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Biomedical subjects

D Ma

Publications and source records attributed to D Ma.

At least 181 records · Page 10Linked to original sources
PubMed1997

Dissociation between the effect of nitrous oxide on spontaneous and reflexly evoked sympathetic activity in dogs.

We have examined the effect of nitrous oxide on spontaneous sympathetic activity and A delta- and C-fibre mediated somatosympathetic reflexes in renal nerves, evoked by supramaximal electrical stimulation of radial nerves in anaesthetized, paralysed dogs undergoing mechanical ventilation. In six preparations, nitrous oxide was administered at end-tidal concentrations of 10%, 30%, 50% and 70%, each for 20 min. Spontaneous renal sympathetic activity increased significantly to 147.8% and 151.2% of control values with 50% and 70% nitrous oxide, respectively (P < 0.05), but there were no significant changes in A delta and C reflexes. We conclude that the large increase in spontaneous sympathetic activity was dissociated from somatosympathetic reflexes which remained unchanged at these concentrations of nitrous oxide.

Anesthetics, Inhalation↗
PubMed1997

Oral immunisation as a strategy for enhancing corneal allograft survival.

AIMS: To determine optimal conditions for enhancing corneal allograft survival through oral administration of donor specific corneal cells. METHODS: A mouse model of penetrating keratoplasty was used to evaluate the efficacy and optimal conditions for preventing immunological rejection of corneal allografts. C3H corneal grafts were transplanted orthotopically to CB6F1 recipients and represented mismatches at the entire major histocompatibility complex (MHC) and multiple minor histocompatibility loci. Tissue cultured C3H corneal epithelial and endothelial cells were administered orally to CB6F1 mice before or shortly after the application of orthotopic C3H corneal allografts. Cultured C3H corneal cells were conjugated with the non-toxic B subunit of cholera toxin as a means of preferentially inducing oral tolerance. RESULTS: Ten oral doses of donor cells administered before keratoplasty reduced the incidence of corneal graft rejection from 100% in untreated hosts to 54% in orally tolerised mice. Conjugation of cholera toxin to corneal cells significantly enhanced the efficacy of oral tolerance such that only 9% of the mice fed 10 doses of cholera toxin conjugated cells rejected their corneal grafts. Even a single oral inoculation of corneal cells conjugated to cholera toxin was able to reduce corneal graft rejection by 36%. CONCLUSIONS: Oral administration of donor specific cells greatly enhances corneal graft survival. Use of cholera toxin adjuvant markedly enhances the efficacy of oral tolerance such that even a single oral dose of donor cells significantly reduces the incidence of rejection. The results support the clinical feasibility of this novel strategy for preventing immunological rejection of corneal transplants.

Administration, Oral↗
PubMed1997

Noradrenergic suppression of synaptic transmission may influence cortical signal-to-noise ratio.

Norepinephrine has been proposed to influence signal-to-noise ratio within cortical structures, but the exact cellular mechanisms underlying this influence have not been described in detail. Here we present data on a cellular effect of norepinephrine that could contribute to the influence on signal-to-noise ratio. In brain slice preparations of the rat piriform (olfactory) cortex, perfusion of norepinephrine causes a dose-dependent suppression of excitatory synaptic potentials in the layer containing synapses among pyramidal cells in the cortex (layer Ib), while having a weaker effect on synaptic potentials in the afferent fiber layer (layer Ia). Effects of norepinephrine were similar in dose-response characteristics and laminar selectivity to the effects of the cholinergic agonist carbachol, and combined perfusion of both agonists caused effects similar to an equivalent concentration of a single agonist. In a computational model of the piriform cortex, we have analyzed the effect of noradrenergic suppression of synaptic transmission on signal-to-noise ratio. The selective suppression of excitatory intrinsic connectivity decreases the background activity of modeled neurons relative to the activity of neurons receiving direct afferent input. This can be interpreted as an increase in signal-to-noise ratio, but the term noise does not accurately characterize activity dependent on the intrinsic spread of excitation, which would more accurately be described as interpretation or retrieval. Increases in levels of norepinephrine mediated by locus coeruleus activity appear to enhance the influence of extrinsic input on cortical representations, allowing a pulse of norepinephrine in an arousing context to mediate formation of memories with a strong influence of environmental variables.

Acetylcholine↗
PubMed1997

[Anatomic study of the facial nerve in parotidectomy].

To explore the course and anatomic characteristics of the extra-cranial section of the facial nerve, the authors carried out this clinical study in 120 patients undergoing parotidectomy by dissecting and measuring the facial nerve and its branches regarding its length, diameter and numbers. The results confirmed that the temporal branch is deeper and has multiple branches; the zygomatic branch is bigger, with consistent location and fewer branches; the buccal branch exhibits three patterns: 1. the upper and lower branches, 2. one trunk and 3. one trunk with two or three branches; the marginal mandibular branch is a small and superficial with two to three branches. The authors discuss how to locate the facial nerve accurately.

Adenolymphoma↗
PubMed1997

[Study on the effect of continuous administration of IL-1ra in BXSB mice].

OBJECTIVE: To explore the consequences of IL-1 blocking in BXSB mice which is an experimental model for human SLE. METHODS: rh IL-1ra was expressed in E. coli and injected in BXSB mice. 13 of 4.5 month-age male BXSB mice were divided into two groups, one group was injected rh IL-1ra 10 times (twice a week) at dose of 400 micrograms per mouse each time, another group was injected PBS at the same time as control. We monitored serum ANA and proteinuria weekly, and detected IgG, C3 deposition and IL-6 expression in kidneys at 40th day. RESULTS: The results showed that the increased level of serum ANA and proteinuria in treatment group were not higher than in control group, the IgG, C3 deposition and IL-6 expression in kidneys and IL-6 activity in serum of the treaed group were lower than the control group, whereas no difference of GPT level in the two groups. CONCLUSION: IL-1 might play a pathogenic role in BXSB mice. Blocking or reducing IL-1 secretion would be of beneficial to the treatment of SLE.

Animals↗
PubMed1997

[The behaviour and treatment of myoepithelial carcinoma of salivary glands].

Nineteen cases of myoepithelial carcinoma (malignant myoepithelioma) in salivary glands were studied clinicopathologically. The clinical features are as follows: arise most frequently within the parotid glands, followed by the submandibular glands; rapidly enlarging mass with extensive invasion of the surrounding tissues in some cases; low rate of cervical lymph node metastasis but high rate of distant metastasis; very frequent recurrence after surgical excision; and poor prognosis. The carcinoma belongs to the high grade malignant tumor. It must be treated radically. The elective neck dissection is generally unnecessary. It is resistant to radiotherapy. It is possible to get rather good result in limited recurrent tumors by prompt surgery.

Adolescent↗
PubMed1997

[Histopathological study on traumatic facial nerve injury in the rabbits].

Six patterns of injuries (exposure, compression, crush, stretch, division and post-division anastomosis) were analysed in 136 facial nerve buccal branches of 68 rabbits in order to establish the experimental model for study of traumatic facial nerve injury. Changes of histopathology at definite time were studied. The results showed that: exposure can create degree I injury; compression, stretch and crush can create degree II-III injury; the prognosis in anastomosis group was obviously better than unanastomosis group. In moderate to serious injuries, changes of histopathology and ENoG were synchronized, but were not so in mild and later stage of serious injury. The 15th day postinjury was the best time of estimating the facial nerve function clinically. The area of injury would obviously influence the mylin lesion, while the quality and degree of injury would obviously influence the axonal lesion.

Animals↗
PubMed1997

[Interleukin-8, a regulator of inflammation in gingival crevicular fluid].

The role of interleuking-8 (IL-8), a neutrophil-attracting and-activating cytokine, was investigated in gingival crevicular fluid (GCF). ELISA was used to detect the levels of IL-8 in GCF collected from 54 adult periodontitis (AP) patients (105 teeth) and 24 healthy subjects (54 teeth). The results showed that 1. The role of IL-8 was dependent upon the concentration of IL-8 in GCF. IL-8, in the low concentration (< or = 30 micrograms/L), was positively correlated with bleeding index (r = 0.36, P < 0.01). While in the high concentration (> 30 micrograms/L), was negatively correlated with bleeding index and probing depth (r = -0.54 and r = -0.65 respectively, P < 0.01). In the majority of periodontitis sites (91%), the concentration of IL-8 in GCF were lower than 30 microliters/L. IL-8 most likely acted as pro-inflammatory factor in these teeth. 2. IL-8 was a two-way regulator of inflammation, pro-inflammation and anti-inflammation. The threshold of IL-8 between inducing and suppressing inflammation was approximately 30 micrograms/L. Within the confined range, IL-8 concentration greater than 30 micrograms/L could be inflammation suppressive, while a less-than-30 micrograms/L concentration of IL-8 might become inflammation inducing.

Adult↗
PubMed1997

[The evidence for existence of interleukin 8 inhibitor and its biological activity in gingival crevicular fluid].

In order to confirm the existence of Interleukin-8 (IL-8) inhibitor and its biological activity in gingival crevicular fluid (GCF), this study examined the GCF taken from 7 adult periodontitis (AP) patients. In neutralization test of IL-8, the results showed that the mean level of IL-8 was less than 1 ng/ml, which had been added into the GCF before ELESAs was performed to measure the amount of IL-8 in GCF. The mean level of IL-8 in the GCF of AP group was significantly lower than that of healthy group (P < 0.001). In biological activity test of IL-8 inhibitor, using pooled GCF taken from 8 AP patients (23 teeth), the results showed that the GCF (without recombinant human IL-8, rhIL-8) caused more white blood cell (WBC) migration than blank control group (physiological saline) did. When the amount of rhIL-8 increased in GCF from 0.1 microgram to 1 microgram, the WBC count increased by 18.6% which was less than the increase rate (49.1%) in control group with same dose of IL-8. In the saline group containing rhIL-8, the WBC chemotactic response appeared as an inverted "V"-shape curve. All these data suggested that 1. Certain kinds of IL-8 inhibitor exist in GCF which can "cleave" IL-8. 2. The level of IL-8 inhibitor(s) increases significantly in the GCF from periodontitis sites. 3. The GCF of adult periodontitis patient has strong chemotactic effects on WBC. IL-8 inhibitor(s) in GCF can slightly suppress the chemotactic effect induced by IL-8. When assessing the role of IL-8 in pathophysiology, the high and low dose of IL-8 might have different sense.

Adult↗
PubMed1997

Expression of the spinach betaine aldehyde dehydrogenase (BADH) gene in transgenic tobacco plants.

Plasmid pLS9 contains a 1.5-kb of spinach cDNA including its complete open reading frame. The 1.5-kb BADH cDNA was cut from pLS9 using restriction enzyme and was inserted into the expression cassette of plasmid pYH between the CaMV 35S promoter and polyA signal sequence. The 35S-BADH cDNA-polyA fragment of pYH was cloned into a polylinker cloning site of the binary vector pBin19. The resulting plasmid pBinBADH-S was transferred to Agrobacterium tumefacies LBA4404. The tobacco plants were transformed with strain LBA4404 containing pBinBADH-S, and more than ninety kanamycin-resistant transformants were selected. Polymerase chain reaction (PCR) detection showed that more than 60% of the transformed tobacco plants contained the foreign BADH gene. The Western blot analysis, BADH enzymatic assay, specific stain for BADH activity, and the test for salt tolerance showed that BADH gene was normally expressed in the transgenic tobacco plants. The BADH enzymes also presented in chloroplasts and cytosol of the transgenic plants. The transgenic tobacco plants having strong expression of BADH gene had strong ability to tolerate high salt stress.

Aldehyde Dehydrogenase↗
PubMed1996

Estrous cycle phase variations in visceromotor and cardiovascular responses to colonic distension in the anesthetized rat.

Visceromotor and cardiovascular responses to colonic distension were measured in female rats, anesthetized with halothane in oxygen, in the proestrus, estrus, metestrus and diestrus phases of the estrous cycle. Ten rats were studied in each group and responses were measured at 5-min intervals for 60 min. A mixed model analysis of variance showed that there was no real change in either the visceral or cardiovascular response with time. There was a highly significant difference in visceromotor responses between the phases of the estrous cycle (P < 0.001). During the phase of proestrus the balloon pressure at which a response was triggered was much lower, with a mean value (95% confidence interval) of 18.7 (16.1, 21.8) mmHg, than the other phases with mean values (95% confidence interval) of 31.9 (27.4, 37.2) mmHg for estrus, 28.1 (24.2, 32.8) mmHg for metestrus, and 31.1 (26.7, 36.3) mmHg for diestrus. The mean arterial blood pressure increased in all groups (range 3.2, 5.4%) as a response to the stimulus, but there was no associated heart rate variability and no significant differences in cardiovascular changes between the groups (P = 0.6). The visceromotor responses measured during the phase of proestrus occurred at a significantly lower threshold than in the other phases of estrous.

Anesthesia↗
PubMed1996

Leishmania donovani possess a NADPH-dependent alkylglycerol cleavage enzyme.

Leishmania parasites possess an abundance of ether-linked hydrocarbons as components of phospholipids and glycosylphosphatidylinositol anchors of glycoproteins and polysaccharides, including important surface molecules such as lipophosphoglycan (LPG) and glycosylinositolphospholipids (GIPLs). Cleavage of the ether bond is an important feature in the turnover pathway of alkylglycerols. In mammals, ether lipid cleavage activity requires a pteridine cofactor (H4 biopterin), suggesting the potential for linkage between the unusual Leishmania pteridine metabolic pathways and lipid metabolism. In this study, we partially purified and characterized an activity in L. donovani capable of cleaving the ether lipid 1-O-alkyl[3H]glycol. Unlike the mammalian enzyme but like that of Tetrahymena, the Leishmania enzyme required NADPH rather than H4-biopterin. The use of divergent cofactors by the parasite and mammalian enzymes may provide a basis for the design of anti-parasitic drugs targeting ether-linked lipid metabolism.

Animals↗
PubMed1996

Recognizing post-polio syndrome.

The disorder consists of fatigue accompanied by new muscle weakness and muscle pain or, for patients whose acute polio had included bulbar involvement, new difficulty in swallowing or change in voice. The epidemiology remains unclear, fueling anxiety among polio survivors. Yet its course is not drastically progressive, and impairment is usually limited.

Persons with Disabilities↗
PubMed1996

The local repressor AcrR plays a modulating role in the regulation of acrAB genes of Escherichia coli by global stress signals.

Genes acrAB encode a multidrug efflux pump in Escherichia coli. We have previously reported that transcription of acrAB is increased under general stress conditions (i.e. 4% ethanol, 0.5 M NaCl, and the stationary phase in Luria-Bertani medium). In this study, lacZ transcriptional fusions and an in vitro gel mobility shift assay have been utilized to study the mechanisms governing the regulation of acrAB. We found that a closely linked gene, acrR, encoded a repressor of acrAB. Nevertheless, the general stress conditions increased transcription of acrAB in the absence of functional AcrR, and such conditions surprisingly increased the transcription of acrR even more strongly than that of acrAB. These results suggest that the general-stress-induced transcription of acrAB is primarily mediated by global regulatory pathway(s), and that one major role of AcrR is to function as a specific secondary modulator to fine tune the level of acrAB transcription and to prevent the unwanted overexpression of acrAB. To our knowledge, this represents a novel mechanism of regulating gene expression in E. coli. Evidence also suggests that the up-regulation of acrAB expression under general stress conditions is not likely to be mediated by the known global regulators, such as MarA or SoxS, although elevated levels of these proteins were shown to increase the transcription of acrAB.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1996

AcrAB efflux pump plays a major role in the antibiotic resistance phenotype of Escherichia coli multiple-antibiotic-resistance (Mar) mutants.

Multiple-antibiotic-resistance (Mar) mutants of Escherichia coli are resistant to a wide variety of antibiotics, and increased active efflux is known to be responsible for the resistance to some drugs. The identity of the efflux system, however, has remained unknown. By constructing an isogenic set of E. coli K-12 strains, we showed that the marR1 mutation was incapable of increasing the resistance level in the absence of the AcrAB efflux system. This experiment identified the AcrAB system as the major pump responsible for making the Mar mutants resistant to many agents, including tetracycline, chloramphenicol, ampicillin, nalidixic acid, and rifampin.

Anti-Bacterial Agents↗
PubMed1996

Sst2, a negative regulator of pheromone signaling in the yeast Saccharomyces cerevisiae: expression, localization, and genetic interaction and physical association with Gpa1 (the G-protein alpha subunit).

Sst2 is the prototype for the newly recognized RGS (for regulators of G-protein signaling) family. Cells lacking the pheromone-inducible SST2 gene product fail to resume growth after exposure to pheromone. Conversely, overproduction of Sst2 markedly enhanced the rate of recovery from pheromone-induced arrest in the long-term halo bioassay and detectably dampened signaling in a short-term assay of pheromone response (phosphorylation of Ste4, Gbeta subunit). When the GPA1 gene product (Galpha subunit) is absent, the pheromone response pathway is constitutively active and, consequently, growth ceases. Despite sustained induction of Sst2 (observed with specific anti-Sst2 antibodies), gpa1delta mutants remain growth arrested, indicating that the action of Sst2 requires the presence of Gpa1. The N-terminal domain (residues 3 to 307) of Sst2 (698 residues) has sequence similarity to the catalytic regions of bovine GTPase-activating protein and human neurofibromatosis tumor suppressor protein; segments in the C-terminal domain of Sst2 (between residues 417 and 685) are homologous to other RGS proteins. Both the N- and C-terminal domains were required for Sst2 function in vivo. Consistent with a role for Sst2 in binding to and affecting the activity of Gpa1, the majority of Sst2 was membrane associated and colocalized with Gpa1 at the plasma membrane, as judged by sucrose density gradient fractionation. Moreover, from cell extracts, Sst2 could be isolated in a complex with Gpa1 (expressed as a glutathione S-transferase fusion); this association withstood the detergent and salt conditions required for extraction of these proteins from cell membranes. Also, SST2+ cells expressing a GTPase-defective GPA1 mutant displayed an increased sensitivity to pheromone, whereas sst2 cells did not. These results demonstrate that Sst2 and Gpa1 interact physically and suggest that Sst2 is a direct negative regulator of Gpa1.

Amino Acid Sequence↗