Alterations in the proportions of skeletal muscle proteins following a unilateral lesion to the substantia nigra pars compacta of rats.

It is well established that mammalian skeletal muscles exhibit a considerable degree of plasticity and one of the main determining factors of this plasticity is the activity pattern and duration of motoneurone discharge. Lesions to the right substantia nigra pars compacta (SNpc) of six adult rats were made to determine whether altered output from the SNpc ultimately leads to a change in the expression of proteins in contralateral skeletal muscles. After 4 months, altered motor performance was identified by the administration of amphetamine. After 7 months, 30-70% of dopaminergic cells in the SNpc had been destroyed. The protein content of muscles was then quantified from densitometric scans of gels, and expressed as a % of the amount of actin (the protein used as a reference in this study). The lesion affected the expression of different protein isoforms in the fast- and slow-twitch muscles. In slow-twitch soleus muscles, the lesion decreased the proportion of alpha-tropomyosin and increased the proportion of beta-tropomyosin. In the fast-twitch extensor digitorum longus muscles, the lesion increased the proportion of the fast isoform of troponin-T1f, and decreased the proportions of the two isoforms of myosin light chain. This study establishes a connection between the chronic effects of a lesion to the SNpc, with a loss of dopaminergic neurones, impaired motor performance, and altered expression of proteins in skeletal muscle. The implication of these results is that the altered motor function observed in Parkinson's disease may be associated with alterations to the expression of skeletal muscle proteins.

Shakeup excitation during optical tunnel ionization.

Shakeup of a two-electron system is investigated in the strong infrared laser field limit, both theoretically and experimentally. During tunnel ionization the electron shakes up a second electron to an excited bound state. Theoretically, a complete analytical theory of shakeup in intense laser fields is developed. We predict that shakeup produces one excited sigma(u) D(+)(2) state in approximately 10(5) ionization events. Shakeup is measured experimentally by using the molecular clock provided by the internuclear motion. The number of measured events is found to be in excellent agreement with theory.

The effects of hypothyroidism on nerve growth factor and norepinephrine concentrations in weight-bearing and non-weight-bearing bones of rats.

Thyroid hormones affect bone remodelling directly via receptors in osteoblasts. Previously, however, we have shown that the euthyroid and hyperthyroid states significantly influence the concentrations of both nerve growth factor (NGF) and norepinephrine (NE) in particular bones. Both NGF and NE directly affect bone metabolism and therefore it is possible that thyroid hormone action on bone may also be indirect via its actions on these two neural-related substances. In light of previous studies, the current experiments aimed to investigate whether hypothyroidism also influenced NGF and NE concentrations in weight-bearing and non-weight-bearing rat bones. Hypothyroidism was induced by oral ingestion of propylthiouricil (PTU; 3.8+/-0.2 mg/kg/day) for 21 days. Histological examination on distal femurs and microparticle enzyme immunoassayed plasma concentrations of T3 and T4 verified the hypothyroid status in treated rats. NGF concentrations were assayed via enzyme-linked immunosorbent assay (ELISA) and NE concentrations were measured via high performance liquid chromatography (HPLC) with electrochemical detection (ECD). NGF concentrations: Femoral NGF concentrations were 207% higher in hypothyroid rats (674.9+/-88.3 ng/g) than in euthyroid rats (326.7+/-63.6 ng/g; p < 0.05). Rib NGF concentrations in hypothyroid rats (3125.1+/-450.2 ng/g) were increased by 342% compared to euthyroid ribs (914.5+/-128.6 ng/g; p < 0.01). Rib NGF concentrations in hypothyroid rats were 463% higher than in femurs of hypothyroid rats (p < 0.001). NE concentrations: In hypothyroid rats, NE concentrations were reduced by approximately 50% in both ribs (38.9 ng/g) and calvaria (41.5 ng/g) compared to euthyroid rats (74.7 ng/g and 87.4 ng/g respectively; p < 0.05 for both). These findings on hypothyroid rats may be taken in conjunction with our companion work on hyperthyroid rats (Yao et al., 2002, JMNI 2:327-334) and put in context with other reports, to indicate that (i) there are several sources of NGF in bone, some of which are stimulated by hypothyroidism and others by hyperthyroidism and (ii) the concentrations of both NGF and NE in bone are sensitive to weight-bearing and thyroid hormone status.

One year comparison of costs of coronary surgery versus percutaneous coronary intervention in the stent or surgery trial.

OBJECTIVES: To compare initial and one year costs of coronary artery bypass grafting (CABG) versus percutaneous coronary intervention (PCI) in the stent or surgery trial. DESIGN: Prospective, unblinded, randomised trial. SETTING: Multicentre study. PATIENTS: 988 patients with multivessel disease. INTERVENTIONS: CABG and stent assisted PCI. MAIN OUTCOME MEASURES: Initial hospitalisation and one year follow up costs. RESULTS: At one year mortality was 2.5% in the PCI arm and 0.8% in the CABG arm (p = 0.05). There was no difference in the composite of death or Q wave myocardial infarction (6.9% for PCI v 8.1% for CABG, p = 0.49). There were more repeat revascularisations with PCI (17.2% v 4.2% for CABG). There was no significant difference in utility between arms at six months or at one year. Quality adjusted life years were similar 0.6938 for PCI v 0.6954 for PCI, Delta = 0.00154, 95% confidence interval (CI) -0.0242 to 0.0273). Initial length of stay was longer with CABG (12.2 v 5.4 days with PCI, p < 0.0001) and initial hospitalisation costs were higher (7321 pounds sterling v 3884 pounds sterling for PCI, Delta = 3437 pounds sterling, 95% CI 3040 pounds sterling to 3848 pounds sterling). At one year the cost difference narrowed but costs remained higher for CABG (8905 pounds sterling v 6296 pounds sterling for PCI, Delta = 2609 pounds sterling, 95% CI 1769 pounds sterling to 3314 pounds sterling). CONCLUSIONS: Over one year, CABG was more expensive and offered greater survival than PCI but little added benefit in terms of quality adjusted life years. The additional cost of CABG can be justified only if it offers continuing benefit at no further increase in cost relative to PCI over several years.

Effects of glycine and proline on the calcium activation properties of skinned muscle fibre segments from crayfish and rat.

The effects of the polar amino acid glycine (20 mmol l(-1)) and the non-polar amino acid proline (20 mmol l(-1)) on Ca(2+)-activated contraction have been examined in four types of striated muscle fibres. Single fibres dissected from the claw muscle of a crustacean (long- and short-sarcomere) and the hindlimb muscles of the rat (slow-twitch from soleus and fast-twitch from extensor digitorum longus) were activated in matched solutions that either contained the amino acid ('test') or not ('control'). The steady-state force produced in these solutions was used to determine the relation between force production and pCa (-log10[Ca2+]). The results show that in the concentrations used, glycine and proline had only small effects on the maximum Ca(2+)-activated force, pCa corresponding to 10, 50 and 90% maximum force (pCa10, pCa50, pCa90, respectively) or on the slope of the force-pCa curves in the four different fibre types. The relative lack of effects of glycine and proline on contractile activation would confer a distinct physiological advantage to force production of muscle of Cherax, where the concentrations of glycine and proline vary considerably. Finally, the results show that glycine and proline may be useful to balance control solutions when the effects of other amino acids or zwitterions on contractile activation are examined.

Time-resolved double ionization with few cycle laser pulses.

Ionization of D2 launches a vibrational wave packet on the ground state of D+2. Removal of the second electron places a pair of D+ ions onto a Coulombic potential. Measuring the D+ kinetic energy determines the time delay between the first and the second ionization. Caught between a falling ionization and a rapidly rising intensity, the typical lifetime of the D+2 intermediate is less than 5 fs when an intense 8.6 fs laser pulse is used. We simulate Coulomb explosion imaging of the ground state wave function of D2 by a 4 fs optical pulse and compare with our experimental observations.

Alignment-dependent strong field ionization of molecules.

We demonstrate a method to measure strong field laser ionization of aligned molecules. The method employs a macroscopic field-free dynamic alignment, which occurs during revivals of rotational wave packets produced by a femtosecond laser pulse. We investigate the dependence of strong field ionization of N2 on molecular orientation. We determine that N2 molecules are four times more likely to ionize when aligned parallel to the field than when aligned perpendicular to it.

Free amino acids in claw muscle and haemolymph from Australian freshwater crayfish at different stages of the moult cycle.

Amino acids were measured in claw muscle and haemolymph in the freshwater decapod crustacean, Cherax destructor, at different stages of the moult cycle. The total pool of amino acids in muscles from animals in intermoult (97+/-13 mmol kg(-1) muscle), premoult (80+/-20 mmol kg(-1)) and postmoult (97+/-19 mmol kg(-1)) were not significantly different. Despite the relatively stable total pool of amino acids, there were changes in the concentrations of alanine, glutamine and proline over the moult cycle. Compared to intermoult, claw muscles from animals in premoult had a lower concentration of proline, and animals in postmoult had higher concentrations of alanine and glutamine, but lower concentrations of proline. Concentrations of alanine and glutamine in claw muscle of animals in postmoult were higher and proline concentrations lower than in the same animals during the premoult stage. The concentration of proline in haemolymph was lower in animals in premoult and postmoult compared to intermoult. The total amino acid pool in the claw muscle of Cherax destructor did not change significantly over the moult which is distinctly different to the changes in amino acids reported in the claw muscles of marine decapod crustaceans.

Nerve growth factor and norepinephrine concentrations in weight-bearing and non-weight-bearing bones of euthyroid and hyperthyroid rats.

UNLABELLED: Thyroid hormone, nerve growth factor (NGF) and norepinephrine (NE) and weight-bearing affect bone metabolism, yet interactions between these factors and osseous tissue have not been investigated. Therefore, the aims of the study were to measure NGF and NE concentrations in weight-bearing and non-weight-bearing bones from euthyroid (control) and hyperthyroid (HT) rats. Hyperthyroidism was induced by oral intake of triiodothyronine (90 mg/kg/day) for 21 days. Histomorphometry on distal femurs verified significant trabecular bone loss in HT rats compared to euthyroid animals. NGF concentrations were assayed via ELISA, whilst NE concentrations were measured via HPLC and ECD. In euthyroid rats: (i) the concentration of NGF in ribs (914 ng/g) was almost 3-fold greater than in femurs (326 ng/g wet weight of tissue) (ii) the concentrations of NE in ribs (74.7 ng/g) and calvaria (87.4 ng/g) were 2.5-3.5-fold greater than either femurs (24.0 ng/g) or tibiae (30.5 ng/g) and (iii) NE concentrations were comparable between ribs (74.7 ng/g) and calvaria (87.4 ng/g) and similar between tibiae (30.5 ng/g) and femurs (24.0 ng/g). In HT rats: (i) the concentration of NGF in ribs (1802 ng/g) was 4-fold greater than in femurs (402 ng/g) (ii) NE concentrations in ribs (23.3 ng/g) and calvaria (13.6 ng/g) were 4.5-fold and 2.6-fold greater respectively than in tibiae (5.2 ng/g), while ribs had almost a 2-fold higher concentration of NE than calvaria. In HT rats compared to euthyroid animals: (i) NGF concentrations almost doubled in ribs but there was little change in the NGF concentration in femurs (ii) there was a reduction in NE concentrations in calvaria by 84%, in ribs by 69% in tibiae by 83% and 55% in femur (NS). CONCLUSIONS: (i) Non-weight-bearing is associated with higher concentrations of NGF and NE than weight-bearing in bones in euthyroid and HT rats; (ii) Hyperthyroidism exerts opposite effects on NGF and NE in bone and (iii) Hyperthyroidism interacts with weight-bearing to determine NGF and NE concentrations in bone. Therefore, the influence of thyroid hormone on NGF and NE in bone may need to be taken into account when considering the action of thyroid hormone on bone in either euthyroid or hyperthyroid states.

Structural studies of an oligodeoxynucleotide containing a trimethylene interstrand cross-link in a 5'-(CpG) motif: model of a malondialdehyde cross-link.

Malondialdehyde (MDA), a known mutagen and suspected carcinogen, is a product of lipid peroxidation and byproduct of eicosanoid biosynthesis. MDA can react with DNA to generate potentially mutagenic adducts on adenine, cytosine, and particularly guanine. In addition, repair-dependent frame shift mutations in a GCGCGC region of Salmonella typhimurium hisD3052 have been attributed to formation of interstrand cross-links (Mukai, F. H. and Goldstein, B. D. Science 1976, 191, 868--869). The cross-linked species is unstable and has never been characterized but has been postulated to be a bis-imino linkage between N(2) positions of guanines. An analogous linkage has now been investigated as a stable surrogate using the self-complementary oligodeoxynucleotide sequence 5'-d(AGGCG*CCT)(2,) in which G* represents guanines linked via a trimethylene chain between N(2) positions. The solution structure, obtained by NMR spectroscopy and molecular dynamics using a simulated annealing protocol, revealed the cross-link only minimally distorts duplex structure in the region of the cross-link. The tether is accommodated by partially unwinding the duplex at the lesion site to produce a bulge and tipping the guanine residues; the two guanines and the tether attain a nearly planar conformation. This distortion did not result in significant bending of the DNA, a result which was confirmed by gel electrophoresis studies of multimers of a 21-mer duplex containing the cross-link.

An investigation into the quality of life of individuals after laryngectomy.

BACKGROUND: Little longitudinal data are available on the general physical, psychological, and social problems experienced as a result of laryngectomy or on the preoperative status of patients in regard to these aspects. In particular, prospective longitudinal data gathered from the same group of subjects over time and examining a variety of such outcomes is rare. This descriptive study addresses these issues. METHODS: The study investigates the progress of a group of 34 laryngectomees from the preoperative stage up to 6 months after surgery. Medical complications, communication, swallowing, diet, physical, and psychosocial adjustment were measured using both the Short-Form Health Survey (SF-36) and original outcome tools. RESULTS: A large percentage of subjects demonstrated significant and persistent communication and swallowing problems throughout the period studied. Low preoperative and postoperative scores on the SF-36 demonstrate that this group had a poorer state of general health in many respects than those with serious medical conditions previously documented. CONCLUSIONS: The results suggest that communication and swallowing difficulties persist for many laryngectomees up to 6 months after surgery and still require further investigation. Poor preoperative and postoperative general health scores indicate that this group may require more long-term social support than is currently being offered to adjust to the laryngectomy.

Laryngeal preservation with supracricoid partial laryngectomy results in improved quality of life when compared with total laryngectomy.

OBJECTIVES/HYPOTHESES: Study 1: To assess the oncologic outcome following supracricoid partial laryngectomy (SCPL). Study 2: To compare the quality of life (QOL) following SCPL to total laryngectomy (TL) with tracheoesophageal puncture (TEP). Study 3: To analyze whole organ TL sections to determine the percentage of lesions amenable to SCPL STUDY DESIGN: Study 1: A retrospective review of patients who underwent SCPL. Study 2: A non-randomized, prospective study using QOL instruments to compare patients who underwent either SCPL or TL Study 3: A retrospective histopathologic study of TL specimens assessed for the possibility of performing an SCPL. METHODS: Study 1: Twenty-five patients with carcinoma of the larynx underwent SCPL between June 1992 and June 1999. Various rates of oncologic outcome were calculated. Study 2: Thirty-one patients participated in the QOL assessment. This included the SF-36 general health status measure, the University of Michigan Head and Neck Quality of Life (HNQOL) instrument, and the University of Michigan Voice-Related Quality of Life (VRQOL) instrument. Study 3: Ninety surgical specimens were obtained and studied from the total laryngectomy cases in the Tucker Collection. Multiple sites were evaluated for the presence of carcinoma A computer program was written to classify whether the patient was amenable to SCPL. RESULTS: Study 1: The overall local control rate was 96% (24/25). The local control rate following SCPL with cricohyoidoepiglottopexy (CHEP) was 95% (20/21). The local control rate following SCPL with cricohyoidopexy (CHP) was 100% (4/4). Study 2: The SCPL had significantly higher domain scores than TL and TEP in the following categories for the SF-36: physical function, physical limitations, general health, vitality, social functioning, emotional limitations, and physical health summary. The significantly higher domains for the SCPL when compared with the TL and TEP for the HNQOL were eating and pain. Finally, when voice-related QOL was assessed with the V-RQOL, the domains of physical functioning and the total score were significantly better with SCPL when compared with TL and TEP. Study 3: Forty of 90 (44%) laryngeal whole organ specimens were determined to be resectable by SCPL. In 16 (18%) specimens, the patients could have undergone SCPL with CHEP and in 24 (27%) specimens the patients could have undergone SCPL with CHP. Among the 40 (44%) specimens determined to be able to have undergone SCPL, 19 were glottic (1 T1, 15 T2, 3 T3) and 21 were supraglottic (9 T2, 12 T3). CONCLUSIONS: 1) A review of the literature and an analysis of the data in this study indicate that excellent local control may be expected following SCPL. 2) The QOL following SCPL, as measured by three validated QOL instruments, is superior to TL with TEP. 3) A histologic assessment of whole organ sections of TL specimens indicates that many patients who have been subjected to TL may have been candidates for SCPL. 4) If the indications and contraindications are rigorously adhered to, SCPLs are reasonable alternatives to TL in selected cases.

An investigation into the quality of life of individuals after laryngectomy

BACKGROUND: Little longitudinal data are available on the general physical, psychological, and social problems experienced as a result of laryngectomy or on the preoperative status of patients in regard to these aspects. In particular, prospective longitudinal data gathered from the same group of subjects over time and examining a variety of such outcomes is rare. This descriptive study addresses these issues. METHODS: The study investigates the progress of a group of 34 laryngectomees from the preoperative stage up to 6 months after surgery. Medical complications, communication, swallowing, diet, physical, and psychosocial adjustment were measured using both the Short-Form Health Survey (SF-36) and original outcome tools. RESULTS: A large percentage of subjects demonstrated significant and persistent communication and swallowing problems throughout the period studied. Low preoperative and postoperative scores on the SF-36 demonstrate that this group had a poorer state of general health in many respects than those with serious medical conditions previously documented. CONCLUSIONS: The results suggest that communication and swallowing difficulties persist for many laryngectomees up to 6 months after surgery and still require further investigation. Poor preoperative and postoperative general health scores indicate that this group may require more long-term social support than is currently being offered to adjust to the laryngectomy. Copyright 2000 John Wiley & Sons, Inc. Head Neck 23: 16-24, 2001.

Amino acids in haemolymph, single fibres and whole muscle from the claw of freshwater crayfish acclimated to different osmotic environments.

The concentrations of free amino acids were measured in whole claw muscle, single fibres and haemolymph of Australian freshwater crayfish, Cherax destructor, during the intermoult stage. The average total pool of amino acids in short-sarcomere fibres (179 mmol kg(-1)) was 60% greater than in long-sarcomere fibres, due to higher concentrations of alanine, cysteine, glutamate, leucine and proline. The two fibre types exhibited differences in the banding pattern of the isoforms of troponin using gel electrophoresis. The average pool of amino acids in haemolymph was 2.7 mmol kg(-1). Cherax has symmetrical claws and the total pool of amino acids from whole muscles (approx. 79 mmol kg(-1)) was similar in left and right claw muscles. In animals acclimated to osmotic environments between 0 and 220 mOsm, the osmotic pressure of the haemolymph increased from 356 to 496 mOsm, but no systematic changes were observed in the amino acid profiles of muscles or haemolymph. The major findings were that (a) concentrations of amino acids differed between the two major fibre types in claw muscle and (b) amino acids in the muscle fibres did not play a major part in intracellular osmoregulation in Cherax, suggesting this species is an anisosmotic regulator.

Effects of BDF 9198 on action potentials and ionic currents from guinea-pig isolated ventricular myocytes.

BDF 9198 (a congener of DPI 201 - 106 and BDF 9148) was found to be a positive inotrope on guinea-pig isolated ventricular muscle strips. The effects of BDF 9198 on action potentials and ionic currents from guinea-pig isolated ventricular myocytes were studied using the whole cell patch clamp method. In normal external solution, at 37 degrees C, action potential duration at 50% repolarization (APD(50)) was 167.4+/-8.36 ms (n=37). BDF 9198 produced a concentration-dependent increase in APD(50) (no significant increase at 1x10(-10) M; and APD(50) values of 273.03+/-35.8 ms at 1x10(-9) M; n=6, P<0.01 and 694.7+/-86.3 ms at 1x10(-7) M; P<0.001, n=7). At higher concentrations in the range tested, BDF 9198 also induced early and delayed and after-depolarizations. Qualitative measurements of I(Na) with physiological [Na](o) showed prolongation of the current by BDF 9198, and the appearance of transient oscillatory inward currents at high concentrations. Quantitative recording conditions for I(Na) were established using low external [Na] and by making measurements at room temperature. The current - voltage relation, activation parameters and time-course of I(Na) were similar before and after a partial blocking dose of Tetrodotoxin (TTX, 1 microM), despite a 2 fold difference in current amplitude. This suggests that voltage-clamp during flow of I(Na) was adequately maintained under our conditions. Selective measurements of I(Na) at room temperature showed that BDF 9198 induced a concentration-dependent, sustained component of I(Na) (I(Late)) and caused a slight left-ward shift in the current - voltage relation for peak current. The drug-induced I(Late) showed a similar voltage dependence to peak current in the presence of BDF 9198. Both peak current and I(Late) were abolished by 30 microM TTX and were sensitive to external [Na]. Inactivation of control I(Na) during a 200 ms test pulse to -30 mV followed a bi-exponential time-course. In addition to inducing a sustained current component, BDF 9198 left the magnitude of the fast inactivation time-constant unchanged, but increased the magnitude of the slow inactivation time-constant. Additional experiments with a longer pulse (1 s) raised the possibility that in the presence of BDF 9198, I(Na) inactivation may be comprised of more than two phases. No significant effects of 1x10(-6) M BDF 9198 were observed on the L-type calcium current, or delayed and inward rectifying potassium currents measured at 37 degrees C. It is concluded that the prolongation of APD(50) by BDF 9198 resulted from selective modulation of I(Na). Reduced current inactivation induced a persistent I(Na), increasing the net depolarizing current during the action potential. This action of the drug indicates a potential for 'QT prolongation' of the ECG. The observation of after-depolarizations suggests a potential for proarrhythmia at some drug concentrations.

Clinical outcomes, risk stratification and practice patterns of unstable angina and myocardial infarction without ST elevation: Prospective Registry of Acute Ischaemic Syndromes in the UK (PRAIS-UK)

AIMS: To determine characteristics, outcomes, prognostic indicators and management of patients with acute coronary syndromes without ST elevation. METHODS AND RESULTS: A prospective registry was carried out with follow-up for 6 months after index hospital admission. A history of acute cardiac chest pain was required plus ECG changes consistent with myocardial ischaemia and/or prior evidence of coronary heart disease. Patients with ST elevation or those receiving thrombolytic therapy were excluded. A total of 1046 patients were enrolled from 56 U.K. hospitals. The mean age was 66+/-12 years and 39% were female. The rate of death or non-fatal myocardial infarction at 6 months was 12.2% and of death, new myocardial infarction, refractory angina or re-admission for unstable angina at 6 months was 30%. In a multivariate analysis, patients >70 years had a threefold risk of death or new myocardial infarction compared with those <60 years (P<0.01) and those with ST depression or bundle branch block on the ECG had a five-fold greater risk than those with normal ECG (P<0.001). Aspirin was given to 87% and heparin to 72% of patients in hospital. At 6 months 56% received no lipid-lowering therapy at all. The 6-month rate of coronary angiography was 27% and any revascularization 15%. CONCLUSIONS: In this cohort there was a one in eight chance of death or myocardial infarction, and a one in three chance of death, new myocardial infarction, refractory angina or re-admission for unstable angina, over 6 months. Age and baseline ECG were useful markers of risk. Aspirin, heparin and statins were not given to about one-sixth, one-third and one-half respectively. Rates of angiography and revascularization appear low. A review of treatment strategies of unstable angina and myocardial infarction without ST elevation is warranted in the U.K. to ensure that patients are receiving optimum treatments to reduce mortality and morbidity.

Human extrapulmonary dirofilariasis in Texas.

Human pulmonary infection due to the dog heartworm, Dirofilaria immitis, has been reported in the medical literature for many decades. Extrapulmonary infection due to this pathogen is less widely reported, including only nine cases in North America. We report a case of extrapulmonary dirofilariasis manifested as asymptomatic nodular lesions in the anterior abdominal wall of a patient having exploratory laparotomy for carcinoma. We review previously reported cases and discuss the pathophysiology of both pulmonary and extrapulmonary dirofilariasis.

Diazepam-induced neuroprotection: dissociating the effects of hypothermia following global ischemia.

Global cerebral ischemia produces hippocampal CA1 neuronal loss which in turn leads to deficits in memory related tasks. Previous studies have shown that the benzodiazepine diazepam is effective at attenuating this cell death and the related behavioural impairments. However these studies have been confounded by diazepam-induced hypothermia. In this study we sought to determine the neuroprotective efficacy of diazepam in the absence of hypothermia. Diazepam (10 mg/kg) was administered to two groups of gerbils at 30 and 90 min following a 5-min ischemic insult. In one group the brain temperature was monitored for 24 h post-ischemically but not regulated. In the second group, post-ischemic brain temperature was maintained at 36.5 degrees C to counteract the hypothermia produced by diazepam. Both behaviour (open field performance) and CA1 cell counts from these groups were compared to those from sham/normal, no drug ischemic and vehicle ischemic groups at 10 days survival. In animals treated with diazepam without temperature regulation, there was significant histological and behavioural protection at 10 days compared to untreated ischemic animals. Preventing hypothermia in diazepam-treated animals resulted in a decrease in the number of cells surviving (from 41.2 to 31.6% of sham) and abolished behavioural protection. Diazepam appears to have limited ability to attenuate neuronal loss and its neuroprotective efficacy is augmented by the concurrent hypothermic actions of the drug itself.

Effect of phosphorylation on L-type calcium current in ventricular myocytes dialysed with proteolytic enzymes.

1. L-Type Ca2+ channels play important roles in cardiac excitation and conduction. The present study used the whole-cell patch-clamp technique to investigate properties of Ca2+ channels in guinea-pig isolated ventricular myocytes. The effects of internal application of the proteolytic enzymes trypsin and carboxypeptidase (CBP) on the whole-cell L-type Ca2+ current (ICa) were determined. When the effects of the enzymes on ICa had reached steady state, the effects of isoprenaline (ISP) or 2,3-butane-dione monoxime (BDM), which increase and decrease channel phosphorylation, respectively, were examined. The effects of these agents were compared with those observed in the absence of enzyme pretreatment. 2. The amplitude and inactivation characteristics of ICa during depolarizing voltage-clamp commands to +10 mV (0.1 Hz) were determined at 37 degrees C. 3. Trypsin and CBP (both at concentrations of 1 mg/mL in the pipette solution) increased the amplitude of ICa 4.2- and 2.8-fold, respectively, and each enzyme increased the time constant of the slowly inactivating current by 50%. 4. Trypsin decreased the potential at which ICa was half maximally activated from (mean +/- SD) -1.4 +/- 2.2 mV (n = 9) to -11.3 +/- 2.5 mV (n = 7). Although CBP increased ICa amplitude, it did not shift the half-maximal activation voltage. Maximum conductance was increased 5.3-fold by trypsin and 2.2-fold by CBP. 5. Isoprenaline (1 mumol/L) had no effects in myocytes dialysed with trypsin, but significantly increased the current in myocytes dialysed with CBP by 8%. 6. At 12 mmol/L, BDM had no effect on current amplitude in the presence of trypsin, but decreased the time constant of slow inactivation to control values. After dialysis with CBP, BDM significantly decreased the maximum current by 11% and also decreased the rate of slow inactivation towards control values. 7. These data suggest that trypsin and CBP may have digested a part of the calcium channel that normally restricts current flow, but to different extents. The enzymes interacted with BDM and ISP in a fashion suggesting that two sites may influence the amplitude of the current and at least two other sites may influence the time course of the slowly inactivating current.

Temporal profile of magnetic resonance imaging changes following forebrain ischemia in the gerbil.

Quantitative T2 magnetic resonance (MR) imaging was used to examine gerbil brains 1, 3, 10, and 30 days after 5 min forebrain ischemia. T2 was increased in the dorsal-lateral striatum 1 and 3 days post-ischemia, and in the hippocampus 3 days post-ischemia. T2 was normal 10 days post-ischemia, and decreased in the hippocampus and dorsal-lateral striatum 30 days post-ischemia. Neuronal counts in the dorsal-lateral striatum and CA1 hippocampal region were uniformly decreased 30 days post-ischemia. The increase in T2 shortly after ischemia is attributed to brain edema localized to regions where neuronal injury developed. The late decrease in T2 may be due to decreased water in gliotic tissue, or to ferritin-positive microglia, following forebrain ischemia. Tissue atrophy at later times gave enlarged ventricles on MR images.