Biomedical subjects

A P Fernandes

Publications and source records attributed to A P Fernandes.

14 recordsLinked to original sources

PubMed2000

Glucose-mediated Ca(2+) signalling in single clonal insulin-secreting cells: evidence for a mixed model of cellular activation.

Using clonal insulin-secreting BRIN-BD11 cells, we have assessed whether the graded response of the whole cell population to glucose can be accounted for by a dose-dependent recruitment of individual cells, an amplification of the response of the recruited cells or both. Cytosolic free Ca(2+) concentration ([Ca(2+)](i)) is an established index of beta-cell function. We used fura-2 microfluorescence techniques to assess the [Ca(2+)](i) responsiveness of single BRIN-BD11 cells to glucose and other secretagogues. Glucose (1-16.7 mM) evoked oscillatory [Ca(2+)](i) rises in these cells resembling those found in parental rat pancreatic beta-cells. The percentage of glucose-responsive cells was 11% at 1 mM and increased to 40-70% at 3-16.7 mM glucose, as assessed by a single-stimulation protocol. This profile was unrelated to possible differences in the cell cycle, as inferred from experiments where the cultured cells were synchronized by a double thymidine block protocol. Individual cells exhibited variable sensitivities to glucose (threshold range: 1-5 mM) and a variable dose-dependent amplification of the [Ca(2+)](i) responses (EC(50) range: 2-10 mM), as assessed by a multiple-stimulation protocol. Glyceraldehyde and alpha-ketoisocaproic acid had glucose-like effects on [Ca(2+)](i). The data support a mixed model for the activation of insulin-secreting cells. Specifically, the graded secretory response of the whole cell population is likely to reflect both a recruitment of individual cells with different sensitivities to glucose and a dose-dependent amplification of the response of the recruited cells.

Animals↗

PubMed1999

Modulation of glucose-induced insulin secretion by cytosolic redox state in clonal beta-cells.

Nutrient stimulation of pancreatic beta-cells increases the cellular reduced pyridine nucleotide content, but the specific role of cytosolic redox state in glucose-induced insulin release (GIIR) remains undetermined. The role of cytosolic redox state has been assessed (as reflected by the lactate/pyruvate ratio) in nutrient- and non-nutrient-induced insulin release using a recently established glucose-sensitive clonal beta-cell line (BRIN-BD11). Long-term exposure to the NAD+ precursor vitamin nicotinic acid (NA, 100 microM) was used to promote a more oxidized state in the cytosol. Glucose (2-16 mM) evoked a dose-dependent rise in the cytosolic NADH/NAD+ ratio which was linearly related to the extent of GIIR. NA suppressed the glucose-induced rise in the NADH/NAD+ ratio and concomitantly reduced GIIR by 44%. It also inhibited, by 47%, the average glucose-induced rise in cytosolic free Ca2+ concentration ([Ca2+]i, assessed by fura-2 microfluorometry from single cells). The latter effect was not accounted for by a reduction in the activity of voltage-sensitive Ca2+ channels, inasmuch as both high K+- and tolbutamide-induced [Ca2+]i rises remained insensitive to NA exposure. NA did not affect insulin release evoked by any of the depolarizing agents, indicating that steps in the stimulus-secretion coupling cascade distal to Ca2+ influx are insensitive to changes in the cytosolic redox state. It is concluded that GIIR is partially controlled by the cytosolic redox state. Moreover, the impairment in GIIR, caused by a shift toward a more oxidized state in the cytosol, originates from an attenuated [Ca2+]i response. The latter is likely mediated by the influence of cytosolic redox state on specific metabolic pathways (NADH shuttle systems and/or the malonyl-CoA pathway), leading ultimately to enhancement of the activity of ATP-sensitive K+ channels.

Animals↗

PubMed1999

An ultrastructural study of spermiogenesis in three species of Physalaemus (Anura, Leptodactylidae).

Ultrastructural aspects of spermiogenesis and testicular spermatozoa of three anuran amphibians, Physalaemus biligonigerus, P. fuscomaculatus and P. gracilis, were investigated by electron microscopy. The nuclei, middle pieces and tails of the three species were similar. In all cases, the nuclei were elongated and the acrosome consisted of a cone-shaped cap. The connecting pieces located in the flagellum implantation zone had transverse striations. The tails had a 9 + 2 axial filament pattern, a juxtaxonemal fiber and an undulating membrane. In contrast to other Leptodactylidae spermatozoa, no axial rod were observed in these Physalaemus species.

Animals↗

PubMed1998

Periodontology's application of multimedia.

This article makes an approach about the use of multimedia resources applied in odontology computer science educational, especially in periodontia. It highlights the importance of the use of these resources, as well as the one that than there is of more recent in this area.

Computer-Assisted Instruction↗

PubMed1998

Cytochemical localization of phosphatases in the germ- and Sertoli cells of Odontophrynus cultripes (Amphibia, Anura, Leptodactylidae).

Ultrastructural cytochemical techniques were used for the localization of phosphatases in spermatid and spermatozoon, as well as in Sertoli cells of Odontophrynus cultripes (Amphibia, Anura, Leptodactylidae). Acid phosphatase was found in the acrosome. Thiamine pyrophosphatase was observed in the Golgi cisternae and in the tail spermatozoon surface. Glucose-6-phosphatase was located in the membrane complex of the acrosomal region. Already, in the Sertoli cells acid phosphatase was located in the lysosomes and glucose-6-phosphatase was observed in association with the endoplasmic reticulum and Golgi complex. These observations support the idea that various phosphatases may play some role in spermatid differentiation and in the interactions germ cells--Sertoli cells during spermiogenesis process.

Acrosome↗

PubMed1998

Spermiogenesis in phytophagous bug (Hemiptera, Pentatomidae): an ultrastructural study.

Ultrastructural and immunocytochemical studies were carried out on spermiogenesis in two species of phytophagous bug, Acrosternum aseadum and Nezara viridula. The nucleus development involved changes in the shape and in the degree of chromatin condensation, with specific aggregation patterns of DNA-histone complex occurring during this process. The acrosome showed a three-layered and the acrosomal content a paracrystalline arrangement. The axoneme presented a 9 + 9 + 2 microtubule pattern and bridges occurred between axonemal microtubules 1 and 5, and mitochondrial derivatives. Two paracrystalline structures embedded in amorphous regions were observed in the mitochondrial derivatives. The use of the negative staining technique shows a zig-zag profile in the mitochondria due to infolding to the cristae, regularly spaced with approximately 40 nm. An electron dense rod was observed near the centriolar adjunct; it presented labelling for tubulin suggesting that this structure may be involved in the microtubule organization during spermiogenesis of these insects.

Animals↗

PubMed1997

Immunosuppressive treatment in severe connective tissue diseases: effects of low dose intravenous cyclophosphamide.

OBJECTIVE: To review our experience with low dose intravenous pulse cyclophosphamide in the treatment of patients with severe connective tissue diseases. PATIENTS: Ninety patients (68F:22M) with severe connective tissue diseases received a total of 883 cyclophosphamide pulses with 78 of 90 patients initially having weekly 500 mg pulses for a median of three (2-10) weeks. Diagnoses included: systemic lupus erythematosus (SLE) (n = 43); systemic vasculitides (n = 42); idiopathic inflammatory myopathies (n = 4); mixed essential cryoglobulinaemic vasculitis (n = 1). The median age was 48 (range 22-76) years with a median disease duration of 94 (18-250) months. RESULTS: Complete or partial remission was noted in 68 of 90 patients (75.5%) after a median follow up of 56 (5-213) months. At follow up significant median changes were noted in SLE patients: erythrocyte sedimentation rate (ESR) from 44 to 22 mm 1st hour; anti-dsDNA antibody concentrations from 81 to 48 IU/ml; proteinuria from 2.5 to 1.5 g/day; serum albumin from 36 to 40 g/l; complement C3 from 0.88 to 0.90 g/l, and C4 from 0.18 to 0.22 g/l. In the vasculitis patients significant median changes were seen in: ESR from 44 to 15 mm 1st hour; C reactive protein (CRP) from 16 to 5 g/dl; neutrophils from 8.55 to 4.3 x 10(9)/l; platelets from 340 to 261 x 10(3)/l, and haemoglobin from 12.6 to 13.2 g/dl. Patients with Churg-Strauss syndrome, Wegener's granulomatosis, and neuropsychiatric lupus showed the best initial response but 58% of Wegener's patients relapsed. Median corticosteroid doses were significantly reduced from 15 (5-60) mg to 10 (3-35) mg daily. Adverse events: infections (7 patients), neutropenia (5), lymphopenia (18), and haemorrhagic cystitis (1 intravenous and 2 oral cyclophosphamide), allergies to mesna (2). None of the women at risk had prolonged amenorrhoea. Five patients doubled their serum creatinine and five died from sepsis (2) or severe disease (3). CONCLUSION: Treatment of severe connective tissue diseases with 'low dose' intravenous cyclophosphamide pulses compares in efficacy with the higher monthly doses previously advocated. Treatment was well tolerated with fewer adverse effects and most significantly, there were no cases of premature ovarian failure.

Adult↗

PubMed1996

Leishmania (V.) guyanensis: isolation and characterization of glucantime-resistant cell lines.

A glucantime sensitive Leishmania (V.) guyanensis strain was used to obtain in vitro resistant cell lines, by increments in glucantime concentrations employing both one step and stepwise protocols. Whereas the effective concentration of drug that inhibited the growth of wild type cells by 50% (EC50 value) was 0.20 mg Sb(v)/mL, the resistant cells were able to grow in glucantime concentrations greater than 8.0 mg/mL. The resistant cell lines were partially characterized by their in vitro response to glucantime, the stability of resistance phenotype, cross resistance to a range of drugs, and also by the analysis of total DNA fragments generated by restriction endonucleases and blot hybridization. Amplified DNA sequence similar to a P-glycoprotein analog from Leishmania tarentolae (ltpgpA gene) was observed in all the resistant cell lines obtained through the one-step protocol. These cell lines showed cross resistance to heavy metals but were sensitive to puromycin, vinblastine, and pentostam.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1993

Evolution of nuclear ribosomal RNAs in kinetoplastid protozoa: perspectives on the age and origins of parasitism.

Molecular evolutionary relationships within the protozoan order Kinetoplastida were deduced from comparisons of the nuclear small and large subunit ribosomal RNA (rRNA) gene sequences. These studies show that relationships among the trypanosomatid protozoans differ from those previously proposed from studies of organismal characteristics or mitochondrial rRNAs. The genera Leishmania, Endotrypanum, Leptomonas, and Crithidia form a closely related group, which shows progressively more distant relationships to Phytomonas and Blastocrithidia, Trypanosoma cruzi, and lastly Trypanosoma brucei. The rooting of the trypanosomatid tree was accomplished by using Bodo caudatus (family Bodonidae) as an outgroup, a status confirmed by molecular comparisons with other eukaryotes. The nuclear rRNA tree agrees well with data obtained from comparisons of other nuclear genes. Differences with the proposed mitochondrial rRNA tree probably reflect the lack of a suitable outgroup for this tree, as the topologies are otherwise similar. Small subunit rRNA divergences within the trypanosomatids are large, approaching those among plants and animals, which underscores the evolutionary antiquity of the group. Analysis of the distribution of different parasitic life-styles of these species in conjunction with a probable timing of evolutionary divergences suggests that vertebrate parasitism arose multiple times in the trypanosomatids.

Animals↗

PubMed1993

[Emphysematous pyelonephritis].

A case of emphysematous pyelonephritis to E. coli, in a 63-year-old female diabetic patient is presented herein. Imaging techniques (plain abdomen X-Ray, ultra-sonography and computed tomography) allowed the authors to make the diagnosis. Percutaneous nephrostomy, combined with medical therapeutics, contributed to a favourable clinical evolution of the patient.

Diabetes Complications↗

PubMedDate not supplied

Oviposition by Schistosoma mansoni during in vitro cultivation.

Observation of Schistosoma mansoni oviposition during in vitro culture of adult worms for a maximum period of 10 days showed three well distinct phases in the kinetics of oviposition: an initial phase with low egg production, a period of maximum oviposition and finally a progressive reduction in the number of eggs during the late phases of culture. The kinetics of oviposition and the number of eggs laid by the parasites are influenced by the number of worm pairs per amount of RPMI 1640 medium, time of parasite development in the vertebrate host and type of serum utilized in the culture medium.

Animals↗

PubMedDate not supplied

Immune responses induced by a Leishmania (Leishmania) amazonensis recombinant antigen in mice and lymphocytes from vaccinated subjects.

In the search for Leishmania recombinant antigens that can be used as a vaccine against American Cutaneous Leishmaniasis, we identified a Leishmania (Leishmania) amazonensis recombinant protein of 33 kD (Larp33) which is recognized by antibodies and peripheral blood leukocytes (PBL) from subjects vaccinated with Leishvacin, Larp33 was expressed in Escherichia coli after cloning of a 2.2 kb Sau3 digested genomic fragment of L. (L.) amazonensis into the pDS56-6 His vector. Immunoblotting analysis indicated that Larp33 corresponds to an approximately 40-kD native protein expressed in promastigotes of L. (L.) amazonensis and L. (Viannia) braziliensis. Northern blots of total RNA also demonstrated that the gene coding for this protein is expressed in promastigotes of the major lineages of Leishmania causing American Cutaneous Leishmaniasis. Larp33 induced partial protection in susceptible mouse strains (BALB/c and C57BL/10) against L. (L.) amazonensis after vaccination using Bacille Calmette-Guerin (BCG) as adjuvant. In vitro stimulation of splenocytes from BALB/c protected mice with Larp33 elicited the secretion of IL-2 and IFN-gamma, suggesting that a Th1 cell-mediated protective response is associated with the resistance observed in these mice. As revealed by its immunogenic and antigenic properties, this novel recombinant antigen is a suitable candidate to compose a vaccine against cutaneous leishmaniasis.

Animals↗

PubMedDate not supplied

Effects of goyazensolide during in vitro cultivation of Schistosoma mansoni.

Goyazensolide, a component extracted of Eremanthus goyazensis showed a significant inhibitory effect on egg-laying of Schistosoma mansoni during in vitro cultivation of this parasite. Motility of the worms was also reduced under treatment with goyazensolide and 90% of mortality was reached with concentrations up to 4 micrograms/ml. It has found that separated worms were more susceptible than worms pairing during drug exposition and female alone was significantly more susceptible than male worm in the same conditions of in vitro cultivation. Natural products isolated from plants represent potential sources for the identification of structures useful for the design of alternative molecules to be used as new drug substances against several infectious diseases.

Animals↗

PubMedDate not supplied

Staphylococcus cohnii: a case report on an unusual pathogen.

Coagulase-negative staphylococci have become increasingly important causes of infection in predisposed hosts. such as patients receiving immunosuppressive therapy and broad-spectrum antimicrobial drugs, patients who have prosthetic devices, or those who have prolonged hospital or intensive care unit stays. However, human infections caused by Staphylococcus cohnii rarely have been reported in the literature. In this report, we review the current literature and describe a 38 year-old immunosuppressed woman who developed catheter-related S. cohnii bacteremia. The case illustrates why microbiology laboratories under certain circumstances should identify coagulase-negative staphylococci to the species level. This information may be critical because it may allow clinicians to identify the source of the infecting organism and to choose appropriate antibiotics. Yet in this era of cost containment many laboratories may decrease costs by decreasing services, including species identification.

Adult↗