EFFECTS OF ACUTE SUPERIOR CERVICAL GANGLIONECTOMY ON CEREBRAL BLOOD FLOW AND METABOLISM IN STROKE-PRONE SPONTANEOUSLY HYPERTENSIVE RATS SUBJECTED TO CEREBRAL ISCHAEMIA

1. The effects of acute bilateral superior cervical ganglionectomy on cerebral blood flow and metabolism were investigated in stroke-prone spontaneously hypertensive rats (SHRsp), before and during cerebral ischaemia. 2. The resting cerebral blood flow was comparable between the control and denervated animals. 3. There was no significant difference in cerebral blood flow or concentration of tissue energy metabolites (adenosine triphosphate [ATP], lactate and pyruvate) between the sham-operated control and denervated animals during ischaemia. 4. The results suggest that sympathetic innervation of cerebral vessels originating from superior cervical ganglia may not play a major role in the progression of cerebral ischaemia in SHRsp.     

Effect of epidural analgesia on postoperative insulin resistance as evaluated by insulin clamp technique

The influence of epidural neural blockade on postoperative insulin resistance was studied using the euglycaemic insulin clamp technique. Eighteen patients undergoing elective upper abdominal surgery of moderate severity were allocated to two groups: group G patients underwent operation under general anaesthesia, and postoperative pain was relieved by systemic administration of analgesia; and group E patients received epidural analgesia during surgery and epidural morphine postoperatively. In each patient the euglycaemic insulin clamp test was performed twice: several days before surgery and on postoperative day 1. Peroperative catecholamine and cortisol responses were also measured to investigate possible endocrine mechanisms of the insulin resistance. Glucose disposal (M) decreased in both groups on postoperative day 1 at plasma insulin concentrations ranging from 1.2 to 10.0 milliunits ml-1, resulting in the downward shift of dose-response curves. However, this downward shift was significantly smaller in group E than in group G patients. Urinary adrenaline excretion increased markedly on the day of operation in group G, but was significantly inhibited in group E. Urinary noradrenaline excretion increased mainly on postoperative day 1 in group G, but was significantly inhibited in group E. Plasma cortisol response was lower in group E than in group G during and shortly after operation, and was significantly inhibited in group E on postoperative day 1. These results indicate that insulin resistance after elective abdominal surgery is due to a postreceptor deficit in glucose utilization, as indicated by the downward shift of the dose-response curves. This disturbance in glucose metabolism was reduced by epidural analgesia, the results being associated with inhibited catecholamine and cortisol responses.     

Neurotoxicity of Clostridium perfringens Epsilon-Toxin for the Rat Hippocampus via the Glutamatergic System

The neurotoxicity of epsilon-toxin, one of the major lethal toxins produced by Clostridium perfringens type B, was studied by histological examination of the rat brain. When the toxin was injected intravenously at a lethal dose (100 ng/kg), neuronal damage was observed in many areas of the brain. Injection of the toxin at a sublethal dose (50 ng/kg) caused neuronal damage predominantly in the hippocampus: pyramidal cells in the hippocampus showed marked shrinkage and karyopyknosis, or so-called dark cells. The dark cells lost the immunoreactivity to microtubule-associated protein-2, a postsynaptic somal and dendric marker, while acetylcholinesterase-positive fibers were not affected. Timm’s zinc staining revealed that zinc ions were depleted in the mossy layers of the CA3 subfield containing glutamate as a synaptic transmitter. The cerebral blood flow in the hippocampus was not altered significantly before or after administration of the toxin, as measured by laser-Doppler flowmetry, excluding the possibility that the observed histological change was due to a secondary effect of ischemia in the hippocampus. Prior injection of either a glutamate release inhibitor or a glutamate receptor antagonist protected the hippocampus from the neuronal damage caused by epsilon-toxin. These results suggest that epsilon-toxin acts on the glutamatergic system and evokes excessive release of glutamate, leading to neuronal damage.     

In vitro early changes in intercellular junctions by treatment with a chemical carcinogen

To examine early intercellular junction changes caused by treatmentwith 9, 10-dimethyl-l, 2-benzanthracene (DMBA), rat lingualepithelium was cultivated in isolation and observed by electrophysiological,freeze-fracture and whole-mount electron microscopy. Electrophysiologicalmeasurements showed a transient decrease in membrane potentialof -10.2 mV 6 h after the treatment. It returned to almost thesame level as that of the control group 1 day later. Six hoursafter treatment, input resistance decreased rapidly to 5.3 Mbut increased to 18.0 M 12 h after treatment. Transient reductionof input resistance and membrane potential occurred prior tothe decrease in the coupling ratio 6 h after treatment withDMBA. In freeze-fracture replicas, the number of gap junctionsdecreased by 45% of the control value 6 h after treatment withDMBA. At 12 h and thereafter, the number and area of gap junctionssubsequently decreased by 60–80% of the control value.Alterations in the number and area of desmosomes were similarto those of the gap junctions. The formation of epithelial cytoskeletons,partially devoid of the 2–4 and 5–8 nm filamentswas also observed. A decrease in the density of filament networksbeneath the plasma membranes was especially apparent. Treatmentwith a carcinogen brought about morphological cellular changesas early as 6 h after treatment, and such early changes mighttrigger metabolic cellular abnormalities. Affected cells appearto move away from normal cells in a process of repeated destructionand revision of intercellular junctions, and cytoskeletons.     

Role of Ca2+-activated K+ channels in acetylcholine-induced dilatation of the basilar artery in vivo

1. We tested the hypothesis that activation of large conductance calcium-activated potassium channels is involved in dilator responses of the basilar artery to acetylcholine in vivo. Using a cranial window in anaesthetized rats, we examined responses of the basilar artery to acetylcholine.
2. Topical application of acetylcholine (10⁻⁶ and 10⁻⁵ M) increased diameter of the basilar artery from 238±7 μm to 268±7 and 288±7 μm, respectively (P<0.05 vs. baseline diameter). Iberiotoxin (10⁻⁸ M), an inhibitor of large conductance calcium-activated potassium channels, did not affect baseline diameter of the basilar artery. In the presence of 10⁻⁸ M iberiotoxin, 10⁻⁶ and 10⁻⁵ M acetylcholine increased diameter of the basilar artery from 239±7 μm to 246±7 and 261±7 μm, respectively. Thus, iberiotoxin attenuated acetylcholine-induced dilatation of the basilar artery (P<0.05).
3. Sodium nitroprusside (10⁻⁷ and 10⁻⁶ M) increased diameter of the basilar artery from 242±9 μm to 310±12 and 374±13 μm, respectively (P<0.05 vs. baseline diameter). In the presence of iberiotoxin (10⁻⁸ M), sodium nitroprusside (10⁻⁷ and 10⁻⁶ M) increased diameter of the basilar artery from 243±6 μm to 259±9 and 311±12 μm, respectively. Thus, iberiotoxin attenuated dilator responses of the basilar artery to sodium nitroprusside (P<0.05).
4. Iberiotoxin partly inhibited dilator responses of the basilar artery to forskolin, a direct activator of adenylate cyclase, but did not affect vasodilatation produced by levcromakalim, a potassium channel opener.
5. These results suggest that dilator responses of the basilar artery to acetylcholine and sodium nitroprusside are mediated, in part, by activation of large conductance calcium-activated potassium channels. Because both acetylcholine and sodium nitroprusside have been shown to activate guanylate cyclase via nitric oxide, activation of large conductance calcium-activated potassium channels may be one of the major mechanisms by which cyclic GMP causes dilatation of the basilar artery in vivo.

     

Epstein-Barr virus-associated gastric carcinoma： Evidence of age-dependence among a Mexican population

AIM: To investigate features of Epstein-Barr virus (EBV)-associated gastric carcinoma (EBVaGC) among a Mexican population. METHODS: Cases of primary gastric adenocarcinoma were retrieved from the files of the Departments of Pathology at the Instituto Nacional de Cancerologia and the Instituto Nacional de la Nutricion in Mexico City. The anatomic site of the gastric neoplasia was identified, and carcinomas were histologically classified as intestinal and diffuse types and subclassified as proposed by the Japanese Research Society for Gastric Cancer. EBV-encoded small non-polyadenylated RNA-1 (EBER-1) in situ hybridization was conducted to determine the presence of EBV in neoplastic cells. RESULTS: We studied 330 consecutive, non-selected, primary gastric carcinomas. Among these, there were 173 male and 157 female patients (male/female ratio 1.1/1). EBER-1 was detected in 24 (7.3%) cases (male/female ratio: 1.2/1). The mean age for the entire group was 58.1 years (range: 20-88 years), whereas the mean age for patients harboring EBER-1-positive gastric carcinomas was 65.3 years (range: 50-84 years). Age and histological type showed statistically significant differences, when EBER-1-positive and -negative gastric carcinomas were compared. EBER-1 was detected in hyperplastic- and dysplastic-gastric mucosa surrounding two EBER-1-negative carcinomas, respectively. CONCLUSION: Among Latin-American countries, Mexico has the lowest frequency of EBVaGC. Indeed, the Mexican population >50 years of age was selectively affected. Ethnic variations are responsible for the epidemiologic behavior of EBVaGC among the worldwide population.