Characterization of chloride efflux from GT1-7 neurons: lack of effect of ethanol on GABAA response

The purpose of this study of GT1-7 neurons was to partially characterize basal Cl- transport and GABAA mediated Cl- efflux and to test the effect of ethanol on a GABAA receptor that lacks a gamma subunit. We measured GABAA function and Cl- transport with 36Cl-. Our results show that basal 36Cl- efflux varied with temperature at 4 degrees C, 23 degrees C, and 37 degrees C. At 23 degrees C, DIDS, an inhibitor of anion exchange, reduced basal 36Cl- efflux maximally by 79.6% with an IC50 of 42.1 microM, whereas bumetanide, an inhibitor of (Na-K-Cl) cotransport, had no effect on basal 36Cl- efflux at concentrations up to 150 microM. At 4 degrees C, muscimol, a GABAA receptor agonist, stimulated 36Cl- efflux with an EC50 of 1.47 microM. Bicuculline, a GABAA receptor antagonist, completely reversed the effect of 20 microM muscimol with an IC50 of 6.08 microM. Ethanol, at concentrations up to 87 mM (0.4% (w/v)), had no effect on muscimol-induced 36Cl- efflux at 4 degrees C or at 32 degrees C. Our results indicate that stimulation of GABAA receptors causes an efflux of Cl- from GT1-7 neurons. This finding is consistent with the concept that stimulation of GABAA receptors produces depolarization of the plasma membrane, increase in cytosolic [Ca2+], and GnRH release. Our results represent the first description of chloride transport in GT1-7 neurons and suggest the presence of a Cl- exchange, but not (Na-K-Cl), transporter mechanism. Furthermore, the lack of an effect of ethanol observed in this study is consistent with the idea that a gamma 2L subunit may be necessary for the effects of low concentrations of ethanol at GABAA receptors.

Solution structures of the R6 human insulin hexamer,

The three-dimensional solution structure of the phenol-stabilized 36 kDa R6 insulin hexamer was determined by NMR spectroscopy and restrained molecular dynamics. The hexamer structures were derived using a stepwise procedure. Initially, 60 monomers were obtained by distance geometry from 665 NOE-derived distance restraints and three disulfide bridges. Subsequently, the hexamer structures were calculated by simulated annealing, using 30 hexamers constructed from the best 36 monomer structures as the starting models. The NMR data show that the aromatic ring of residue Phe(B25) can take two different orientations in the solution hexamer: one in which it points inward (molecule 1, about 90%) and one in which it points outward from the surface of the monomer (molecule 2, about 10%). Therefore, two hexamer structures were calculated: a symmetric hexamer consisting of six molecule 1 monomers and a nonsymmetric hexamer consisting of five molecule 1 monomers and one molecule 2 monomer. For each of the six monomers, the restraints used in the calculations of the hexamer structures include, in addition to the intramonomeric restraints, 25 NOEs between insulin and phenol, 23 NOEs and two hydrogen bonds across the dimer interface, nine NOEs across the trimer interface, and five intramonomeric or two intermonomeric NOEs, respectively, specifying the different orientations of the Phe(B25) ring. The coordination of the two Zn atoms was defined by eight distance restraints. Thus, a total of 4394 and 4391 distance restraints, respectively, were used in the two hexamer calculations. The NOE restraints were classified in an iterative process as intra- or intermonomeric on the basis of their consistency or inconsistency with the structure of the monomer. The assignment of the dimer- and trimer-specific NOEs was made using the crystal structure of the R6 hexamer as the starting model. For both solution hexamers, the average backbone rms deviation is 0.81 A, if the less well-defined N- and C-terminal residues are excluded. The corresponding rms deviations for all heavy atoms are 1.17 and 1.19 A for the nonsymmetric and symmetric hexamer, respectively. The overall solution structure of the R6 insulin hexamer is compact, rigid, and symmetric and resembles the corresponding crystal structure. However, the extension of the B-chain alpha-helix, which characterizes the R state, is shorter in the solution structure than in the crystal structure. Also, the study shows that the orientation of the Phe(B25) ring has no effect on the structure of the rest of the molecule, within the uncertainty of the structure determination. The importance of these findings for the current model for the insulin-receptor interaction is discussed.

Effects of chromium on health status, blood neutrophil phagocytosis and in vitro lymphocyte blastogenesis of dairy cows

The objective of this study was to determine the effects of supplemental dietary chromium (Cr) on health status and mastitis-related parameters, as well as neutrophil phagocytic activity of dairy cows during late pregnancy and early lactation. In addition, possible interactions and involvements of Cr with insulin, cortisol, somatotropin (rBST) and insulin-like growth factor-1 (IGF-1) were directly investigated in vitro based on blastogenic responses using peripheral blood lymphocytes (PBL) of eight cows fed the control diet. Forty pregnant Holsteins, 18 primiparous and 22 multiparous, at week (wk) 6 before the expected calving dates were randomly assigned to treatments: control and supplemental chelated Cr (0.5 ppm) in the diet. All cows were managed in a normal production operation and health status was assessed by recording the incidence of health problems during the experimental period of wks 6 before and 16 after calving (-6 to 16 wks). Mastitis-related parameters included somatic cell counts (SCC), bacterial colony counts of milk samples from each mammary gland quarter of all cows during wk 1 to wk 8 postpartum. Peripheral blood neutrophil phagocytic function of eight cows fed either control or supplemental Cr diet was determined by the ability to take up uniform fluorescent beads measured by flow cytometry. Supplemental Cr had no effect (P > 0.10) on health status of cows during late pregnancy and early lactation, or on SCC and bacterial colonies of quarter milk samples from early lactation (wks 1 to 8). Supplemental Cr also did not affect neutrophil phagocytic function of cows from 6 wks prepartum to 6 wks postpartum. However, in the in vitro study of PBL (from control animals, not fed Cr diet) blastogenesis with addition of insulin or cortisol at two levels (0.05 and 0.5 ng ml-1), insulin and cortisol enhanced or had no effect on PBL proliferations with or without concanavalin A (con A) simulation. However, further Cr addition in the culture medium containing supplemental insulin or cortisol, particularly CrCl3, additively increased (P < 0.05) BPL blastogenic activities with or without con a stimulation. Conversely, addition of rBST or IFG-1 (0.5 and 5.0 ng ml-1) in the culture medium enhanced PBL proliferation, but addition of Cr gave no additional effect. These results indicated that supplemental Cr had no beneficial effect on health status, mastitis-related parameters or neutrophil phagocytic activity of dairy cows. However, in vitro study confirmed and extended our previous observations that Cr has an effect on lymphocyte proliferation and this may associate with insulin or cortisol actions.

Antenatal diagnosis and management of Dandy-Walker syndrome

The Dandy-Walker syndrome (DWS) can be accurately diagnosed in utero by sonographic demonstration of characteristic morphologic changes of the fetus, which includes hydrocephalus, incomplete cerebellar vermis and a posterior fossa cyst. We present a case of Dandy-Walker syndrome diagnosed antenatally. The associated anomalies are reviewed, and the value of antenatal diagnosis is discussed.

Cordocentesis: a useful method for prenatal diagnosis

OBJECTIVE

To evaluate the efficacy and safety of cordocentesis for prenatal diagnosis of various fetal diseases.

PATIENTS AND METHODS

Fetal blood sampling was performed in 30 pregnancies from gestational week 19 to 36 for various prenatal diagnoses. We used Aloka SSD-650 real-time ultrasound scanner with 3.5 mHz curvilinear transducer during the procedure. A regular 22-gauge spinal needle was used for fetal blood sampling.

RESULTS

Twenty-five cordocentesis were successful at the first attempt. A second attempt of cordocentesis succeeded in three cases. In the remaining two cases, intrahepatic vein sampling and cardiocentesis were employed respectively. The duration of procedure was shorter than 15 minutes in 25 cases. 1-6 ml of fetal blood was obtained from each case. Fetal blood was diluted with amniotic fluid in four samples. Maternal blood contamination never happened. No lethal complication occurred in our series.

CONCLUSION

It is believed that cordocentesis is a safe and useful method for prenatal diagnosis, and intrahepatic vein sampling is an alternative choice when cordocentesis has failed.

[Effect of hedgehog hydnum on the delay of fatigue in mice]

Two groups of mice were fed with either hedgehog hydnum powder or extract for sixty days. For the assay of fatigue, the activity of serum lactate dehydrogenase, the serum urea nitrogen content, blood lactic acid, hepatic and muscular glycogen, and the physical stamina of the mice were determined. The activity of serum lactate dehydrogenase and the hepatic and muscular glycogen content in the experimental mice were evidently higher than that in the control mice (P < 0.05 or P < 0.01). After exercise, the increase in blood lactic acid and serum urea nitrogen in the experimental mice was significantly lower than that in the control mice (P < 0.05 or P < 0.01), but the rate of elimination of blood lactic acid in the experimental mice was significantly higher than that in the control mice (P < 0.05). In the physical stamina swimming, the experimental mice drowned after a longer period of time than the control mice (P < 0.05). In conclusion hedgehog hydnum had a significant effect on raising physical stamina and delaying fatigue in mice.

[Cordocentesis for prenatal diagnosis of fetal diseases]

For the purpose of prenatal diagnosis, 30 fetal blood samplings were performed in 30 pregnant women from 19 to 36 gestational weeks. The samples were taken with a 22-gauge needle guided by ultrasound. Twenty-five cordocenteses were succeeded at the first attempt. A second attempt was needed in other 5 cases. The duration of procedure was less than 15 minutes in 83.3% cases. 1-6 ml fetal blood was obtained for each case. No lethal complication occured in our series. It is believed that cordocentesis could be a useful tool for prenatal diagnosis, and the intrahepatic-vein sampling is a preferable alternative choice if cordocentesis fails.

Partial characterization of K(+)-induced increase in [Ca2+]cyt and GnRH release in GT1-7 neurons

Secretion of pituitary gonadotropins is regulated centrally by the hypothalamic decapeptide gonadotropin releasing hormone (GnRH). Using the immortalized hypothalamic GT1-7 neuron, we characterized pharmacologically the dynamics of cytosolic Ca2+ and GnRH release in response to K+-induced depolarization of GT1-7 neurons. Our results showed that K+ concentrations from 7.5 to 60 mM increased [Ca2+]cyt in a concentration-dependent manner. Resting [Ca2+]cyt in GT1 -7 cells was determined to be 69.7 +/- 4.0 nM (mean +/- S.E.M.; n = 69). K+-induced increases in [Ca2+]cyt ranged from 58.2 nM at 7.5 mM [K+] to 347 nM at 60 mM [K+]. K+-induced GnRH release ranged from about 10 pg/ml at 7.5 mM [K+] to about 60 pg/ml at 45 mM [K+]. K+-induced increases in (Ca2+]cyt and GnRH release were enhanced by 1 microM BayK 8644, an L-type Ca2+ channel agonist. The BayK enhancement was completely inhibited by 1 microM nimodipine, an L-type Ca2+ channel antagonist. Nimodipine (1 microM) alone partially inhibited K+-induced increases in [Ca2+]cyt and GnRH release. Conotoxin (1 microM) alone had no effect on K+-induced GnRH release or [Ca2+]cyt, but the combination of conotoxin (1 microM) and nimodipine (1 microM) inhibited K+-induced increase in [Ca2+]cyt significantly more (p < 0.02) than nimodipine alone, suggesting that N-type Ca2+ channels exist in GT1-7 neurons and may be part of the response to K+. The response of [Ca2+]cyt to K+ was linear with increasing [K+] whereas the response of GnRH release to increasing [K+] appeared to be saturable. K+-induced increase in [Ca2+]cyt and GnRH release required extracellular [Ca2+]. These experiments suggest that voltage dependent N- and L-type Ca2+ channels are present in immortalized GT1-7 neurons and that GnRH release is, at least in part, dependent on these channels for release of GnRH.

Supplemental chromium and niacin for stressed feeder calves

The effects of supplemental inorganic chromium (Cr) and (or) nicotinic acid (niacin) were compared with those of an organic source of Cr on performance, morbidity and blood metabolites were investigated of 135 crossbred steer calves, purchased at three sales in Ontario. Calves of 236-kg average weight were randomly assigned to control, 0.75 mg kg−1 (dry matter) organic Cr from Cr yeast, 0.75 mg kg−1 inorganic Cr from CrCl3∙6H2O, 100 mg kg−1 niacin, or CrCl3∙6H2O + niacin for the 28-d stress and 28-d growing periods. During the first 2 wk Cr supplementation was doubled. The basal diet was 75% alfalfa silage, 23% high-moisture corn and 2% mineral and vitamin supplement. Treatments had no beneficial effect on overall morbidity. Inorganic Cr and niacin alone had no beneficial effect (P > 0.10) on performance. Inorganic Cr and niacin used together, however, tended to increase weight gain by 39% (P = 0.09) and feed efficiency by 47% (P = 0.08) during the 28-d stress period, with no improvement during the later growing period. Inorganic Cr together with niacin increased serum iron concentration (P = 0.01) and serum total iron-binding capacity (P = 0.01) of healthy calves but had no effect on these metabolites in morbid calves. This study suggested that supplemental inorganic Cr is not as effective as an organic source for ruminants. Supplemental inorganic Cr with niacin tended to improve performance of stressed calves, suggesting that niacin may be a limiting factor for absorption and (or) use of inorganic Cr. Key words: Chromium, niacin, stressed calves, iron, iron-binding capacity, cortisol

[An experimental study on changes in collagen content after homologous cartilage implantation]

This experiment studied the changes in cartilage collagen content during 1-20 weeks after allografting of cartilage. The results showed that the collagen content was reduced beginning from the 3rd week, and reached the lowest point in the 4th week (P < 0.05). Then it rose continuously and attained the normal level in the 8th week (P > 0.05). The study suggests that the changes in cartilage collagen content may help us to assess the cartilage structure and the elasticity after a cartilage allotransplantation.

[Sonographic diagnosis of ruptured corpus luteum with hemoperitoneum]

This article reports sonographic characteristics of a ruptured corpus luteum with hemoperitoneum in 44 cases. Sonographic findings were classified and compared with laparotomy and pathology. From sonographic imaging, it was found that the ruptured corpus luteum cyst was pathognomonic. There was a good correlation between ultrasound findings and surgical results when bleeding was over 100 ml. The sonographic value in diagnosis of ruptured corpus luteum with hemoperitoneum is discussed in detail.

The cystic fibrosis mutation (delta F508) does not influence the chloride channel activity of CFTR

The cystic fibrosis transmembrane conductance regulator (CFTR) is a phosphorylation-regulated Cl- channel. In most mammalian cells, the functional consequences of the most common CF mutation, delta F508-CFTR, cannot be assessed as the mutant protein undergoes biosynthetic arrest. However, function can be studied in the baculovirus-insect cell expression system where delta F508-CFTR does not appear to undergo such arrest. Our results show that phosphorylation-regulated Cl- channel activity of delta F508-CFTR is similar to that of wild-type CFTR. This observation was confirmed in comparative studies of purified delta F508-CFTR and CFTR reconstituted in planar lipid bilayers. Therefore, we suggest that this common mutation does not result in a significant alteration in CFTR function.

Chelated chromium for stressed feeder calves

Using crossbred calves obtained at feeder sales in Ontario, we evaluated two different sources of organically complexed chromium (Cr) for supplementing corn silage. A preliminary trial was conducted with 12 unstressed steers with or without 1 mg kg−1 chelated Cr during a 56-d growing period. Chelated Cr markedly decreased (P < 0.05) serum cortisol and glucose levels. In the main trial, 72 calves, weighing 233 kg, were randomly allotted to four treatments: control, high-Cr yeast, chelated Cr, and chelated Cr plus chelated Zn, Cu and Mn for the initial 7 d. Morbidity was determined by visual detection followed by rectal temperature checks. One third of morbidity occurred by day 12; two thirds, by day 16. High-Cr yeast tended to reduce morbidity; however, chelated Cr was more effective, resulting in 16.5% morbidity, or less (P < 0.05) than one third of the control. Daily gain was 41% higher (P < 0.05) with chelated Cr during the first 21 d after arrival, mainly due to the marked reduction in number of sick calves. During days 21–35, compensatory gain occurred with the morbid or antibiotic-treated calves. These data indicate that early (relative to peak morbidity) supplementation of stressed feeder calves with chelated Cr markedly reduces morbidity. Key words: Chromium, stress, calves, morbidity, cortisol, steers

Carcass characteristics and tissue-mineral contents of steers fed supplemental chromium

This study investigated the effects of supplemental chromium (Cr) (0 or 0.2 mg kg−1 from high-Cr yeast) on performance, carcass characteristics and tissue-mineral contents of growing–finishing steers fed corn silage supplemented with either urea–corn or soybean meal during the growing period and a high-grain diet during the finishing period. Ninety-six Charolais-crossed steers, divided into four treatment groups with 24 animals each, were fed for a 70-d growing period followed by a 68-d finishing period. After continuous supplemental Cr, steers were commercially slaughtered and their carcass characteristics were evaluated. Tissue samples, including loin-eye lean and rib fat, liver and kidney, were analyzed for Cr and other minerals (P, Ca, Mg, Fe, Zn and Cu). Supplemental Cr had no effects (P > 0.05) on average daily gain (ADG), dry-matter intake, (DMI), feed efficiency (ADG/DMI), and carcass characteristics, including dressing percentage, loin-eye area, backfat thickness, marbling score, kidney fat and liver weight. Proportion of lean, fat and bone in rib sections was not affected (P > 0.05) by Cr supplementation. Supplemental Cr also did not affect (P > 0.05) total-tissue Cr and other mineral concentrations. However, supplemental Cr increased (P < 0.05) the Cu level of livers in steers fed urea–corn supplements during the growing period. This study showed that continuous supplementation of Cr (0.2 mg kg−1) to unstressed growing-finishing steers had no effect on carcass composition and several minerals in various tissues. Key words: Chromium, steer, carcass, tissue

Supplemental chromium for stressed and growing feeder calves

The effects of supplemental chromium (Cr) from high-Cr yeast were investigated with steer calves fed corn silage diets. One hundred eight Charolais-crossed calves, weighing 245 kg after marketing and transport, were allotted to one of four treatments during the initial 28-d stress period: control, .4 ppm of Cr in the diet, long-acting injectable oxytetracycline (LAOTC), and Cr + LAOTC. Those fed Cr received 4 mg of Cr/d for the first 3 d sprinkled onto a small amount of hay over the silage. Chromium without LAOTC increased (P less than .05) ADG by 30% (.61 vs .79 kg/d) and ADG/DMI by 27% (.123 vs .156). Oxytetracycline alone increased (P less than .05) ADG by 30% and DMI by 15%. Chromium had no effect on morbidity. However, LAOTC tended (P less than .14) to reduce morbidity (26.0 vs 14.0%) after its administration. After d 28, steers were processed. Two weeks later, they were rerandomized within Cr groups to urea-corn vs soybean meal supplementation of corn silage during a 70-d growing period. Level of Cr was reduced to .2 ppm. Jugular blood was collected from eight steers on each treatment on two occasions. Chromium had no effect on ADG or ADG/DMI. However, Cr decreased (P less than .05) serum cortisol (75.0 vs 55.6 nmol/L). Furthermore, Cr increased (P less than .05) serum immunoglobulin M and total immunoglobulins in calves fed diets with soybean meal but had no effect in calves with urea-corn supplementation.(ABSTRACT TRUNCATED AT 250 WORDS)