Gustation in fish: search for prototype of taste perception.

Fish perceive water-soluble chemicals at the taste buds that are distributed on oropharyngeal and trunk epithelia. Recent progress in molecular analyses has revealed that teleosts and mammals share pivotal signaling components to transduce taste stimuli. The fish orthologs of taste receptors, fT1R and fT2R, show mutually exclusive expression in taste buds, and both are coexpressed with phospholipase C-beta2 and the transient receptor potential M5 channel as common downstream components of taste receptor signals. Interestingly, fT1R heteromers are activated by various L-amino acids but not by sugars. This may reflects that in fish the energy metabolism depends primarily on gluconeogenesis from amino acids. fT2Rs are activated by denatonium benzoate, which is a bitter substance for mammals. It is thus likely that the preferable and aversive tastes for vertebrates, though their taste modalities somewhat vary, are transduced by the sensory conserved pathways. The comparative molecular biology of the fish taste system would lead to understanding a general logic of encoding taste modalities in vertebrates.

Construction of a taste-blind medaka fish and quantitative assay of its preference-aversion behavior.

In vertebrates, the taste system provides information used in the regulation of food ingestion. In mammals, each cell group within the taste buds expresses either the T1R or the T2R taste receptor for preference-aversion discrimination. However, no such information is available regarding fish. We developed a novel system for quantitatively assaying taste preference-aversion in medaka fish. In this study, we prepared fluorescently labeled foods with fine cavities designed to retain tastants until they were bitten by the fish. The subjects were fed food containing a mixture of amino acids and inosine monophosphate (AN food), denatonium benzoate (DN food) or no tastant (NT food), and the amounts of ingested food were measured by fluorescence microscopy. Statistical analysis of the fluorescence intensities yielded quantitative measurements of AN food preference and DN food aversion. We then generated a transgenic fish expressing dominant-negative Galpha(i2) both in T1R-expressing and in T2R-expressing cells. The feeding assay revealed that the transgenic fish was unable to show a preference for AN food and an aversion to DN food. The assay system was useful for evaluating taste-blind behaviors, and the results indicate that the two taste signaling pathways conveying preferable and aversive taste information are conserved in fish as well as in mammals.

[A case of falciparum malaria successfully treated with intravenous artesunate].

The case was a 47-year-old Nigerian male who was thought to have contracted malaria in Nigeria and then manifested fever with chill, arthralgia and diarrhea in Japan. The blood test at International Medical Center of Japan revealed thrombocytopenia and anemia. Ring forms of 0.03% of his RBCs and ICT Malaria P.f/P.v test was also positive for Plasmodium falciparum. We prescribed mefloquine to him, but the number of the paresites in his peripheral blood did not decrease, and, in fact, they came to increase (maximum 6.66%) 20 hours after the drug treatment. As clinical condition of malaria were liable to change seriously, intravenous Artesunate (a qinghaosu derivative) was decided to be given additionally to the patient. Consequently the parasites disappeared in 20 hours from his blood but a low grade fever still continued possibly because of cholecystitis. At the same time of Artesunate treatment, hemoglobinuria started and anemia worsened partly because of his G-6-PD deficiency. All pending problems were improved by the time he left Japan and those parasites were finally found to be susceptible for mefloquine by the in vitro susceptibility test. This is the first reported case of falciparum malaria successfully treated with intravenous Artesunate in Japan.

Two cases of long lasting bacteremia due to Mycobacterium avium complex despite new macrolides-containing regimens in patients with acquired immunodeficiency syndrome.

The prognosis of Mycobacterium avium complex (MAC) infection has been improved by new macrolides-containing regimens and the use of highly active antiretroviral therapy (HAART) in the treatment of acquired immunodeficiency syndrome (AIDS). We report on two AIDS cases with long lasting bacteremia due to MAC under this regimen. Both patients experienced problems due to side effects from the anti-MAC regimen and from an immune-reconstitution syndrome related to HAART. MAC infection persisted despite treatment, however, no anti-MAC drug-resistant isolates emerged throughout the clinical course in either case. These cases demonstrate that therapy for disseminated MAC infection is sometimes difficult even with HAART and macrolides-containing regimens.

Evaluation of the AMPLICOR CMV, COBAS AMPLICOR CMV monitor and antigenemia assay for cytomegalovirus disease.

The AMPLICOR CMV (qualitative DNA assay by PCR), COBAS AMPLICOR CMV Monitor (quantitative DNA assay by PCR), and antigenemia assay were tested for their ability to diagnose cytomegalovirus (CMV) infection in 115 immunocompromised patients. The AMPLICOR qualitative assay and the antigenemia assay were positive for all nine patients with a clinical diagnosis of CMV disease. The AMPLICOR quantitative assay was negative for one of the nine patients. In 106 patients without CMV disease, the AMPLICOR qualitative test was positive in 22, the quantitative test was positive in 23, and the antigenemia test was positive in 55 patients. The AMPLICOR qualitative and quantitative assays had specificities of 79% and 78% in patients without CMV disease, while that of the antigenemia assay was 48%. Diagnostic efficiencies were 79% for the AMPLICOR qualitative assay, 69% for the AMPLICOR quantitative assay, and 48% for the antigenemia assay. All three tests yielded positive results before, or at the same time as, the onset of CMV disease in most cases, which suggests they can be used to predict disease before the onset of symptoms. During antiviral treatment, test results tended to decrease quantitatively and finally became negative; negative results were followed by remission of symptoms. This suggests that the AMPLICOR quantitative assay and the antigenemia assay could be useful for monitoring therapeutic efficacy. The AMPLICOR qualitative and quantitative assays, as well as the antigenemia assay were considered effective for all of the following: diagnosing CMV disease, predicting the onset of disease, and evaluating the effectiveness of antiviral chemotherapy. The antigenemia assay was at times difficult to perform in the case of severely neutropenic patients, whereas the AMPLICOR assays could be used in such cases.

Complications during clinical courses of Pneumocystis carinii pneumonia in patients with acquired immunodeficiency syndrome.

OBJECTIVE: To describe the incidence of complications before and during therapy of Pneumocystis carinii pneumonia (PCP) in patients with acquired immunodeficiency syndrome (AIDS). METHODS: A retrospective review of the patient's medical records. PATIENTS: A total of 29 patients with AIDS and PCP who were admitted to the AIDS Clinical Center, International Medical Center of Japan from July 1996 to November 1999. RESULTS: Adverse effects were found in 24 (88.9%) of 27 patients treated with trimethoprim/sulfamethoxazole (T/S), 6 (46.1%) of 13 treated with parenteral pentamidine, and 2 (20%) of 10 treated with inhaled pentamidine. Infectious and/or non-infectious complications were found in 25 (86.2%) of 29 study patients. Regarding infectious complications, 16 (55.2%) were found on admission and 10 cases (34.5%) with infectious complications were identified during admission; including oral candidiasis (37.9% and 17.2%, respectively) and genital herpes (3.4% and 6.9%, respectively). Cytomegalovirus antigenemia was detected in 4 cases (13.8%) on admission and 12 cases (41.4%) during admission. Non-infectious complications affected 11 cases (37.9%) on admission, and 6 cases (20.7%) during admission, the latter included heart failure (10.3%) and pneumothorax (6.9%). PCP was successfully treated in all but one patient who suffered from repeated pneumothorax. CONCLUSION: Treatment of PCP can be problematic and it is important to be aware of the high incidence of various complications that can occur during the treatment of PCP.

An actin-binding protein, CAP, is expressed in a subset of rat taste bud cells.

Single cell cDNA libraries were constructed from taste bud cells of rat circumvallate papillae. Using three steps of screening, including differential hybridization, sequence analyses and in situ hybridization, a clone encoding a rat homolog of yeast adenylyl cyclase-associated protein (CAP) was identified to be highly expressed in a subset of taste bud cells.

Sustained cytomegalovirus-specific CD4+ T cell response associated with prevention of recurrence of cytomegalovirus retinitis without secondary prophylaxis after highly active antiretroviral therapy in patients with AIDS.

It has been demonstrated that the cytomegalovirus (CMV)-specific CD4(+) T cell response could be restored after ganciclovir and highly active antiretroviral therapy (HAART) in AIDS patients. In this study, we first confirmed the above observation cross-sectionally. We then performed a prospective longitudinal study over a period of 48 weeks. The second study included nine patients. All patients had received HAART. Five patients had a history of retinitis that was, however, under control after discontinuation of anti-CMV therapy more than 1 year before this study (group A). The other four had active CMV retinitis at the start of this study and anti-CMV therapy was required to control retinitis (group B). Median periods between commencement of HAART and the start of this study in group A and in group B were 27 and 4.5 months, respectively. Within both groups, the number of CD4(+) T cells that produced tumor necrosis factor alpha in response to CMV antigen did not vary throughout the observation period (Friedman test; p > 0.05). However, the median number of responsive CD4(+) T cells in group A patients was significantly higher than in group B (p < 0.05). Our results demonstrate that the number of CMV-responsive CD4(+) T cells increased when HIV was well controlled with HAART and was then maintained, and suggest that these cells may play an important role in the control of retinitis in patients with AIDS.

Seroprevalence of antibodies to Chlamydia spp. in human immunodeficiency virus-infected subjects in Japan.

To evaluate the seropositivity of Chlamydia spp. in human immunodeficiency virus (HIV)-infected subjects in Japan, Chlamydia-specific antibodies in sera collected from 106 HIV-infected subjects were measured by the microimmunofluorescence test. The prevalence of C. pneumoniae-specific IgA, C. trachomatis-specific IgG and IgA and mean titers were significantly higher in the homosexual and heterosexual HIV-infected subjects than in the hemophilic patients and HIV-negative controls. These data indicate that the higher C. pneumoniae and C. trachomatis seroprevalence among HIV-infected subjects is probably due to an HIV risk factor, such as promiscuous sexual behavior, rather than to HIV infection itself.

Comprehensive study on G protein alpha-subunits in taste bud cells, with special reference to the occurrence of Galphai2 as a major Galpha species.

Previous studies have identified many cDNA species that encode a variety of G protein alpha-subunits occurring in taste buds. These include the cDNA encoding a taste-bud-specific Galpha, gustducin (G(gust)). Here we carried out comprehensive analyses of Galpha species that occur in the taste buds of rat circumvallate papillae and also in their single cells isolated from the taste buds. Reverse transcriptase-polymerase chain reaction showed the presence of 10 kinds of Galpha cDNAs, including a splice variant of Galphas, among which G(gust), Galphas, Galphai2 and Galphai3 cDNAs were shown to be major species. In situ hybridization and immunohistochemistry showed that Galphai2, as well as G(gust), expressed in a subset of taste bud cells, and the frequency of Galphai2-expression appears to be higher than that of G(gust). Southern analyses of the amplified cDNA from single cells showed that each taste bud cell expresses multiple Galpha mRNA species. For example, some Galphai2-positive cells also express one or more other Galpha species, including Galphas, Galphai3 and G(gust), and there is no apparent correlation in expression among the three Galpha species.

A 5-day course of oral desensitization to trimethoprim/sulfamethoxazole (T/S) in patients with human immunodeficiency virus type-1 infection who were previously intolerant to T/S.

BACKGROUND: Trimethoprim/sulfamethoxazole (T/S) is an essential drug in patients with human immunodeficiency virus type-1 (HIV-1) infection to prevent opportunistic infections. About 40% to 60% of them develop skin rash which leads to discontinue the medication. A precise mechanism of the reaction is not known. OBJECTIVE: To make the patients more tolerable to the medication and to make clear whether or not the reaction is caused by serum sulfamethoxazole-specific IgE. METHODS: We established a 5-day protocol, in which T/S was administered orally as a granular form in increasing doses beginning with 0.005 g (it contains trimethoprim 0.4 mg and sulfamethoxazole 2 mg) and doubled every 12 hours until the therapeutic dose was achieved. We tried to desensitize T/S in 17 patients with HIV-1 infection who were previously intolerant to T/S and measured the specific IgE in sera. RESULTS: Desensitization was successfully completed in 15 (88.2%) of the patients. In two patients who failed the desensitization, one was due to fever and the other was gastric irritation. During followup in a mean period of 16.6 months (range, 8 to 23 months) as of May, 1999, none has had Pneumocystis carinii pneumonia (PCP) while receiving T/S after desensitization. Sulfamethoxazole-specific IgE did not increase, indicating that it was not the major cause of skin rash due to T/S in our cases. CONCLUSION: These preliminary results show that most patients who were thought to be intolerant to T/S and had no sulfamethoxazole-specific IgE can be safely desensitized and received the drug subsequently as an effective prophylaxis for PCP.

Addition of signal leader sequences to the N-termini of olfactory receptor proteins enhances their expression in Xenopus oocytet.

Several recent papers have reported the difficulties in expressing olfactory receptor proteins (ORs) in heterologous systems, and proposed that some sequences in ORs have negative effects on their efficient expression. To obtain an efficient expression system of ORs, we modified N-terminal sequences of ORs through the addition of exogenous sequences. Three kinds of sequences, designated as 5HT, V, and VL, were used. 5HT and V corresponded to the signal leader (SL) sequences of 5HT 3R and VIPR, respectively. VL corresponded to the first extracellular region of VIPR containing the SL sequence and three potential asparagine- (Asn-) linked glycosylation sites. The myc epitope was also added to the C-termini of the sequences. Several ORs including 17 of rat, GUST43 of rat, Y1 of medaka, FOR1-3 of pufferfish, 47E of carp, and ODR-10 of nematode were subjected to the modifications, and the RNAs encoding modified ORs were injected into Xenopus oocytes. The membrane fraction of the oocytes were analyzed by Western blotting to examine the expression of the proteins. In the cases of ORs modified with 5HT and V, only ODR-10 and 47E, both of which have more than two Asn-linked glycosylation sites in their extracellular regions, were detected as the bands of predicted molecular weights. On the other hand, most of the ORs modified with VL showed the bands of predicted molecular weights. These results suggest that SL sequences together with potential Asn-linked glycosylation sites have positive effects on the expression of ORs in heterologous systems.