Peripheral blood mitochondrial DNA content correlates with lipid oxidation rate during euglycemic clamps in healthy young men

Both qualitative and quantitative changes in mitochondrial DNA (mtDNA) have been implicated in the pathogenesis of diabetes mellitus. It was previously found that decreased mtDNA content preceded the development of diabetes and mtDNA content correlated with the clinical parameters of insulin resistance syndrome, including diastolic blood pressure and waist-hip ratio. These results prompted one to look whether there are correlations between mtDNA content and the biochemical parameters of insulin resistance in non-diabetic subjects. MtDNA content of peripheral blood leukocytes was measured in Korean healthy young men, and this was correlated with various parameters of fuel metabolism at baseline and during euglycemic hyperinsulinemic clamps with indirect calorimetry. MtDNA content in peripheral blood leukocytes did not correlate with insulin sensitivity index or other metabolic variables such as body mass index (BMI), waist-to-hip ratio (WHR) and blood pressure. However, mtDNA content showed a positive significant correlation with fat oxidation rate during euglycemic clamps (r = 0.61, P < 0.05). Changes in fat oxidation rate and carbohydrate oxidation rate during the clamps were significantly correlated with mtDNA content (r = 0.65, P < 0.05, r = -0.65, P < 0.05, respectively). These results suggest that mtDNA content in peripheral blood may not correlate with insulin resistance per se but with some aspect of insulin resistance in healthy young men.

Changing trend in susceptibility pattern of Streptococcus pneumoniae to penicillin in India

Prior to 1995 all strains of Streptococcus pneumoniae isolated at a tertiary care hospital in south India were uniformly susceptible to penicillin. However, since late 1995 strains of S. pneumoniae with intermediate resistance to penicillin have been observed. Altogether there were 25 such isolates, 9 from invasive (5 from CSF as well as blood, 1 from pleural fluid and 3 from CSF alone) and 16 from noninvasive sites (6 from throat, 6 from sputum, 3 from eye and 1 from ear) respectively, thus 4.6 per cent of S. pneumoniae showed intermediate resistance of a total of 535 strains studied so far. The minimum inhibitory concentration (MIC) values of penicillin, erythromycin, chloramphenicol and cefotaxime were determined by agar dilution method and for confirmation, E test was carried out for penicillin alone. The MIC range obtained for penicillin was between 0.125-1.0 microgram/ml. Kirby-Bauer disc diffusion method was adopted for testing of erythromycin, chloramphenicol, co-trimoxazole, cefotaxime, tetracycline and vancomycin. We observed that none of the strains with intermediate resistance to penicillin were multidrug resistant. These strains belonged predominantly to serotype 14 (n = 10), 7B (n = 9), 19A (n = 3), 7F (n = 2) and 23F (n = 1). Clonality was not observed in the 5 representative strains subjected to Box A finger printing method.

Prooxidant effects of ascorbate in rat brain slices

Ascorbate is a well-known reducing agent, but it can generate oxidative potential under appropriate condition. In rat cerebral cortex homogenate, 1 mM ascorbate decreased thiobarbituric acid-reactive substances (TBARS) content to 86% +/- 4% of control values, confirming that ascorbate is a reducing agent. However, ascorbate increased TBARS, in a dose-related manner, in slices prepared from cerebral cortex. Ferrous ion (Fe2+) had little effect on ascorbate-induced lipid oxidation in cortical slices, and EDTA did not have an influence on the ascorbate-induced oxidative action. Conversely, ascorbate plus Fe2+ elevated TBARS content to more than threefold over ascorbate alone in tissue homogenates. In summary, ascorbate is a reducing agent in the brain tissue homogenate but has an oxidizing effect in brain slices. A hypothesis is proposed to explain the oxidative effects of ascorbate in cortical slices, wherein extracellular ascorbate is oxidized to dehydroascorbate, which is rapidly carried into the cells via a glucose transporter (GLUT). The dehydroascorbate in cytosol is then reduced back to ascorbate, and, during the reduction process, cellular components are oxidized.

Central injection of nicotine increases hepatic and splenic interleukin 6 (IL-6) mRNA expression and plasma IL-6 levels in mice: involvement of the peripheral sympathetic nervous system

Accumulating evidence suggests that plasma levels of interleukin 6 (IL-6), a major cytokine stimulating the synthesis of acute-phase proteins, are intimately regulated by the central nervous system. Nicotine, one of the major drugs abused by humans, has been shown to affect immunological functions. In the present study, effects of intracerebroventricular (i.c.v.) injection of nicotine on plasma IL-6 levels were investigated in mice. Nicotine administered i.c.v. dose-dependently increased plasma IL-6 levels; the lowest effective dose was 0.3 ng/mouse and the maximal effect was attained with the dose of 105 ng/mouse. The nicotine (105 ng/mouse, i.c.v.)-induced plasma IL-6 levels peaked at 3 h and approached basal levels 6 h after injection. Mecamylamine, a nicotinic receptor antagonist, blocked nicotine-induced plasma IL-6 levels. Depletion of peripheral norepinephrine with 6-hydroxydopamine [100 mg/kg, intraperitoneal (i. p.)] inhibited the nicotine-induced plasma IL-6 levels by 57%, whereas central norepinephrine depletion with 6-hydroxydopamine (50 microgram/mouse, i.c.v.) had no effect. Pretreatment with prazosin (alpha1-adrenergic antagonist; 1 mg/kg, i.p.), yohimbine (alpha2-adrenergic antagonist; 1 mg/kg, i.p.), and ICI-118,551 (beta2-adrenergic antagonist; 2 mg/kg, i.p.), but not with betaxolol (beta1-adrenergic antagonist; 2 mg/kg, i.p.), inhibited nicotine-induced plasma IL-6 levels. Among the peripheral organs, including the pituitary, adrenals, heart, lung, liver, spleen, and lymph nodes, nicotine (105 ng/mouse, i.c.v.) increased IL-6 mRNA expression only in the liver and spleen, which was inhibited by peripheral norepinephrine depletion. These results suggest that stimulation of central nicotinic receptors induces plasma IL-6 levels and IL-6 mRNA expression in the liver and spleen via the peripheral sympathetic nervous system, alpha1-, alpha2-, and beta2-adrenoreceptors being involved.

Measurement of fluid shift in CAPD patients using segmental bioelectrical impedance analysis

OBJECTIVE

To determine, using segmental bioelectrical impedance analysis (BIA), the characteristics of fluid shift of each body segment in continuous ambulatory peritoneal dialysis (CAPD) patients during and after peritoneal dialysis (PD) solution exchange.

DESIGN

Observational study with repeated measurements of bioelectrical impedance, which is inversely related to tissue fluid content.

PATIENTS

Thirteen clinically stable CAPD patients.

METHODS

Bioelectrical impedance was measured at frequencies of 5, 50, 250, and 500 kHz in each body segment four times: (1) before and (2) after drainage of dialysate, and (3) at 1 hour and (4) at 2 hours after exchange of new 1.5% dextrose PD solution.

RESULTS

Impedance of both arms was significantly increased at 1 hour post exchange at all frequencies. In the trunk, impedance at all frequencies increased significantly after drainage, decreased significantly at 1 hour post exchange, and then increased again for the next hour without significance. Impedance of both legs showed a decreasing tendency at all frequencies during and after exchange. Net calculated water volume changes between the time before drainage and 2 hours post exchange were -0.5 L in the trunk, -0.25 L in both arms, +0.47 L in both legs, -0.28 L in total. The change in body weight between the time before drainage and 2 hours post exchange was -0.21 kg, on average, and significantly correlated with total net calculated water volume change (p = 0.009).

CONCLUSIONS

Each body segment of the CAPD patient has its own characteristic pattern of fluid shift in response to PD solution exchange or dwell. Segmental BIA may be a useful tool for understanding the physiological changes in fluid shift in CAPD patients.

Spread of drug-resistant Streptococcus pneumoniae in Asian countries: Asian Network for Surveillance of Resistant Pathogens (ANSORP) Study

Antimicrobial susceptibility of 996 isolates of Streptococcus pneumoniae from clinical specimens was investigated in 11 Asian countries from September 1996 to June 1997. Korea had the greatest frequency of nonsusceptible strains to penicillin with 79.7%, followed by Japan (65.3%), Vietnam (60.8%), Thailand (57.9%), Sri Lanka (41.2%), Taiwan (38.7%), Singapore (23.1%), Indonesia (21.0%), China (9.8%), Malaysia (9.0%), and India (3.8%). Serotypes 23F and 19F were the most common. Pulsed-field gel electrophoresis (PFGE) of 154 isolates from Asian countries showed several major PFGE patterns. The serotype 23F Spanish clone shared the same PFGE pattern with strains from Korea, Japan, Singapore, Taiwan, Thailand, and Malaysia. Fingerprinting analysis of pbp1a, pbp2x, and pbp2b genes of 12 strains from six countries also showed identical fingerprints of penicillin-binding protein genes in most strains. These data suggest the possible introduction and spread of international epidemic clones into Asian countries and the increasing problems of pneumococcal drug resistance in Asian countries for the first time.

Intraspinal epidermoid cyst occurring 15 years after lipomyelomeningocele repair. Case report

The authors report the case of a spinal epidermoid cyst that developed in a patient who had undergone surgery for lipomyelomeningocele repair 15 years earlier. The patient presented with symptoms of retethering. Magnetic resonance imaging revealed a cystic intraspinal mass that extended from L-2 to L-5. The mass proved to be an epidermoid cyst. Spinal epidermoid cysts can cause retethering after a repair of lipomyelomeningocele, and the risk of this development can be present for decades.

Spontaneous regression of a herniated cervical disc in a patient with myelopathy. Case report

The authors present a case of spontaneous regression of a herniated cervical nucleus pulposus in a patient with myelopathy. This 37-year-old woman developed sudden quadriparesis; she had reported no history of trauma. Magnetic resonance (MR) imaging revealed a large disc herniation and increased signal intensity of the cord at the C5-6 level. The extruded disc fragment was found to have resolved on follow-up MR imaging after 28 months, despite the fact that the patient had undergone no specific treatment. The patient's symptoms had subsided almost totally. This is the first case of MR-documented regression of a cervical disc herniation in a patient with myelopathy.

Decreased mitochondrial DNA content in peripheral blood precedes the development of non-insulin-dependent diabetes mellitus

Qualitative changes in mitochondrial DNA (mtDNA), such as mutations and deletions, have been implicated in the pathogenesis of diabetes mellitus. In addition to the qualitative changes, mtDNA is subject to quantitative changes, and is vulnerable to oxidative stress, resulting in both qualitative and quantitative changes. This study was performed to investigate whether quantitative changes in mtDNA occur in non-insulin-dependent diabetes mellitus (NIDDM) patients and also in pre-diabetic subjects. MtDNA content from peripheral blood was measured by slot-blot analysis in 55 NIDDM patients and 29 age- and sex-matched control subjects. We have also analysed the mtDNA copies by quantitative polymerase chain reaction (PCR) method in 23 pre-diabetic subjects who converted to diabetic in 2 years and 22 age- and sex-matched control subjects who remained non-diabetic. Mean mtDNA quantity measured by slot blot method was 35% lower in patients with NIDDM than in control subjects (12.3+/-8.1 vs. 19.1+/-8.2 AU/microg DNA; P < 0.05). MtDNA quantities did not correlate with age, body mass index, duration of diabetes or HbA1c levels. We have also found that the mtDNA copies in subjects who converted to diabetes in 2 years were lower than in controls even before the development of diabetes (102.8+/-41.5 vs. 137.8+/-67.7 copies/pg template DNA P < 0.05). Inverse correlations were noted between mtDNA content and baseline waist hip circumference ratio (WHR) (r = -0.31, P < 0.05), and fasting glucose level (r = - 0.35, P < 0.05), diastolic blood pressure (r = -0.36, P < 0.05), and WHR (r = -0.40, P < 0.01) after development of diabetes. In conclusion, we demonstrate that the content of mtDNA decreases in peripheral blood of patients with NIDDM and the lower mtDNA levels precede the development of diabetes.

Emergence and spread of antimicrobial resistance of Streptococcus pneumoniae in Korea

Pneumococcal resistance has become a global issue during the past three decades. One of the major foci of pneumococcal resistance worldwide is the Asian region including Korea, Japan, and Hong Kong. Korea had not been recognized as a focus of pneumococcal resistance until 1995, when serial reports documented the alarmingly high prevalence of penicillin resistance among clinical isolates. Serial reports on penicillin resistance among pneumococcal isolates in Korea ranged from 68% to 77% as of 1995. Multidrug resistance was also noted in 34% of Korean isolates. Penicillin-binding protein profile analysis, pulsed-field gel electrophoresis, ribotyping, and fingerprinting analysis of pbp genes showed that antibiotic-resistant pneumococci isolated in Korea were genetically related. Data documented the extensive spread of a resistant clone within Korea and between different countries. Besides the injudicious use of antimicrobial agents or the high prevalence of serotypes 23 and 19, the spread of a resistant clone may play an important role in the rapid increase of penicillin resistance in Korea.

Cine MR CSF flow study in hydrocephalus: what are the valuable parameters?

To evaluate the changes of intracranial cerebrospinal fluid (CSF) dynamics in hydrocephalus, we studied the various parameters of cine phase contrast (PC) magnetic resonance (MR) CSF flow images in cases of acutely progressive hydrocephalus, comparing them with those in normal CSF circulation. The MR images were obtained with 1.5 T unit using the 2 dimensional cine PC sequence with cardiac gating in 10 non-obstructive hydrocephalus (NOH), 3 obstructive hydrocephalus (OH), and 10 controls. The temporal velocity information from the anterior and posterior cervical pericord spaces, third and fourth ventricles, and aqueduct were plotted as wave form. The wave forms were analyzed for configurations, amplitude parameters (Smax, Smin, Sdif), and temporal parameters (R-S, R-SMV, R-D, R-DMV). The statistical significance of each parameter was examined with paired t-test. All patients with OH underwent endoscopic thrid ventriculostomy, whereas all NOH underwent shunting procedures. In 5 ROIs, distinct reproducible configuration features were obtained at aqueductal and cervical pericord spaces. Statistically significant differences between control and hydrocephalus only in temporal parameters were determined. In NOH, the graph showed R-DMV shortening (p < 0.01) at anterior cervical pericord space. In OH, there were R-DMV shortening (p < 0.05) at anterior cervical pericord space, R-SMV shortening (p < 0.02) at posterior cervical pericord space. Also the level of obstructions could be determined in all OHs. The analysis of MR CSF flow images may give us valuable information on the site of obstruction, explaining the cause of hydrocephalus, thus deciding the necessity of shunting procedures using in vivo images.

Surgical options of hypertensive intracerebral hematoma: stereotactic endoscopic removal versus stereotactic catheter drainage

The authors analyzed the difference between two surgical procedures, stereotactic endoscopic removal (SER) and stereotactic catheter drainage (SCD), in 18 patients of ganglionic intracerebral hematoma (ICH). Ten patients underwent SCD and eight SER within 24 hours of insult. The mean age was 53.3 (33-81) years and male to female ratio was 11:7. The mean volume of hematoma was 34.4 (23-105) ml. All patients had major neurological deficits without signs of transtentorial herniation. Mean follow-up was 8 (6-10) months. Under local anesthesia, Otzuki's cannula was placed through a burr hole. ICH was removed with suction and forceps under endoscopic guidance. Hemostasis was performed with Nd-YAG laser. For SCD, we used silicone catheter and urokinase. The hematoma was drained in 3-5 days in SER, whereas 7-10 days in SCD. Postoperative rebleeding occurred in one case of SER. Mortality rate was 13% in SER, 10% in SCD. The patients who gained most from these treatments were those who had been admitted with an impaired level of consciousness. The whole procedure can be done under direct vision in SER, so SER might replace SCD with similar mortality.

Cloning of leukemia inhibitory factor (LIF) and its expression in the uterus during embryonic diapause and implantation in the mink (Mustela vison)

Leukemia inhibitory factor (LIF) is essential for embryo implantation in mice. Whether LIF plays a role in termination of embryonic diapause and initiation of implantation in carnivores, especially in species with obligate delayed implantation such as the mink, is not known. The objectives of this study were to clone the LIF coding sequence in the mink and determine its mRNA abundance in the uterus through embryonic diapause, implantation, and early postimplantation. We show that the mink LIF cDNA contains 609 nt encoding a deduced protein of 203 amino acids. The homologies are 80.6, 90, 88.2, 87.6, and 86.8% in coding sequence and 79.2, 90.1, 91, 90.1 and 85.4% in amino acid sequence with mouse, human, pig, cow, and sheep respectively. Glycosylation sites and disulfide bonds present in other species are generally conserved in the mink LIF sequence. Quantitation by polymerase chain reaction amplification indicates that LIF mRNA is expressed in mink uterus just prior to implantation and during the first two days after implantation, but not during diapause or later after implantation pregnancy. The abundance of LIF mRNA was significantly higher in the uterus at the embryo expansion stage (P < 0.05) than at days 1-2 of postimplantation. By immunohistochemical localization it was shown that LIF is expressed in the uterine epithelial glands at time of embryonic expansion and in early postimplantation. The coincidence of LIF expression with implantation in this species suggests that LIF is involved in the implantation process, and may be a maternal signal which terminates obligate embryonic diapause.

Luteotropic hormone receptors in the ovary of the mink (Mustela vison) during delayed implantation and early-postimplantation gestation

The reproductive cycle of the mink displays rigid seasonality and obligate embryonic diapause. After ovulation, the corpus luteum (CL) involutes, and it secretes basal progesterone until activated prior to implantation. To study changes in the relative abundance of luteal prolactin and LH receptor mRNA through gestation, ovaries and serum were collected from pregnant female mink at 2-day intervals (n = 3 per date) through embryonic diapause and CL activation (March 19-31) and at 5-day intervals through implantation and early-postimplantation gestation (March 31-April 15). To determine the effect of endogenous prolactin, mink received Alzet osmotic minipumps releasing 2 mg/day 2-bromo-alpha-ergocryptine (bromocriptine) or saline on March 19. Ovaries and serum were taken from 3 animals every 2 days until March 31. Prolactin receptor mRNA in ovaries was low during CL activation but increased 3-fold through embryo implantation. Its abundance correlated with prolactin binding to ovarian membranes and with circulating prolactin. Bromocriptine suppressed endogenous prolactin levels and prevented the increase in prolactin receptor mRNA. There was a transient peak in LH receptor mRNA in the ovaries at March 19-23, which declined to basal levels by March 25 and remained constant through midgestation. Bromocriptine prevented the preimplantation peak in LH receptor mRNA and reduced its abundance below pretreatment levels. The results suggest that prolactin up-regulates its receptor and maintains the LH receptor in the mink CL. The pattern of LH receptor mRNA argues for a role for LH in CL reactivation and termination of embryonic diapause in mink.

The depression system: preliminary studies

The learned helplessness paradigm was used to test the notion that lesions of a theatrical depression system in the rat will produce antidepression similar to antidepressive medication. Lateral brain stem lesions were effective in producing antidepression and unilateral lesions were as effective as bilateral lesions. Ibotenic acid lesions were not effective, indicating that the effective target site was in a fiber tract and not a cell nucleus.

Ion channels as targets for insecticides

Most insecticides are neurotoxicants causing various forms of hyperexcitation and paralysis in animals. A variety of neuroreceptors and ion channels have been identified as the major target sites of these neurotoxic insecticides. This paper gives the highlights of some of the recent development in this area. Pyrethroids keep the sodium channel open for unusually long times causing a prolonged flow of sodium current. The prolonged sodium current elevates and prolongs the depolarizing after-potential which reaches the threshold membrane potential to initiate repetitive after-discharges. We have developed the method with which the percentage of sodium channel population that needs to be modified to cause repetitive after-discharges can be measured accurately. In rat cerebellar Purkinje neurons, only 0.6% of sodium channels needs to be modified for hyperexcitation resulting in a large toxicity amplification. This concept is applicable to other neuroactive drugs that act through the threshold phenomenon. The mechanisms of selective toxicity of pyrethroids in mammals and insects have been quantitatively determined to be due mainly to the different sensitivity of the sodium channels to pyrethroids and the negative temperature dependence of pyrethroid action on the sodium channels. The degradation of pyrethroids play only a minor role. The negative temperature dependence of pyrethroid action is due to the increased sodium current flow at low temperature. The major site of action of dieldrin and hexachlorocyclohexane is the GABA(A) receptor chloride channel complex. Dieldrin exerts a dual action, initial stimulation and subsequent suppression, and the latter is responsible for hyperexcitation of animals. Dieldrin stimulation requires the gamma2s subunit in the GABA receptor, whereas dieldrin suppression occurs in the presence or absence of the gamma2s subunit.

Cloning, developmental expression, and immunohistochemistry of cyclooxygenase 2 in the endometrium during embryo implantation and gestation in the mink (Mustela vison)

Cyclooxygenase (COX) is the first rate-limiting enzyme in the biosynthesis of PGs. There are two isoforms, COX-1, a constitutive enzyme and COX-2, the induced form, products of two different genes. In this study, we report COX-2 complementary DNA cloning, uterine expression, and immunohistochemical localization in the mink uterus during postimplantation gestation. The open reading frame of mink COX-2 contains 1812 nucleotides encoding 604 amino acids. The homologies are 86%, 83%, 83%, 83%, 85%, and 84% in nucleotides and 86%, 87%, 87%, 85%, 86%, and 88% in amino acids with human, mouse, rat, guinea pig, sheep, and rabbit, respectively. All domains associated with biological activity are conserved in the mink. Northern analysis revealed a transcript of 4.2 kb for COX-2 in mink uterus and adrenal. Semiquantitative RT-PCR showed that COX-2 messenger RNA is not present during diapause. The abundance of COX-2 messenger RNA reached its maxima (P < 0.05) on days 3-5 of postimplantation, gradually decreased through day 9, and was not present thereafter. By immunohistochemistry, COX-2 was present in uterine epithelium, stroma, and necks of endometrial glands at sites of implantation. COX-2 expression appears to be induced in the endometrium by the embryo and may play a role in implantation and placentation in the mink.

Percutaneous biopsy in diffuse renal disease: comparison of 18- and 14-gauge automated biopsy devices

PURPOSE

To compare 18-gauge-needle automated biopsy guns to 14-gauge systems for diagnostic efficacy and safety in percutaneous renal biopsy.

MATERIALS AND METHODS

One hundred sixty-one computed tomographic (CT) guided biopsies for diffuse renal disease were retrospectively reviewed. An automated biopsy gun with an 18-gauge needle was used in 74 procedures, and a 14-gauge needle was used in 87 cases.

RESULTS

Adequate tissue for histologic diagnosis was obtained in 96% (71 of 74) of cases with use of the 18-gauge needle, compared with 99% (86 of 87) in the 14-gauge group. The mean glomeruli per specimen were 10.7 and 13.7, respectively. Major hemorrhagic complications occurred in two cases (2.7%) of the 18-gauge group and in three cases (3.4%) of the 14-gauge group.

CONCLUSION

The use of a biopsy gun with an 18-gauge needle provides high tissue recovery rate, comparable to that with the 14-gauge system. The complication rate was acceptably low, with no statistically significant difference from the 14-gauge needles (P = .80).

Differentiation of the corpus luteum of the mink (Mustela vison): mitogenic and steroidogenic potential of luteal cells from embryonic diapause and postimplantation gestation

The mink corpus luteum (CL) involutes after ovulation and remains dormant, synthesizing low amounts of progesterone until reactivated to terminate embryonic diapause. We examined the mitotic and steroid synthetic capacity of luteal cells from the diapause and postimplantation phases of mink gestation. Cells from diapause divided in vitro, reaching confluence in 7-8 days. Three phenotypes were distinguishable: a fusiform cell in whorls, a hypertrophied epithelioid cell, and a small epithelioid cell. The first and second cell types divided in vitro after confluence, evidenced by localization of proliferating cell nuclear antigen (PCNA) in their nuclei. The small epithelioid cells were present in cell nests and showed no PCNA activity. Cells derived from reactivated CL did not reach confluence and had no PCNA activity. Progesterone accumulation was enhanced in luteal cells from diapause by LH, FSH, and dibutyryl (Bu2)cAMP, and by LH and (Bu2)cAMP in cells from reactivated CL. In luteal cells from the diapause phase of gestation, LH and (Bu2)cAMP induced increases in mRNA coding for steroidogenic acute regulatory protein, while cytochrome P450 side-chain cleavage enzyme mRNA was increased by prolactin, LH and (Bu2)cAMP. Cellular concentrations of 3beta-hydroxysteroid dehydrogenase-delta5-4-isomerase mRNA were increased by prolactin and (Bu2)cAMP. Thus, luteinization in the mink CL does not engender exit from the cell cycle, as both fusiform and hypertrophied cells from diapause divide in vitro. Reactivation appears to represent terminal differentiation. LH is capable of stimulating steroidogenesis in vitro in luteal cells from diapause, and prolactin and LH appear to have both specific and overlapping stimulatory effects on the CL of this species.

Modulation of the neuronal nicotinic acetylcholine receptor-channel by the nitromethylene heterocycle imidacloprid

Nitromethylene heterocycle insecticides are known to act on the nicotinic acetylcholine receptor-channel. The effects of the nitromethylene heterocycle, imidacloprid, on the nicotinic acetylcholine receptor-channel of clonal rat phaeochromocytoma (PC12) cells were studied using whole-cell and single-channel patch clamp methods. Imidacloprid suppressed carbachol-induced whole-cell currents in a dose-dependent manner, and this compound itself generated small currents. Multiple conductance states of single-channel currents were also evoked by imidacloprid at the nicotinic acetylcholine receptor-channels. The most frequently generated single-channel currents showed two conductance states, 25.4 and 9.8 pS, which were identical to the conductance states of acetylcholine-generated currents. The mean open time and burst duration of the main conductance currents induced by imidacloprid were shorter than those induced by acetylcholine. Co-application of imidacloprid and acetylcholine caused some interactions at the two conductance states. Mean open time and mean burst duration of the main conductance state currents evoked by acetylcholine were decreased by the co-application of imidacloprid as compared with those induced by acetylcholine alone. In conclusion, imidacloprid has both multiple agonist and antagonist effects on the neuronal nicotinic acetylcholine receptor-channels.

Luteal and placental characteristics of carnivore gestation: expression of genes for luteotrophic receptors and steroidogenic enzymes

Experiments were carried out to investigate the abundance of mRNA for luteotrophic receptors and steroidogenic elements in the ovaries and corpora lutea of mink during the embryonic diapause, peri-implantation and postimplantation pregnancy. The second aim was to determine whether the mink placenta synthesized progesterone. Homologous cDNA probes for the mink LH and prolactin receptors were generated by the polymerase chain reaction. Heterologous cDNA probes for steroidogenic acute regulatory protein (StAR), cytochrome P450 side chain cleavage (P450scc) and 3 beta-hydroxysteroid dehydrogenase-delta 4-delta 5 isomerase (3 beta HSD) were also used. The abundance of mRNA encoding the prolactin receptor was low during the period of embryonic diapause and increased concurrent with circulating progesterone. The abundance of LH receptor message reached peak values during the peri-implantation period followed by maintenance of a steady-state after implantation. The abundance of StAR and P450scc messages appeared not to vary during gestation, while that for 3 beta HSD was correlated with changes in circulating progesterone. There was no evidence of 3 beta HSD activity or transcripts in the placenta. These results indicate that prolactin and LH are necessary for activation of the corpus luteum during the period of embryonic diapause, and for its maintenance during postimplantation gestation. The mink placenta does not synthesize progesterone.

Oxidative stability of docosahexaenoic acid-containing oils in the form of phospholipids, triacylglycerols, and ethyl esters

The peroxidative stability of docosahexaenoic acid (DHA)-containing oils (DHA at 10.7 mol% of the total fatty acids), in the form of phospholipids (PL), triacylglycerols (TG), and ethyl esters (EE) with the same constituent fatty acids, was investigated in the dark at 25 degrees C in a bulk phase, and compared with that of control palm oil (supplemented with 20% soybean oil). The oxygen absorption of the DHA-containing oil was significantly lower in the form of PL than in the form of TG and EE during a 10-week oxidation, and the oxygen absorption of PL was almost equivalent to that of the control oil. A gas chromatographic analysis showed that 90% of initial DHA was retained in the form of PL after the 10-week oxidation, while TG and EE respectively more rapidly decayed with the loss of 97% and 64% of DHA. Tocopherol in the form of TG and EE had also completely decayed after the oxidation, while 37% of the initial tocopherol remained in the form of PL. The peroxide and carbonyl values of TG and EE showed large increases after the oxidation, but no such increase was observed for PL. These results show that DHA-containing oil in the form of PL was more resistant to the oxidative degradation of DHA than that in the form of TG and EE in a bulk phase.

Direct actions of anticholinesterases on the neuronal nicotinic acetylcholine receptor channels

Recent studies have suggested that anticholinesterases including organophosphates and carbamates act directly on the nicotinic acetylcholine receptor (AChR) channel. We performed whole-cell and single-channel patch-clamp experiments to elucidate the mechanism of action of anticholinesterases on the nicotinic AChR in rat clonal phaeochromocytoma (PC12) cells. Neostigmine and carbaryl showed a biphasic effect; enhancement and suppression of carbachol-induced whole-cell currents. The currents induced by 100 microM carbachol was enhanced by the first co-application with 10 or 100 microM neostigmine, and the current was eventually suppressed below the control level during repeated co-applications. The decay phase of current was accelerated by neostigmine. Carbaryl at 0.1 microM greatly potentiated the carbachol-induced current, and at higher concentrations (0.3-3 microM), current was suppressed. In single-channel experiments, these compounds increased the short closures or gaps during channel opening without changing the single-channel conductance. Mean open time and burst duration were decreased in the presence of neostigmine and carbaryl. These results indicate that neostigmine and carbaryl directly block the nicotinic AChR channel.

Neurons of the rostral para-ambiguual field have activity correlated to the 10-Hz rhythm in sympathetic nerve discharge of urethane-anesthetized cat

Using the techniques of time domain correlation (mid-signal spike-triggered averaging) and frequency domain correlation (neuron-to-nerve coherence), 24% (54) of a sample of 229 neurons of the rostral para-ambiguual field have shown to have activity correlated to the 8- to 13-Hz rhythm in the inferior cardiac sympathetic nerve discharge (SND) of urethane-anesthetized cat. This correlation existed in both baroreceptor-innervated and -denervated animals. Of the correlated neurons, 37% (20) were non-rhythmically firing and displayed flat autospectra, while 63% (34) fired rhythmically and contained well-defined peaks in their autospectra. The group firing rate of these neurons was 4.3 +/- 0.4 spikes/s, indicating that they are not pacemaker neurons for the 10-Hz SND rhythm. The group time of firing of these neurons to the next peak of the SND slow wave was 52 +/- 4 ms. Correlation of the activity of medullary neurons with the 8-13-Hz rhythm of the SND was previously claimed only for rostral ventrolateral medulla, caudal raphe, and rostral caudal ventrolateral medulla. This present finding suggests that this behavior may be more widely spread throughout the medulla.

Effects of the neuroprotective agent riluzole on the high voltage-activated calcium channels of rat dorsal root ganglion neurons

The effects of riluzole, a neuroprotective drug, on high voltage-activated (HVA) calcium channels of rat dorsal root ganglion neurons were studied using the whole-cell patch-clamp technique. Riluzole inhibited HVA calcium channel currents in a dose-dependent, time-dependent and reversible manner. The apparent dissociation constants for riluzole inhibition of the transient and sustained components of the current were 42.6 and 39.5 microM, respectively. Riluzole accelerated the activation kinetics of calcium channels without affecting the voltage dependence of activation. It accelerated the fast component of deactivation kinetics without affecting the slow component. It also accelerated fast and slow inactivation kinetics of the HVA channels. However, only one of the two components in the steady-state inactivation curve for the HVA channels was shifted in the hyperpolarizing direction by riluzole, which indicates differential block of the multiple-type HVA channels. By use of the specific blockers nimodipine, omega-conotoxin GVIA and omega-agatoxin IVA, the HVA calcium channels were found to comprise L-type (10%), N-type (63%), P/Q-type (23%) and R-type (9%). Riluzole blocked N- and P/Q-type channels, but not L-type channel, with the order of efficacy of P/Q- > N- >> L-type channels. Riluzole inhibition of N- and P/Q-type calcium channels may result in reduced calcium influx at presynaptic terminals, which thereby decreases excessive excitatory neurotransmitter release, especially glutamate, a mechanism known to cause neuronal death in ischemic conditions.

Differential action of riluzole on tetrodotoxin-sensitive and tetrodotoxin-resistant sodium channels

The effects of riluzole, a neuroprotective drug, on tetrodotoxin-sensitive (TTX-S) and tetrodotoxin-resistant (TTX-R) sodium channels in rat dorsal root ganglion neurons were studied using the whole-cell patch clamp technique. At the resting potential, riluzole preferentially blocked TTX-S sodium channels, whereas at more negative potentials, it blocked both types of sodium channels almost equally. The apparent dissociation constants for riluzole to block TTX-S and TTX-R sodium channels in their resting state were 90 and 143 microM, respectively. Riluzole shifted the voltage dependence of activation of TTX-R sodium channels in the depolarizing direction more than that of TTX-S sodium channels. The voltage dependence of the fast inactivation of both types of sodium channels was shifted in the hyperpolarizing direction in a dose-dependent manner, and the apparent dissociation constants for riluzole to block the inactivated channels were estimated to be 2 and 3 microM for the TTX-S and TTX-R sodium channels, respectively, indicating a much higher affinity for the inactivated channels than for the resting channels. Riluzole was equally effective in blocking both types of sodium channels in their slow inactivated state. Since more TTX-S channels are inactivated than TTX-R channels at the resting potential, riluzole blocks TTX-S sodium channels more potently than TTX-R sodium channels. It was concluded that one of the mechanisms by which riluzole exerts its neuroprotective action is to preferentially block the inactivated sodium channel of damaged or depolarized neurons under ischemic conditions, thereby suppressing excess stimulation of the glutamatergic receptors and massive influx of Ca++.

G-proteins are involved in riluzole inhibition of high voltage-activated calcium channels in rat dorsal root ganglion neurons

Effects of riluzole on high voltage-activated (HVA) calcium channels of rat dorsal root ganglion neurons were studied using the whole-cell patch-clamp technique. Riluzole at 30 microM inhibited the HVA currents. The onset and offset of riluzole inhibitory effect were slow usually taking more than 3 min. Riluzole inhibition of the HVA currents was abolished and partially reduced by addition of 500 microM GDP-beta-S and 1 mM N-ethylmaleimide, respectively, to the pipette solution. Pre-treatment with pertussis toxin or application of depolarizing pre-pulses did not affect riluzole's inhibitory effect on the HVA currents. Riluzole inhibition of the HVA currents was also blocked by internal application of 50 microg/ml protein kinase A inhibitory peptide. It was concluded that pertussis toxin-insensitive G-proteins and protein kinase A may be involved in riluzole inhibition of the HVA currents.

Magnetic resonance imaging of the wrist in defining remission of rheumatoid arthritis

OBJECTIVE

To assess the efficacy of magnetic resonance imaging (MRI) in objectively defining a state of remission in rheumatoid arthritis (RA) after treatment.

METHODS

Ten patients with RA involving the wrist were evaluated before treatment with methotrexate and hydroxychloroquine, and then mean 14 mo later with a followup evaluation. Clinical variables, laboratory measurements, and MRI using various techniques (T1 weighted image, T2 weighted image, fat suppression T2 weighted image, postcontrast T1 weighted image, postcontrast dynamic image, postcontrast 3 dimensional image) were observed. Remission was defined by ACR criteria. MRI changes were observed using 3 variables: extent of synovial proliferation; extent of bone marrow edema; and development of new erosion. In 6 of 10 patients, synovial signal intensity time curve changes at 30 s (E30 ratio) were determined for quantitative assessment of synovitis.

RESULTS

Four patients achieved remission and 6 did not. All patients in remission showed decrease in extent of synovial proliferation and bone marrow edema with no newly developed erosion after treatment, compared to baseline. Five of 6 patients in nonremission showed newly developed erosions with variable changes in extent of synovial proliferation and bone marrow edema. E30 ratio was determined in 3 patients in the remission group and 3 in the nonremission group, with 48% reduction in the former compared to 9% reduction in the latter.

CONCLUSION

MRI is feasible for objectively defining remission and assessing the therapeutic effect of antirheumatic drugs; utility of MRI measures in clinical remission criteria remains to be verified.

Lead modulation of the neuronal nicotinic acetylcholine receptor in PC12 cells

Lead is known to modulate several ligand- and voltage-gated ion channels, including the nicotinic acetylcholine receptor (AChR) channel. We examined the effects of lead on the nicotinic AChR in rat clonal phaeochromocytoma PC12 cells using whole-cell and single-channel patch-clamp techniques to clarify the detailed mechanism of action. Lead suppressed acetylcholine-induced currents in a dose-dependent manner with an EC50 value of 37 microM and a Hill coefficient of 0.82. At the single-channel level, 1-10 microM lead shortened the opening and burst durations, and increased the duration of mean closed time. The open probability was significantly decreased by lead. These changes of single-channel kinetics result in a significant decrease in the total charge carried through the open AChR channels explaining the suppressive effect of lead on acetylcholine-induced whole-cell currents.

Association between genetic variations of apo AI-CIII-AIV cluster gene and hypertriglyceridemic subjects

Several studies have suggested that genetic variations of the apolipoprotein (apo) AI-CIII-AIV cluster gene are associated with hyperlipidemia or atherosclerosis. These investigations were carried out mainly with Caucasian groups; there have been few associated studies involving non-Caucasian groups. This study was conducted to elucidate the association between five restriction fragment length polymorphisms (RFLPs) of the apo AI-CIII-AIV cluster gene and Korean hypertriglyceridemic subjects. The rare allele frequencies of the XmnI and SstI polymorphic sites in the patients were significantly higher than those of the control group (P <0.05). These two polymorphic sites had relation to linkage disequilibrium in the hypertriglyceridemic subjects (delta = -0.2733). In addition, S2 allele frequency of the SstI RFLP in Koreans was more frequent than that of Caucasians reported previously. The rare allele of XmnI and SstI polymorphic sites was associated with increased triglyceride concentrations in the hypertriglyceridemic group (P <0.005). Koreans have a much lower prevalence of hyperlipidemia than Caucasians. Nevertheless, this study showed a similar trend with results from Caucasian groups, thereby confirming that genetic variations of the apo AI-CIII-AIV cluster gene are likely to be significant markers for hypertriglyceridemic subjects. Thus, RFLP loci of the apo AI-CIII-AIV cluster gene may be a useful genetic marker for clinical or population studies.

Involvement of NMDA receptor in the regulation of plasma interleukin-6 levels in mice

MK-801 ((+)-5-methyl-10,11-dihydro-5H-dibenzo(a,d)cyclopepten-5,10-imine maleate), a non-competitive NMDA receptor antagonist (0.01-1 micrograms), injected intracerebroventricularly (i.c.v.) dose dependently increased the baseline levels of plasma interleukin-6 in mice. In the 1-h immobilization-stressed animals, MK-801 (1 micrograms) administered i.c.v. produced an additive increase of plasma interleukin-6. NMDA (N-methyl-D-aspartate) (3, 10 ng) administered i.c.v. attenuated dose dependently the 1-h immobilization stress-induced rise in plasma interleukin-6 level. Neither 6-cyano-7-nitro-quinoxaline-2,3-dione (CNQX) (0.01-0.5 micrograms) nor alpha-methyl-4-carboxyphenylglycine (MCPG) (1-20 micrograms), antagonists of non-NMDA and metabotropic glutamate receptors, respectively, i.c.v. administered, affected the basal and stress-induced plasma interleukin-6 levels. These data indicate that NMDA receptors may be involved in the suppressive regulation of the plasma interleukin-6 levels.

Differential block of two types of sodium channels by anticonvulsants

The differential effects of the anticonvulsants phenytoin and carbamazepine on the sodium channels of rat dorsal root ganglion (DRG) neurons were studied using the patch clamp technique. The action potentials from tetrodotoxin-resistant (TTX-R) cells were less sensitive to phenytoin and carbamazepine than those from tetrodotoxin-sensitive (TTX-S) cells. The steady-state inactivation curve for TTX-S sodium channels was shifted by as much as 20.6 mV and 11.4 mV by phenytoin and carbamazepine at 300 microM, respectively, yet the curve for TTX-R sodium channels was shifted only by 6.0 mV and 6.9 mV, respectively. Thus, the differential action potential block of TTX-S and TTX-R cells by phenytoin and carbamazepine is due to different voltage dependence of and differential drug effects on the inactivation kinetics of two types of sodium channels.

Potent modulation of neuronal nicotinic acetylcholine receptor-channel by ethanol

Controversies remain over which ion channels are the most sensitive to ethanol. We have found that ethanol potently modulates the neuronal nicotinic acetylcholine receptor-channel at micromolar concentrations with an EC50 of 88.5 microM, which is significantly lower than most values previously reported for other ion channels. Prolonged application of ethanol accelerated the decay phase of acetylcholine-induced currents, caused single-channels to open in bursts, and shortened the mean open time, all of which reflect increased receptor desensitization. However, ethanol slowed the decay phase of the current induced by a brief application of acetylcholine, which may indicate that ethanol manifests its action by causing an increase in the affinity of the receptor for acetylcholine. These results suggest that neuronal nicotinic acetylcholine receptors may be important target sites of ethanol, particularly in the early stages of ethanol intoxication.

A new trend in operative technique for intracerebral hemorrhage: a comparative study of stereotactic endoscopic removal and stereotactic catheter drainage

The development of less invasive methods to evacuate intracerebral hematomas (ICHs) has improved outcome in patients with traumatic brain injury. Eighteen patients with ICHs underwent surgery via one of two methods: stereotactic endoscopic removal (SER) or stereotactic catheter drainage (SCD). The outcome results were then compared. The patient population was composed of 11 men and seven women with a mean age of 53.3 years (range 33-81 years), all suffering from ICH in the basal ganglia. The mean hematoma volume was 34.4 ml (range 23-105 ml). All patients had major neurological deficits, but showed no sign of transtentorial herniation. Ten patients underwent SCD and eight had SER. All procedures were performed within 24 hours of insult. After local anesthesia was induced in the patient, an intracranial pressure (ICP) monitoring catheter and an Otzuki cannula were placed through separate burr holes in the skull. Using the SER technique, the ICH was removed using suction and forceps through the side window of the cannula until the ICP had decreased significantly. Hemostasis was attained by lesioning with a Nd-YAG laser. In the SCD procedure, we placed a silicone catheter into the hematoma to drain it and then added urokinase. The hematoma was drained for 3 to 5 days in the SER method and 7 to 10 days in the SCD method. Rebleeding occurred in one of the early cases in which we used the SER procedure. At follow-up evaluation, the mortality rate was 13% in the SER group and 10% in the SCD group. The patients in whom outcome was most improved from these treatments were those who had been admitted with an impaired level of consciousness. Stereotactic catheter drainage is a precise, safe, and brief procedure with a very low rebleeding rate, but its outcome effect was more delayed than other procedures. Stereotactic endoscopic removal can easily replace SCD, with a similar mortality rate. Both procedures can be accomplished under direct visualization so as to eliminate any undesirable event or outcome.

The effects of the muscle relaxant, CS-722, on synaptic activity of cultured neurones

1. The pharmacological properties of the centrally acting muscle relaxant, CS-722, were studied in cultured hippocampal cells and dorsal root ganglion cells of the rat using the whole-cell variation of the patch clamp technique. 2. CS-722 inhibited the occurrence of spontaneous excitatory and inhibitory postsynaptic currents in hippocampal neurones at concentrations of 100-300 microM, but had no effect on postsynaptic currents evoked by the application of glycine, gamma-aminobutyric acid, glutamate or N-methyl-D-aspartate. 3. CS-722 reduced voltage-gated sodium currents, while shifting the sodium channel inactivation curve to more negative membrane potentials. This effect is similar to that reported for local anaesthetics. Voltage-gated potassium currents were decreased by CS-722 by approximately 20%, whereas voltage-activated calcium currents were inhibited by about 25%. 4. CS-722 inhibited evoked inhibitory postsynaptic currents. However, the spontaneous quantal release of inhibitory transmitter was not affected. 5. The inhibitory effect of CS-722 on spontaneous inhibitory postsynaptic currents and excitatory postsynaptic currents in hippocampal cultures probably results from an inhibition of both sodium and calcium currents. This inhibitory effect is likely to be amplified in polysynaptic neuronal circuits.

Vertex epidural hematomas: considerations in the MRI era

Two cases of vertex epidural hematomas are described to illustrate their unique diagnostic and treatment problems. Due to its specific location, a correct diagnosis of the intracranial hematoma was delayed in the first case. Quantitative analysis of the hematoma volume was performed in the second case. We would like to emphasize the usefulness of the magnetic resonance imaging and quantitative analysis of vertex epidural hematoma in choosing treatment options in such patients.

Subconductance-state currents generated by imidacloprid at the nicotinic acetylcholine receptor in PC 12 cells

Nitromethylene heterocyclic insecticides are known to act on the nicotinic acetylcholine receptor-channel complex. The effects of the nitromethylene heterocycle imidacloprid on the nicotinic acetylcholine receptor of clonal rat pheochromocytoma (PC 12) cells were studied using the single-channel patch clamp technique. Imidacloprid generated single-channel currents of multiple conductance states in PC12 cells. Both acetylcholine and imidacloprid induced single-channel currents of main conductance and subconductance states with conductances of 33.3 and 9.4 pS by acetylcholine and 30.4 and 9.8 pS by imidacloprid. However, the main conductance currents were generated predominantly by acetylcholine, whereas the subconductance currents were generated predominantly by imidacloprid. Partial block of acetylcholine-induced currents by imidacloprid may be explained on the basis of the single-channel behavior.

Modulation of sodium channels of rat cerebellar Purkinje neurons by the pyrethroid tetramethrin

The pyrethroid insecticides are known to slow the kinetics of the activation and inactivation gates of sodium channels. This results in prolonged openings of individual sodium channels and prolonged flow of whole-cell sodium current, which in turn cause hyperexcitation in animals. The aim of the present study was to solve three important remaining questions. First, the percentages of the sodium channels modified by the pyrethroid tetramethrin were measured and compared with the threshold concentration to initiate repetitive discharges in rat cerebellar Purkinje neurons. Tetramethrin at 0.1 microM modified only 0.6% of the sodium channels and generated repetitive afterdischarges. Thus, the pyrethroid toxicity is greatly amplified from the sodium channel to the whole animal. The pyrethroid sensitivity of Purkinje neuron sodium channels was lower than that of invertebrate sodium channels by a factor of > or = 10. Chloramine-T at 200 microM removed the sodium channel inactivation and increased the percentage of sodium channel modification by tetramethrin through open channel modification. Second, temperature had a profound effect on the ability of tetramethrin to cause repetitive afterdischarges; at 0.1 to 0.3 microM tetramethrin, repetitive discharges were induced at l5 degrees C and 20 degrees C, but this effect subsided at 25 degrees C to 35 degrees C. This negative temperature dependence could be explained by an increase in charge movement during slow tail current as temperature was lowered. The Q10 value for the charge movement during tail current was 0.22 between 20 degrees C and 30 degrees C. Third, the selective toxicity of pyrethroids between mammals and insects could be explained quantitatively on the basis of sodium channel factors that include temperature dependence, intrinsic sensitivity and recovery rate and detoxication factors.

Differential effects of the pyrethroid tetramethrin on tetrodotoxin-sensitive and tetrodotoxin-resistant single sodium channels

The differential effects of the pyrethroid tetramethrin on tetrodotoxin-sensitive (TTX-S) and tetrodotoxin-resistant (TTX-R) single sodium channel currents in rat dorsal root ganglion (DRG) neurons were investigated using the outside-out configuration of patch-clamp technique. Channel conductances were 10.7 and 6.3 pS for TTX-S and TTX-R sodium channels, respectively, at a room temperature of 24-26 degrees C. The single-channel current of TTX-S sodium channels at the test potential of -30 mV was -1.27 +/- 0.25 pA, and was not changed after exposure to 10 microM tetramethrin (-1.28 +/- 0.23 pA). The open time histogram of TTX-S single-channel currents could be fitted by a single exponential function with a time constant of 1.27 ms. After exposure to 10 microM tetramethrin, the open time histogram could be fitted by the sum of two exponential functions with time constants of 1.36 ms (tau fast) and 5.73 ms (tau slow). The percentage of contribution of each component to the population was 62% for the fast component representing the normal channels and 38% for the slow component representing the tetramethrin modified channels. The amplitude of TTX-R single-channel currents was slightly changed from -0.72 +/- 0.14 to -0.83 +/- 0.07 pA by 10 microM tetramethrin. The open time histogram of TTX-R single-channel currents could be fitted by a single exponential function with a time constant of 1.92 ms. In the presence of 10 microM tetramethrin, the open time histogram could be fitted by the sum of two exponential functions with time constants of 2.07 ms (tau fast) and 9.75 ms (tau slow). The percentage of contribution of each component was 15% for the fast, unmodified component and 85% for the slow, modified component. Differential effects of tetramethrin on the open time distribution of single sodium channel currents explains the differential sensitivity of TTX-S and TTX-R sodium channels.