Spinal cord blood flow decreases following microinjection of sodium nitroprusside into the nucleus tractus solitarii of anesthetized rats

This study was undertaken to examine whether or not nitric oxide (NO) is involved in synaptic transmission in the nucleus tractus solitarius (NTS) during control of the spinal cord circulation. Employing urethane-anesthetized, paralyzed and artificially ventilated rats, sodium nitroprusside (SNP), which produces NO, was microinjected unilaterally into the NTS and the spinal cord blood flow (SCBF) was determined using labeled microspheres. Arterial blood pressure (ABP) was decreased by unilateral microinjection of SNP into the NTS, but its value was kept within the normotensive range by blood transfusion, in order to measure SCBF at normotension. After microinjection of SNP into the NTS, the SCBFs of the cervical, thoracic and lumbar cords decreased significantly from 63 +/- 8 (mean +/- S.E.M.) to 49 +/- 7 (P < 0.05), from 54 +/- 7 to 37 +/- 7 (P < 0.05), and from 77 +/- 9 to 58 +/- 8 (P < 0.05) ml/min/(100 g), respectively (n = 10). Prior microinjection of NG-monomethyl-L-arginine (L-NMMA), an inhibitor of the formation of NO from L-arginine, into the NTS blocked the spinal cord vasoconstrictor response produced by microinjection of L-glutamate into the NTS (n = 10). Prior microinjection of NG-monomethyl-D-arginine (D-NMMA), which does not inhibit the formation of NO from L-arginine, did not block the spinal cord vasoconstrictor response elicited by microinjection of L-glutamate (n = 11). Unilateral microinjection of L-NMMA into the NTS exerted no effect on the spinal cord circulation (n = 9). These findings suggest that NO may be involved in the control of the spinal cord circulation in the NTS.

Scalp-recorded direct current potential shifts induced by hypocapnia and hypercapnia in humans

Shifts in scalp-recorded direct current (DC) potential were studied in relation to the changes in end-tidal partial CO2 (PACO2) or O2 (PAO2) of the expired gas either during hyperventilation (HV), hypoventilation (HYPO) or inhalation of high CO2 content air during HV or HYPO in 10 healthy subjects. The DC potential was obtained through a chopper stabilized type of DC amplifier from Cz referred to linked earlobes. Each session was comprised of 3 min control, 3 min experimental and 5 min recovery periods. HV induced a negative shift of the DC potential of 765.5 +/- 203.0 microV (mean +/- SEM). Inhalation of 6% CO2 air during HYPO induced a positive shift of the DC potential of 280.6 +/- 62.8 microV (mean +/- SEM). The magnitude of the DC potential shifts was linearly dependent on the changes in the end-tidal PACO2 (r = 0.78, P < 0.0001). There was no change in the cephalic inter-electrodes impedance during each experimental session. The results suggest that the scalp-recorded DC potentials reflect the changes in cortical excitability associated with the PACO2 level.

Blood pressure variability at annual periodic health examination for employees and cardiovascular risk factors

The employees with hypertension at the annual periodic health examination (HE) for employees in Japan usually receive a re-examination of blood pressure (BP) on another day and are often found to be normotensive. In this study, we analyzed data from the HE at the workplace to determine whether or not such employees should receive medical care. Two groups of subjects were selected. One group (group 1) was composed of 50 subjects with normotension at the HE (controls). Another group (group 2) was composed of 33 subjects with hypertension at the annual HE but with normotension in re-examinations. Cardiovascular risk factors were significantly higher in group 2 than in group 1: mean values of the body mass index (group 1, 22 +/- 2.7 vs. group 2, 24.3 +/- 3.1 kg/m2, p < 0.01), total cholesterol (group 1, 197 +/- 36 vs. group 2, 222 +/- 42 mg/dl, p < 0.01), and low density lipoprotein (group 1, 118 +/ 32 vs. group 2, 137 +/- 38 mg/dl, p < 0.05). The proportion of the employees with high-normal BP in group 2 (42.5%) was significantly higher than that in group 1 (28.0%) (p < 0.01). These indicate that the employees with hypertension at the annual HE but with normotension in the re-examination require further medical attention and should receive medical supervision. The occupational physician should supervise these employees.

Spinal cord lactate concentration during chemical stimulation of the nucleus tractus solitarii in anesthetized rats

This study was conducted to determine the mechanism of spinal cord blood flow (SCBF) decrease following the nucleus tractus solitarii (NTS) activation. In urethane-anesthetized, paralyzed and artificially ventilated rats, neurons in the NTS were chemically stimulated by microinjection of L-glutamate (1.7 nmol; 50 nl) and the lactate concentration, one of indicators of local neuronal metabolism, in the spinal cord was monitored in real time using an enzyme electrode. Before the chemical stimulation study, the responses of the enzyme electrode and its specificity were tested in vitro and in vivo. The electrode responded to step changes in lactate concentration and a calibration plot and regression line were obtained in vitro. The lactate concentration was significantly (P < 0.01) increased during induced apnea in vivo (n = 8). The lactate concentration in the spinal cord was not significantly changed by chemical stimulation of the NTS when arterial blood pressure (ABP) remained above the lower limit of spinal cord autoregulation (n = 21). When chemical stimulation of the NTS decreased ABP to below the lower limit of autoregulation (n = 18), the lactate concentration in the spinal cord was significantly (P < 0.01) increased. This may only be due to hypotensive effects because the lactate concentration was also significantly (P < 0.01) increased when the ABP was passively decreased below the lower limit of autoregulation by controlled hemorrhage in intact (n = 11) and sinoaortic denervated rats (n = 10). Intravenous lactate injection produced no significant increase in the current from the enzyme electrode in the spinal cord (n = 4). Using the electrode with inactivated enzyme solution, the current from the electrode did not change with the increase in lactate in the spinal cord. These findings indicate that the enzyme electrode can detect rapid changes of lactate, a product of anaerobic metabolism. These results also indicate that the spinal cord vasoconstrictor response elicited by chemical stimulation of the NTS, which was performed above the lower limit of spinal cord autoregulation in our previous study, may be due to neurogenic regulatory mechanism, but not to the secondary effects of changes in metabolism.

Activation of sympathetic outflow by recombinant human interleukin-1 beta in conscious rats

The present study was undertaken to determine the effects of interleukin-1 beta (IL-1 beta) on renal sympathetic nerve activity (RSNA), arterial blood pressure (AP), heart rate (HR), and body temperature in conscious rats. Either intravenous or intracerebroventricular administration of IL-1 beta elicited increases in AP, HR, and RSNA accompanied by a rise in body temperature. The maximum changes in AP, HR, and RSNA occurred 10-15 min after intravenous injection of IL-1 beta (100 ng) and 20-25 min after intracerebroventricular injection (5 ng). The responses induced by the intravenous and intracerebroventricular injections lasted for approximately 15-30 min and did not appear when the animals were pretreated with the cyclooxygenase inhibitor indomethacin (10 mg/kg iv). Moreover, intracerebroventricular injection of prostaglandin E2 (1 microgram) produced responses similar to those induced by IL-1 but with shorter latency. Plasma norepinephrine and adrenocorticotropic hormone concentrations were increased after IL-1 beta injection. The results suggested that IL-1 beta augments cardiovascular and sympathetic outflow through the central action of prostaglandin E2 in conscious rats.

Growth hormone-independent expression of insulin-like growth factor I messenger ribonucleic acid in extrahepatic tissues of the chicken

The sex-linked dwarf (SLD) chicken, which lacks GH receptor (GHR), and its normal littermates provide a useful experimental system to investigate GH-dependent cellular responses. The GH dependence of insulin-like growth factor I (IGF-I) expression in tissues was examined in SLD and normal chickens of the Gifu 20 strain. Four weeks after hatching, the most abundant expression of IGF-I messenger RNA (mRNA) was observed in liver of normal chickens, whereas no IGF-mRNA expression was detected in that organ of dwarf chickens. On the contrary, in extrahepatic tissues such as spleen, lung, brain, kidney, heart, intestine, thymus, and muscle, IGF-I mRNA expression was equally observed in normal and GHR-lacking dwarf chickens. In the testis, expression of IGF-I mRNA was enhanced by about 5-fold in dwarf chickens showing an expression level comparable to that in normal liver. On day 16 in the embryonic stage, IGF-I mRNA was expressed in muscle, brain, eye, heart, and lung in both normal and SLD chick embryos. However, no IGF-I mRNA expression was observed in liver or kidney of normal and dwarf chick embryos. These results suggest that in chicken, IGF-I mRNA is expressed in liver in a GH-dependent manner after hatching, whereas in other tissues, mRNA expression is independent of GH and GHR before and after hatching, except for testis, in which GH seems to inhibit IGF-I mRNA expression.

Expression of aberrantly spliced growth hormone receptor mRNA in the sex-linked dwarf chicken, Gifu 20

The structure and expression of the growth hormone receptor (GHR) gene have been studied in a sex-linked dwarf (SLD) chicken strain, Gifu 20. No gross structural change in the receptor gene was observed by Southern blot analysis, however, a transcript of 5.5 killobases (kb), which was approximately 1 kb larger than the usual chicken full length-GHR mRNA was detected in the dwarf chicken by Northern blot analysis. GHR cDNA was obtained from dwarf chicken liver RNA by reverse transcription-polymerase chain reaction, and nucleotide sequence analysis revealed that it contained an intron sequence of the GHR gene. The unspliced intron showed a single point mutation at the donor site from GT to GC, and an aberrant stop codon was generated in the extracellular domain-coding region. Thus, the mutation resulting in an inappropriate splicing of the GHR gene transcript is considered to be the cause of this dwarf chicken.

Sympathetic reinnervation of unilaterally denervated rat lung

The effect of unilateral sympathetic denervation and reinnervation of the lung on a variety of circulatory parameters was investigated in urethane-anaesthetized rats. The left main stem bronchus together with its surrounding nerves was cut and reanastomosed in 40 rats: 12 intact rats served as controls. Final experiments were performed after 0 days to 10 months: the left stellate ganglion was stimulated. The effect was greatest at 20 Hz. Pulmonary arterial pressure increased significantly (P < 0.05) by 10% and pulmonary flow decreased significantly (P < 0.05) by 16% in the control rats; no effect on these parameters was found in acutely denervated rats. The stimulus-elicited change in pulmonary arterial pressure reappeared 1 week after unilateral hilar stripping and gradually returned during reinnervation. After 10 months, the increase in pressure was significantly (P < 0.05) larger than that of the control by 50%, whereas the noradrenaline content of the reinnervated lung was significantly (P < 0.05) smaller than that of the intact side by 48%. This discrepancy may reflect denervation hypersensitivity of vascular muscle cells. The operations had no effect on systemic circulation: heart rate and systemic arterial pressure increased and aortic blood flow decreased to the same extent in all experimental groups during nerve stimulation. These results suggest that sympathetic reinnervation of the rat lung starts within 1 week but that reinnervation is still incomplete 10 months after unilateral hilar stripping.

Chemical stimulation of the nucleus tractus solitarii decreases spinal cord blood flow in anesthetized rats

L-Glutamate was microinjected into the nucleus tractus solitarii (NTS) in anesthetized (chloralose and urethane), paralyzed and artificially ventilated rats, and spinal cord blood flow (SCBF) was determined using a combination of labeled microspheres. Unilateral chemical stimulation of the NTS (n = 13) significantly decreased SCBF in the cervical cord from 43 +/- 6 (mean +/- SEM) to 28 +/- 4 (P < 0.05), in the thoracic cord from 35 +/- 3 to 24 +/- 4 (P < 0.01), and in the lumbar cord from 49 +/- 3 to 40 +/- 3 ml min-1 (100 g)-1 (P < 0.05). The decrease in SCBF was not due to the decrease in arterial blood pressure (ABP) because the SCBF during the chemical stimulation of the NTS was significantly smaller (P < 0.05) than the SCBF during controlled hemorrhagic hypotension (n = 11). Chemical stimulation of the NTS did not affect the reactivity of the spinal cord vessels to hypercapnia (n = 5). Microinjection of the vehicle solution into the NTS had no effects on spinal cord circulation (n = 9). These results suggest that the cell bodies within the NTS may play a role in the control of spinal cord circulation.

Role of vasopressin on cardiovascular changes during hemorrhage in conscious rats

Hypotensive hemorrhage decreases heart rate (HR) and renal sympathetic nerve activity (RSNA). Hemorrhage is a potent stimulus for arginine vasopressin (AVP) release; therefore, AVP may contribute to such inhibitory action of HR and RSNA during hemorrhage. We evaluated the roles of vasopressin on the regulation of blood pressure (BP), HR, and RSNA during hemorrhage using nonpeptide and selective V1- and V2-receptor antagonists (OPC-21268 and OPC-31260) in conscious rats. After hemorrhage (20 ml/kg body wt) BP decreased by 62 +/- 10 mmHg along with bradycardia (-110 +/- 15 beats/min) and renal sympathoinhibition (-50 +/- 8). Pretreatment of V1-receptor antagonist (5 mg/kg iv) did not affect the initial fall of BP but attenuated subsequent BP recovery. Bradycardic and renal sympathoinhibitory responses following hemorrhage were abolished (-14 +/- 24 beats/min and -7 +/- 9) by V1-receptor antagonist. Pretreatment of V2-receptor antagonist (1 mg/kg iv) did not affect the response of BP; however, it did slightly strengthen bradycardia and prolong renal sympathoinhibition. Hemorrhage increased the plasma AVP concentration more than 50-fold. These results indicate that when the plasma concentration of AVP is extremely high during hemorrhage, vasopressin via V1 receptor contributes to BP recovery by the peripheral vasoconstriction and exerts an inhibitory action on RSNA, and vasopressin via V2 receptor exerts opposite stimulatory action on RSNA.

Effects of centrally administered endothelin-3 on renal sympathetic nerve activity and renal blood flow in conscious rats

Effects of intracerebroventricular (i.c.v.) administration of endothelin-3 (ET-3) on renal sympathetic nerve activity (RSNA) and renal blood flow (RBF), arterial blood pressure and heart rate were examined in conscious rats. Administration of ET-3 (1-50 pmol) through a chronically implanted cannula evoked an increase in arterial blood pressure and decreases in heart rate and RSNA, whereas RBF measured by Doppler flow probes did not change. Maximum changes in these responses occurred 10-15 min after i.c.v. administration of ET-3 and the responses returned to the control level after approximately 60 min. In sinoaortic denervated (SAD) rats, the decrease in RSNA induced by i.c.v. ET-3 was attenuated but still significantly persistent. During the experiments, we found that the injection of ET-3 (50-100 pmol) induced a barrel rotation, with an onset latency of 10-15 min. In those cases, prominent increases in arterial blood pressure and RSNA were observed, and these lasted for more than 60 min. The result shows that ET-3 can have centrally mediated effects on autonomic nerve activity as well as on cardiovascular function.

Missing peaks in auditory brainstem responses and negative symptoms in schizophrenia

Auditory brainstem responses (ABRs) were examined in 30 schizophrenic patients and 29 normal subjects. The psychotic symptoms were assessed by the Brief Psychiatric Rating Scale (BPRS) and the Scale for Assessment of Negative Symptoms (SANS) in the patients. At least one of the waves I, II or III was found missing on either side at 80 dBHL (hearing level) in 8 (27%) of the patients but in only one (3%) of the normal subjects. There was a significant association between the missing peaks and the BPRS negative symptom cluster or the total score of the SANS. These results suggest that some schizophrenics, especially those with negative symptoms, have an abnormality of input processing of auditory information in the lower brainstem.

Cerebral vasoconstrictive response produced by chemical stimulation of the caudal ventrolateral medullary depressor area is mediated via the rostral ventrolateral medullary pressor area and the cervical sympathetic nerves

It was investigated that the cerebral blood flow (CBF) decrease response elicited by chemical stimulation of the caudal ventrolateral medullary depressor area (VLDA) is mediated via the rostral ventrolateral medullary pressor area (VLPA) and the cervical sympathetic nerve. The CBF was determined by radiolabeled microsphere technique in urethane (1.1-1.5 g.kg-1, i.p.) anesthetized Wistar rats. (i) Microinjection of L-glutamate (1.7 nmol) into the VLDA produced a significant (P < 0.01) decrease in CBF from 64 +/- 9 (mean +/- SEM) to 48 +/- 9 ml.min-1.(100 g)-1 and a significant (P < 0.01) increase in cerebrovascular resistance (CVR) from 1.7 +/- 0.2 to 2.4 +/- 0.4 mmHg per [ml.min-1.(100 g)-1] in the cerebral cortex ipsilateral to the stimulated VLDA side (n = 9). (ii) After cervical sympathectomy, L-glutamate was unilaterally microinjected into the VLDA. The CBF and CVR did not change significantly (n = 10). (iii) After depression of the VLPA neurons with muscimol (GABA agonist), L-glutamate was unilaterally microinjected into the VLDA. The CBF and CVR did not change significantly (n = 14). These results suggest that the pathway from the VLDA to control cerebral vessels may be mediated via the VLPA and the cervical sympathetic nerves.

Caudal ventrolateral medullary depressor area controls cerebral circulation via rostral ventrolateral medullary pressor area

The cerebral blood flow (CBF) was determined by radiolabeled microsphere technique in urethane (1.1-1.5 g.kg-1, i.p.) anesthetized Wistar rats. Microinjection of L-glutamate (1.7 nmol) into the ventrolateral medullary depressor area (VLDA) produced a significant (P < 0.01) decrease in CBF from 64 +/- 9 (mean +/- S.E.M.) to 48 +/- 9 ml.min-1.(100g)-1 and a significant (P < 0.01) increase in cerebrovascular resistance (CVR) from 1.7 +/- 0.2 to 2.4 +/- 0.4 mmHg per [ml.min-1.(100g)-1] in the cerebral cortex ipsilateral to the stimulated VLDA side but not in other structures such as brain stem and cerebellum (n = 9). Cervical sympathectomy blocked the decrease in CBF and increase in CVR elicited by chemical stimulation of the VLDA (n = 10). Depression of the ventrolateral medullary pressor area (VLPA) neurons induced by microinjection of muscimol into the VLPA blocked the CBF decrease and CVR increase following chemical stimulation of the VLDA (n = 11). Microinjection of the vehicle solution into the VLDA had no effects on systemic and cerebral circulation (n = 7). These results suggest that a vasoconstrictor pathway to control cerebral vessels involves an excitatory projection from the VLDA to the VLPA and the changes in cerebral circulation are mediated by the cervical sympathetic nerves.

Nutrient-induced thermogenesis (NIT) following amino acid infusion

Nutrient-induced thermogenesis (NIT) induced by parenteral infusion of amino acid (AA) mixtures of different composition and of the same AA mixtures given via different routes (parenteral or intraportal infusion) were investigated in rats using a small animal indirect calorimeter. When 8 different AA solutions of differing composition but with the same total concentration were infused parenterally, both standard NIT (each AA is assumed to generate 3.28 kcal/g) and specific NIT (heat energy of each AA is calculated assuming that it is oxidized to carbon dioxide and water, and metabolised to urea and sulphuric acid) values of the leucine (Leu)-rich and the glycine (Gly)-rich solutions were significantly greater than those of the control solution. Removal of Leu or Gly from the respective AA solutions reversed the increase of both NIT values down to control levels. When the parenteral and portal infusion routes were used in one rat, both NIT values for parenteral infusion of the Leu-rich solution were again significantly greater than those of the control. Likewise, both NIT values for intrportal infusion of the Leu-rich solution were also significantly greater than those of the control. However, no difference in NIT values was found between parenteral and portal infusion of either solution. The result of this study indicated that Leu and Gly may be thermogenic AAs, and the thermogenic effect of Leu is not dependent upon the route of infusion.

Deficiency of the E1 beta subunit in the branched-chain alpha-keto acid dehydrogenase complex due to a single base substitution of the intron 5, resulting in two alternatively spliced mRNAs in a patient with maple syrup urine disease

A patient with maple syrup urine disease (MSUD) associated with a E1 beta subunit deficiency of the branched-chain alpha-keto acid dehydrogenase (BCKDH) complex was investigated at the molecular level. The defect responsible for the deficiency of the E1 beta subunit protein was identified by analysis of cDNA and genomic DNA by polymerase chain reaction. Total RNA isolated from lymphoblastoid cells was transcribed into cDNA and amplified using a set of primers located within exon 3 and exon 9 of the E1 beta gene. Agarose gel electrophoresis of cDNA amplification products revealed two shortened bands as well as a faint band of normal size. Nucleotide sequencing of the shortened cDNA amplification products showed that sequences corresponding to exon 5 and both exons 5 and 6 were absent. Nucleotide sequencing of the proband's amplified genomic DNA corresponding to this region of the E1 beta gene revealed a single base substitution from G to T of the invariant GT dinucleotides at 5' splice site of the intron 5. Analysis of family members using primer-specified restriction map modification showed that the patient is homozygous for this mutation. We postulate that this mutation leads to the skipping of either exon 5 or both exons 5 and 6, thus producing two shortened E1 beta mRNA. The percentage of normal and two shortened transcripts was estimated to be 9, 71 and 20%, respectively. To our best knowledge, this is the first documented example of exon skipping in the E1 beta gene as the cause of MSUD and the novel mutation of the invariant G at the 5' splice site which results in two alternatively spliced mRNA due to the skipping of the preceding exon as well as both preceding and following exon.

Heterogeneity of mutations in maple syrup urine disease (MSUD): screening and identification of affected E1 alpha and E1 beta subunits of the branched-chain alpha-keto-acid dehydrogenase multienzyme complex

Maple syrup urine disease (MSUD) is an autosomal recessive disease caused by a deficiency in subunits of the branched-chain alpha-keto-acid dehydrogenase complex (BCKDH). To characterize the mutations present in five patients with MSUD (four classic and one intermediate), three-step analyses were established: (1), identification of the involved subunit by complementation analysis using three different cell lines derived from homozygotes having E1 alpha, E1 beta or the E2 mutant gene; (2), screening for a mutation site in cDNA of the corresponding subunit by RT-PCR-SSCP and (3), mutant analysis by sequencing the amplified cDNA fragment. Four single-base missense mutations, R115W, Q146K [corrected], A209T and I282T, were detected in the E1 alpha subunit. A single-base missense mutation H156R and three frame-shift mutations to generate stop codons downstream, including an 11-bp deletion of the tandem repeat in exon 1, a single-base (T) deletion and a single-base (G) insertion, were identified in the E1 beta subunit gene. All except one (11-bp deletion in E1 beta (Nobukuni, Y., Mitsubuchi, H., Akaboshi, I., Indo, Y., Endo, F., Yoshioka, A. and Matsuda, I. (1991) J. Clin. Invest. 87, 1862-1866)) were novel mutations. The sites of amino-acid substitution were all conserved in other species. Thus, mutations causing MSUD are heterogenous.

Characterization of a small cryptic plasmid, pPF1, from Phormidium foveolarum and vector construction

The 1509 bp cryptic plasmid, pPF1, from Phormidium foveolarum, a strain of filamentous cyanobacteria of the LPP group, was completely sequenced. The pPF1 nucleotide sequence had 97.8% overall similarity with that of a small plasmid from Plectonema boryanum. The structural organization of pPF1 and vector construction are discussed.