Sequential interferon-alpha and beta treatment in patients with chronic hepatitis C

To assess the effectiveness and side effects of sequential interferon (IFN)-alpha and beta treatment for patients with chronic hepatitis C, 25 patients were enrolled in a trial of this regimen. The patients were given 6 million units (MU) of natural human INF-beta daily for 2 weeks followed by 6 MU of natural human IFN-alpha three times a week for 10 to 22 weeks. Serum alanine aminotransferase (ALT) levels normalized for at least 24 weeks in 10 patients (40%), of whom 4 (40%) had no detectable serum hepatitis C virus (HCV) RNA. Three variables were significant in predicting a sustained response: a low serum HCV RNA level, a low Knodell's fibrosis score, and a low indocyanine green retention rate at 15 minutes. Elevated serum ALT and proteinurea were observed with IFN-beta treatment but these side effects were mild and disappeared when INF-beta treatment ended. While all patients completed the entire regimen, we concluded that sequential IFN-alpha and beta treatment provides no additional antiviral effects in chronic hepatitis C.

Glycosides of megastigmane and of the simple alcohols from Alangium premnifolium

From the water-soluble fraction of a methanol extract of leaves of Alangium premnifolium, two new megastigmane glycosides, alangionosides N and O, along with three known megastigmane glycosides, dendranthemoside A and alangionosides A and B, were isolated. Shimaurinosides A and B, xylopyranosyl(1-->6)glucopyranosides of simple alcohols were also found to be constituents of the water-soluble fraction. Structures were determined by spectroscopic analyses.

Evaluation of interferon treatment in cirrhotic patients with hepatitis C

The aim of this study was to examine the effects of interferon on cirrhotic patients with hepatitis C and the incidence of adverse reactions. The subjects were 35 cirrhotic patients, and 29 chronic active hepatitis patients without cirrhosis (CAH) served as controls. The cirrhotic patients received 3 or 6 million units of human lymphoblastoid interferon daily for one or two weeks and then three times a week for 22 or 23 weeks, while the CAH patients received 6 million units daily for 2 weeks and then three times a week for 14 or 16 weeks. Discontinuation of interferon treatment or dose reduction was required in the 7 cirrhotic patients. The most frequent reason was thrombocytopenia. Dose reduction alone was necessary in two CAH patients. Five cirrhotic patients (14.3%) and nine CAH patients (31.0%) were classified as complete responders to interferon treatment. In all five complete responders with cirrhosis, the hepatitis C virus RNA level before treatment was less than 5 log copies/50 microliters. The results of this study confirm the beneficial effect of interferon in selected patients with cirrhosis on basis of pre-treatment virus levels and platelet count.

Anti-HIV-1 activity of thiadiazole derivatives: structure-activity relationship, reverse transcriptase inhibition, and lipophilicity

The structure-activity relationship of the non-nucleoside HIV-1-specific reverse transcriptase (RT) inhibitors 4-phenyl-1,2,5-thiadiazol-3-yl N,N-dialkylcarbamate (TDA) derivatives was investigated with respect to their anti-HIV-1 activity, RT inhibition, and lipophilicity. 4-Phenyl-1,2,5-thiadiazol-3-yl N,N-dimethylcarbamate inhibited HIV-1-induced cytopathic effect (CPE) by 50% at a concentration of 28.8 microM in MT-4 cells. The activity increased more than 100-fold when the hydrogens at the 2-position and the 6-position in phenyl moiety were substituted by chlorines. However, the derivative with a chlorine at the 4-position of phenyl moiety did not show any inhibition of HIV-1 replication at its non-toxic concentrations. All of the 4-(2,6-dichlorophenyl)-1,2,5-thiadiazol-3-yl N-methyl-N-alkylcarbamates proved inhibitory to HIV-1 replication in the nanomolar concentration range. The TDA derivatives that showed anti-HIV-1 activity also inhibited RT activity in an enzymatic assay. However, the TDA derivatives did not show any specific inhibition of a non-nucleoside RT inhibitor (NNRTI)-resistant mutant and its RT activity. When the TDA derivatives were examined for their inhibitory effect on HIV-1 replication in the presence of 50% human serum, the activity significantly decreased depending on-their lipophilicity.

Clinical and histopathological analysis of proliferative potentials of recurrent and non-recurrent meningiomas

Proliferative potentials of meningiomas from 127 patients were examined immunohistochemically using the anti-Ki-67 monoclonal antibody, MIB-1, on paraffin sections, and the correlation among MIB-1 staining index (SI), histopathological finding, and clinical course of the disease was analyzed retrospectively. The mean MIB-1 SI of 50 male patients with meningioma was 5.5%, whereas that of 77 female patients was 2.7%. Higher MIB-1 SI were observed for younger patients. These age- and sex-related differences in MIB-1 SI were statistically significant. The patients were assigned to one of three groups: those with non-recurrent meningioma (n = 73); those with recurrent meningioma in whom the specimens obtained during the initial surgery were used to calculate the MIB-1 SI (n = 21); and those with recurrent meningioma for whom the specimens obtained during the surgery for recurrent tumors were used to calculate the MIB-1 SI (n = 33). The mean MIB-1 SI in these patients were 1.6%, 3.6%, and 8.8%, respectively, and there were statistically significant differences among these three groups. Statistical analyses reveal that meningiomas with a MIB-1 SI of 3% or more have a significantly high tendency for recurrence during the clinical courses, especially within the first 10-year follow-up periods. Moreover, there is statistically significant correlation between MIB-1 SI and recurrence in each Simpson's grade. The time interval to the next recurrence for recurrent meningiomas is associated with the proliferative potential represented by the MIB-1 SI, and a correlation equation has been proposed to predict the date of the next recurrence. Analyses on cellularity of meningiomas revealed no statistically significant difference in cellularity between non-recurrent and recurrent meningiomas. There was no statistically significant relationship between cellularity and MIB-1 SI of meningiomas. In conclusion, examination on proliferative potentials of meningiomas using MIB-1 SI is very important for biological and histopathological analyses and the prediction of future recurrence.

[Trials and analysis of umbilical cord blood collection, separation and cryopreservation methods for transplantation]

Placental and umbilical cord blood, as an alternative course of haematopoietic stem cells for bone marrow reconstitution, have recently been showed to yield successful sibling-donor cord blood grafts children. The advantages of using cord blood are related to the high number of haematopoietic progenitors in circulation at birth. In our study there was a remarkable heterogeneity of volume, number of nucleated cells and the number of progenitors from sample to sample. Seven out of 40 samples of more than 61 ml blood volume contained 1.8 (+/- 1.0) x 10(5) CFU-GM or 6.0 (+/- 4.8) x 10(8) nucleated cells. 10 ml of whole blood was necessary for laboratory tests including ABO blood type, screening of infectious markers, HLA typing, as well as frozen sera and cells for the possible future tests. Collected cord blood of more than 70ml in volume may have sufficient numbers of CFU-GM for engraftment to pediatric patients weighing about 20 kg. A cord blood bank project is now going on by collecting blood with informed consent of the mother in cooperation with obstetrics and gynecology staff.

Stimulation of the activities of hepatic fatty acid oxidation enzymes by dietary fat rich in alpha-linolenic acid in rats

The activities of hepatic fatty acid oxidation enzymes in rats fed perilla oil rich in alpha-linolenic acid (alpha-18:3) were compared with those fed saturated fats or safflower oil (the mixture of safflower oil and olive oil, 94:8, w/w) containing the same amount of polyunsaturated fatty acids with perilla oil exclusively as linoleic acid (18:2). When the rats were fed the diets containing 15% coconut, safflower, and perilla oils for 1 week, the rate of mitochondrial and peroxisomal oxidation of palmitoyl-CoA (16:0-CoA) in the liver homogenates was the highest in rats fed perilla oil. Among the rats fed the diets containing 15% palm, safflower, and perilla oils for 2 weeks, the rates of mitochondrial and peroxisomal oxidations of 16:0-, 18:2-, and alpha-18:3-CoAs were the highest in rats fed perilla oil, and the rate of oxidation of alpha-18:3-CoA by both pathways was higher than those of other acyl-CoAs in all groups. Dietary perilla oil relative to palm and safflower oils significantly increased the activities of carnitine palmitoyltransferase, acyl-CoA dehydrogenase, acyl-CoA oxidase, and 2,4-dienoyl-CoA reductase. The substrate specificity of carnitine palmitoyltransferase appeared to be responsible for differential rates of the mitochondrial oxidation of acyl-CoAs. The substrate specificity of acyl-CoA oxidase did not account for the preferential peroxisomal oxidation of alpha-18:3 relative to 18:2. The preferential mitochondrial and peroxisomal beta-oxidation of alpha-18:3-CoA relative to 16:0- and 18:2-CoAs was also confirmed in rats fed laboratory chow irrespective of the substrate/albumin ratios in the assay mixture. It was suggested that both substrate specificities and alterations in the activities of the enzymes in beta-oxidation pathway play a significant role in the regulation of the serum lipid concentrations in rats fed a diet rich in alpha-18:3.

An immunosuppressant, FK506, protects hippocampal neurons from forebrain ischemia in the mongolian gerbil

We examined whether an immunosuppressant, FK506, inhibits delayed neuronal death in the gerbil hippocampal CA1 sector after 5-min forebrain ischemia. After reperfusion, gerbils were injected intravenously with FK506. Gerbils in the early injection group were injected with FK506 immediately after reperfusion, and gerbils in the delayed injection group were injected with FK506 1 or 2 h postischemia. The body temperature of the FK506-treated gerbils in the normothermic group was maintained at 37.5-38.0 degrees C for 2 h postischemia. In the chronic survival group, neuroprotection was assessed after recovery for 45 days. Seven or 45 days after reperfusion, neuronal density in the CA1 was assessed following perfusion fixation. FK506 ameliorated cell death in the CA1 in a dose-dependent manner in every group, although it showed a hypothermic effect. FK506 is neuroprotective against forebrain ischemia in gerbils.

[Telomerase]

Telomerase is expected to be a powerful tool for cancer diagnosis and cancer chemotherapeutics because of its selective expression exclusively in various cancer tissues at a high frequency (90%) in human somatic tissues. Some precancerous tissues also express telomerase at a high frequency. Normal somatic tissues are mostly telomerase negative. Cancer cells die after a loss of telomerase activity.

Transient ischemia depletes free ubiquitin in the gerbil hippocampal CA1 neurons

We investigated ubiquitin immunoreactivity in the post-ischemic gerbil hippocampus using a panel of ubiquitin antibodies. Immunostaining for ubiquitin in the hippocampus was strongly dependent on the antibodies used. With rabbit polyclonal antibody U-5379, immunoreactivity disappeared from the hippocampus in the early reperfusion period and reappeared in the dentate granule cells and CA3 pyramidal cells but never in the CA1 pyramidal cells. In contrast, rat monoclonal antibody DF2 and mouse monoclonal antibody MAB1510 showed sustained immunoreactivity in the CA1 during the 48-hour reperfusion period. On the immunoblots of gerbil brain homogenates, three antibodies, U-5379, DF2 and MAB1510, exhibited similar specificities; all three labeled free ubiquitin most strongly. Immunoprecipitation disclosed that, under nondenaturing conditions, U-5379 bound exclusively free ubiquitin, whereas DF2 and MAB1510 had little affinity for free ubiquitin but appeared to have more affinity for conjugated ubiquitin. Immunoabsorption of these antibodies with free ubiquitin confirmed the above result. It is most likely that U-5379 recognized free ubiquitin in the tissue, whereas DF2 and MAB1510 recognized preferentially conjugated ubiquitin. Thus, transient ischemia depletes free ubiquitin but not conjugated ubiquitin in the CA1. This depletion may be caused by impaired conversion from conjugated to free ubiquitin and/or failure of de novo ubiquitin synthesis.

Distribution of diaphragm blood flow during sevoflurane anaesthesia in dogs

PURPOSE

The purpose of this study was to determine the effect of increasing the concentrations of sevoflurane anaesthesia on the distribution of diaphragm blood flow (Qdi) in ten dogs during mechanical ventilation.

METHODS

Animals were divided into two groups, sevoflurane (n = 6) and time control (n = 4) groups. Blood flow to the crural and the costal diaphragm (Qcru, Qcost) was determined by the hydrogen clearance technique at 0, 0.5, 1.0 and 1.5 minimum alveolar concentration (MAC) of sevoflurane after a 30 min period of steady-state conditions. Cardiac output (CO) and the mean arterial blood pressure (MBP) were also measured.

RESULTS

Sevoflurane anaesthesia caused a reduction in CO (L.min-1) from a control value of 1.51 +/- 0.21 to 1.38 +/- 0.1 (0.5 MAC), 1.09 +/- 0.15 (1.0 MAC) and 0.98 +/- 0.12 (1.5 MAC) (Mean +/- SD). Mean blood pressure, Qcru and Qcost also decreased with increasing depth of anaesthesia. In addition, the decrease of Qcru was greater than that of Qcost at all levels of MBP and CO. No change occurred in these variables in the time control group.

CONCLUSION

Sevoflurane anaesthesia changes the distribution of Qdi with a greater reduction occurring in Qcru than in Qcost.

An experimental animal model of primary biliary cirrhosis induced by lipopolysaccharide and pyruvate dehydrogenase

Previously, we found that the antibody titer belonging to the IgM class produced against the bacterial antigen (Lipid A) was elevated in sera from patients with primary biliary cirrhosis (PBC). On the other hand, the targets of the mitochondrial autoantibodies have been identified as being components of the pyruvate dehydrogenase complex (PDH). We tried to produce an experimental animal model for the investigation of the association between hepatic bile duct alteration and bacterial infection. Female C57/BL mice, aged 4 weeks, were used. An emulsion consisting of lipopolysaccharide (LPS) derived from Salmonella minnesota Re595, PDH, and Freund's adjuvant was prepared. This emulsion was subcutaneously injected on the back of the mice. The mice were divided into a control group (n = 5), a group given LPS (n = 5) alone, those given PDH alone (n = 5), and those given a combination of LPS and PDH (n = 5). The antigens were administered once a week every week with a maximum duration of administration of 24 weeks. The serum levels of IgM after 24 weeks in the LPS and LPS + PDH groups were 2.5 times higher than those in the control and PDH groups. The light microscopic findings of liver tissue revealed that infiltration of lymphocytes and plasma cells in the portal area, proliferation of the bile duct, and degeneration of the biliary epithelial cells were more prominent in the PDH and LPS + PDH groups than in the other groups. These results indicate that our animal model may be useful in investing the pathogenesis of PBC.

Regulation of calcium release channel in sarcoplasmic reticulum

In this review, we summarized the results obtained mainly by flux measurements through Ca2+ channel in HSR vesicles. The Ca2+ channel has a large pore which passes not only divalent cations such as Ca2+, Mg2+, and Ba2+ and monovalent cations such as Na+, K+, and Cs+, but also large ions such as choline and tris. The permeation rates of choline and glucose through the Ca2+ channel were measured quantitatively by the light scattering method. The slow permeation of such molecules may reflect the structure of pores since the permeation process is the rate-limiting step for such large molecules. Neutral molecules such as glucose became permeable in the presence of submolar KCl, which suggests that pore size of the channel becomes larger in KCl. The apparent permeation rates of Ca2+ and Mg2+ obtained from the flux measurement were the same, although their single-channel conductances were different. This discrepancy was explained by the fact that flux measurements reflects the open rate of the channel. Thus, complementarity between the flux measurement and single-channel recording was demonstrated. From the effects of K+ on the action of regulators on Ca2+ channel, it was suggested that the Ca2+ channel has many binding sites for activators and inhibitors. There are two kinds of Ca2+ binding sites for activation and inhibition. Activation sites for Ca2+, caffeine, and ATP are different and inhibition sites for Ca2+ and procaine are different. The binding sites for ruthenium red and Mg2+ are the same as the activation and/or inhibition sites for Ca2+. Ryanodine-treated Ca2+ channel became permeable to glucose even in the absence of KCl. The conformational state of the channel opened by ryanodine is different from that opened by Ca2+, caffeine, and ATP. The maximal flux rates of choline and glucose induced by ryanodine were smaller than those attained by caffeine and ATP. This result is consistent with the observation obtained by single-channel recording; the maximal value of single-channel conductance after ryanodine treatment becomes 40-50% of the value before the treatment. It is likely that the radius of the pore opened by ryanodine is smaller than that opened by Ca2+, caffeine, or ATP. The flexibility of the channel may be decreased in the open locked state induced by ryanodine. The Ca2+ response to open the channel by micromolar Ca2+ was lost when calsequestrin was released from the vesicles. It is possible that calsequestrin acts as an endogenous regulator of Ca2+ channel through triadin in excitation-contraction coupling.

Effect of dietary soybean phospholipid and fats differing in the degree of unsaturation on fatty acid synthesis and oxidation in rat liver

The activities of enzymes in fatty acid oxidation and synthesis in the liver of rats fed soybean phospholipids and soybean oil corresponding to the dietary levels of 3% fatty acid added to the diets containing a saturated fat (coconut oil) and a polyunsaturated fat (safflower oil) at the amounts corresponding to 12% fatty acid levels were compared. Soybean phospholipid compared with soybean oil added to both coconut and safflower oil diets significantly reduced the activities of enzymes in fatty acid synthesis (fatty and synthetase, glucose-6-phosphate dehydrogenase and malic enzyme). However, there were no significant differences in the activities of enzymes in fatty acid oxidation (carnitine palmitoyltransferase, acyl-CoA dehydrogenase and acyl-CoA oxidase) between the groups of rats fed soybean phospholipid and soybean oil added to coconut and safflower oil diets except for one occasion. Soybean phospholipid compared with soybean oil added to coconut oil diet significantly decreased the concentrations of triacylglycerol, cholesterol and phospholipid in the serum and of triacylglycerol and cholesterol in the liver. However, the dietary phospholipid added to safflower oil diet failed to alter these values. These results suggested that the alteration in the rate of fatty acid synthesis, but not oxidation, in the liver is responsible for the lipid-lowering effect of dietary soybean phospholipid added to a saturated fat diet.

A cDNA clone encoding an IgE-binding protein from Brassica anther has significant sequence similarity to Ca(2+)-binding proteins

Thirteen cDNA clones encoding IgE-binding proteins were isolated from expression libraries of anthers of Brassica rapa L. and B. napus L. using serum IgE from a patient who was specifically allergic to Brassica pollen. These clones were divided into two groups, I and II, based on the sequence similarity. All the group I cDNAs predicted the same protein of 79 amino acids, while the group II predicted a protein of 83 amino acids with microheterogeneity. Both of the deduced amino acid sequences contained two regions with sequence similarity to Ca(2+)-binding sites of Ca(2+)-binding proteins such as calmodulin. However flanking sequences were distinct from that of calmodulin or other Ca(2+)-binding proteins. RNA-gel blot analysis showed the genes of group I and II were preferentially expressed in anthers at the later developmental stage and in mature pollen. The recombinant proteins produced in Escherichia coli was recognized in immunoblot analysis by the IgE of a Brassica pollen allergic patient, but not by the Ige of a non-allergic patient. The cDNA clones reported here, therefore, represent pollen allergens of Brassica species.

Slit ventricle syndrome successfully treated by a lumboperitoneal shunt

The authors present the case of a 17-year old man with slit ventricle syndrome, presenting as progressive neurological deterioration after head trauma. Serial computed tomography scans revealed slight ventricular enlargement, suggesting shunt malfunction. Communication between the lumbar subarachnoid space and the lateral ventricles was confirmed by computed tomography cisternography. He underwent a lumboperitoneal shunt, resulting in complete resolution of the symptoms. A lumboperitoneal shunt is considered to be a promising option for the treatment of slit ventricle syndrome.

IgE-mediated allergy to spider mite, Panonychus citri in occupationally exposed individuals

This paper is the first report on allergy caused by a spider mite, Panonychus citri. Some of fruitgrowers cultivating Citrus junos were manifested immediate allergic symptoms by farming, especially by harvest. By examining C. junos trees, we found the trees cultivated by the fruitgrowers were infested with P. citri. Twelve subjects complaining of immediate allergic symptoms were examined by intradermal test and RAST using allergen extracts prepared from P. citri and Dermatophagoides spp. In intradermal test, ten out of twelve showed a positive response to P. citri and twelve positive to D. farinae. Positive RAST to P. citri were obtained in seven of twelve. Six of them also had positive RAST to D. farinae and D. pteronyssinus. In ELISA inhibition using a serum from Case 4, the inhibition with P. citri extract reached to 92% at the highest concentration used but at the same concentration D. farinae and D. pteronyssinus extracts did not inhibit the binding of specific IgE antibodies to allergen of P. citri. In Case 7, the extracts of P. citri, D. farinae and D. pteronyssinus inhibited at the same concentration 94%, 81%, and 87%, respectively. These results lead to the following conclusions: Seven subjects positive to P. citri in intradermal test and RAST are sensitized to P. citri. P. citri has a specific allergenic determinant in addition to a common determinant with Dermatophagoides spp.

Telomerase activity in preneoplastic and neoplastic gastric and colorectal lesions

Recent evidence indicates that telomerase activity may be necessary for cell immortality, which is required for the sustained and indefinite growth of most malignant cells. We analyzed telomerase activity in gastric and colorectal cancers and in gastric and colorectal precancerous lesions to determine whether malignant progression depends on the activation of telomerase and at what stage of carcinogenesis cells have detectable telomerase activity. Telomerase activity was measured by the telomeric repeat amplification protocol assay and was detected in 17 (85%) of 20 primary gastric carcinoma tissues and in 19 (95%) of 20 primary colorectal carcinomas, regardless of tumor staging and histological types. All nodal metastases, peritoneal metastases, and a recurrent gastric cancer tumor were positive. All cell lines established from gastric and colorectal cancers contained telomerase activity. In precancerous lesions, 10 (100%) of 10 colorectal tubular adenomas were telomerase positive, in addition to 3 (23%) of 13 gastric intestinal metaplasias and 1 (50%) of 2 gastric adenomas, whereas the corresponding gastric normal mucosas as well as colorectal mucosas were negative. These results indicate overall that reactivation of telomerase may occur at an early stage of carcinogenesis and may correlate well with malignant progression of gastric cancer. Telomerase activity thus may serve as a powerful additional tool for cancer diagnosis.

Restoration of the cellular senescence program and repression of telomerase by human chromosome 3

Telomeres, at the end of chromosomes, shorten with each cell division, resulting in cellular senescence. Tumor cells, unlike normal somatic cells, express a telomerase that maintains the telomere length. Deletion of a gene(s) on chromosome 3 is common in human renal cell carcinoma (RCC) and reintroduction of a normal chromosome 3 into an RCC immortal cell line restored the program of cellular senescence. The loss of indefinite growth potential was associated with the loss of telomerase activity and shortening of telomeres in the RCC cells with a normal chromosome 3. However, microcell hybrids that escaped from senescence and microcell hybrids with an introduced chromosome 7 or 11 maintained telomere lengths and telomerase activity similar to those of the parental RCC23. Thus, restoration of the cellular senescence program by chromosome 3 is associated with repression of telomerase function in RCC cells.

Increase in expression levels of interferon-inducible genes in senescent human diploid fibroblasts and in SV40-transformed human fibroblasts with extended lifespan

The normal human fibroblast line, TIG-3 which senesces at around 80 population doubling levels (PDLs), expressed interferon (IFN)-inducible genes such as 6-16, 2', 5'-oligoadenylate synthetase (2,5-A) and HLA B7 near the end of the proliferative lifespan. Other normal fibroblast line such as MRC-5 also expressed IFN-inducible genes when senesced. Clones transformed with SV40 T-antigen, which extended their proliferative lifespan by about 20-30 PDLs, also expressed IFN-inducible genes during their extended life. Anti-IFN-beta antibodies added in culture medium repressed the expression of IFN-inducible gene in both normal senescent and life-extended SV40-transformed cells. IFN-beta repressed DNA synthesis in normal TIG-3 and induced IFN-inducible genes in both normal and SV40-transformed TIG-3. Conditioned medium recovered from life-extended SV40-transformed cells contained IFN-beta, but not IFN-alpha, IFN-gamma or TNF-alpha and possessed an activity that inhibited DNA synthesis of young TIG-3. Addition of anti-IFN-beta antibodies into the medium enhanced the serum-induced DNA synthesis of near senescent (91% lifespan completed) TIG-3, while it neither induced DNA synthesis in fully senescent TIG-3 nor extended the proliferative lifespan of TIG-3. These results suggest that normal and SV40-transformed human fibroblasts increase expression of IFN-beta with increasing proliferative age especially near the end of their lifespan resulting in induction of IFN-inducible genes and possibly in growth repression.

Effects of a continuous infusion of dopamine on the ventilatory and carotid body responses to hypoxia in cats

1. We investigated how a continuous infusion of dopamine (DA; 5 micrograms/kg per min), which is often used clinically, would affect the ventilation and carotid chemoreceptor neural activity in anaesthetized cats. 2. In anaesthetized, spontaneously breathing cats, tidal volume (VT) and respiratory frequency (f) were continuously monitored at five levels of inspired oxygen (PIO2 = 110, 130, 150, 170, 760 mmHg) during Da or saline infusion. VT and f were sampled for 1 min after 3 min exposure to each level of PIO2. Time control study was also performed. 3. DA infusion significantly lowered VT under both normoxia and hypoxia in seven of eight cats. Respiratory frequency was not affected by DA infusion. Depression of ventilation during post-hypoxic hyperoxia was augmented by DA infusion. Chemodenervation abolished the ventilatory response to hypoxia and DA did not further affect the ventilatory response to hypoxia. 4. In a second group of artificially ventilated cats, carotid chemoreceptor neural activity was recorded at five levels of arterial oxygen tension. DA infusion significantly depressed carotid chemoreceptor neural activity during normoxia and hypoxia in six of seven cats. 5. These findings suggest that changes in ventilation during low dosage of DA infusion closely correlate with carotid body neural output. A predominant effect of this dosage of DA (5 micrograms/kg per min) was depression in the ventilatory response to hypoxia due to an inhibition of carotid body neural output.

The cholinergic hypothesis revisited--an unfinished story

Though exogenously delivered acetylcholine excites the carotid body, past evidence has been considered as unsupportive in assigning acetylcholine an excitatory role during hypoxia or hypercapnia. With ganglionic transmission used as the model, data is presented which aims at blocking the postsynaptic cholinergic receptors, at preventing the presynaptic release of acetylcholine, and at quantitating its release under stimulating conditions. The data support an excitatory role for acetylcholine during hypoxia.

Effect of aminophylline on high-energy phosphate metabolism and fatigue in the diaphragm

BACKGROUND

Diaphragmatic fatigue causes respiratory failure, for which aminophylline has been used as therapy. Because the mechanism of action of aminophylline in reversing diaphragmatic fatigue is unclear, we used in vivo 31P magnetic resonance spectroscopy (MRS) to determine the relation between diaphragmatic activation, force output, and aerobic metabolism.

METHODS

Bilateral phrenic stimulation was used to pace the diaphragm in pentobarbital-anesthetized piglets (6-10 weeks old; n = 44). Esophageal and abdominal pressures were measured to calculate transdiaphragmatic pressure (Pdi) (Pdi = abdominal pressure-esophageal pressure) as an index of force output. Activation was determined by the amplitude of the compound action potential of the diaphragmatic electromyogram. Aerobic metabolism was assessed with a 31P MRS surface coil on the right hemidiaphragm with the animal in a 4.7-T magnet. The animals were divided into four groups based on aminophylline loading dose: saline, aminophylline 10 mg/kg (A10), aminophylline 20 mg/kg (A20), and aminophylline 40 mg/kg (A40). After aminophylline loading the diaphragm was paced for 25 min followed by a 10-min recovery.

RESULTS

Aminophylline concentrations were 12.2 +/- 0.7, 21.9 +/- 2.4, and 44.9 +/- 3.6 mg/l in the A10, A20, and A40 groups, respectively. Compound action potential amplitude decreased in all groups by 30% after 25 min of pacing. Conversely, Pdi remained at 100 +/- 3% of the initial value after 5 min of pacing in the A40 group but decreased to 75 +/- 3% in the saline group. Pdi recovered completely (103 +/- 17%) in the A40 group but remained depressed (72 +/- 6%) in the saline group. Pdi values were intermediate in the A10 and A20 groups. MRS data revealed inadequate energy supply/demand ratio in the saline group such that the ratio of inorganic phosphate to phosphocreatine (Pi/PCr) increased to 1.01 +/- 0.09 after 5 min of pacing. Pi/PCr remained unchanged in the A40 group and was intermediate in the A10 and A20 groups. beta-Adenosine triphosphate and intracellular pH did not differ among groups or as a function of pacing. Diaphragmatic blood flow increased from a resting value of 35-60 to 300-410 ml.min-1 x 100 g-1 during pacing in all groups and was not affected by aminophylline dose.

CONCLUSIONS

Aminophylline, in a dose-dependent fashion, delays the onset of fatigue and improves recovery from fatigue. Delayed fatigue is associated with improved aerobic metabolism as reflected in a low Pi/PCr ratio.

Inhibitors of cGMP-dependent protein kinase block senescence induced by inactivation of T antigen in SV40-transformed immortal human fibroblasts

Immortal human fibroblasts isolated following transfection with thermolabile simian virus 40 T antigen lost division potential upon shift up in temperature due to heat inactivation of the antigen. Such cells showed a concomitant change in the distribution of a mortality marker, mortalin, from a juxtanuclear cap like distribution of immortal cells to a uniform cytosolic distribution of mortal cells. We made an attempt to modulate the above inducible system of cellular senescence using various protein kinase inhibitors. Among the indolocarbazole type inhibitors tested, only KT5823, defined as a specific inhibitor of cGMP-dependent protein kinase, blocked the loss of division potential as determined by cell growth and colony forming ability. This inhibitor also prevented the above change in mortalin distribution due to temperature shift. In addition, the isoquinoline sulfonamide derivatives H8, H9, H88 and H89, all shown to inhibit cGMP-dependent protein kinase, suppressed the senescence. Inhibitors specific to other types of protein kinases, protein phosphatases or tyrosine kinases tested had no effect. Since there was no difference between the effective and non-effective inhibitors in their effects on cell cycle progression, cell cycle arrest by itself cannot account for the above phenomenon. These results suggest that a signaling pathway possibly mediated by cGMP-dependent protein kinase is involved in the induction of cellular senescence.