Solution structure of a mini IGF-1

Mini insulin-like growth factor 1, an inactive insulin-like growth factor 1 mutant lacking the C region, was studied by 2D NMR spectroscopy. Resonances were assigned for almost all protons of the 57 amino acid residues. The 3D structure of the protein was determined by distance geometry methods. Three helical segments; Ala 8-Cys 18, Gly 42-Phe 49, and Leu 54-Cys 61, were identified, corresponding to those present in wild-type insulin-like growth factor 1 and in single-chain insulin. Their relative orientation, however, was found to be changed. This change is connected with a displacement of the Phe 23-Tyr 24-Phe 25-Asn 26 beta-strand-like segment, i.e., of aromatic side chains known to be important for receptor binding. Thus, deletion of the C region of IGF-1 results in a substantial tertiary structural rearrangement that accounts for the loss of receptor affinity.

Engineering the C-region of human insulin-like growth factor-1: implications for receptor binding

Recombinant wild-type human IGF-1 and a C-region mutant in which residues 28-37 have been replaced by a 4-glycine bridge (4-Gly IGF-1) were secreted and purified from yeast. An IGF-1 analogue in which residues 29-41 of the C-region have been deleted (mini IGF-1) was created by site-directed mutagenesis and also expressed. All three proteins adopted the insulin-fold as determined by circular dichroism. The significantly raised expression levels of mini IGF-1 allowed the recording of two-dimensional NMR spectra. The affinity of 4-Gly IGF-1 for the IGF-1 receptor was approximately 100-fold lower than that of wild-type IGF-1 and the affinity for the insulin receptor was approximately 10-fold lower. Mini IGF-1 showed no affinity for either receptor. Not only does the C-region of IGF-1 contribute directly to the free energy of binding to the IGF-1 receptor, but also the absence of flexibility in this region eliminates binding altogether. As postulated for the binding of insulin to its own receptor, it is proposed that binding of IGF-1 to the IGF-1 receptor also involves a conformational change in which the C-terminal B-region residues detach from the body of the molecule to expose the underlying A-region residues.

The protective effect of MK-801 on infarct development over a period of 24 h as assessed by diffusion-weighted magnetic resonance imaging

Diffusion-weighted MRI has been used to investigate therapeutic intervention with MK-801 in an animal model of permanent focal cerebral ischaemia. The animals were imaged continuously for 4 h and again at 24 h following occlusion of the middle cerebral artery (MCA) allowing the development of the ischaemic lesion to be monitored continuously in the same animals. An increased DWI signal, seen as a region of hyperintensity, was detected 1 h after MCA-occlusion in the lateral cortex and caudate nucleus in both control and MK-801 (administered at a dose of 3 mg/kg i.p. 5 min post-ischaemia) treated animals. However, the volume of hemispheric and cortical hyperintensity was smaller in the MK-801-treated animals. The area of hyperintensity progressively increased in the control group over the 4 h imaging time and there was also an increase in the area of hyperintensity between 4 and 24 h. At these time points the area of hyperintensity encompassed the dorsolateral cortex and caudate nucleus. MK-801 treated animals also demonstrated some progressive increase in the area of hyperintensity between 1 and 3 h, but no significant increase in the area of hyperintensity was seen after this time. The hyperintense regions at 4 and 24 h were restricted to the so-called 'core areas' of the lesion in MK-801-treated animals. Thus, using DWI the tissue 'at risk' following ischaemia could be identified and the protective effect of therapeutic intervention demonstrated.

Ultrastructural morphological changes are not characteristic of apoptotic cell death following focal cerebral ischaemia in the rat

We have used a permanent middle cerebral artery occlusion (MCAO) model in the rat to ascertain if the DNA fragmentation seen in nuclei, shows the characteristic ultrastructural features of apoptosis. Results from light and electron microscopic studies were compared with those from a neonatal model of excitotoxic cell death in which classical apoptotic changes were seen in a subpopulation of cells. At 6 and 24 h following occlusion, cells were either swollen or dark and shrunken showing a disordered cytosol. At 24 h survival a high number of cells in the lesion core and lesion border showed internucleosomal DNA breaks, which were detected in sections using terminal dUTP nick-end-labelling (TUNEL). Electron microscopy of cells with TUNEL positive spherical structures of condensed chromatin in the lesion core showed an advanced stage of cellular disintegration as opposed to an apoptotic morphology of a subpopulation of cells with chromatin condensation in the cortex and mammillary body of N-methyl-D-aspartate (NMDA) treated neonatal rats. We conclude that in focal cerebral ischaemia internucleosomal DNA fragmentation associated with chromatin condensation is a late consequence of ischaemic cell death rather than a hallmark of apoptosis.

Biosensor measurement of the binding of insulin-like growth factors I and II and their analogues to the insulin-like growth factor-binding protein-3

Most insulin-like growth factor (IGF) molecules in the circulation are found in a 150-kDa complex containing IGF-binding protein-3 (IGFBP-3) and an acid-labile subunit, which does not itself bind IGF. Affinities (Kd values) between 0.03 and 0.5 nM have been reported for IGF-I/IGFBP-3 binding, but no kinetic data are available. In this study we measured the high affinity binding of unlabeled IGFs and IGF analogues to recombinant unglycosylated IGFBP-3, using a BIAcoretrade mark instrument (Pharmacia Biosensor AB). IGF-I binding showed fast association and slow non-first-order dissociation kinetics, and an equilibrium Kd of 0.23 nM. IGF-II had similar kinetics with slightly higher affinity. Analogues with mutations in the first 3 amino acids of the B-region (des(1-3) IGF-I and long IGF-I) showed 25 and 50 times lower affinity than IGF-I. Replacement of residues 28-37 by Gly-Gly-Gly-Gly or deletion of residues 29-41 in the C-region had little effect on the kinetic parameters, contrasting with the markedly impaired binding of these analogues to the IGF-I receptor. Swapping of the disulfide bridges in IGF-I and the C-region mutants decreased the affinity dramatically for IGFBP-3, primarily by decreasing the association rate. Insulin had approximately 1000 times lower affinity than IGF-I.

Production of extracellular proteases and amylases by some acidophilic and alkalophilic bacteria

Twelve bacteria were isolated from two effluent sources of Shaw-Wallace Gelatins, Jabalpur. Six bacteria from dicalcium phosphate plant effluent (pH-5) and six from main drain of the factory (pH-10) were isolated. Two facultatively acidophilic and two facultatively alkalophilic bacteria were selected and tentatively identified as Plesiomonas shigelloides, Aeromonas hydrophilla, Klebsiella pneumoniae and Staphylococcus saprophyticus respectively. Acidic amylases were produced in higher amounts on 4th day of incubation by Plesiomonas shigelloides and on 6th day by Aeromonas hydrophilla. Alkaline amylases were produced in higher amounts on 4th day of incubation by Klebsiella pneumoniae and on 8th day by Staphylococcus saprophyticus in vitro.

Coronary flow reserve and oesophageal dysfunction in syndrome X

The relative prevalence of abnormalities of coronary flow reserve and oesophageal function was ascertained in 32 syndrome X patients with typical angina chest pain, a positive exercise test, and normal coronary arteries. Coronary flow reserve in response to a hyperaemic dose of papaverine was measured using an intracoronary Doppler catheter positioned in the left anterior descending coronary artery. An abnormal coronary flow reserve was defined as being < 3.0. Patients were investigated for oesophageal dysfunction by manometry and 24-hour pH monitoring. Thirteen patients had an impaired coronary flow reserve (group 1) and 19 patients had a normal flow reserve (group 2). Eight of the 13 group 1 patients (62%) and 13 of the 19 group 2 patients (68%, p = NS) had evidence of oesophageal dysfunction on either manometry or pH studies. Therefore, a total of 26 (81%) syndrome X patients had either an abnormality of coronary flow reserve or oesophageal dysfunction suggesting that chest pain in these patients may be due to myocardial ischaemia or oesophageal dysfunction, thus confirming the heterogeneous nature of this syndrome. The prevalence of oesophageal abnormalities was independent of any abnormalities of coronary flow reserve.

Neuropsychologic dysfunction after cardiac surgery: what is the problem?

Twenty years ago Aberg published his seminal studies on the neuropsychologic consequences of cardiopulmonary bypass (CPB). Twenty years later, what is the state of current research on the problem of post-CPB neurologic injury, and what different management techniques have been employed to influence this outcome? This article reviews the definition and assessment of postoperative neuropsychologic dysfunction; epidemiologic data and associated risk factors assessing post-CPB neuropsychologic dysfunction are critically appraised.

Novel solid-phase extraction strategy for the isolation of basic drugs from whole blood. Preliminary study using commercially available extraction cartridges

A novel strategy for the solid-phase extraction of basic drugs has been developed using commercial extraction cartridges. The procedure involves the sequential application of very different isolation mechanisms, viz. hydrophobic extraction on non-porous carbon followed by ionic extraction on a strong cation exchanger. This approach to extraction achieves both high recoveries and clean extracts when analysed by GC-MS. The potential for automation has been demonstrated using commercial sample preparation equipment.

Sepsis reduces isoflurane MAC in a normotensive animal model of sepsis

Patients with sepsis often require anaesthesia for surgical procedures. Anaesthesia can be unpredictable and the most haemodynamically stable agents are used. No data are available for the minimum alveolar concentration (MAC) requirements in such patients or in animal models of sepsis. We have characterized the effect of sepsis on the MAC of isoflurane in a normotensive rodent model of sepsis. The minimum inhibitory concentration (MIC) of isoflurane to an identical stimulus was determined for rodents subjected to caecal ligation and perforation (CLP n = 8), or sham laparotomy (n = 7). The calculated MAC of isoflurane was reduced in the septic animals compared with the sham animals (MAC of isoflurane, CLP = 0.8%, sham = 1.4% P < 0.003). No statistical differences were found in the haemodynamic variables measured in either group. Isoflurane leads to haemodynamic stability during anaesthesia in this animal model of sepsis. However, the MAC requirement for isoflurane is reduced by sepsis.

The neuroprotective effect of the glycine site antagonist 3R-(+)-cis-4-methyl-HA966 (L-687,414) in a rat model of focal ischaemia

3R-(+)-cis-4-Methyl-HA966 (L-687,414) is a novel and selective, low intrinsic activity, partial agonist at the glycine site of the N-methyl-D-aspartate (NMDA) receptor. Thus, while it acts primarily to block NMDA receptor function in the presence of glycine, it fails to produce a complete block of NMDA receptor activation. In this study, we have investigated its neuroprotective effects in a rat model of focal ischaemia, involving permanent occlusion of the left middle cerebral artery. L-687,414 was administered as a bolus dose of 17.6 mg/kg i.v. straight after the occlusion or as a bolus dose + infusion for 4 h. The doses of L-687,414 used for the infusion studies were 7 mg/kg i.v. + 7 mg/kg/h, 14 mg/kg + 14 mg/kg/h, or 30 mg/kg + 30 mg/kg/h. The 17.6-mg/kg dose gave an estimated peak plasma level of 24 micrograms/ml, which decayed with a t1/2 of 56 min. The three infusion dosing regimens gave mean plasma levels over the 4 h of 11, 25 and 61 micrograms/ml plasma, respectively. The 17.6-mg/kg dose of L-687,414 gave no significant protection against the volume of hemispheric, cortical, or caudate damage when compared with the control group of animals. The lowest infusion dosing regimen of L-687,414 which gave a plasma level of 11 micrograms/ml over the 4 h was also ineffective against the volume of infarction measured in the different brain regions.(ABSTRACT TRUNCATED AT 250 WORDS)

Erod measurement using post mitochondrial supernatant (pms) in roach (Rutilus rutilus L.), a possible biomonitor for PAH contamination in the freshwater environment

The use of hepatic post-mitochondrial supernatant (pms) as a source of monooxygenase activity in roach following intra peritoneal injection of beta-naphthoflavone was investigated. Pms was found to be three times less active than microsomes although the level of induction was similar (9 fold). No effect of dicumarol on Ethoxyresorufin O-deethylase (EROD) measurement using pms was recorded. EROD induction in roach peaked 2-4 days post treatment with beta-naphthoflavone. Given the ubiquitous nature and pollution tolerance of roach, their hepatic pms may serve as a convenient biomonitor of PAH contamination in the freshwater environment. Field studies are now underway to investigate this further.

A comparison of the early development of ischaemic damage following permanent middle cerebral artery occlusion in rats as assessed using magnetic resonance imaging and histology

Recent developments in diffusion-weighted imaging (DWI) have enabled the pathological changes that occur during cerebral ischaemia to be studied. The present studies utilised DWI to investigate the development of early ischaemic changes following permanent middle cerebral artery (MCA) occlusion in the rat, which represents a model of stroke. An increased DWI signal was seen in the region of the occluded MCA and this was detectable as early as 1 h postocclusion. DWI images were obtained at nine stereotactic levels throughout the brain, providing a quantifiable measure of the volume of increased signal intensity in each animal. At 1 h post-MCA occlusion the hyperintense areas were seen in the frontoparietal cortex and lateral caudate nucleus; these areas represent the core of the infarct and no protection is seen with any compounds in these areas. There was a progressive increase in the area of hyperintensity up to 4 h post-MCA occlusion, and at this time point the hyper-intensity was seen in the dorsolateral cortex and caudate nucleus. At 4 h post-MCA occlusion there was a significant correlation between the volume of hemispheric and cortical ischaemic damage measured using DWI and histology. Thus, it appears that the increased DWI signal seen during the early time points after MCA occlusion was demarcating tissue that was destined for infarction. The area beyond the hyperintense region at 1 h represents the so-called "penumbral" region, because with increasing time (post-MCA occlusion) this area became incorporated into the infarct. There was also a slight increase in infarct size between 4 and 24 h, when assessed using DWI or histology, although two groups of animals were being compared, as opposed to the time-course study, in which just one group of animals was used. At 24 h post-MCA occlusion there was a good correlation between DWI, histology, and conventional T2 weighted imaging. There was no further increase in size of the infarct between 24 h and 7 days as assessed using histology and T2-weighted imaging. DWI could not be used to quantify infarct volume at 7 days because there was no uniform signal in the damaged area. At 7 days the area of infarction actually appeared to be darker in the diffusion-weighted images. The hyperintensity seen in diffusion-weighted images appears to decrease some time between 24 h and 7 days.(ABSTRACT TRUNCATED AT 400 WORDS)

The neuroprotective effects of the decahydroisoquinoline, LY 215490; a novel AMPA antagonist in focal ischaemia

LY 215490 (3RS,4aRS,6RS,8aRS)-6-[2-(1(2)H-tetrazole-5- yl)ethyl]decahydroisoquinoline-3-carboxylic acid), a novel, selective, competitive and systemically active AMPA receptor antagonist was tested as a neuroprotective agent against focal ischaemia in a model of permanent MCA occlusion in the rat. LY 215490 was administered at a dose of 10, 30 or 100 mg/kg 30 min prior to and post-MCA occlusion. The animals were allowed to survive for 24 hr, following which time the brains were processed for volumetric analysis of the infarct size. The low dose of LY 215490 was not effective against the infarct volume in the hemisphere, cortex or caudate. The 2 x 30 mg/kg dose of LY 215490 resulted in 25 and 31% protection against the volume of hemispheric and cortical ischaemic damage, respectively. The highest dose of LY 215490 resulted in a reduced neuroprotective effect with 23 and 27% protection against the volume of hemispheric and cortical ischaemic damage, respectively. The slightly reduced neuroprotective effect of the highest dosing regimen may be due to the respiratory problems seen with this dose. Neither of the two neuroprotective doses of LY 215490 produced any reduction in the volume of caudate damage which represents the core of the infarct.

Multiplane transesophageal echocardiography: our initial experience

We present our experience in the diagnostic assessment of a wide spectrum of cardiovascular disorders using multiplane transesophageal echocardiography (MP-TEE). Two hundred and seventeen patients in the age range of 11-71 years were subjected to MP-TEE from January to November 1993. The male:female ratio was 1.1:1. One hundred and ten patients had predominantly mitral valve disease of rheumatic origin, eleven had mitral valve prolapse, twenty patients had aortic valve disease and thirty seven patients had more than one valve involvement. Six patients with suspected prosthetic heart valve dysfunction and ten patients of hypertrophic cardiomyopathy were also studied. Two patients had unexplained pulmonary hypertension, three had pericardial disease and three had proximal aortic dissections. Twenty six patients with congenital heart disease were studied of which nineteen had atrial septal defects, one had corrected transposition of great vessels with pulmonic stenosis and one adult had Ebstein's anomaly of the tricuspid valve. In our experience, MP-TEE enhances the versatility of TEE by providing incremental diagnostic information and enhancing delineation of pathology. The procedure was well-tolerated and no complications occurred.

Activation of natural killer cells by mouse mammary tumor virus C4 in BALB/c and T-cell receptor V beta 2-transgenic mice

Lymphocytic infiltrates of BALB/c C4 hyperplastic alveolar nodule (HAN) have elevated natural killer (NK) activity, which correlates positively with the progression of C4 HAN to tumor: C4 HAN produces an infectious mouse mammary tumor virus, MMTV(C4), which encodes a superantigen that activates and deletes T-cells with the V beta 2 segment in the T-cell receptor. In this report, NK activation by both MMTV(C4) and MMTV(C4) superantigen was tested. NK activity was measured in naive BALB/c mice, BALB/c mice depleted of V beta 2+ T-cell, or V beta 2-transgenic mice after they received injections of either purified MMTV(C4) or MMTV(C4)-infected splenocytes. Elevated NK activity was observed in BALB/c mice receiving MMTV(C4) or MMTV(C4)-infected splenocytes. Depletion of V beta 2+, but not V beta 8+, T-cells by specific anti-V beta hybridoma before injection of MMTV(C4)-infected cells reduced but did not eliminate NK activation. NK activation in V beta 2-transgenic mice occurred before massive CD4 T-cell deletion took place and was more pronounced than that in the nontransgenic littermates. These results indicate that MMTV activates NK cells through superantigen-dependent and -independent pathways and supports the role of MMTV(C4) in the augmented NK activity observed in C4 HAN infiltrates. The progression of C4 HAN to tumor represents a model system for the analysis of how tumorigenesis may be affected by lesion-associated viruses.

Cloning and expression of a rat neuronal nitric oxide synthase coding sequence in a baculovirus/insect cell system

A DNA sequence encoding rat neuronal NO synthase (nNOS) was isolated and cloned into the baculovirus expression vector pVL1393 to generate pVLRBNOS. Transfection of Spodoptera frugiperda Sf-21 cells with the construct pVLRBNOS resulted in the synthesis of high levels of neuronal NO synthase. Analysis of the expression pattern revealed soluble, enzymatically active NO synthase in the cytoplasm of cell extracts. Active enzyme could also be purified from culture supernatants using 2'-5' ADP sepharose affinity chromatography. This enzyme was recognised by antibodies to the native nNOS and showed a similar degree of inhibition by arginine analogs as the native nNOS. The majority of the NOS synthesised had accumulated as insoluble "inclusion-body" material. The purification of recombinant nNOS from insect cells should facilitate characterisation of neuronal NO synthase.

Somatic embryogenesis in Nicotiana tabacum L.: induction by thidiazuron of direct embryo differentiation from cultured leaf discs

Induction of somatic embryogenesis by different growth regulators was examined in leaf disc cultures of Nicotiana tabacum L. Direct differentiation of somatic embryos occurred on media supplemented with naphthaleneacetic acid (NAA) and N(6)-benzylaminopurine (BAP). Thidiazuron (N-phenyl-N'-1, 2,3,-thiadiazol-5-ylurea; TDZ) not only substituted for the most effective NAA-BAP combination but also induced a higher frequency of somatic embryogenesis. Regenerated somatic embryos were capable of developing into plants.

Morphoregulatory role of thidiazuron : substitution of auxin and cytokinin requirement for the induction of somatic embryogenesis in geranium hypocotyl cultures

Somatic embryogenesis was induced in hypocotyl explants of geranium (Pelargonium x hortorum) cultured on media supplemented with various concentrations of N-phenyl-N'-1,2,3-thiadiazol-5-ylurea (thidiazuron). In less than 2 weeks, somatic embryos were observed in treatments containing levels of thidiazuron (TDZ) ranging from 0.2 to 1.0 micromolar. The use of N(6)-benzylaminopurine in combination with indole-3-acetic acid also evoked embryogenesis, but the efficiency of somatic embryo production was significantly lower than that obtained with TDZ. Hypocotyl culture for only 2 days on TDZ-supplemented medium before transfer to a basal medium was sufficient for inducing somatic embryogenesis. This distinction between the induction and expression of embryogenesis may provide an experimental system for studying the developmental biology of somatic embryogenesis. Substitution of the auxin-cytokinin requirement for the induction of somatic embryogenesis by TDZ suggests the possibility of a novel mode of its action by modulation of endogenous growth regulators.

Direct somatic embryogenesis and regeneration of plants from seedling explants of peanut (Arachis hypogaea): promotive role of thidiazuron

An efficient procedure has been developed for inducing direct somatic embryogenesis, organogenesis, and regeneration of plants from tissue cultures of peanut (Arachis hypogaea L.). Thin transverse sections of the cotyledons and juvenile leaves were cultured on Murashige and Skoog medium supplemented with N6-benzylaminopurine (BAP) or a substituted phenylurea, thidiazuron (TDZ). Somatic embryos or shoot buds differentiated from cut surfaces of the cotyledons and midrib region of the leaves. The application of BAP induced differentiation of shoot buds whereas the treatment with TDZ resulted in the production of somatic embryos. Somatic embryos developed into plants after subculturing on a basal meduim. Agar-solidified medium was found to be superior to the liquid medium for the development of embryos and shoot buds. The procedure of TDZ-induced somatic embryogenesis and plant regeneration was successfully applied to three genotypes of peanut. A distinct feature of this study is the induction of the morphogenic competence in cultures of seedling expiants of peanut that so far have remained recalcitrant to somatic embryogenesis in vitro. Key words: peanut, Arachis hypogaea, shoot regeneration, somatic embryogenesis, thidiazuron, plant regeneration.

Induction by thidiazuron of somatic embryogenesis in intact seedlings of peanut

In planta differentiation of somatic embryos was induced in seedlings of peanut (Arachis hypogaea L.) obtained from mature seeds germinated on a medium supplemented with thidiazuron (TDZ: N-phenyl-N(1)- (1,2,3 thiadiazol-yl)urea). At optimum levels of TDZ (10 μM), all germinating seeds produced embryogenic seedlings, and somatic embryos developed in the apical region and on the surface of cotyledons and hypocotyls. These somatic embryos matured, germinated, and formed shoots which eventually developed into whole plants. Thidiazuron-induced direct embryogenesis from morphologically intact seedlings may provide an excellent experimental system for investigating somatic embryogenesis and the morphoregulatory role of TDZ.