Biomedical subjects

C Lara

Publications and source records attributed to C Lara.

At least 37 records · Page 2Linked to original sources

PubMed1996

[Usefulness of cerebral biopsy in focal cerebral lesions in patients with human immunodeficiency virus infection].

Brain mass lesions (BML) occurred in 10% of patients infected by the human immunodeficiency virus (HIV), as expression of severe and sometimes treatable diseases. However, the management of them is not well established. We analyzed, retrospectively, 26 brain biopsies (22 estereotaxic) in patients with HIV infection and BML to know their usefulness and safety. The inclusion criteria were: Failure of the anti-Toxoplasma empirical treatment, atypical scan appearance for toxoplasmosis, or severe neurological picture. Brain biopsy yielded a diagnosis in 19 patients (73.1%): Progressive multifocal leukoencephalopathy (n = 8; 30.8%), primary central nervous system lymphoma (n = 6; 23.1%), mycobacteriosis (n = 2; 7.7%), toxoplasmosis (n = 2; 7.7%), criptococcosis (n = 1), cryptosporidiosis (n = 1) and HIV-encephalitis (n = 1). In one case there was a multiple diagnosis: mycobacteriosis, toxoplasmosis, and lymphoma. Brain biopsy results decided a change in therapy in 65.4%, the resolution or improvement of the neurological process in 30.8%, and the determination of the prognosis in 30.8%. In 8 cases (30.7%) there were biopsy complications, with secondary mortality in one. Brain biopsy of BML in HIV-infected patients is a diagnostic method with a high overall diagnostic rentability and uncommon non reversible complications, offering the possibility to prescribe a specific and potentially curative treatment.

Adult↗

PubMed1996

Discrepancy of hepatitis C virus genotypes as determined by phylogenetic analysis of partial NS5 and core sequences.

The use of phylogenetic analyses of partial NS5 and core regions for hepatitis C virus (HCV) genotyping was evaluated by analysing seven Honduran and 24 European HCV strains. Core primers were designed with which HCV genotypes 1, 2, and 3 were readily amplified. The reliability of phylogenetic analysis of a 111-bp core sequence was verified by comparing the typing results with those obtained using the whole core gene of 52 reference strains. Accordant genotypes (1a, 1b, 2b, and 3a) were obtained when phylogenetic analyses were undertaken on both the partial core and a 222-bp NS5 sequence in all of the European HCV strains. Genotypes 1a, 1b, and 3a were identified among the Honduran strains by phylogenetic analysis of the partial NS5 sequence. Interestingly, two of three Honduran type 3a strains, as determined by the NS5 sequence analysis, turned out to be type 1a by core sequence analysis. These two strains were also classified as type 1a, but not 3a, by a core type-specific PCR. Furthermore, the E2/NS1 regions were similar to HCV-PT, a representative strain of genotype 1a. The results indicate that chimeral HCV strains exist, although in most cases a good concordance is found when phylogenetic analysis of partial core and NS5 sequences are used for genotyping. This finding should be taken into account when HCV is genotyped by phylogenetic analysis of a partial HCV sequence from a single genomic region.

Amino Acid Sequence↗

PubMed1996

[Kikuchi-Fujimoto disease associated with acute infection by herpesvirus 6].

The histiocytic necrotizing lymphadenitis or Kikuchi-Fujimoto disease is a very rare entity in Spain. We present a 34-year-old arabic male admitted to hospital because one-month story of asthenia, anorexia, weight loss, fever and lymphadenopathies in all palpable sites. Analytic studies were all within normal limits except LDH levels and globular sedimentation rate, both raised. After cervical lymph node biopsy performance high grade Non-Hodgkin lymphoma was initially diagnosed. During admission he complained from pain in both shoulders and an erythematous desquamative eruption in trunk appeared. Some days later, a second lymph node biopsy was performed and Kikuchi-Fujimoto disease was diagnosed. Serologic tests for human herpes virus 6 were positive demonstrating active associated infection. He begun treatment with indomethicin, fever and general symptoms disappeared one week later discontinuing treatment. Two months after discharge, all lymphadenopathies had disappeared. A review on epidemiological, clinical, pathological and differential diagnosis issues is made.

Adult↗

PubMed1994

Ethnic differences between Maori, Pacific Island and European New Zealand women in prevalence and attitudes to urinary incontinence.

AIMS: To assess the prevalence of urinary incontinence in New Zealand women of European, Maori and Pacific Island descent aged 18 years and over. METHODS: A questionnaire, designed to be self administered, was sent to a group of 1028 women selected at random from the electoral roll in central Wellington. Incontinence was defined as any involuntary loss of urine. If present, details were sought regarding the occurrence, type, and severity of the incontinence so that the prevalence and nature of the problem within ethnic groups could be determined. RESULTS: The prevalence for Maori women (46.8%) was significantly greater than for either Pacific Island (29.2%) or European women (31.2%) (chi 2 = 14.02, p = 0.001). Increasing age, and parity were associated with increasing prevalence of incontinence for all ethnic groups. Of the incontinent women, 9% were continually incontinent, 28% once or more daily, and 37% more than twice monthly. A further 26% were incontinent less than twice monthly. The most reported type of incontinence was stress incontinence (48% of incontinent women), with 27% reporting urge incontinence, and 21% a mixed picture of stress and urge. There was no significant difference in the frequency of these symptoms between the different ethnic groups. Fifty per cent of incontinent women reported wanting help for their urinary problems, but only one third had sought medical assistance, with many regarding incontinence as a normal occurrence. CONCLUSIONS: Urinary incontinence is common in New Zealand women irrespective of ethnic group. The low proportion of women seeking medical assistance emphasises the need for much greater awareness and public education of what is largely a treatable clinical problem. Urinary incontinence is estimated to affect more than one quarter of the female population. The prevalence varies according to different age groups, and although it is recognised that incontinence is more common in the elderly, a significant number are young with nearly 20% of female children experiencing episodes of urinary leakage. The medical, personal and social impact of urinary incontinence is substantial, but surprisingly it is largely ignored, both by women with the condition, and by those providing health services to them such that it has been described as 'the hidden epidemic'. In New Zealand, research has been carried out on the prevalence of urinary incontinence and reasons for not seeking treatment in the European community, but the other major ethnic groups in New Zealand (Maori and Pacific Island) have not been investigated. The aim of this study was to assess the prevalence of urinary incontinence in these ethnic groups and to determine any differences to the prevalence of incontinence in European women in a similar socioeconomic environment. In addition, it was hoped to obtain some understanding of the attitudes of the women in each group to incontinence and their perception of the currently available treatments and medical services.

Adolescent↗

PubMed1994

Ammonium-sensitive protein kinase activity in plasma membranes of the cyanobacterium Anacystis nidulans.

Cytoplasmic membranes prepared from nitrate-grown Anacystis nidulans cells exhibit a Mg(2+)-dependent protein kinase activity able to phosphorylate in vitro plasma membrane polypeptides with molecular masses of 98, 93, 83, 47, 44 and 31 kDa. The protein kinase activity was inhibited in cytoplasmic membrane preparations from nitrate-grown cells which had been exposed to ammonium for 5 min. Parallely, ammonium exposure also resulted in a more than two-fold activation of an alkaline phosphatase activity present in the soluble fraction. These results are discussed in relation to the well-known inhibition by ammonium of nitrate transport activity, and a hypothesis for the regulatory mechanism involved is presented.

Alkaline Phosphatase↗

PubMed1994

Immunohistochemical localization of filaggrin in benign, premalignant and malignant cervical tissue.

Epithelial distribution of filaggrin, a histidine-rich protein related to squamous terminal differentiation, was investigated in 87 cervical biopsies using an avidin-biotin-peroxidase technique with a monoclonal anti-human filaggrin antibody (AKH1). Normal squamous cervical epithelium exhibited a positive homogeneous immunoperoxidase stain in the upper parabasal, intermediate and superficial cell layers. Similar findings were obtained in cervical condylomas, although full-thickness staining was observed in 35.7% of the cases (P < 0.001). Filaggrin expression in CIN was inversely related to the severity of the lesion (P < 0.001). An irregular staining pattern was present in most high-grade CIN. Filaggrin expression was closely connected to the degree of tumour differentiation (P < 0.05) in squamous cell carcinomas of the cervix. Abnormal filaggrin stainings identified a premalignant/malignant cervical squamous lesion with a positive predictive value of 92.3%. Non-squamous epithelia showed lack of filaggrin expression. Filaggrin may therefore be considered a marker of squamous differentiation in both the normal and pathological human uterine cervix.

Adult↗

PubMed1992

Nitrate transport in the cyanobacterium Anacystis nidulans R2. Kinetic and energetic aspects.

Nitrate transport has been studied in the cyanobacterium Anacystis nidulans R2 by monitoring intracellular nitrate accumulation in intact cells of the mutant strain FM6, which lacks nitrate reductase activity and is therefore unable to reduce the transported nitrate. Kinetic analysis of nitrate transport as a function of external nitrate concentration revealed apparent substrate inhibition, with a peak velocity at 20-25 microM-nitrate. A Ks (NO3-) of 1 microM was calculated. Nitrate transport exhibited a stringent requirement for Na+. Neither Li+ nor K+ could substitute for Na+. Monensin depressed nitrate transport in a concentration-dependent manner, inhibition being more than 60% at 2 microM, indicating that the Na(+)-dependence of active nitrate transport relies on the maintenance of a Na+ electrochemical gradient. The operation of an Na+/NO3- symport system is suggested. Nitrite behaved as an effective competitive inhibitor of nitrate transport, with a Ki (NO2-) of 3 microM. The time course of nitrite inhibition of nitrate transport was consistent with competitive inhibition by mixed alternative substrates. Nitrate and nitrite might be transported by the same carrier.

Biological Transport↗

PubMed1991

Nitrate-dependent o(2) evolution in intact leaves.

Evolution of O(2) by illuminated intact detached leaves from barley (Hordeum vulgare L. cv Athos) and pea (Pisum sativum L. cv Lincoln) in a CO(2)-saturating atmosphere was enhanced when KNO(3) (1-2.5 millimolar) had been previously supplied through the transpiration stream. The extra O(2) evolution observed after feeding KNO(3) increased with the light intensity, being maximal at near saturating photon flux densities and resulting in no changes in the initial slope of the O(2)versus light-intensity curve. No stimulation of O(2) evolution was otherwise observed after feeding KCl or NH(4)Cl. The data indicate that nitrate assimilation uses photosynthetically generated reductant and stimulates the rate of non-cyclic electron flow by acting as a second electron-accepting assimilatory process in addition to CO(2) fixation.

Journal Article↗

PubMed1990

Distribution of involucrin in normal and pathological human uterine cervix.

A study was undertaken to determine the potential value of involucrin immunostaining, a protein synthesized by mature squamous epithelial cells, in distinguishing benign from neoplastic lesions in cervical pathology. A total of 146 cervical biopsies were analyzed using an indirect immunoperoxidase method and polyclonal antibody. A suprabasal homogeneous cytoplasmic staining pattern was consistently observed in normal squamous cervical epithelium. In contrast, 43.7% of cervical condylomas showed involucrin at all levels of the epithelium including the basal layer. Variable patterns were seen in cervical intraepithelial neoplasia (CIN), with 46% of full-thickness stainings, although no significant difference was obtained among the different grades of CIN lesions. Distribution of involucrin was correlated (P less than 0.05) with the degree of tumor differentiation in squamous cell carcinomas, being absent in 71.4% of poorly differentiated carcinomas and focally present in 75% of well-differentiated carcinoma. Lesions of endocervical origin, either benign or malignant, were entirely negative for involucrin. It is concluded that involucrin seems unable to establish a reliable differential diagnosis between benign and neoplastic conditions in cervical pathology, and should therefore be considered only a specific marker of squamous differentiation in both normal and pathological human uterine cervix.

Adult↗

PubMed1989

Determination of intracellular nitrate.

A sensitive procedure has been developed for the determination of intracellular nitrate. The method includes: (i) preparation of cell lysates in 2 M-H3PO4 after separation of cells from the outer medium by rapid centrifugation through a layer of silicone oil, and (ii) subsequent nitrate analysis by ion-exchange h.p.l.c. with, as mobile phase, a solution containing 50 mM-H3PO4 and 2% (v/v) tetrahydrofuran, adjusted to pH 1.9 with NaOH. The determination of nitrate is subjected to interference by chloride and sulphate when present in the samples at high concentrations. Nitrite also interferes, but it is easily eliminated by treatment of the samples with sulphamic acid. The method has been successfully applied to the study of nitrate transport in the unicellular cyanobacterium Anacystis nidulans.

Biological Transport↗

PubMed1989

Relationship between a 47-kDa cytoplasmic membrane polypeptide and nitrate transport in Anacystis nidulans.

The polypeptide composition of cytoplasmic membranes of the cyanobacterium Anacystis nidulans changes in response to variations in the nitrogen source available to the cells, differing specifically in the amount of a polypeptide of 47-kDa molecular mass. Synthesis of the polypeptide and expression of nitrate transport activity are repressed by ammonium. Transfer of ammonium-grown cells to a medium containing nitrate as the sole nitrogen source results in parallel development of the 47-kDa polypeptide and nitrate transport activity of the cells. These results suggest the involvement of the 47-kDa cytoplasmic membrane polypeptide in nitrate transport by A. nidulans.

Carrier Proteins↗

PubMed1989

Distribution of epithelial antigens in the human uterine cervix: a review.

Epithelial antigen immunostaining in the uterine cervix has been claimed to be helpful in the identification and classification of rare lesions, evaluation of basement membrane integrity, study of atypical condylomas, immunodetection of proliferating processes and early diagnosis of malignant transformation. The present review attempts to demonstrate the potential value of immunohistological techniques as a means of identifying normal and abnormal patterns of antigenic expression in cervical epithelium.

Antigens, Neoplasm↗

PubMed1989

Precocious appearance of markers of squamous differentiation in metaplastic cells of human endocervix.

We used immunoperoxidase methods employing antibodies against involucrin and filaggrin, both markers of squamous terminal differentiation, to study squamous metaplastic transformation in the human endocervix. Expression of involucrin and filaggrin was restricted to squamous metaplastic cells whereas columnar epithelial cells were constantly negative. Immature squamous metaplastic epithelium also showed a positive immunostaining. In mature squamous metaplasia a suprabasal homogeneous staining pattern similar to that found in the exocervical epithelium was detected, although with full-thickness filaggrin immunoreactivity in 45% of cases (P less than 0.05). These results support the hypothesis of an epithelial origin of reserve subcolumnar cells, and suggest that precocious squamous differentiation seems to take place in metaplastic cells of the human endocervix.

Adult↗

PubMed1989

Changes in Net O(2) Exchange Induced by Inorganic Nitrogen in the Blue-Green Alga Anacystis nidulans.

The response of net O(2) exchange to light intensity by intact Anacystis nidulans cells in the presence of saturating NaHCO(3) concentrations followed a curve with an inflection near the light-compensation point. Addition of either KNO(3) or NH(4)Cl stimulated O(2) uptake in the dark and at light intensities below the light-compensation point. This resulted in steeper slopes of the curve calculated below and above the light-compensation point. At O(2) concentrations limiting dark respiration, addition of inorganic nitrogen had no effect on either dark respiration or O(2) exchange in the light. The apparent changes in photosynthetic yield observed under normal O(2) concentration disappeared when respiration was limited by O(2) availability, indicating that the effects of inorganic nitrogen on O(2) exchange at low light intensities are due to stimulation of respiration rather than to increases in photosynthetic yield.

Journal Article↗

PubMed1987

Modulation of nitrate uptake in Anacystis nidulans by the balance between ammonium assimilation and CO2 fixation.

Gradual inhibition of ammonium assimilation in Anacystis nidulans cells by increasing concentrations of 5-hydroxylysine resulted in a progressive enhancement of nitrate uptake. For 5-hydroxylysine-treated cells, the magnitude of the inhibition of nitrate uptake promoted by added ammonium was dependent on the ammonium assimilation capacity. In cells with a moderate ammonium assimilation activity, acceleration of CO2 fixation induced by bicarbonate addition antagonized the negative effect of ammonium, allowing full nitrate uptake activity. The results support the contention that nitrate utilization is under the feed-back control exerted by products of its own assimilation via ammonium, the inhibitory effect being potentiated by ammonium addition and alleviated by enhanced CO2 fixation. Results of amino acid analysis in cells exhibiting different capacities to utilize nitrate speak against these compounds as direct effectors of nitrate uptake.

Amino Acids↗

PubMed1987

Photosynthetic Assimilation of NO(3) by Intact Cells of the Cyanobacterium Anacystis nidulans: Influence of NO(3) and NH(4) Assimilation on CO(2) Fixation.

Illuminated suspensions of Anacystis nidulans, supplied with saturating concentrations of CO(2) evolved O(2) at a greater rate when nitrate was simultaneously present. The extent of the stimulation of noncyclic electron flow induced by nitrate was dependent on light intensity, being maximal under light saturating conditions. Accordingly, nitrate depressed the rate of CO(2) fixation at limiting but not at saturating light, this depression reflecting the competition between both processes for assimilatory power. In contrast, ammonium stimulated CO(2) fixation at any light intensity assayed, the stimulation being dependent on the incorporation of ammonium to carbon skeletons. The positive effect of ammonium on CO(2) fixation also appeared to occur when nitrate was the nitrogen source, since with either nitrogen source an increase in the incorporation of newly fixed carbon into acid-soluble metabolites took place. From these results, the in vivo partitioning of assimilatory power between photosynthetic nitrogen and carbon assimilation and the quantitative and qualitative effects of inorganic nitrogen assimilation on CO(2) fixation are discussed.

Journal Article↗

PubMed1987

Regulated nitrate transport in the cyanobacterium Anacystis nidulans.

Intracellular accumulation of nitrate, indicative of the operation of an active nitrate transport system, has been measured in intact cells of the cyanobacterium Anacystis nidulans. The ability of the cells to accumulate nitrate was effectively hindered by either ammonium addition or selective inhibition of CO2 fixation by DL-glyceraldehyde, with the effect of either compound being prevented by previously blocking ammonium assimilation. The results support the contention that nitrate utilization in cyanobacteria is regulated at the level of nitrate transport through the concerted action of ammonium assimilation and CO2 fixation.

Ammonia↗

PubMed1986

Distinctive Light and CO(2)-Fixation Requirements of Nitrate and Ammonium Utilization by the Cyanobacterium Anacystis nidulans.

The effect of light intensity on the rates of ammonium and nitrate uptake and of CO(2) fixation has been determined in intact Anacystis nidulans cells. Ammonium uptake became saturated at photon flux values of about 60 microeinsteins per square meter per second, whereas both nitrate uptake and CO(2) fixation reached saturation at about 250 microeinsteins per square meter per second, the rates of the two latter processes being tightly correlated at any light intensity assayed. Inhibition of ammonium assimilation resulted in the loss of correlation between CO(2) fixation and nitrate uptake, the latter process exhibiting then a reduced light requirement. The results establish a clear distinction between ammonium utilization and nitrate utilization with regard to their light requirement and to the nature of their dependence upon CO(2) fixation.

Journal Article↗