[Influence of nitric oxide synthetase inhibitor on the blood pressure action of clonidine in rats]

We are investigating the influence of NO synthetase inhibitor on the clonidine-induced cardiovascular actions in urethane-anesthetized rats. The systemic blood pressure was measured from right femoral artery, heart rate from the pressure pulse under inhalation of O2. Nw-nitro-L-arginine-methylester (L-NAME, 5 mg/kg), NO synthetase inhibitor, administered intravenously increased blood pressure slightly, although decreased heart rate. The responses to L-NAME were stable about 10 min after the injection. Clonidine (5 mg/kg) administered intravenously indicated the transient increase blood pressure and following continuous decrease of blood pressure. The early transient hypertension of clonidine was potentiated by pretreatment with L-NAME and later continuous hypotension was markedly inhibited. While, the early transient hypertension of clonidine was inhibited by pretreatment with L-arginine and later continuous hypotension was potentiated. The hypertension and tachycardia of intravenous tyramine was enhanced by L-NAME. Clonidine administered into the cerebroventricle did not indicate the early transient hypertension, though produced the later continuous hypotension. These results suggest that L-NAME modifies the cardiovascular responses to clonidine and NO may participate in the modulation.

Mode of action of (1'S,2'R)-9-[[1',2'-bis(hydroxymethyl) cycloprop-1'-yl]methyl]guanine (A-5021) against herpes simplex virus type 1 and type 2 and varicella-zoster virus

The mode of action of (1'S,2'R)-9-([1', 2'-bis(hydroxymethyl)cycloprop-1'-yl]methyl)guanine (A-5021) against herpes simplex virus type 1 (HSV-1), HSV-2, and varicella-zoster virus (VZV) was studied. A-5021 was monophosphorylated at the 2' site by viral thymidine kinases (TKs). The 50% inhibitory values for thymidine phosphorylation of A-5021 by HSV-1 TK and HSV-2 TK were comparable to those for penciclovir (PCV) and lower than those for acyclovir (ACV). Of these three agents, A-5021 inhibited VZV TK most efficiently. A-5021 was phosphorylated to a mono-, di-, and triphosphate in MRC-5 cells infected with HSV-1, HSV-2, and VZV. A-5021 triphosphate accumulated more than ACV triphosphate but less than PCV triphosphate in MRC-5 cells infected with HSV-1 or VZV, whereas HSV-2-infected MRC-5 cells had comparable levels of A-5021 and ACV triphosphates. The intracellular half-life of A-5021 triphosphate was considerably longer than that of ACV triphosphate and shorter than that of PCV triphosphate. A-5021 triphosphate competitively inhibited HSV DNA polymerases with respect to dGTP. Inhibition was strongest with ACV triphosphate, followed by A-5021 triphosphate and then (R,S)-PCV triphosphate. A DNA chain elongation experiment revealed that A-5021 triphosphate was incorporated into DNA instead of dGTP and terminated elongation, although limited chain extension was observed. Thus, the strong antiviral activity of A-5021 appears to depend on a more rapid and stable accumulation of its triphosphate in infected cells than that of ACV and on stronger inhibition of viral DNA polymerase by its triphosphate than that of PCV.

Antiherpesvirus activities of (1'S,2'R)-9-[[1',2'-bis(hydroxymethyl)cycloprop-1'-yl]methyl]guanine (A-5021) in cell culture

Antiherpetic activity of (1'S,2'R)-9-([1',2'-bis(hydroxymethyl)cycloprop-1'yl]methyl)guanine (A-5021) was compared with those of acyclovir (ACV) and penciclovir (PCV) in cell cultures. In a plaque reduction assay using a selection of human cells, A-5021 showed the most potent activity in all cells. Against clinical isolates of herpes simplex virus type 1 (HSV-1, n = 5) and type 2 (HSV-2, n = 6), mean 50% inhibitory concentrations (IC50s) for A-5021 were 0.013 and 0.15 microgram/ml, respectively, in MRC-5 cells. Corresponding IC50s for ACV were 0.22 and 0.30 microgram/ml, and those for PCV were 0.84 and 1.5 micrograms/ml, respectively. Against clinical isolates of varicella-zoster virus (VZV, n = 5), mean IC50s for A-5021, ACV, and PCV were 0.77, 5.2, and 14 micrograms/ml, respectively, in human embryonic lung (HEL) cells. A-5021 showed considerably more prolonged antiviral activity than ACV when infected cells were treated for a short time. The selectivity index, the ratio of 50% cytotoxic concentration to IC50, of A-5021 was superior to those of ACV and PCV for HSV-1 and almost comparable for HSV-2 and VZV. In a growth inhibition assay of murine granulocyte-macrophage progenitor cells, A-5021 showed the least inhibitory effect of the three compounds. These results show that A-5021 is a potent and selective antiviral agent against HSV-1, HSV-2, and VZV.

Synthesis and pharmacological activities of 13-dehydro derivatives of primary prostaglandins

13-Dehydro derivatives of prostaglandin E1, E2, E3, F1 alpha and F2 alpha were synthesized. Compared with natural prostaglandins, 13-dehydro analogues were found to exhibit more potent inhibitory activity against human platelet aggregation and relaxation of guinea-pig isolated trachea, while they showed less potent activity of contraction of guinea-pig isolated ileum.

Effect of interleukin 1 beta-induced fever on hepatic drug metabolism in rat

1. A fever-induced model in rat was created by repeated injection of interleukin 1 beta (IL-1 beta) in the cerebroventricle and the influence of fever on hepatic drug metabolism was investigated. Fever apparently decreased the content of cytochrome P450 (CYP) and the activities of NADPH-ferrihaemoprotein reductase (fp2), aminopyrine N-demethylase, aniline hydroxylase, FAD-monooxygenase, p-nitrophenol UDP-glucuronosyl-transferase and glutathione S-transferase. Immunoblot analysis of the CYP isozymes indicated that CYP2C11 and CYP3A were extensively decreased in the IL-1 beta-induced fevered rat. 2. Repeated administration (5 days) of mefenamic acid in the fevered rat could not restore the activities of fp2, aminopyrine N-demethylase and aniline hydroxylase to control levels, although their hyperthermic state had been improved. The CYP content in the mefenamic acid-treated fevered rat was also lower than that in the control. 3. These findings suggest that fever impairs the hepatic drug-metabolizing capacity (both oxidation and some conjugations) and that the fever-induced impairments are partially retained, even if the hyperthermia has been offset by the administration of antipyretics.

[Acute mediastinitis due to esophageal perforation--a case report]

A 55-year-old female consulted her family physician because of pharyngeal discomfort after eating a fish. She underwent rigid fiberscopy and was pointed out a fish bone. Family physician failed to extract the bone and the patient was referred to our hospital. However, there was no fish bone in the esophagus when she underwent second rigid fiberscopy. After eight days she complained of dyspnea and was referred to our hospital again. Chest X ray film showed marked enlargement of the mediastinum and she was diagnosed as acute mediastinitis. She underwent mediastinal drainage by thoracotomy. So tiny perforation was found in cervical esophagus by endoscopy that primary suture was not done. After two months' follow up with intravenous hyperalimentation, there was still esophageal perforation. She underwent the second operation of primary closure with reinforcement using sternocleidomastoid muscle. Two weeks after the second operation esophagogram still showed a fistula. So she received injections of alprostadil and factor XIII. One month after the injections esophagogram showed a diverticulum without leakage.

Synthesis and antiviral activity of novel acyclic nucleosides: discovery of a cyclopropyl nucleoside with potent inhibitory activity against herpesviruses

A series of acyclic nucleosides with two hydroxymethyl groups mimicking the 3'- and 5'-hydroxyl groups of the 2'-deoxyribose moiety were prepared and evaluated for their antiherpetic activity. Among those, 9-[[cis-1', 2'-bis(hydroxymethyl)cycloprop-1'-yl]methyl]guanine (3) showed extremely potent antiviral activity against herpes simplex virus type-1 (HSV-1) with good selectivity. Both enantiomers of 3 were synthesized starting from chiral epichlorohydrins, and only one of the enantiomers with 1'S,2'R-configuration (3a) exhibited strong antiherpetic activity (IC50 of 0.020 microg/mL against HSV-1 Tomioka vs 0.81 microg/mL for acyclovir). Enantiomer 3a was also more inhibitory than acyclovir against varicella-zoster virus (VZV) but ineffective against human immunodeficiency virus (HIV). Compound 3a is phosphorylated by HSV-1 thymidine kinase (TK) very efficiently. The relationship between conformation and antiherpetic activity in this series of compounds is discussed.

Assessment of malignancy of glioma by positron emission tomography with 18F-fluorodeoxyglucose and single photon emission computed tomography with thallium-201 chloride

The histological diagnosis and proliferative potential measured by bromodeoxyuridine (BrdU) labelling index (LI) were correlated with preoperative CT and contrast-enhanced, MRI, 18F-fluorodeoxyglucose positron emission tomography (PET) and 201T1 single photon emission computed tomography (SPECT) in 43 patients with various grades of glioma. 201T1 SPECT had slightly higher sensitivity to tumours with BrdU LI > or = 5% (showing 10/10) than 18F-FDG PET (7/8 tumours). 18F-FDG PET was better for identifying tumours of BrdU LI < 1% (13/15) than 201T1 SPECT (13/22). Accumulation of 201T1 in the tumour was slightly different from contrast enhancement on CT and/or MRI, and gave "false-positive" results in some low-grade gliomas. However, 201T1 SPECT, which is available in many hospitals and may cost less, provided useful information to supplement that from CT and MRI.

[The diagnosis of the early stage of hepatocellular carcinoma by US-angiography with intraarterial Albunex (sonicated serum albumin) infusion]

Contrast-enhanced ultrasonography (arterial infusion) has been clinically established as a qualitative diagnosis imaging tool for hepatocellular carcinoma (HCC). Contrast-enhanced ultrasonography (CEUS) was performed after of Albunex (sonicated serum albumin) or Carbon Dioxide (CO2) microbubble by hand, into the hepatic artery as a diagnostic modality for the early HCC. Here, we discussed the diagnosis of the early HCC by CEUS using Albunex as a contrast medium. Briefly, a diagnosis of the early HCC was made CEUS examination of the hemodynamics of the arteries showed a hypovascular pattern. And tumor size was under 20 mm in diameter, the histopathologic examination was essential to reach a final diagnosis, well-differentiated HCC.

Inflammatory pseudotumor of the liver--MR imaging findings

Using retrospective studies, we have investigated the possibility of obtaining characteristic findings of inflammatory pseudotumor of the liver by magnetic resonance (MR) imaging. We examined 8 patients (involving 8 masses) who had been histologically diagnosed as having an inflammatory pseudotumor in the liver. The histological studies were performed on an excised specimen of 1 mass, and on aspiration needle biopsy specimens and the clinical courses of the other 7 masses. T1 weighted images (T1WI) and T2 weighted images (T2WI) were obtained on MR imaging. MR imagings were analyzed for visualized patterns, patterns of internal structure and patterns of contrast enhancement of dynamic MR imaging. The 8 masses were visualized as hypointense on T1WI and hyperintense on T2WI by MR imaging. Dynamic MR imaging revealed that 1 mass was markedly enhanced peripherally while another mass was homogeneously enhanced, and that enhancement was most marked immediately after injection of contrast medium and then gradually disappeared. Vessels were observed in 4 masses (the portal vein in 2 masses, the hepatic vein in 1 mass, and portal and hepatic veins in 1 mass), and these vessels were clearly visualized on T1WI. The MR imaging findings from the early stage of an inflammatory pseudotumor showed a pattern similar to that of hepatic tumors with rich blood flow. The portal vein or hepatic vein was found in the tumor in half the patients, suggesting that this characteristic was useful for diagnosis of an inflammatory pseudotumor in the liver.

A nitric oxide donor NOC 7 suppresses renal responses induced by norepinephrine and angiotensin II in the NO-depleted denevated rabbit kidney

Intrarenal arterial infusion of norepinephrine (30 ng/kg per min) or of angiotensin II (4 ng/kg per min) reduced the glomerular filtration rate and urinary Na+ excretion in denervated kidneys of anesthetized rabbits pretreated intrarenally with a nitric oxide (NO) synthase inhibitor N(omega)-nitro-L-arginine methyl ester (50 microg/kg per min). Angiotensin II but not norepinephrine reduced fractional Na+ excretion. Intrarenal administration of a spontaneous NO donor 1-hydroxy-2-oxo-3-(N-methyl-3-aminopropyl)-3-methyl-1-triazene (NOC 7, 30 ng/kg per min) in L-NAME pretreated kidneys did not affect basal values, but attenuated the reduction in urinary Na+ excretion induced by these agonists without affecting the angiotensin II-induced reduction in glomerular filtration rate. The results suggest that NOC 7 can suppress the norepinephrine-induced hypofiltration and the angiotensin II-evoked tubular reabsorption and thereby attenuates the agonist-induced antinatriuresis in the denervated and endogenous NO-depleted rabbit kidney.

Boards of directors under fire: an examination of nonprofit board duties in the health care environment

Attorney Ono presents a detailed discussion of fiduciary duty principles as applied to the directors of nonprofit health care corporations in the current health care environment. The article reviews general corporate responsibilities, the implication of the taxpayer's Bill of Rights 2, the care of In re Caremark International Inc. Derivative Litigation and particular issues faced by boards in nonprofit conversions.

Surgical management of Mycobacterium avium complex disease

Between July 1991 and October 1996, eight patients with Mycobacterium avium complex (MAC) underwent pulmonary resection in our department. There was equal distribution of men women. The length of the preoperative period averaged 8.1 months (range: 1 to 30 months). Surgical resection was complete, consisting of lobectomy in 4 patients, lobectomy with partial resection in 2, segmentectomy in 1, and segmentectomy with partial resection in 1. There were no major complications postoperatively. No patients had positive sputum culture with MAC just after operation; however, one patient had positive sputum culture 6 months after operation. Our results show the good outcome of resectional surgery for MAC in properly selected patients, who should be operated as early as possible.

[Significance of rectal contractions during multichannel urodynamic study]

BACKGROUND

The influence of rectal contractions on urination was examined using multichannel urodynamic study.

METHODS

We reviewed a total of 246 consecutive urodynamic studies. Each study consisted of a uroflow measurement and multi-channel urodynamic study, evaluating total vesical pressure, abdominal (rectal) pressure, subtracted detrusor pressure and perianal electromyography. Rectal contractions were defined as periodic fluctuations over 5 cmH2O in abdominal pressure detected by a rectal balloon catheter. No relationship of these contractions with cough and breathing was observed.

RESULTS

Of the 246 patients, 17 (6.9%) had a positive study for rectal contractions. The patients, who had positive rectal contractions, averaged 70-year-old were older than negative subjects averaged 62-year-old. In multichannel urodynamics, the flow rate was significantly decreased, and electromyographic activity was increased at the moment of each rectal contractions.

CONCLUSIONS

The rectal contractions are not artifactual and may be regarded as one of causes responsible for urinary difficulty in the elderly.

Evaluation of magnetic resonance angiography on portosystemic collaterals in cirrhotic patients

OBJECTIVE

We examined the usefulness of imaging portosystemic collaterals accompanying liver cirrhosis by magnetic resonance angiography (MRA), which facilitates imaging of the vascular system without contrast medium.

METHODS

MRA was performed in 30 patients with liver cirrhosis. Of the 30 patients, percutaneous transhepatic portography (PTP) was performed in 10 patients, and conventional arterial portography (CAP) was performed in 20 patients. The three-dimensional (3D) phase contrast method was used for MRA. Study 1: The ability to image portosystemic collaterals was compared between PTP or CAP and MRA. Study 2: The usefulness of MRA for evaluating the effect of treatment on gastric and esophageal varices was examined.

RESULTS

Study 1: In comparing PTP and MRA (n = 10), the left gastric vein (n = 10), splenorenal (gastrorenal) shunt (n = 5), and paraumbilical vein (n = 2) were imaged similarly. However, MRA did not reveal any esophageal varices (n = 10). In comparing CAP and MRA (n = 20), the left gastric vein (n = 17), splenorenal (gastrorenal) shunt (n = 10), and paraumbilical vein (n = 4) were imaged similarly. Whereas CAP revealed esophageal varices (n = 4) in four patients, MRA revealed esophageal varices in only one patient. Study 2: When the effect of treatment for varices was evaluated, MRA 3 wk after embolization therapy for gastric varices (n = 4) confirmed the disappearance of gastrorenal shunt. However, it was impossible to evaluate esophageal varices by MRA.

CONCLUSIONS

It was possible to image portosystemic collaterals accompanying liver cirrhosis by MRA. MRA was useful as a routine examination. Furthermore, it was useful for evaluating the effect of embolization therapy on gastric varices.

Repeated elicitation of contact hypersensitivity induces a shift in cutaneous cytokine milieu from a T helper cell type 1 to a T helper cell type 2 profile

We previously demonstrated that repeated application of 2,4,6-trinitro-1-chlorobenzene resulted in a site-restricted shift in the time course of Ag-specific hypersensitivity responses from a typical delayed-type to an early-type response. Here we demonstrated that the cutaneous microenvironment at the time of Ag presentation to T cells in the elicitation, but not the induction, phase of contact hypersensitivity is responsible for the shift. To investigate the differences in the cutaneous cytokine milieu between the acute and chronic phases of contact hypersensitivity, sequential cytokine dynamics after 2,4,6-trinitro-1-chlorobenzene application were assessed in the acute vs chronic lesions. In the acute lesions, increased mRNA levels for IFN-gamma and IL-2 were rapidly detected at 1 h and remained elevated at 12 h, while mRNA expression for IL-4 and IL-10 was minimally up-regulated between approximately 12 and 24 h. In chronic lesions, high levels of constitutive expression of IL-4 mRNA were observed and IL-10 mRNA was dramatically up-regulated at 1 approximately 3 h in an Ag-specific fashion, whereas the expression of Th1-type cytokines was markedly reduced. Increased mRNA levels for Th2-type cytokines in the chronic lesions was also reflected at the protein level. These results indicate that repeated elicitation with Ag alters the balance of cytokines released locally, with a shift toward Th2-dominated responses, which would represent the natural evolution processes directed toward reducing a more deleterious Th1 response.

Repeated elicitation of contact hypersensitivity induces a shift in cutaneous cytokine milieu from a T helper cell type 1 to a T helper cell type 2 profile

We previously demonstrated that repeated application of 2,4,6-trinitro-1-chlorobenzene resulted in a site-restricted shift in the time course of Ag-specific hypersensitivity responses from a typical delayed-type to an early-type response. Here we demonstrated that the cutaneous microenvironment at the time of Ag presentation to T cells in the elicitation, but not the induction, phase of contact hypersensitivity is responsible for the shift. To investigate the differences in the cutaneous cytokine milieu between the acute and chronic phases of contact hypersensitivity, sequential cytokine dynamics after 2,4,6-trinitro-1-chlorobenzene application were assessed in the acute vs chronic lesions. In the acute lesions, increased mRNA levels for IFN-gamma and IL-2 were rapidly detected at 1 h and remained elevated at 12 h, while mRNA expression for IL-4 and IL-10 was minimally up-regulated between approximately 12 and 24 h. In chronic lesions, high levels of constitutive expression of IL-4 mRNA were observed and IL-10 mRNA was dramatically up-regulated at 1 approximately 3 h in an Ag-specific fashion, whereas the expression of Th1-type cytokines was markedly reduced. Increased mRNA levels for Th2-type cytokines in the chronic lesions was also reflected at the protein level. These results indicate that repeated elicitation with Ag alters the balance of cytokines released locally, with a shift toward Th2-dominated responses, which would represent the natural evolution processes directed toward reducing a more deleterious Th1 response.

Requirements of DFR1/Heartless, a mesoderm-specific Drosophila FGF-receptor, for the formation of heart, visceral and somatic muscles, and ensheathing of longitudinal axon tracts in CNS

DFR1 encodes a mesoderm-specific fibroblast growth factor receptor in Drosophila. Here, we identified and characterized a protein-null mutant of DFR1 and examined DFR1 expression in embryos using anti-DFR1 antibody. Mutant phenotypes were completely rescued by a genomic fragment from the DFR1 locus. After invagination, mesodermal cells expressing DFR1 undergo proliferation and spread out dorsally to form a monolayer beneath the ectoderm. In mutant embryos, however, the mesoderm is not capable of extending to the normal dorsal limit and consequently mesodermal cells fail to receive ectodermal signals and thus rendered incapable of differentiating into primordia for the heart, visceral and somatic muscles. DFR1 is also required for normal development of the central nervous system. The absence of DFR1 resulted in the failure of longitudinal glia to enwrap longitudinal axon tracts. DFR1 mutant phenotypes were partially mimicked by the targeted expression of activated Yan, thus demonstrating the MAP kinase pathway to be involved in differentiation of mesoderm.

Basal interhemispheric supra- and/or infrachiasmal approaches via superomedial orbitotomy for hypothalamic lesions: preservation of hypothalamo-pituitary functions in combination treatment with radiosurgery

Although several approaches to the hypothalamus have been used, none is able to give full views of the hypothalamus. The risk of permanent morbidity for hypothalamo-pituitary functions is still high, especially in patients with craniopharyngioma. Basal interhemispheric supra-chiasmal or infra-chiasmal approaches via superomedial orbitotomy were developed for better visualization of the hypothalamus. Operative techniques and results, including combination treatment with radiosurgery, are reported. Twelve patients with tumors compressing the hypothalamus upward or extending into the III ventricle, or both, were operated on: 3 tumors were removed totally, 6 tumors subtotally and 3 tumors partially. Six patients received radiosurgery for residual tumor. Four patients with hypopituitarism preoperatively required oral corticosteroids and thyroid hormones postoperatively. The basal interhemispheric approach via superomedial orbitotomy is useful for better visualization of the hypothalamus and preservation of hypothalamo-pituitary functions.

Renal effects of a nitric oxide donor, NOC 7, in anesthetized rabbits

Intrarenal arterial infusion of angiotensin II (4 ng/kg per min) reduced glomerular filtration rate and urinary Na+ excretion without affecting fractional Na+ excretion. Infusion of norepinephrine (30 ng/kg per min) reduced both urinary Na+ excretion and fractional Na+ excretion with a slight hypofiltration. The angiotensin II- and the norepinephrine-induced renal responses were suppressed during simultaneous infusion of a spontaneous nitric oxide donor 1-hydroxy-2-oxo-3-(N-methyl-3-aminopropyl)-3-methyl 1-triazene (NOC 7, 30 ng/kg per min) which itself had little influence on the renal parameters. The results suggest that in the rabbit kidney in vivo NOC 7 can interfere with the angiotensin II-induced hypofiltration and norepinephrine-evoked tubular reabsorption and thereby suppresses their antinatriuretic actions.

An unusual variant of ependymoma with extensive tumor cell vacuolization

We report a case of ependymoma with unusual vacuolar features arising in the left occipital lobe of a 2-year-old child. The tumor was composed of cells with single or multiple cytoplasmic vacuoles and clear cells. Some cells showed a signet ring-like configuration. Clear cells were compactly arranged and showed an oligodendro-glioma-like appearance. In addition, there were cellular ependymoma-like areas including perivascular pseudorosettes. On immunohistochemistry, glial fibrillary acidic protein and vimentin were mainly detected in cytoplasmic processes, and epithelial membrane antigen (EMA) staining showed granular and small vesicular reactivity. Ultrastructural investigation demonstrated intercellular microrosettes with or without cilia and long zonula adherens-type junctions that are typical of ependymoma. Furthermore, many intracytoplasmic lumina (ICL) were observed. Some ICL had microvilli and some did not. The latter varied in size, and may have fused with each other to develop giant ICL which could correspond to the signet ring-like configuration. Small ICL without microvilli had an appearance similar to that of distended endoplasmic reticula. Serial semithin and ultrathin sections revealed that EMA-positive structures were consistent with ICL containing microvilli and intercellular microrosettes. To determine the presence of unusual vacuolated ependymoma, electron microscopical examination was required. However, light microscopy was useful for detecting EMA-positive microvesicular and granular structures.

Three cases of renal angiomyolipoma

We report three non-typical cases of renal angiomyolipoma including clinical features, imaging examinations (with ultrasonography, computed tomography (CT), magnetic resonance imaging (MRI) and angiography) and histological findings. Microaneurysms observed by angiography were common to the three cases and were considered to be an important finding in the diagnosis of renal angiomyolipoma. Moreover, the short tau inversion recovery (STIR) method of MRI, which suppresses photon signals of fat, was considered to be useful for the diagnosis. Case 1 was accompanied by spontaneous rupture, Case 2 was difficult to diagnose because of little fat tissue and Case 3 revealed a very small tumor.

Effects of intrathecal nonnarcotic analgesics on chronic tactile allodynia in rats: alpha 2-agonists versus somatostatin analog

The effects of the intrathecal alpha 2-agonists tizanidine and clonidine and the somatostatin analog octreotide on an experimental rat model of tactile allodynia were investigated to determine the therapeutic potential for treating chronic neuropathic pain. Allodynia was induced by ligating the rat sciatic nerve. The mechanical threshold for paw withdrawal was assessed by applying von Frey hairs to quantify analgesic actions. Mean 50% paw withdrawal thresholds were converted to the percentage of maximum possible effect (%MPE) where %MPE = (postdrug threshold-predrug threshold) divided by (15 g-predrug threshold) x 100. Dose-response curves were plotted for suppression of paw withdrawal 30 minutes after intrathecal injection of various doses of tizanidine, clonidine, and octreotide. Thresholds on the non-lesioned side were greater than 15 g. The lesioned side had baseline thresholds of less than 4.5 g. Dose-response curves were established for the antiallodynia effects of each drug. Tizanidine and clonidine at a 25-micrograms dose increased the threshold to greater than 97% of the MPE, but caused transient hindpaw weakness or sedation. No side effect was observed at a 10-micrograms dose, at which the threshold was 88-96% of MPE. Intrathecal octreotide modestly increased the threshold to only 49-67% of MPE, showing a lesser analgesic effect, although no side effect was observed at a 4-micrograms dose. The antiallodynic effects of intrathecal tizanidine and clonidine were more potent than that of octreotide.

A theoretical integration of Cambrian explosion and post-Permian quiescence

Trophic dynamics is internally causative. Each trophic level is causative in initiating changes in trophic flow either as a supplier towards the upper level or as a consumer towards the lower. Resource presentation followed by its subsequent exploitation makes suppliers causative, while resource exploitation followed by its subsequent presentation makes consumers causative. Trophic dynamics of supplier domination gradually alternates with that of consumer domination while being punctuated by occasional mass extinctions due to depletion of the resources towards the lowest trophic level. The Cambrian explosion could be associated with trophic dynamics of supplier domination, whereas the post-Permian quiescence with that of consumer influencing supplier domination.

Interplay of causation between suppliers and consumers in evolutionary trophic dynamics

Natural selection, conceived as the process of small causes making small effects on the level of molecular evolutionary dynamics of a population, can yield global effects on the level of evolutionary trophic dynamics of populations, including those of mass extinctions. Occurrence of mass extinctions is due to the interplay of causation between suppliers and consumers in trophic dynamics. If the case of supplier causation is available such that resource exploitation by consumers on the upper trophic level follows in time resource presentation by suppliers on the lower, instead of resource exploitation followed by resource presentation, mass extinctions could be a norm of the evolutionary trophic dynamics.

Ubiquity of omnivores in natural ecosystems

Evolutionary ubiquity of omnivores in natural food webs derives from the measurement dynamics of intra and inter trophic levels. It is recognized that inter-level communication for the maintenance of energy flow continuity takes longer than intra-level communication does. Although the collapse of food webs due to depletion of the lower levels is inevitable according to the measurement dynamics; participation of omnivores could extend the evolutionary durability of the food webs.

Effects of tri-, di- and monobutyltin on synaptic parameters of the cholinergic system in the cerebral cortex of mice

Triorganotin compounds like tributyltin have been reported to be biodegraded to diorganotin, monoorganotin and then inorganic tin in animals after they have been ingested. Effects of tributyltin, dibutyltin and monobutyltin on various cholinergic parameters that are involved in synaptic transmission in the mouse cerebral cortex were investigated in vitro. Tributyltin and dibutyltin, but not monobutyltin, inhibited the activity of choline acetyltransferase, both the high-affinity and low-affinity uptakes of choline into synaptosomes, and the binding of [3H]quinuclidinyl benzilate to muscarinic acetylcholine receptors. Tributyltin and dibutyltin, but not monobutyltin, had a slightly suppressive effect on the K(+)-induced release and synthesis of acetylcholine in slices of the cortex. All three butyltins at concentrations from 10(-6) to 10(-4) M had no effect on the activity of acetylcholinesterase. The extent of the inhibitory effects on the cholinergic parameters, apart from the activity of acetylcholinesterase, was slightly greater in the case of tributyltin than dibutyltin, in particularly at the highest concentration (10(-4) M) tested. Therefore, it is concluded that tributyltin metabolites inhibit various parameters of cholinergic activity with a potency ranking of tributyltin > dibutyltin > monobutyltin.

Intercostal hemangioma

Chest wall tumors are uncommon and there have been only a few reports of intercostal hemangioma during the past 20 years. We treated a 33-year-old man who presented with intercostal hemangioma. We resected tumor and surrounding muscles beyond the limits of the lesion without removing any bone or lung tissue. The patient is free of any recurrence 3 years after surgery.

Effects of some calcium-related agents on the protoplast transfection of Lactobacillus casei with phage PL-1 DNA

To clarify the mechanism of Ca2+ involvement in the DNA transfer through cell membrane, we studied the effects of Ca2+-chelator, Ca2+-ionophore, and Ca2+-channel blocker on the protoplast transfection of Lactobacillus casei ATCC 27092 by PL-1 phage DNA in the presence of Ca2+. Ca2+-chelators, citrate, EDTA, and dipicolinic acid, inhibited the transfection probably by compensating the effect of Ca2+. Ca2+-ionophores, A23187 and N,N,N', N'-tetracyclohexyl-3-oxapentanediamide, which were expected to accelerate transfection by introducing Ca2+ into cells, inhibited the transfection. This fact indicated the absence of correlation between the entry of Ca2+ and the transport of DNA into protoplasts. Verapamil, which blocks voltage-dependent Ca2+-channel besides beta-adrenergic receptor, inhibited the transfection with little effect on the survival of the protoplasts. Both flunarizine and vinpocetine, voltage-dependent Ca2+-channel blockers, did not show the selective toxicity. D-alpha-Aminoadipic acid, a glutamate receptor-operated Ca2+-channel blocker, had no effect. Propranolol, which blocks beta-adrenergic receptor as does verapamil, inhibited the transfection without severely damaging the protoplasts. These results suggested that a kind of receptor-operated Ca2+-channel was involved in the transport of PL-1 phage DNA into the cells and that the cell membrane might have a receptor structure somewhat similar to the beta-adrenergic receptor found in mammalian cells.

CD19 regulates B lymphocyte signaling thresholds critical for the development of B-1 lineage cells and autoimmunity

CD19 serves as a cell surface response regulator that establishes signaling thresholds critical for B lymphocyte development and activation. B lymphocytes from CD19-deficient mice are hyporesponsive to transmembrane signals, while B lymphocytes from mice that overexpress CD19 to even a small extent (25% increase) become hyperresponsive. The B-1 subpopulation of B lymphocytes is particularly sensitive to CD19 regulation, since their development is severely decreased in CD19-deficient mice. The effect of altered CD19 expression levels on the development of B cells was therefore examined using transgenic mice that express varying levels of cell surface CD19. In this study, immature B cells within the bone marrow of wild-type mice were found to specifically up-regulate CD19 expression levels by twofold as they mature, while CD5+ B cells within the spleen and peritoneum expressed even higher levels of CD19. The development of CD5+ B cells was severely decreased in CD19-deficient mice, while there was a linear correlation between increased CD19 expression levels and the increased frequency of CD5+ B cells within the peritoneum and spleen. In fact, CD5+ B cells became a major B lymphocyte population in mice that overexpressed CD19. Increased expression of CD19 also correlated with increased levels of endogenous anti-DNA Abs and rheumatoid factor. These results indicate that up-regulated expression of CD19 is functionally important for B cell development and that CD19 establishes signaling thresholds that regulate the generation of B-1 lymphocytes as well as the development of autoantibodies.

CD19 regulates B lymphocyte signaling thresholds critical for the development of B-1 lineage cells and autoimmunity

CD19 serves as a cell surface response regulator that establishes signaling thresholds critical for B lymphocyte development and activation. B lymphocytes from CD19-deficient mice are hyporesponsive to transmembrane signals, while B lymphocytes from mice that overexpress CD19 to even a small extent (25% increase) become hyperresponsive. The B-1 subpopulation of B lymphocytes is particularly sensitive to CD19 regulation, since their development is severely decreased in CD19-deficient mice. The effect of altered CD19 expression levels on the development of B cells was therefore examined using transgenic mice that express varying levels of cell surface CD19. In this study, immature B cells within the bone marrow of wild-type mice were found to specifically up-regulate CD19 expression levels by twofold as they mature, while CD5+ B cells within the spleen and peritoneum expressed even higher levels of CD19. The development of CD5+ B cells was severely decreased in CD19-deficient mice, while there was a linear correlation between increased CD19 expression levels and the increased frequency of CD5+ B cells within the peritoneum and spleen. In fact, CD5+ B cells became a major B lymphocyte population in mice that overexpressed CD19. Increased expression of CD19 also correlated with increased levels of endogenous anti-DNA Abs and rheumatoid factor. These results indicate that up-regulated expression of CD19 is functionally important for B cell development and that CD19 establishes signaling thresholds that regulate the generation of B-1 lymphocytes as well as the development of autoantibodies.

Intrapleural pirarubicin (4'-O-tetrahydropyranyladriamycin) for treatment of malignant pleural effusion

Pirarubicin (4'-O-tetrahydropyranyladriamycin), a new anthracyline derivative, was administered as a single agent into the pleural cavity of 42 patients (total 46 courses) with malignant pleural effusion at a dose of 20, 40, 60 or 80 mg/body. All 46 courses were evaluable for non-hematological toxicities. Fever and chest pain (> or = WHO grade 2) were seen in 67.4% and 13.0% of courses, respectively. Patients receiving a dose of 80 mg/body developed fever of > or = 39 degrees C in 45.5%, and chest pain lasting more than three days and requiring pentazocine more than three times in 36.4%. In contrast, patients receiving a dose of < or = 60 mg/body presented these toxicities in only 8.6% and 2.9%, respectively. Nausea-vomiting (> or = WHO grade 2) was observed in only 4.3% of the total 46 courses and alopecia was not observed. Thirty-eight courses (36 patients) were evaluable for hematological toxicities. Myelosuppression (leukocyte nadir count < or = 1900, WHO grade 3 or 4) was seen in four courses (10.5%), and thrombocytopenia (< or = 49,000, WHO grade 3 or 4) in only two (5.3%). Although the mean AUC (0-24) for pirarubicin in plasma during the four courses that produced myelosuppression was significantly higher than that during the 11 courses without myelosuppression, the difference in the mean dose was not significant. Furthermore, no significant correlation was shown between dose (mg/m2) and AUC in plasma. It is considered that myelosuppression is not a dose-related toxicity at a dose of 20-80 mg/body. The dose-limiting toxicity was fever or chest pain, although unexpected myelosuppression was also encountered. The maximum tolerated dose was 80 mg/body. With regard to clinical efficacy, the overall response rate was 73.7% in 38 evaluable courses (38 patients). The mean T(1/2) of pirarubicin concentration in pleural effusion and plasma was 22.1 h and 8.8 h, respectively. We recommend a dose of 40 or 60 mg/body pirarubicin for this pleurodesic treatment.

A comparison of children with suprasellar germ cell tumors and craniopharyngiomas: final height, weight, endocrine, and visual sequelae after treatment

BACKGROUND

Although treatment results of craniopharyngiomas and germ cell tumors in children have been reported extensively, the relationship between various posttreatment sequelae and the nature of the tumor is not well understood.

METHODS

From 1968-94, 47 children with 23 suprasellar germ cell tumors and 24 craniopharyngiomas were treated at Gunma University Hospital, Japan. Forty survivors were assessed with regard to Karnofsky scores, visual scores, final height, final weight, and other endocrine sequelae as long-term functional prognostic indicators.

RESULTS

Kaplan-Meier life-table estimates and Karnofsky scores were not significantly different between the two histologic groups. The visual function of survivors did not differ significantly at diagnosis. However, the final visual function following treatment in the germ cell tumor group was better than in the craniopharyngioma group (p < 0.05). Antidiuretic hormone secretion was significantly impaired at diagnosis in the germ cell tumor group (p < 0.0001). However, there was only a marginally significant difference in posttreatment persistent diabetes insipidus. Craniopharyngioma children were shorter and more obese at diagnosis (p < 0.02), and became much more obese than germinoma children with the same hormone therapy (p < 0.003), although the height difference became insignificant following growth hormone treatment.

CONCLUSIONS

Children with craniopharyngiomas tended to have more visual disturbances, increased dwarfism and obesity, and less diabetes insipidus than patients with germ cell tumors despite adequate therapy. The method of quantifying visual function may in itself be useful.

Effects of insulin on calcium metabolism and platelet aggregation

The influence of insulin on platelets in vitro has not been exhaustively investigated. To clarify whether insulin affects Ca2+ metabolism in platelets directly or through alteration of other systems regulating intracellular Ca2+ homeostasis, we examined the effect of insulin both alone and in combination with prostaglandin E1 on platelet aggregation and Ca2+ metabolism. Incubation of rat platelets with insulin reduced thrombin-induced Ca2+ influx but did not change thrombin-evoked release of Ca2+ from internal stores or the size of internal Ca2+ stores. The interactive effects of insulin with prostaglandin E1 were only additive, and insulin did not augment the effects of prostaglandin E1 on platelet Ca2+ metabolism. In contrast, insulin did not inhibit thrombin-induced platelet aggregation but did augment inhibition of platelet aggregation by prostaglandin E1. Our results suggest that insulin inhibits platelet function by both prostaglandin E1-dependent and -independent mechanisms.

Platelet Ca2+ is not increased in stroke-prone spontaneously hypertensive rats: comparative study with spontaneously hypertensive rats

We have reported that cytosolic Ca2+ concentration ([Ca2+]i) is increased in platelets from spontaneously hypertensive rats (SHR) in both basal and thrombin-stimulated conditions. To determine whether the correlation between blood pressure and cellular Ca2+ metabolism exists in stroke-prone SHR (SHRSP), we investigated Ca2+ handling using fura 2 and aggregation response in platelets of 12- to 13-week-old male SHRSP, SHR, and Wistar-Kyoto rats (WKY). Systolic pressure was highest in SHRSP and lowest in WKY (213 +/- 8, 172 +/- 7, and 135 +/- 5 mm Hg, respectively). Basal [Ca2+]i was significantly higher in SHR than WKY (45.9 +/- 4.5 versus 41.2 +/- 4.8 nmol/L, P<.05), and that in SHRSP (40.2 +/- 2.8 nmol/L) was similar to that in WKY. Thrombin (0.1 IU/mL)-stimulated [Ca2+]i rise was greater in SHR and smaller in SHRSP than in WKY in the presence of extracellular Ca2+ (530 +/- 50 and 408 +/- 52 versus 475 +/- 50 nmol/L, respectively; P<.05). The recovery rate from the peak [Ca2+]i response to thrombin was greatest in SHRSP and least in WKY. Ionomycin (5 micromol/L)-stimulated [Ca2+]i rise was similar in WKY, SHR, and SHRSP (731 +/- 97, 743 +/- 88, and 683 +/- 70 nmol/L, respectively). Thrombin-induced maximum platelet aggregation response was higher in SHR and lower in SHRSP than WKY (82 +/- 4 percent and 61 +/- 15 percent versus 73 +/- 6 percent, respectively; P<.05). In contrast to SHR, basal [Ca2+]i in SHRSP was similar to that in WKY, and thrombin-stimulated [Ca2+]i was attenuated. These result suggest that platelet Ca2+ handling differs between SHR substrains and that an increased [Ca2+]i is not obligatory in genetically hypertensive rats.

Liver haem metabolism in adjuvant-induced arthritic rats

1. Adjuvant-induced arthritic (AA) rats show a striking decrease in the level of cytochrome P450, a key microsomal haemoprotein involved in electron transport and drug metabolism in the liver. In the present study, we examined the relationship between the reduction of P450 content and haem metabolism in the liver of AA rats. 2. The activities of many enzymes catalyzing the biosynthesis of haem in the liver were significantly higher in AA rats than in normal rats, whereas only coproporphyrinogen oxidase activity in AA rats was markedly lower than that in normal rats. Furthermore, the activity of haem oxygenase, a key enzyme in the haem degradative pathway, increased significantly in AA rats. In addition, the degree of increase in the activity of this enzyme was clearly higher than that in the activity of 5-aminolevulinate synthase, a key enzyme in the haem synthetic pathway. 3. These results suggest that the reduction of live P450 content in AA rats is based on the lowering of liver haem content due to the combined action of the increased haem oxygenase activity and the decreased coproporphyrinogen oxidase activity. The changes in these enzyme activities were apparently suppressed by the continuous administration of indomethacin, which improved the arthritic states of the animals.

Purification and Properties of Flavin- and Molybdenum-Containing Aldehyde Oxidase from Coleoptiles of Maize

Aldehyde oxidase (AO; EC 1.2.3.1) that could oxidize indole-3-acetaldehyde into indole-3-acetic acid was purified approximately 2000-fold from coleoptiles of 3-d-old maize (Zea mays L.) seedlings. The apparent molecular mass of the native enzyme was about 300 kD as estimated by gel-filtration column chromatography. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed that the enzyme was composed of 150-kD subunits. It contained flavin adenine dinucleotide, iron, and molybdenum as prosthetic groups and had absorption peaks in the visible region (300-600 nm). To our knowledge, this is the first demonstration of the presence of flavin adenine dinucleotide and metals in plant AO. Other aromatic aldehydes such as indole-3-aldehyde and benzaldehyde also served as good substrates, but N-methylnicotinamide, a good substrate for animal AO, was not oxidized. 2-Mercaptoethanol, p-chloromercu-ribenzoate, and iodoacetate partially inhibited the activity, but well-known inhibitors of animal AO, such as menadione and estradiol, caused no reduction in activity. These results indicate that, although maize AO is similar to animal enzymes in molecular mass and cofactor components, it differs in substrate specificity and susceptibility to inhibitors. Immunoblotting analysis with mouse polyclonal antibodies raised against the purified maize AO showed that the enzyme was relatively rich in the apical region of maize coleoptiles. The possible role of this enzyme is discussed in relation to phytohormone biosynthesis in plants.

[Treatment of refractory hypoxemia due to right-to-left interatrial shunt complicating right ventricular infarction: successful short-term percutaneous catheter closure of the patent foramen ovale]

Refractory hypoxemia as a complication of right ventricular infarction is rare. A 74-year-old man developed persistent hypoxemia due to right-to-left interatrial shunting through a patent foramen ovale during the acute phase of right ventricular infarction. Short-term percutaneous transvenous closure of the patent foramen ovale with a large balloon occlusion catheter was life-saving.

MRI in thorotrastosis

Magnetic resonance imaging (MRI) and computed tomography (CT) were performed in four patients with thorotrastosis. On CT scan, Thorotrast (thorium oxide) deposition was shown as high-density areas in the liver and spleen and the abdominal lymph nodes. These deposits were not found on MRIs. Splenic volume was significantly small due to atrophy. The contrast-noise ratio in the spleen on T1-weighted images was significantly lower. Thorotrast deposition does not affect MRI appearance; therefore it may be useful for the early detection of malignant tumors as a complication of thorotrastosis.

[A semi-quantitative measurement of glycocalyx and an ATP bioluminescent assay for the analysis of Pseudomonas aeruginosa biofilm]

BACKGROUND

In order to analyze each element of a bacterial biofilm, a semi-quantitative measurement of glycocalyx using toluidine blue and an improved ATP bioluminescence assay were developed.

RESULTS

In the toluidine blue assay, a linear correlation was obtained between optical density and the amount of gellan gum, which is an exopolysaccharide derived from Pseudomonas elodea. By using the improved ATP assay, ATP at concentration of 1 x 10(-4) mol/l or floating bacterial cells of 10(3) cfu could be detected. The applicability of these two methods was examined in evaluating a total amount of glycocalyx and ATP content of Pseudomonas aeruginosa biofilms, which were developed or treated with antimicrobial agents in a modified Robbins device.

CONCLUSION

The changes in optical density and ATP luminescence were reasonable, and well correlated with those obtained by scanning electron microscopy. These results indicate that the toluidine blue assay and ATP assay are useful in analyzing bacterial biofilms.

Effect of the transmembrane gradient of magnesium and sodium on the regulation of cytosolic free magnesium concentration in human platelets

1. To clarify the mechanism by which cytosolic free Mg2+ concentrations ([Mg2+]i) are regulated in human platelets, we investigated platelet membrane permeability to Mg2+ by altering extracellular Mg2+ concentrations, and tested the existence of a Na(+)-Mg2+ exchanger by manipulating the transmembrane Na+ gradient. 2. Platelet [Mg2+]i was 421 +/- 52 mumol/l in healthy men. [Mg2+]i remained constant during a 120 min exposure to nominally zero (low) or 5 mmol/l (high) external Mg2+ concentrations. 3. Preincubation of platelets with 10(-4) mol/l ouabain effectively decreased the transmembrane Na+ gradient. The ouabain-induced increase in [Mg2+]i was statistically significant after 30 min of exposure (14.6 +/- 2.0%) and reached 24.6 +/- 4.5% after 60 min. Similarly, the replacement of extracellular Na+ with N-methyl-D-glucamine significantly increased [Mg2+]i by 48.5 +/- 3.9% and 78.8 +/- 12.5%, respectively. 4. These results suggest that [Mg2+]i is well controlled in the presence of large transmembrane Mg2+ concentration gradients, and a Na(+)-Mg2+ exchanger may be involved in the regulation of [Mg2+]i in human platelets.

Intravenous administration of L-arginine inhibits angiotensin-converting enzyme in humans

The iv administration of L-arginine, a precursor of endothelium-derived relaxing factor/nitric oxide, is known to decrease blood pressure in humans by its direct vasodilatory effects. The purpose of the present study was to determine whether L-arginine infusion modifies the renin-angiotensin (Ang)-aldosterone system as well as blood pressure and renal hemodynamics. L-Arginine and saline vehicle were iv administered to 10 healthy male subjects in random order on different days. L-Arginine infusion (500 mg/kg over 30 min) decreased mean blood pressure (from 81.2 +/- 2.7 to 74.0 +/- 2.5 mm Hg; P < 0.001) and renal vascular resistance (from 0.085 +/- 0.007 to 0.074 +/- 0.006 mm Hg/mL.min; P < 0.01) and increased heart rate (from 60.3 +/- 2.7 to 69.7 +/- 2.1 beats/min; P < 0.001) and renal plasma flow (from 616.6 +/- 37.8 to 701.0 +/- 49.2 mL/min; P < 0.05). L-Arginine reduced serum Ang-converting enzyme activity (from 10.4 +/- 0.6 to 8.9 +/- 0.5 nmol/mL.min; P < 0.05) and plasma Ang-II (from 19.3 +/- 3.3 to 12.7 +/- 2.8 pg/mL; P < 0.001), but had no effect on PRA or the glomerular filtration rate. The saline vehicle did not alter any of these parameters. The iv administration of L-arginine (endothelium-derived relaxing factor/nitric oxide) may reduce the plasma Ang-II concentration by inhibiting Ang-converting enzyme. The mechanism by which L-arginine infusion decreases blood pressure can be at least in part explained by inhibition of the renin-Ang system.

Expression of adult T-cell leukemia-derived factor in bronchoalveolar lavage cells after canine lung transplantation

Lung transplantation is now an accepted therapeutic option for patients with end-stage lung disease, and an early diagnosis of rejection is essential in the management of these patients. Adult T-cell leukemia-derived factor (ADF), known as a human homolog of thioredoxin, has been shown to be induced by a variety of stresses. In this study we examined ADF expression in lung tissues and bronchoalveolar lavage cells after canine lung transplantation to determine whether it could be induced by allogenic stimulations and could be used to diagnose early rejection. Allotransplantations were performed in adult mongrel dogs, and immunosuppression was performed from the day of operation to the fifth postoperative day. No immunosuppressant was given from the sixth to the tenth postoperative days. Animals were put to death on the tenth postoperative day. Bronchoalveolar lavage was performed on the fifth and tenth postoperative days, and the lavage cells and lung tissues were examined immunohistochemically with anti-ADF antibody. The grades of rejection were as follows: grade 1 in two animals, grade 2 in three animals, and grade 3 in two animals. The percentages of ADF high-producer cells in bronchoalveolar lavage cells on the fifth and tenth postoperative days were 4.29% +/- 2.65% and 26.6% +/- 3.99%, respectively (p < 0.01). The percentages of ADF high-producer cells in normal healthy dogs and in those with grade 1, grade 2, and grade 3 rejection were 3.00% +/- 1.64%, 20.5% +/- 9.00%, 25.5% +/- 6.06%, and 34.5% +/- 6.50%, respectively. The percentage in each rejection group was significantly higher than that in normal healthy dogs (p < 0.05). These results suggest that examination of bronchoalveolar lavage cells with ADF staining may be useful in the early diagnosis of rejection.

Characterization of chitin synthase 2 of Saccharomyces cerevisiae. Implication of two highly conserved domains as possible catalytic sites

Chitin synthase 2 of Saccharomyces cerevisiae was characterized by means of site-directed mutagenesis and subsequent expression of the mutant enzymes in yeast cells. Chitin synthase 2 shares a region whose sequence is highly conserved in all chitin synthases. Substitutions of conserved amino acids in this region with alanine (alanine scanning) identified two domains in which any conserved amino acid could not be replaced by alanine to retain enzyme activity. These two domains contained unique sequences, Glu561-Asp562-Arg563 and Gln601-Arg602-Arg603-Arg604-Trp605, that were conserved in all types of chitin synthases. Glu561 or arginine at 563, 602, and 603 could be substituted by glutamic acid and lysine, respectively, without significant loss of enzyme activity. However, even conservative substitutions of Asp562 with glutamic acid, Gln601 with asparagine, Arg604 with lysine, or Trp605 with tyrosine drastically decreased the activity, but did not affect apparent Km values for the substrate significantly. In addition to these amino acids, Asp441 was also found in all chitin synthase. The mutant harboring a glutamic acid substitution for Asp441 severely lost activity, but it showed a similar apparent Km value for the substrate. Amounts of the mutant enzymes in total membranes were more or less the same as found in the wild type. Furthermore, Asp441, Asp562, Gln601, Arg604, and Trp605 are completely conserved in other proteins possessing N-acetylglucosaminyltransferase activity such as NodC proteins of Rhizobium bacterias. These results suggest that Asp441, Asp562, Gln601, Arg604, and Trp605 are located in the active pocket and that they function as the catalytic residues of the enzyme.

Influences of beta-blocking agents on cardiovascular actions induced by endothelin-3 administered intracerebroventricularly in anesthetized rats

Possible involvement that the pressor and positive chronotropic effects of endothelin-3 (ET-3) administered intracerebroventricularly (i.c.v.) participate in the central beta-adrenoceptor has been studied in urethane anesthetized rats. ET-3 administered i.c.v. at dose of 50 pmol elicited the increase in blood pressure and heart rate over a long duration, but a dose of 30 pmol had a minimal effect. These cardiovascular responses to ET-3 were significantly reduced by intravenous pretreatment with pentolinium, ganglionic blocking agent, and phentolamine, alpha-blocker. Also pressor responses to ET-3 were abolished dose-dependently by i.c.v. pretreatment with propranolol at a dose of 1 mumol, nonselective beta-blocker and ICI 118551, beta 2-selective adrenoceptor blocker, but not by i.c.v. pretreatment with metoprolol, atenolol, beta 1-selective blocker, procaine and phentolamine. These results suggest that ET-3 may play a role in cardiovascular regulation through the activation of the sympathetic nervous system involved in the central beta 2-adrenoceptor system.

Assessment of platelet cytosolic concentration of free magnesium in healthy subjects

We measured basal cytosolic concentration of free Mg2+ ([Mg2+]i) in platelets from 30 healthy volunteers by using mag-fura-2, a new fluorescent Mg2+ indicator. The mean [Mg2+]i was 381 +/- 22 mumol/L, with values ranging from 226 to 771 mumol/L. The day-to-day intrasubject coefficient of variation was relatively small (3.6%). [Mg2+]i was significantly higher in men than in women (430 +/- 38 vs 332 +/- 17 mumol/L, p < 0.03), and was not correlated with age. There was no significant relation between platelet [Mg2+]i and serum total Mg concentration. The results indicate that the gender but not age may decide intracellular Mg2+ status. In addition, the mechanisms that regulate [Mg2+]i may be independent of those that influence the extracellular concentration of Mg.