Fibroblast growth factor-2 regulation of Sprouty and NR4A genes in bovine ovarian granulosa cells

Fibroblast growth factors (FGFs) alter ovarian function, at least in part by inhibiting steroid hormone secretion and affecting survival of granulosa cells. The mechanism of action of FGFs in ovarian follicle cells is largely unknown; in the present study we identified the major pathways used by FGF2 in non-luteinizing granulosa cells cultured under serum-free conditions. FGF2 increased abundance of mRNA encoding SPRY1, 2, and 4, but not SPRY3. Common pathways employed by FGF2 in the regulation of SPRY1, 2, and 4, as demonstrated by immunoblot and inhibitor studies, included ERK1/2 and Akt signaling. In contrast, PKC activation was necessary for FGF2-stimulated expression of SPRY1 and 4, but not for SPRY2. Intracellular calcium flux is critical and sufficient for SPRY2 expression, but not for SPRY1 and 4. We also identified the orphan nuclear receptor NR4A1 as a potential early response gene in FGF2 signaling, whose expression, like that of SPRY2, is critically dependent on calcium signaling. Together, these data identify FGF2-target genes in follicular granulosa cells, and demonstrate alternative pathway use for the differential control of SPRY genes.

[Experimental study of recording and analysing electrophysiological signals from corticospinal tract in rats]

OBJECTIVE

To explore the recording method of the electrophysiological signals in corticospinal tract (CST) of adult rats by plugging microelectrodes and analyze the characteristics of these signals. These could provide some valuable and basic neural electrophysiological information for further research of recovering and refunctioning after spinal cord injury.

METHODS

The microelectrodes were plugged into the corticospinal tract at the T8 spinal section of Sprague-Dawley rats and the neuro-electrical signals were identified and recorded from CST by means of the Cerebus System. The characteristics of the recorded signals were described with the help of the Offline sorter and Neuroexplorer softwares, including the wavelength, amplitude, discharging frequency, the synchrony among the multi-discharging units from the same electrode and two different electrodes, analysis of interspike interval (ISI), etc.

RESULTS

The continuous and steady spontaneous electrophysiological signals were recorded from CST. Three or four types of discharging signals originated from different discharging units were collected with each electrode. The waveform of the signals appeared bidirectional. The wavelengths were 0.6 - 1.3 ms with wave amplitudes at a grade of hundred microvoltage and high signal-noise ratios. The LFB staining proved that the electrodes were accurately plugged into the corticospinal tract.

CONCLUSION

The neuro-electrical signals at a grade of hundred microvoltage could be recorded stably from the corticospinal tract of rats by the Cerebus System with the microelectrodes, which provided valuable and basic neural electrophysiological information for further research on recovering and refunctioning after spinal cord injury (SCI) by analyzing the characteristics of electrophysiological signals.

[The relationship of the content of AVP and the expression of V1b receptors in some brain areas with the sexual difference in the susceptibility of motion sickness in rats]

OBJECTIVE

To measure the content of arginine vasopressin (AVP) and V1b receptor expression in the brain areas in rats of both genders and after rotatory stimulation and thereby, to identify the involvement of AVP in the mechanisms of motion sickness.

METHODS

SD rats were rotated about a horizontal axis for 30 min, the content of AVP and the expression of V1b receptors in some brain areas were then measured with radioimmunological analysis and immunofluorescent method respectively.

RESULTS

We proved that: (1) In female rats, the content of AVP in each area we measured in rotation group did not show any significant change compared with that in control group (P > 0.05). In male rats, the AVP content of control group in each area was higher than that of female rats, but reduced by rotatory stimulation in forebrain, diencephalon and pontine (P < 0.05 or 0.01), however, the changes in the cerebellum and medulla of rotation group were not significant (P > 0.05). (2) The positive cell number of V1b receptor expression in the supraoptic nucleus of female rats in rotation group was lower, but higher in the vestibular nucleus and area postrema than that in control group (P < 0.05 or 0.01). In male rats, the V1b receptor positive cell number in the supraoptic nucleus and vestibular nucleus of rotation group did not show significant change compared with that of control group (P > 0.05), but a slight increase in the medulla of rotation group rats was observed (P < 0.05).

CONCLUSION

The gender difference in the susceptibility of motion sickness is potentially associated with the discrepancies in AVP content in the forebrain, diencephalon and pontine, in the expression of AVP-V1 receptors in the vestibular nucleus and area postrema, and in responses to rotatory stimulation, and that the vestibular nucleus and area postrema may be the areas targeted by AVP V1 receptor antagonist for antimotion sickness.

Neuroprotective effect of L-serine against temporary cerebral ischemia in rats

To investigate the neuroprotective effect of L-serine and its underlying mechanisms, focal cerebral ischemia was induced in rats by occlusion of middle cerebral artery (MCAO) with a suture, and reperfusion was given by filament withdrawal 2 hr later. Meanwhile, rat hippocampal neurons were primarily cultured, and incubated in serum-free medium in an incubator containing 1% O(2) for hypoxic exposure of 5 hr, or incubated in serum-free medium containing 1 mM glutamate for glutamate exposure of 2 hr. Brain tissue injury and cell damage were then measured. L-serine dose-dependently decreased the neurology deficit score and infarct volume, elevated the cell viability and inhibited the leakage of lactate dehydrogenase. These effects were blocked by strychnine in both MCAO rats and cultured hippocampal neurons. Furthermore, L-serine (168 mg.kg(-1)) reduced the brain water content, permeability of blood-brain barrier, neuronal loss and the expression of activated caspase-3 in the cortex. In addition, L-serine effectively protected the brain from damage when it was administered within 6 hr after the end of MCAO. It is suggested that L-serine could exert a neuroprotective effect on the ischemic-reperfused brain and on the hypoxia- or glutamate-exposed hippocampal neurons, which may be mediated by activating glycine receptors.

Inhibition of NMDA receptors underlies the neuroprotective effect of ginsenoside Rb3

In order to investigate the mechanisms underlying the neuroprotective effect of ginsenoside Rb3, rat hippocampal neurons were primarily cultured, and exposed to 1 mM N-methyl-D-aspartate (NMDA), cell viability and lactate dehydrogenase leakage were measured. Ca2+ influx was determined by calcium imaging with a laser confocal microscopy. The influences of ginsenoside Rb3 on these variables were examined. Patch-clamp technique was used to observe the effects of ginsenoside Rb3 on NMDA-evoked current. The results show that treatment of Rb3 raised the neuronal viability, reduced the leakage of lactate dehydrogenase, and inhibited NMDA-elicited Ca2+ influx in a dose-dependent manner. In the presence of Rb3, NMDA-evoked peak current was inhibited, and Ca2+-induced desensitization of NMDA current was facilitated. It is suggested that ginsenoside Rb3 could exert a neuroprotective role on hippocampal neurons, a role which was partly mediated by the facilitation of Ca2+-dependent deactivation of NMDA receptors, and the resultant reduction of intracellular free Ca2+ level.

Ginsenoside Rg1 protects neurons from hypoxic-ischemic injury possibly by inhibiting Ca2+ influx through NMDA receptors and L-type voltage-dependent Ca2+ channels

The purpose of this study is to assess the neuroprotective effect of Rg1, a ginsenoside. We measured cell viability and lactate dehydrogenase (LDH) release from primary culture of rat hippocampal neurons and electrical activities in hippocampal slices of rats, before and after the neurons were deprived of oxygen and glucose. In addition, cerebral damage was evaluated with magnetic resonance imaging after middle cerebral artery was occluded transiently. Nissl staining was used for histological observation and immunohistochemistry analysis for activated caspase-3 expression of the brain. Furthermore, calcium influx was measured with laser confocal microscopy in neurons perfused with KCl (50 mM) or N-methyl-d-aspartate (NMDA, 1 mM), or deprived of oxygen and glucose. The influences of ginsenoside Rg1 on these parameters were determined simultaneously. We found that treatment of Rg1: 1) increased the neuronal viability; 2) promoted the recovery of electrical activity in hippocampal slices; 3) reduced the release of LDH, cerebral damage area, neuronal loss and expression of caspase-3; and 4) inhibited calcium influx induced by NMDA, KCl or oxygen/glucose deprivation. However, the protective effect of Rg1 was blocked by mifepristone, an antagonist of glucocorticoid receptors. Taken together, these results suggest that ginsenoside Rg1 can reduce neuronal death, including apoptotic cell death, induced by hypoxic-ischemic insults. This neuroprotective effect is probably mediated by the activation of glucocorticoid receptors, and by the inhibition of calcium influx through NMDA receptors and L-type voltage-dependent Ca2+ channels and the resultant reduction of intracellular free Ca2+.

Neuroprotective effect of taurine against focal cerebral ischemia in rats possibly mediated by activation of both GABAA and glycine receptors

To investigate the neuroprotective effect of taurine and the involved mechanisms, middle cerebral artery occlusion (MCAO) was induced with suture for 2h in rat, and the brain tissue was then reperfused. The infarct volume and cerebral damage area were measured, respectively, with 2,3,5-triphenyltetrazolium chloride (TTC) staining and MRI. Nissl staining was used for histological observation, and immunohistochemistry and Western-blot analysis for detecting the activated caspase-3 expression. Both pre- (200mgkg(-1)) and post-treatment of taurine decreased the neurology deficit score, infarct volume and brain water content. Taurine post-treatment (67, 200 and 600mgkg(-1)) showed a dose-dependent neuroprotective effect. Taurine (200mgkg(-1)) significantly decreased neuronal loss in the cerebral cortex and hippocampus, and reduced the expression of caspase-3 as well. The neuroprotective effect of taurine was partly blunted by strychnine or bicuculline alone, and almost completely blocked by coapplication of both antagonists of glycine and GABA(A) receptors. It is suggested that taurine exerts a neuroprotective role on the brain when administered before or after MCAO. Such effect is possibly mediated by the activation of both GABA(A) receptors and strychnine-sensitive glycine receptors. Moreover, inhibition of caspase-3 expression is involved in this neuroprotective effect. These results imply a potential therapeutic use of taurine for stroke.

[Relationship among sexual differences of susceptibility to motion sickness, AVP levels of plasma and pituitary and V1b receptor expression of pituitary in rats]

AIM

To investigate the relationship among sexual differences of motion sickness (MS), AVP levels of plasma and pituitary and the expression of pituitary V1b receptors for further understanding of the MS mechanisms.

METHODS

The conditioned taste aversion (CTA) of 0.15% saccharin sodium solution (SSS) was served as MS model. 98 (49 male and 49 female) rats were used in this experiment, 50 for the detection of the AVP level in plasma and pituitary with radioimmunoassay (RIA), 12 for the observation of the number of V1b receptor-positive neurons in the pituitary with the fluorescence immunohistochemistry method, the rest for the evaluation of the expression of V1b receptor in the pituitary by Western blot.

RESULTS

With regard to male rats, decrease of the drinking volume of 0.15% SSS was greater in female rats after rotatory stimulation. The plasma AVP concentration of female rats was significantly higher than that of males under normal conditions, but reduced significantly after rotatory stimulation. However, no significant change was found in male rats. In addition, the pituitary AVP level of the female rats was significantly higher than that of the male rats under normal conditions, but decreased at 8 h and significantly at 24 h after rotation. Similarly, the pituitary AVP level of male rats also decreased significantly at 8 h after rotation, but this decrease was not comparable to that of the females. At 24 h after rotation the pituitary AVP level almost recovered in male rats. In the pituitary, which was related to the stress response, the V1b receptor-positive neurons and the expression level of V1b receptor in female rats were significantly higher than those of the male rats, but they decreased significantly after rotation, while no apparent change was detected in the male rats.

CONCLUSION

The changes of plasma and pituitary AVP and V1b receptor level of the pituitary after rotatory stimulation are different between male and female rats and the AVP secretion of the pituitary may be involved in the sexual difference in susceptibility to motion sickness.

[Effects and mechanisms of ginsenoside Rb3 on glutamate excitotoxic injury in cultured neurons of rat hippocampus]

AIM

To observe protective effects of ginsenoside Rb3 on glutamate excitotoxic injury in cultured hippocampal neurons and involved mechanisms.

METHODS

On cultured rat hippocampal neurons treated with glutamate at toxic concentration, we made the following investigations: by using MTT assay, LDH leakage detection, tests of total NOS, iNOS and cNOS activity, and the protective effects of ginsenoside Rb3.

RESULTS

Ginsenoside Rb3 can enhance the hippocampal neuronal viability, decrease the LDH leakage, elevate the viability of cNOS, and in the same time weaken iNOS's viability.

CONCLUSION

Ginsenoside Rb3 has the significant protective effects on glutamate excitotoxic injury. The involved mechanism may include antagonizing the injury of neuron membrane, inhibiting the viability of iNOS, and increasing the activity of cNOS.

Inhibitory influence of ginsenoside Rb3 on activation of strychnine-sensitive glycine receptors in hippocampal neurons of rat

Whole-cell patch-clamp technique was used to investigate the effect of ginsenoside Rb(3) (Rb(3)), an active constituent of Panax ginseng, on glycine receptor activity in immature hippocampal neurons, which were dissociated acutely from hippocampal CA(1) area in Sprague-Dawley rats aging 10-14 days using the method of enzyme digestion with mechanical dissociation. As a result, glycine elicited an inward current (I(gly)) in a concentration-dependent manner in approximately 86% of those isolated neurons tested. This current was strychnine-sensitive. Rb(3) itself did not elicit any membrane currents. However, coapplication of Rb(3) inhibited peak current of I(gly). This depressant effect of Rb(3) varied with its concentrations. At a concentration of 0.1 micromol/L, ginsenoside Rb(3) had the most significant inhibition, with a net reduction of 31% in average. Moreover, the inhibition of I(gly) by Rb(3) did not depend on the membrane potential. Rb(3) (0.1 micromol/L) presented inhibitory effect on I(gly) mainly at higher glycine concentrations (>100 micromol/L), and decreased maximal glycine efficacy. This effect was the same as that of a non-competitive antagonist of glycine receptors. Finally, we found that Rb(3) prolonged the time constant of activation of I(gly). It is therefore suggested that ginsenoside Rb(3), possibly as a non-competitive antagonist, could inhibit strychnine-sensitive glycine current at a dose-dependent manner in acutely dissociated hippocampal CA(1) neurons of young rats, and decrease of affinity of glycine to receptors and delay of receptor activation may be involved in this inhibition. Inhibitory effect of ginsenoside Rb(3) on I(gly) is possibly one of the bases of many pharmacological actions of Panax ginseng.

Plasma vasopressin, an etiologic factor of motion sickness in rat and human?

Arginine vasopressin (AVP) is considered as an etiologic hormone in motion sickness. However, the possible role of plasma AVP in motion sickness is still controversial. A number of studies have found a gender difference in susceptibility to motion sickness in humans and experimental animals, with female subjects being more susceptible. However, the existence of a gender difference in the AVP response to motion sickness is not known. This study was designed to verify the assumption that plasma vasopressin plays a role in motion sickness. Changes in plasma vasopressin were observed after motion sickness-inducing rotatory stimuli in both sexes in human subjects and rats receiving or not anti-motion-sickness treatments. Plasma vasopressin levels in motion sickness rats exhibited a decrease after rotation in female, but not in male rats. The vasopressin content of the pituitary increased in both sexes. Plasma vasopressin in rats of both sexes tended to increase after a 15-day adaptive training of rotation, but pituitary vasopressin content was not affected under this condition. In contrast, in human subjects, plasma vasopressin levels increased after rotation in all males, but not in females. When anti-motion-sickness drugs (domperidone 10 mg + flunarizine 5 mg) were administered, plasma vasopressin levels were elevated in both females and males. It is concluded that plasma vasopressin increases after motion sickness-induced stimulation provided subjects have become trained to motion sickness. These results do not support an etiologic role of plasma vasopressin in the genesis of motion sickness.

Genistein directly blocks glycine receptors of rat neurons freshly isolated from the ventral tegmental area

The effects of tyrosine kinase inhibitors on the glycine-induced current (I(Gly)) were studied in rat neurons freshly isolated from the ventral tegmental area (VTA). Genistein reversibly and concentration-dependently depressed I(Gly), with an IC(50) of 13 microM. Preincubation with genistein had no effect on I(Gly), indicating that genistein is effective only when glycine is bound to the receptor and channels are most likely open. Genistein depressed maximum I(Gly) without significantly changing the EC(50) for glycine. Genistein-induced inhibition of I(Gly) was sensitive to membrane voltage, being greater at positive membrane potentials. A kinetic analysis indicated that genistein lengthens the time constant of I(Gly) activation, but has no effect on deactivation or desensitization. When genistein was rapidly washed out, a transient rebound current probably reflected a faster dissociation of genistein, with respect to glycine. Results of competition experiments suggest that genistein acts on the same region of the glycine receptor as picrotoxin. Daidzein, an analog of genistein that does not act on protein kinases, also inhibited I(Gly). Co-application of lavendustin A, a specific inhibitor of tyrosine kinase, had no effect on I(Gly). Our results extend to neurons isolated from the VTA, the previous finding that genistein directly inhibits glycine receptors of hypothalamic brain slices.

Protein kinase C epsilon is involved in ethanol potentiation of glycine-gated Cl(-) current in rat neurons of ventral tegmental area

Previously, we demonstrated that ethanol potentiates glycine current (I(Gly)) in 35% of neurons freshly isolated from the ventral tegmental area (VTA) of rats (J. Pharmacol. Exp. Ther. 296 (2001) 77). In the present study, we examined the role of protein kinase C (PKC) in this action of ethanol on VTA neurons from young rats. Extracellular ethanol and intracellular ATP-gamma-S when applied separately potentiated I(Gly). However, ethanol potentiation of I(Gly) was significantly reduced in neurons dialyzed with 2 mM ATP-gamma-S. Phorbol-12-myristate-13-acetate (PMA, 10 nM), a PKC activator also increased I(Gly) and reduced ethanol potentiation of I(Gly). In addition, GF109203X (0.2 microM), a PKC inhibitor antagonized the potentiation effects produced either by PMA or by ethanol. Thus, ethanol potentiation of I(Gly) may be associated with PKC activation. While intracellular application of 1,2-bis(aminophenoxy)-ethane-N,N,N,N'-tetraacetic acid, a Ca(2+) chelator or Gö6976, an inhibitor of Ca(2+)-dependent PKC had no appreciable effect on ethanol potentiation of I(Gly), translocation inhibitor peptide (PKC(epsilon)-TIP) (500 nM) significantly reduced ethanol potentiation, an action the translocation inhibitor peptide negative control (PKC(epsilon)-TIP-NC) (500 nM) did not have. These results suggest that the activation of PKC(epsilon) isoenzyme contributes to ethanol-induced potentiation of GlyR function.

[The preparation of Ag/AgCl nanoparticle and its resonance scattering spectroscopic study]

Putting the AgCl nanoparticle as crystal nucleus and in the condition of the existence of tri-sodium citrate, the Ag+, which covers the surface of AgCl nanoparticle, photochemically reduces to Ag and thus Ag/AgCl composite nanoparticle is obtained. The spectroscopic characters of Ag/AgCl nanoparticle in aqueous solution have been studied. There are two resonance scattering peaks at 310 and 590 nm, and an absorption peak at 400 nm.

[The determination of lorazepam in human urine by gas chromatography/nitrogen-phosphorus detector]

A method to assay lorazepam in human urine has been developed. After addition of hydroxyethylflurazepam (internal standard) and hydrolysis with beta-glucuronidase, the lorazepam and hydroxyethylflurazepam were extracted with ethyl ether at pH 10.8. The analysis was performed on an HP-5 capillary column with nitrogen-phosphorus detector(NPD). The detection limit and recovery of analytes in urine were 5 micrograms/L and (83.4 +/- 3.1)% respectively. The method was successfully applied to urine specimens collected from healthy human volunteers who have ingested 2 mg of lorazepam. The method was sensitive enough to assay urine specimen excreted at 32 h after taking the medicine by volunteers.

Local high-capacity adenovirus-mediated mCTLA4Ig and mCD40Ig expression prolongs recombinant gene expression in skeletal muscle

Multiple forms of muscular dystrophy are due to the absence of cytoskeletal muscle proteins that normally protect the integrity of muscle cells. The lack of any adequate treatments for these devastating diseases propels research toward the development of strategies for gene delivery to skeletal muscle. High-capacity adenoviral vectors (HC-AdV) devoid of all viral coding sequences have been developed to avoid expression of viral proteins by the gene therapy vector. However, the capsid proteins that are an essential component of the input viral vector and any residual helper virus in the vector preparation could induce an immune response. Furthermore, the therapeutic protein provided by a gene transfer vector presents the potential to induce an immune response in a patient who does not express a normal cellular protein due to genetic mutation. Therefore, we hypothesize that some immune suppression will be required with therapeutic gene delivery designed for the treatment of patients with inherited muscle diseases. In this study, we constructed and rescued three HC-AdVs expressing murine CTLA4Ig, murine CD40Ig, or both. The backbone vector without a gene insert was rescued as a negative control vector. The production of relevant proteins from each vector was determined in vitro. In vivo function of each of the immunosuppressant vectors was assayed by co-injection with an enhanced green fluorescent protein (EGFP)-expressing first-generation adenoviral vector (AdEGFP) into the tibialis anterior muscle of C57BL/10 mice. Higher levels of muscle EGFP expression were observed in animals receiving an immunosuppressant vector. Furthermore, the production of total anti-AdV and anti-EGFP antibodies was reduced in mice treated with each of the three immunosuppressant vectors. A second intramuscular administration of AdEGFP alone 4 weeks after the initial co-injection was successful in all immunosuppressant vector-treated groups, but not in the negative control vector-treated group. All groups had a high antibody response to adenoviral proteins after the second injection of AdEGFP alone, indicating that the initial co-injection did not tolerize against vector capsid antigens.

[Glutamate-related mechanism of ginsenosides against anoxic-ischemic brain damage]

AIM AND METHODS

To observe the antagonist effect of ginsenosides upon excitatory neurotoxicity of glutamate in rat hippocampal slices, and to observe the inhibitory and facilitated effects of ginsenosides upon glutamate release from cultured mice cortical neurons and upon glutamate uptake by cultured astrocytes, respectively, during simulated ischemia, in order to elucidate whether the protective effect of ginsenosides against anoxic-ischemic brain damage is related to reducing the excitatory neurotoxicity of glutamate.

RESULTS

The orthodromic population spikes (OPS) recorded in hippocampal slice decreased in amplitude and disappeared finally during 20-min glutamate (1 mmol/L) exposure, and recovered less 1 h after the end of this exposure. However, OPS recovered well after the use of ginsenosides at different concentrations, especially at 20 microg/ml. In cultured mice cortical neurons and astrocytes, glutamate released from neurons up to several times of control and its uptake by astrocytes decreased markedly during simulated ischemia, ginsenosides (20 microg/ml) could significantly inhibit glutamate release from neurons and facilitate glutamate uptake by astrocytes during the same ischemia exposure.

CONCLUSIONS

Reducing the excitatory neurotoxicity of glutamate may be an important mechanism of ginsenosides against anoxic-ischemic brain damage.

[Research of the extraction method of morphine from biological fluids]

A solid-phase extraction method of morphine from urine and blood has introduced. The effect of 5 SPE columns, 3 eluents and pH on morphine recovery has been investigated systematically. Derivative GC was used as a method of detection. The result showed that the column and the eluent of such as GDX-301, GDX-403 and C18 chloroform:isopropanol (9:1) had good behaviors to extraction of morphine. When GDX-301 was used as a sorbent, the recovery of morphine from urine was above 90% at pH 9, then went down with the increase of pH. While the recovery from blood was growing with the increase of pH, which reached above 90% in strong alkaline. The extraction method is simple, inexpensive, efficient and reproducible, which provides an effective and practical method to extract morphine and similar illicit drugs from biological fluids.

Rise in plasma oxidized glutathione by experimental hypoglycemia

Changes in plasma glutathione were investigated under hypoglycemic status. Twelve rabbits were randomly divided into hypoglycemic group (n=6) and saline-injected control group (n=6). Hypoglycemia was induced by intravenous injection of insulin as 10 U/kg and recovered by intravenous glucose injection after 60 minutes. In the control group, saline was intravenously injected in stead of insulin. Plasma levels of oxidized glutathione (GSSG) rose significantly (p<0.01) and remarkably decrease in plasma GSH/GSSG ratio (p<0.05) accompanying increase in serum enzymes in the hypoglycemic group. These results suggest that hypoglycemia might cause change in plasma GSSG which is related to increase of serum enzymes by hypoglycemia.

Muscle damage induced by experimental hypoglycemia

To determine organ damage due to hypoglycemia, we studied the effects of insulin dose and hypoglycemia duration on serum enzyme activity in rabbits. Thirty rabbits were randomly divided into five groups according to hypoglycemia duration and insulin dose: A2, hypoglycemia for 30 minutes with 2 U/kg insulin; A10, hypoglycemia for 30 minutes with 10 U/kg insulin; B2, hypoglycemia for 60 minutes with 2 U/kg insulin; B10, hypoglycemia for 60 minutes with 10 U/kg insulin; and C, no hypoglycemia with 10 U/kg insulin and 50% glucose. Insulin-induced hypoglycemia was reversed by intravenous injection of glucose. Alterations in serum enzyme activity and creatine kinase (CK) isoenzyme distribution were determined before and after insulin injection. Serum CK activity increased significantly in all hypoglycemic groups compared with preinjection values, and tended to remain high for 24 hours in both groups A10 and B10. Serum activity of alanine aminotransferase (ALT), aspartate aminotransferase (AST), and lactate dehydrogenase (LDH) increased only in group B10. In addition, the level of band 4 of serum CK isoenzymes, which exists predominantly in skeletal muscle and myocardium, increased significantly in group B10. These results suggest that the increase in both serum enzyme and CK band 4 isoenzyme activities during hypoglycemia is primarily due to damage in muscle rather than liver, and that the hypoglycemia duration and insulin dosage may influence the extent of organ damage.

Cardiac angiotensin converting enzyme and endothelin receptor in rats with chronic myocardial infarction

To ascertain the pathophysiological roles of the renin-angiotensin system and endothelin in heart failure and cardiac hypertrophy, we assessed changes in cardiac angiotensin converting enzyme (ACE) and endothelin-1 (ET-1) receptor using rats in which myocardial infarction was induced by left coronary ligation. The animals were decapitated 1 or 8 months after the operation. Cardiac ACE and ET-1 receptor were quantified by computerized in vitro autoradiography using 125I-MK351A (a lisinopril derivative) and 125I-ET-1. One month after myocardial infarction, cardiac weight and plasma atrial natriuretic peptide had increased in rats with infarction, compared to sham-operated controls, indicating the presence of chronic left ventricular dysfunction, although exchangeable body sodium and plasma renin activity were unchanged. Cardiac ACE increased markedly in the infarcted area and moderately in hypertrophied myocardium without any change in affinity compared to sham-operated rats. On the other hand, there was no change in cardiac ET-1 receptors in infarcted rats. The same results were found even at 8 months after myocardial infarction. The present study indicates that cardiac ACE may participate in tissue repair at the site of myocardial infarction and may also play a role in the pathophysiology of cardiac hypertrophy in rats with chronic heart failure. However, the present results do not reveal whether ET-1 receptor participates in the pathophysiology of cardiac hypertrophy in this model.

Mortality among benzene-exposed workers in China

A large cohort of 74,828 benzene-exposed and 35,805 nonexposed workers employed between 1972 and 1987 in 12 cities in China was followed to determine mortality from all causes. Benzene-exposed study subjects were employed in a variety of occupations including coating applications, and rubber, chemical, and shoe production. Mortality was slightly increased among workers with greater cumulative exposure to benzene (ptrend < 0.05), but this excess was largely due to cancer deaths (ptrend < 0.01). Deaths due to lymphatic and hematopoietic malignancies (ptrend = 0.01) and lung cancer (ptrend = 0.01) increased with increasing cumulative exposure to benzene. Investigations continue to relate benzene exposure to specific lymphatic and hematopoietic malignancies and other causes of death.