Visual cycle and its metabolic support in gecko photoreceptors.

Photoreceptors of nocturnal geckos are transmuted cones that acquired rod morphological and physiological properties but retained cone-type phototransduction proteins. We have used microspectrophotometry and microfluorometry of solitary isolated green-sensitive photoreceptors of Tokay gecko to study the initial stages of the visual cycle within these cells. These stages are the photolysis of the visual pigment, the reduction of all-trans retinal to all-trans retinol, and the clearance of all-trans retinol from the outer segment (OS) into the interphotoreceptor space. We show that the rates of decay of metaproducts (all-trans retinal release) and retinal-to-retinol reduction are intermediate between those of typical rods and cones. Clearance of retinol from the OS proceeds at a rate that is typical of rods and is greatly accelerated by exposure to interphotoreceptor retinoid-binding protein, IRBP. The rate of retinal release from metaproducts is independent of the position within the OS, while its conversion to retinol is strongly spatially non-uniform, being the fastest at the OS base and slowest at the tip. This spatial gradient of retinol production is abolished by dialysis of saponin-permeabilized OSs with exogenous NADPH or substrates for its production by the hexose monophosphate pathway (NADP+glucose-6-phosphate or 6-phosphogluconate, glucose-6-phosphate alone). Following dialysis by these agents, retinol production is accelerated by several-fold compared to the fastest rates observed in intact cells in standard Ringer solution. We propose that the speed of retinol production is set by the availability of NADPH which in turn depends on ATP supply within the outer segment. We also suggest that principal source of this ATP is from mitochondria located within the ellipsoid region of the inner segment.

Impaired monocyte function in patients successfully treated for Whipple's disease.

Peripheral blood mononuclear cells (monocytes) from patients with Whipple's disease in long-term remission were tested for their ability to handle intracellular microorganisms. Phagocytosis and lysis of Candida tropicalis by monocytes of patients (n = 12) and controls (n = 8) were quantified after 30 min of incubation. Phagocytosis was similar in both groups but intracellular killing of Candida tropicalis was significatively lower in patients (p < 0.001). We concluded that our study showed an in vitro defect in the intracellular killing function of monocytes in subjects in remission many years after diagnosis of Whipple's disease. The defective function did not seem to be related to relapse or to the susceptibility to other infections.

Natural killer suppressor factors in sera from HIV-infected subjects.

We investigated the presence of NK suppressor factors in HIV+ sera. We further investigated if gp120 could be one of the substances responsible for the impairment of NKC regulation found in HIV+ asymptomatic patients. Our results indicate that HIV+ sera inhibit significantly normal NKC in a dose-dependent way, even at concentrations as low as 1%. The inhibitory effect of HIV+ sera decreased, but was not completely removed, by adsorptions of IgG or by treatment with a MoAb against human FcIgG. Pretreatment of normal effector cells with anti-CD16 MoAb slightly reduced their cytotoxic capability, but did not modify the suppressor effect of HIV+ sera. The The preincubation of normal PBMC with recombinant gp120 had also a suppressor effect even at 10 ng/ml. Pretreatment of HIV+ sera with anti-gp120 or anti-FcIgG MoAb reduced, but not completely, their inhibitory effect. In conclusion, HIV+ serum has a dose-dependent inhibitory effect on normal NKC. Most of this inhibition is caused by IgG, but other substances, such as gp120, can also contribute to it. Since the removal of IgG and further treatments of HIV+ sera were not able to abrogate completely the NK suppression, other serum factors still undetermined (TNF-alpha, other cytokines), should be considered.

Decreased phagolysosomal fusion of peripheral blood monocytes from patients with thalassemia major.

We evaluated the phagolysosomal fusion of peripheral blood monocytes from 15 patients with thalassemia major and 10 thalassemia major carriers using a cytomorphological method with acridine orange as fusion marker. The monocyte phagolysosomal fusion of thalassemic patients was decreased (49.6 +/- 8.6%, mean +/- SD) and differed significantly (p < 0.05) from those of carriers and normal controls (65.7 +/- 11.4% and 74.6 +/- 5.7%, respectively). In vitro deferoxamine partially improved monocyte phagolysosomal fusion of patients with thalassemia major, and did not affect monocyte function in carriers and healthy subjects. Furthermore, in vitro addition of ferrous sulfate decreased normal phagolysosomal fusion. We conclude that the monocyte phagolysosomal fusion dysfunction of thalassemic patients could be related to iron overload.

Impaired phagolysosomal fusion of peripheral blood monocytes from HIV-infected subjects.

We evaluated phagolysosomal fusion in peripheral blood monocytes from 20 HIV-infected individuals and 40 normal controls, using a fluorescence assay with acridine orange as marker. The percentages of phagolysosomal fusion of monocytes from HIV-infected subjects, after 30 and 60 min of yeast ingestion, (mean +/- standard deviation) 57.2 +/- 17 and 63.2 +/- 18.6, respectively, when compared to normal controls (72.4 +/- 7.8 and 77 +/- 8.1), did not differ significantly. However, there was a direct linear association between the percentages of phagolysosomal fusion and CD4+ lymphocytes (P < 0.001) or CD4/CD8 T-cell ratio (P < 0.01). These results suggest that phagolysosomal dysfunction becomes evident at late stages of HIV infection and progresses as CD4+.T-lymphocyte count and CD4/CD8 T-cell ratio decrease. On the other hand, recombinant gp120 inhibited significantly normal phagolysosomal fusion at concentrations ranging between 1 and 1000 ng/ml. Taking together the results obtained, we can conclude that gp120 could be responsible for monocyte phagolysosomal dysfunction observed in HIV infected patients.

[Neutrophil chemotactic dysfunction in multitransfused thalassemia patients]. / Disfunción quimiotáctica de los neutrófilos en pacientes talasémicos politransfundidos.

PURPOSE: To evaluate the chemotactic capability of neutrophils in thalassaemic patients under poly-transfusion regimens and in thalassaemia carriers. PATIENTS AND METHODS: Twenty-one patients in multi-transfusion regimen diagnosed in the Ricardo Gutiérrez Children Hospital were studied. Of them, 17 had thalassaemia major, 3 S/beta thalassaemia and one sickle-cell anaemia. Twenty-one normal subjects comprised a control group. Chemotaxis was evaluated by two methods, namely, migration under agarose layer and in microchemotaxis chamber under stimulation with N-formyl-methionyl-n-phenylalanine at optimal concentrations of 10(-5) M and 10(-6) M, respectively. RESULTS: In thalassaemia major patients, directed mobility of neutrophil assessed by both methods was significantly decreased with regard to the normal controls, whereas random mobility was preserved. The four patients under poly-transfusion who had not thalassaemia major showed the same neutrophil defect. On the contrary, chemotaxis and random mobility of the neutrophils from thalassaemia carriers (thalassaemia minor) were similar to those of the normal controls. CONCLUSIONS: These results suggest that the defect found in the patients might be caused by transfusion overload.

Defect of NK regulation in HIV-infected patients.

PIP: In Buenos Aires, Argentina, health workers obtained peripheral blood samples from 22 HIV-infected people with either no symptoms or persistent lymphadenopathy to examine natural killer cytotoxicity (NKC) of asymptomatic HIV-infected (HIV+AS) cases and the effect of factors that regulate normal NKC. Researchers compared these results with those of 10 healthy heterosexual controls. Even though NK cells of the HIV+AS cases were present in the same numbers and functioned as well as those in the controls, an inducer of interferon (Concanavalin A or ConA) could not force the cell system in vitro which demonstrated NK defectiveness. NK response to ConA of HIV+AS cases was lower than that of the healthy controls (p.05). On the other hand, the NK response to a prostaglandin antagonist (Indomethacin or IM) matched that of the healthy controls. Cell supernatants from normal peripheral blood mononuclear cells increased normal NK cell function (p.001), but those from HIV+AS cases did not do so. Thus it appeared that the HIV+AS cases were unable to produce sufficient NK enhancer factors. Cell supernatants from HIV+AS reduced normal NKC below baseline (p.05) indicating the presence of NK suppressor factors. The researchers believed products of the arachidonic acid metabolism by the cyclooexgenase pathway, maybe PGE2, may have contributed to NK suppression since IM negated suppressor activity of cell supernatants from HIV+AS subjects on normal NK function. They concluded that reduced production of enhancing factors, additional release of inhibitory factors, and deficiency at the NK effector system are likely to be the underlying causes for NK deficient function in AIDS. They noted that these effects function synergistically.^ieng

Lymphocyte subpopulations and cytokine production in paracoccidioidomycosis patients.

Despite the postulated role of the immune system in the control of the infection by Paracoccidioides brasiliensis, only a few studies have addressed this point in patients. The determination of total lymphocytes and their subpopulations in 6 untreated patients with the chronic form of paracoccidiodomycosis showed that half of them were lymphopenic, because of low number of CD4+ T-lymphocytes. All patients had low CD4/CD8 ratios. On the contrary, B-lymphocytes were normal in all patients. An additional patient, studied on treatment with ketoconazole, had normal lymphocyte counts in all subpopulations, as did one of the patients previously studied at diagnosis when he received specific antimycotic treatment. The production of interferon and tumor necrosis factor, determined by bioassay in supernatants of mononuclear blood cells of the patients, induced by interleukin 2 in vitro was significantly lower than that of normal subjects. These results show that patients with paracoccidioidomycosis have a defect in blood lymphocyte subsets as well as in the ability to produce regulatory cytokines.

[AIDS and pregnancy: a case of mother-child transmission]. / SIDA y embarazo: un caso de transmisión madre-hijo.

We report the case of a 4 month old baby in an advanced stage of HIV infection with AIDS according to the CDC definition. The HIV-infected mother was sexually promiscuous and a drug addict. The timing and route of the infection are speculative. The child was born by cesarean delivery, did not receive blood or blood products and was not breast-fed. It is postulated that the most probable route of HIV infection in this child was intrauterine vertical transmission.

SIDA y embarazo: un caso de transmisión madre-hijo. / [AIDS and pregnancy: a case of mother-child transmission]

We report the case of a 4 month old baby in an advanced stage of HIV infection with AIDS according to the CDC definition. The HIV-infected mother was sexually promiscuous and a drug addict. The timing and route of the infection are speculative. The child was born by cesarean delivery, did not receive blood or blood products and was not breast-fed. It is postulated that the most probable route of HIV infection in this child was intrauterine vertical transmission.

[The monocyte-macrophage system in Hodgkin's disease]. / El sistema monocito-macrófago en la enfermedad de Hodgkin.

Hodgkin's disease (HD) is considered as a tumor of the lymph nodes histologically characterized by a variety of cell types, resembling a nonspecific inflammatory reaction. The Reed-Sternberg cells present in the granuloma are considered neoplastic due to cytogenetic alterations, tissue culture properties and heterotransplantability. They originate from a macrophage-derived interdigitating reticulum cell. The lymph node is an immunologic organ and its alterations reveal qualitative and/or quantitative defects of the immune system. These are observed in HD at very early stages even with a minimum of lymph node involvement. Considering HD as a neoplasm of the monocyte-macrophage system, our objective was to investigate the functional capability of peripheral blood monocytes transformed into macrophages in vitro. The phagocytic and lytic activities were evaluated by the generation of toxic oxygen metabolites as due to an excessive production of PGE-2. This defect could be corrected by cyclo-oxygenase inhibitors. The defect was present at very early stages of HD and persisted even during prolonged continuous complete remissions. We also found a defect in the ingestion of candida which could not be modified by drug treatment, indicating the existence of a global dysfunction of the phagocyte. Presently, more than 90% of HD patients respond to specific therapy and remain in prolonged remission, being considered "cured". This fact may contribute to the diminished number of reports in relation to the biology of the monocyte-macrophage system in this disease.

[Immunologic studies in thalassemia major]. / Estudios inmunológicos en talasemia mayor.

It is accepted that the immune alterations in patients with thalassemia major (TM) are secondary to the continuous transfusion-related antigenic stimulation together with iron overload. We evaluated the immune status of TM patients and found quantitative alterations in the distribution of peripheral blood lymphocyte subpopulations as well as functional alterations in natural killer (NK) cytotoxicity, B-cell differentiation, T-cell immunoregulation and phagocyte functional activities. TM patients, 10 years old or younger, have a lymphocyte profile and phagocytic activity similar to normal controls. Non-splenectomized thalassemic patients, older than 10, present lymphocytosis due to an increase in B lymphocytes and with splenectomy the T-CD8+ lymphocytes increase. With respect to phagocytes, the capacity to ingest candida is preserved while the candidacidal activity and the generation of toxic oxygen metabolites during the respiratory burst are diminished, and are inversely proportional with age and serum ferritin concentration, that is, older in age and higher in iron overload, more profound are the phagocyte dysfunctions. The altered B-cell function, the dysfunction of T immunoregulatory cells and the defective NK activity observed in TM patients were independent of the age of the patients and they were observed even in children younger than 10 years old and in general are attributed to blood transfusions. Moreover, there are some alterations that thalassemic carriers can express such as a defect at the level of NK and at B-cell function regulations, suggesting a possible genetic origin. Although complex, TM constitutes a human model that allows the dissection of specific immune defects, involving multiple factors, and can provide a better comprehension of how this complex immunoregulatory system works.

Dysfunction of the monocyte-macrophage system in the idiopathic minimal change nephrotic syndrome.

We studied the function of phagocytes and the distribution of lymphocyte subpopulations in 23 patients with Idiopathic Minimal Change Nephrotic Syndrome. All the patients were in relapse at the time of the study. The latter was performed before specific therapy was started. Our control group consisted of 26 normal children who were studied while undergoing routine analysis prior to plastic surgery. Polymorphonuclear leukocytes from the patients showed no alterations in their ability to ingest and to kill candidas. On the contrary, peripheral blood monocytes had a normal phagocytic function with a decreased candidacidal activity when compared to normal controls (p less than 0.001). No correlation was found between serum immunoglobulin levels and the monocyte lytic function. The absolute number of B lymphocytes was significantly increased (p less than 0.05), whereas the absolute number of total lymphocytes, T lymphocytes and T4+ and T8+ cell subsets did not differ from those of the age-matched normal controls. Natural killer cells were functionally normal.

El sistema monocito-macrófago en la enfermedad de Hodgkin. / [The monocyte-macrophage system in Hodgkins disease]

Hodgkins disease (HD) is considered as a tumor of the lymph nodes histologically characterized by a variety of cell types, resembling a nonspecific inflammatory reaction. The Reed-Sternberg cells present in the granuloma are considered neoplastic due to cytogenetic alterations, tissue culture properties and heterotransplantability. They originate from a macrophage-derived interdigitating reticulum cell. The lymph node is an immunologic organ and its alterations reveal qualitative and/or quantitative defects of the immune system. These are observed in HD at very early stages even with a minimum of lymph node involvement. Considering HD as a neoplasm of the monocyte-macrophage system, our objective was to investigate the functional capability of peripheral blood monocytes transformed into macrophages in vitro. The phagocytic and lytic activities were evaluated by the generation of toxic oxygen metabolites as due to an excessive production of PGE-2. This defect could be corrected by cyclo-oxygenase inhibitors. The defect was present at very early stages of HD and persisted even during prolonged continuous complete remissions. We also found a defect in the ingestion of candida which could not be modified by drug treatment, indicating the existence of a global dysfunction of the phagocyte. Presently, more than 90

of HD patients respond to specific therapy and remain in prolonged remission, being considered [quot ]cured[quot ]. This fact may contribute to the diminished number of reports in relation to the biology of the monocyte-macrophage system in this disease.