrome P450 isoforms. METHODS: The kinetics of the formation of 4'-hydroxymephenytoin and cycloguanil in human liver microsomes from 10 liver samples were determined, and inhibition of formation was studied using specific chemical inhibitors and monoclonal antibodies directed towards specific CYP450 isoforms. Expressed CYP450 enzymes were used to characterize further CYP isoform contribution in vitro. Livers were genotyped for CYP2C19 using PCR amplification of genomic DNA followed by restriction endonuclease digestion. RESULTS: All livers were wildtype with respect to CYP2C19, except HLS#5 whose genotype was CYP2C19*1/CYP2C19*2. The Km, Vmax and CLint values for the formation of 4'-hydroxymephenytoin from (S)-mephenytoin and the formation of cycloguanil from proguanil ranged from 50.8 to 51.6 and 43-380 microm, 1.0-13.9 and 0.5-2.5 nmol mg-1 h-1, and 20.2-273.8 and 2.7-38.9 microl h-1 mg-1, respectively. There was a significant association between the Vmax values of cycloguanil and 4'-hydroxymephenytoin formation (rs=0.95, P=0.0004). Cycloguanil formation was inhibited significantly by omeprazole (CYP2C19/3A), troleandomycin (CYP3A), diethyldithiocarbamate (CYP2E1/3A), furafylline (CYP1A2), and (S)-mephenytoin. 4'-Hydroxymephenytoin formation was inhibited significantly by omeprazole, diethyldithiocarbamate, proguanil, furafylline, diazepam, troleandomycin, and sulphaphenazole (CYP2C9). Human CYP2E1 and CYP3A4 monoclonal antibodies did not inhibit the formation of cycloguanil or 4'-hydroxymephenytoin, and cycloguanil was formed by expressed CYP3A4 and CYP2C19 supersomes. However, only expressed CYP2C19 and CYP2C19 supersomes formed 4'-hydroxymephenytoin. CONCLUSIONS: The oxidative metabolism of (S)-mephenytoin and proguanil in vitro is catalysed by CYPs 2C19 and 1A2, with the significant association between Vmax values suggesting that the predominant enzymes involved in both reactions are similar. However the degree of selectively of both drugs for CYP isoforms needs further investigation, particularly the involvement of CYP3A4 in the metabolism of proguanil. We assert that proguanil may not be a suitable alternative to (S)-mephenytoin as a probe drug for the CYP2C19 genetic polymorphism.     

Distribution of inorganic elements in human autopsy tissue

In the practice of forensic medicine, we find many of cases of death where the actual cause is not determinable with autopsy, histological or toxicological examinations. In these cases of death, we can consider cardiac dysfunction of unknown origin, in the background of which such a physiologic cardiac insufficiency occurs that cannot be detected with the previously mentioned methods. The dysfunction is possibly associated with a significant change in certain inorganic elements, primarily in the conduction system of the heart. In the absence of published data, our goal was to determine the concentration of inorganic elements in the specialized rhythm determining muscle cell groups in the heart: sinus node (SN), atrioventricular node (AV), septum (SE), left ventricle anterior wall (LVAW). With microwave technology we destroyed the muscle tissue and measured the concentration of ions (Na, Mg, K, Ca, Mn, Fe, Cu, Zn, P, S) using Inductive Completed Plasma Atom Emission Spectrometry (ICP-AES) equipment. Of the 24 cases examined, the average ion concentrations in microgram/g were the following; Sinus: Na 2602 +/- 493, Mg 120 +/- 24, K 1787 +/- 347, Ca 244 +/- 41, Mn 0.129 +/- 0.011, Fe 58 +/- 12, Cu 2.171 +/- 0.46, Zn 10.4 +/- 2.027, P 1147 +/- 227, S 2301 +/- 245; Septum: Na 1452 +/- 315, Mg 243 +/- 56, K 3269 +/- 689, Ca 105 +/- 26, Mn 0.17 +/- 0.05, Fe 74 +/- 16, Cu 3.557 +/- 0.952, Zn 25.75 +/- 8.4, P 2764 +/- 494, S 3001 +/- 523; Av: Na 2614 +/- 517, Mg 242 +/- 40.2, K 2010 +/- 395, Ca 271 +/- 27.3, Mn 0.13 +/- 0.029, Fe 54 +/- 12, Cu 2.369 +/- 0.297, Zn 15 +/- 3.2, P 1625 +/- 291, S 2535 +/- 346; Lvaw: Na 1340 +/- 201, Mg 250 +/- 37, K 3659 +/- 532, Ca 88 +/- 22, Mn 0.175 +/- 0.05, Fe 76 +/- 19, Cu 3.62 +/- 0.58, Zn 27.13 +/- 3.1, P 3025 +/- 441, S 3140 +/- 440.     

Smooth muscle and parasympathetic nerve terminals in the rat urinary bladder have different subtypes of alpha(1) adrenoceptors

Neurally evoked contractions and release of (3)H- acetylcholine (ACh) during electrical field stimulation were measured in rat urinary bladder strips. The alpha(1) agonist phenylephrine (PE, 2-8 microM) increased the amplitude of neurally evoked contractions, facilitated the release of ACh and increased the baseline tone of the bladder strips. The PE-induced facilitation of the contractions did not significantly change during a prolonged exposure to PE (120 min), whereas the PE-induced rise in baseline tone gradually decreased to 65% of the initial value. Low concentrations of specific alpha(1A) antagonists, 5-methyl urapidil (5-MU), REC15/2739 and WB-4101 competitively inhibited the facilitation of the neurally-evoked contractions (pA(2:) 8.77; 9.59 and 9.62, respectively), whereas higher concentrations of 5-MU (IC(50): 48 nM) were required to suppress the PE-rise in baseline. WB-4101 (100 microM) inhibited the PE-induced facilitation of ACh release. The irreversible alpha(1B) antagonist chloroethyl-clonidine (CEC, 10-50 microM) inhibited the PE-evoked rise in base line tone, but did not affect the PE-induced facilitation of the neurally evoked contractions nor the facilitation of ACh release. However, CEC increased the area and amplitude of the neurally-evoked contractions by 261+/-33 and 47.2+/-8.4%, respectively. Atropine significantly inhibited the CEC evoked increase in area and amplitude of the electrically evoked contractions (76.5+/-4.8 and 40.8+/-3%, respectively) indicating that CEC facilitated the cholinergic responses of the electrically stimulated bladder strips. It is concluded that alpha(1A) and CEC sensitive alpha(1B) and/or alpha(1D) adrenoceptors are expressed in the rat bladder in different locations. On the cholinergic nerve terminals alpha(1A) adrenoceptors mediate prejunctional facilitation, whereas postjunctional alpha(1B)/alpha(1D) adrenoceptors mediate smooth muscle contraction.     

Experiences on the local adriamycin treatment of bladder tumours

Following repeated resections, local cytostatics have recently been increasingly applied for preventing the recurrence of superficial bladder tumours. Fifty-five patients at stages Tis, Ta, Tl were treated intravesically by adriamycin for 16 to 24 months. After the treatment period, the total number of tumour recurrences decreased by more than half. In 18 cases there were no tumour recurrences. The administered cytostatics did not produce any systemic side-effects. Chemocystitis and haematuria were the most frequently associated side-effects. Based on favourable experiences, local adriamycin treatment is looked upon as an effective prevention of recurrences.     

Conformality and homogeneity of dose distributions in interstitial implants at idealized target volumes: a comparison between the Paris and dose-point optimized systems.

BACKGROUND AND PURPOSE: The use of high dose rate stepping source in interstitial brachytherapy provides more possibility to conform the dose distribution to the target volume compared to the classical systems. The purpose of this study was to evaluate implants made according to the Paris, the stepping source and the conformal dosimetry system with respect to dose homogeneity and conformality, and to compare these systems using volumetric parameters. MATERIALS AND METHODS: Single-plane and double-plane implants with catheters arranged in square and triangle pattern were used in the analysis. Twenty-seven idealized planning target volumes (PTV) were generated. They formed slabs with rectangular or trapezoidal cross-section. The lengths were 3, 5 and 7 cm, the widths and heights were determined according to the Paris system for catheter separation of 1, 1.5 and 2 cm. The dose specification was selected such that the coverage index was 0.95 for each implant. Optimal active lengths were determined according to the best conformality at the optimized implants. From the dose-volume histogram (DVH) the following indices were calculated for every implant: conformal (COIN), external volume (EI), relative dose homogeneity (HI) and overdose volume (OI). Furthermore, the mean central dose (MCD) and minimum target dose (MTD) was also determined. The dosimetry systems were compared through the mean values of these parameters and the volumetric indices were analyzed according to the geometry of the PTV. RESULTS: For the optimized systems the optimal active length was 0.5-1.0 cm shorter than the target volume length, depending on the catheter separation and geometry of the PTV. For the Paris, the stepping source and the conformal dosimetry system, the mean COIN was 0.66, 0.82 and 0.82; the mean HI was 0.71, 0.68 and 0.68; the mean EI was 0.44, 0.17 and 0.17; the mean OI was 0.11, 0.13 and 0.12, respectively. The statistical analysis showed that the Paris system differed from the optimized systems significantly. For the Paris, the stepping source and the conformal dosimetry system, the mean reference isodose was 85, 90 and 95%, the MCD was 100, 100 and 109%, the MTD was 67, 71 and 73%, respectively. Regarding geometry of the PTV, the most conformal and homogeneous dose distributions occurred when the catheter separation was small, the target volume was long and its shape was a thick rectangular slab. CONCLUSIONS: Positioning the catheters according to the rules of the Paris system, but applying optimization on dose points placed either between the catheters in the whole target volume or on the surface of the target volume, and selecting the reference isodose by DVH, can provide highly conformal dose distribution to the target volume, with only a slightly worsened dose homogeneity compared to the Paris system.