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Biomedical subjects

R A Torres

Publications and source records attributed to R A Torres.

At least 37 records · Page 2Linked to original sources
PubMed1996

Interresidue hydrogen bonding in a peptide nucleic acid.RNA heteroduplex.

Previous molecular mechanics calculations suggest that strands of peptide nucleic acids (PNAs) and complementary oligonucleotides form antiparallel duplexes stabilized by interresidue hydrogen bonds. In the computed structures, the amide carbonyl oxygen nearest the nucleobase (O7') forms an interresidue hydrogen bond with the backbone amide proton of the following residue, (n + 1)H1'. Of the 10 published two dimensional 1H NMR structures of a hexameric PNA.RNA heteroduplex. PNA(GAACTC).r(GAGUUC), 9 exhibit two to five potential interresidue hydrogen bonds. In our minimized average structure, created from the coordinates of these 10 NMR structures, three of the five possible interresidue hydrogen bond sites within the PNA backbone display the carbonyl oxygen (O7') and the amide proton (n + 1)H1' distances and N1'-H1'-(n - 1)O7' angles optimal for hydrogen bond formation. The finding of these interresidue hydrogen bonds supports the results of our previous molecular mechanics calculations.

Computer Simulation↗
PubMed1996

Lower Helicobacter pylori infection and peptic ulcer disease prevalence in patients with AIDS and suppressed CD4 counts.

OBJECTIVE: The prevalence of Helicobacter pylori (HP) has previously been reported to be lower in AIDS patients. This study evaluated the prevalence of HP and peptic ulcer disease in relation to absolute CD4 counts in HIV-seropositive patients with GI symptoms. DESIGN: Seventy-two patients (48 HIV-positive and 24 HIV-negative) with GI symptoms were evaluated with upper endoscopy and antral gastric biopsy. Samples were prepared with Giemsa stain and reviewed by a single pathologist to determine status of HP infection. The patients were stratified on the basis of HIV status and CD4 count: group A, HIV-positive patients with a CD4 count greater than 200, group B, HIV-positive patients with CD4 counts less than 200, and group C, an HIV-negative control group. RESULTS: The prevalence of HP infection in the three groups was as follows: group A 69% (11/16), group B 13% (4/32), and group C 63% (15/24). Peptic ulcer prevalence in group A was 19% (3/16), group B 3% (1/32), and group C 25% (6/24). CONCLUSIONS: The prevalence of HP in HIV-positive patients with a CD4 count less than 200 is significantly lower (p < 0.001) than that found in HIV-negative patients. The number of peptic ulcers in the HIV-positive group with CD4 < 200 was significantly less (p = 0.035) than that of the HIV-negative patients. These results suggest a role of CD4 cell and immune function in sustaining HP infection and HP-related peptic ulcer disease.

AIDS-Related Opportunistic Infections↗
PubMed1994

Oral atovaquone compared with intravenous pentamidine for Pneumocystis carinii pneumonia in patients with AIDS. Atovaquone Study Group.

OBJECTIVE: To test the hypothesis that the therapeutic success rate of oral atovaquone is not worse than that of intravenous pentamidine in the primary treatment of mild and moderate Pneumocystis carinii pneumonia in patients with the acquired immunodeficiency syndrome and to detect differences in the toxicity rates of the two treatments. DESIGN: Patients were randomly assigned to receive 21 days of open-label therapy with either atovaquone, 750 mg orally with meals three times daily, or intravenous pentamidine, 3 to 4 mg per kg body weight once daily. SETTING: Multicenter study including university and community treatment facilities. PATIENTS: Patients with human immunodeficiency virus infection and clinical presentations consistent with mild or moderate P. carinii pneumonia were eligible. For efficacy and safety analyses, patients with histologically confirmed P. carinii pneumonia were emphasized. MEASUREMENTS: Patients were monitored by clinical and laboratory evaluations for therapeutic efficacy and adverse events during the acute treatment phase and for 8 weeks after therapy was discontinued. RESULTS: As initial therapy for a histologically confirmed episode of P. carinii pneumonia, 56 patients received atovaquone and 53 received pentamidine. More patients were successfully treated with atovaquone (57%) than with pentamidine (40%), a difference of 17% (95% CI, -3% to 38%; P = 0.085), but more patients failed to respond to atovaquone (29%) than to pentamidine (17%), a difference of 12% (CI, -6% to 29%; P = 0.18). Discontinuation of original therapy because of treatment-limiting adverse events was more frequent in the pentamidine group (36%) than in the atovaquone group (4%) (difference, -32%; CI, -48% to -17%; P < 0.001). Nine patients in each treatment group died during the study. CONCLUSIONS: Oral atovaquone and intravenous pentamidine have similar rates for successful treatment of mild and moderate P. carinii pneumonia, but atovaquone has significantly fewer treatment-limiting adverse events.

AIDS-Related Opportunistic Infections↗
PubMed1994

[New interpretation of the quantitative fecal examination in humans].

The pattern of spatial disposition of eggs of the parasites (Ascaris lumbricoides, Trichuris trichiura and Ancylostomidae) into the faeces was found overdispersed, independently of the technique of coprodiagnosis used (Direct smear without standarisation, Stoll, Shore & Lynch, Kato-Katz and Mc Master). Therefore, differences were not detected in the interpretation of the results among the techniques at the population level, in quantitative studies. In an overdispersed pattern, only few hosts are the major responsibles for the environmental contamination. The importance of this spatial arrangement for parasite control purposes, is discussed.

Adolescent↗
PubMed1993

Molecular evolution of the intergenic spacer in the nuclear ribosomal RNA genes of cucurbitaceae.

The intergenic spacer (IGS) of a 10-kbp repeat (clone pRZ7D) of the nuclear 18S, 5.8S, and 25S ribosomal RNA genes of Cucurbita pepo (zucchini) was sequenced and compared to the IGS sequences of two other Cucurbitaceae, Curcurbita maxima (squash), and Cucumis sativus (cucumber). The nucleotide sequence and the structural organization of the IGS of C. pepo and C. maxima are rather similar (between 75 and 100% sequence similarity depending on the region compared). The IGS are mainly composed of three different repeated elements interspersed into unique sequences: GC-rich clusters, a 422-bp AT-rich element including the transcription initiation site (TIS) for RNA polymerase I, and 260-bp repeats in the 5' external transcribed spacer (D repeats). The TIS is duplicated in the 10-kbp repeat class of C. pepo, as it is also described for the 11.5-kbp rDNA repeat of C. maxima. The IGS of Cucumis sativus is also composed of different repeated elements; however, obvious sequence identity to the Cucurbita species only occurs around the TIS and the preceding AT-rich region. GC-rich clusters with different primary sequences are present in the IGS of all three plants. Remarkably, the repeated elements in the 5'ETS accumulate TpG and TpNpG motifs, whereas CpG and CpNpG motifs less frequently occur. This accumulation might be caused by the transition of methylated cytosines (in mCpG or mCpNpG motifs) into thymidine via deamination in a previously GC-rich ancestor. The following singular region exhibits 50% G + C in C. pepo, 53% G+C in C. maxima, and 63% G + C in C. sativus.(ABSTRACT TRUNCATED AT 250 WORDS)

Base Composition↗
PubMed1993

Randomized trial of dapsone and aerosolized pentamidine for the prophylaxis of Pneumocystis carinii pneumonia and toxoplasmic encephalitis.

PURPOSE: Pneumocystis carinii pneumonia (PCP) and toxoplasmic encephalitis are the most frequent pulmonary and central nervous system opportunistic infections associated with human immunodeficiency virus (HIV) infection. We designed a prospective study to compare the effects of aerosolized pentamidine and dapsone in the prophylaxis of these infections in HIV-infected persons with CD4+ lymphocyte counts less than 250/mm3. PATIENTS AND METHODS: Two hundred seventy-eight patients seropositive for HIV who had acquired immunodeficiency syndrome (AIDS) or advanced AIDS-related complex were randomly assigned to receive intermittent dapsone (100 mg twice weekly) or aerosolized pentamidine (100 mg every 2 weeks). The proportion of patients remaining free of PCP or toxoplasmosis was analyzed with the log-rank test as a function of time, as were the effects of zidovudine or prophylaxis on survival. RESULTS: Dapsone and aerosolized pentamidine demonstrated similar efficacy in the primary and secondary prophylaxis of PCP, with 15 (18%) failures among patients receiving dapsone compared to 15 (14%) among those receiving aerosolized pentamidine (p = 0.4), after a mean length of follow-up of 42 and 44 weeks, respectively. Dapsone was more effective in the primary prophylaxis of toxoplasmic encephalitis, with six toxoplasmic encephalitis events occurring among those receiving aerosolized pentamidine, compared to none among those taking dapsone (p = 0.01). Primary prophylaxis for PCP was more effective than secondary prophylaxis with either therapy. Zidovudine therapy did not prevent PCP yet prolonged the PCP-free interval for those in whom either prophylactic therapy failed. Kaplan-Meier estimates did not show a difference in survival between the patients receiving either therapy, yet zidovudine use was associated with improved survival, independent of race and risk factor (Cox proportional hazards model, p = 0.001). The 1-month survival for patients developing PCP despite prophylaxis was better with those in whom dapsone failed than it was for those in whom aerosolized pentamidine failed (p = 0.08). CONCLUSION: Dapsone is as effective as aerosolized pentamidine in preventing PCP and has the advantage of a lower cost, easier administration, and possibly an additional preventive effect against toxoplasmosis. Zidovudine prolongs the PCP-free interval for patients receiving prophylaxis, regardless of which prophylactic agent is used.

AIDS-Related Opportunistic Infections↗
PubMed1993

Future therapies in the management of critically ill AIDS patients.

The advent of antiviral therapy for HIV infection and anti-infective agents for the treatment and prophylaxis of Pneumocystis carinii pneumonia has had a significant impact on the survival and quality of life of persons with AIDS and associated conditions. This article discusses zidovudine and other antiviral therapies for HIV infection, as well as some of the new treatment and prophylactic strategies to manage opportunistic infections which can ameliorate the course of advanced HIV infection in patients who may require critical care.

AIDS-Related Opportunistic Infections↗
PubMed1992

Zidovudine-induced leukocytoclastic vasculitis.

Cutaneous reactions, including acne, pruritus, urticaria, and nail dyschromia, have been associated with zidovudine use. Cutaneous leukocytoclastic vasculitis is characterized by distinctive patterns of dermal perivascular inflammation without visceral involvement. We treated two cases of cutaneous leukocytoclastic vasculitis associated with fever in patients with severe human immunodeficiency virus-related immunodeficiency in which symptoms resolved on withdrawal of zidovudine therapy and recurred after rechallenge with the drug. This unusual hypersensitivity reaction to zidovudine is probably related to the immune dysregulation and the propensity toward allergic phenomena found in human immunodeficiency virus infection.

Adult↗
PubMed1991

Acoustic schwannoma and epidermoid cyst occurring as a single cerebellopontine angle mass.

The case of a 66-year-old man with a 3-year progressive hearing loss and a homogeneous left cerebellopontine angle mass on magnetic resonance imaging scan is described. At surgery, the major portion of the mass was a typical encapsulated, solid, acoustic schwannoma, but the most rostral portion was a distinct, flaky, cystic mass without a well-defined capsule, typical of an epidermoid cyst. The radiographic and operative findings of this unique coexistence of two different benign cerebellopontine angle masses are presented.

Aged↗
PubMed1991

Non-neoplastic pineal cysts.

We identified 53 patients with non-neoplastic cysts of the pineal gland. In contrast to patients with pineal neoplasms, pineal cysts are usually asymptomatic. They infrequently obstruct the aqueduct to cause hydrocephalus or compress the tectum to produce the neuro-ophthalmologic signs of dorsal midbrain dysfunction. Obstructive hydrocephalus was present in only five patients (9.4%); three of them showed clinical signs of Parinaud's syndrome. CT and MRI typically reveal a cystic mass that averages 1.6 cm in anteroposterior (A-P) diameter with calcification at the periphery and faint rim-like contrast enhancement. Sagittal MRI is the most useful diagnostic test because it shows the anatomic relationship of the cyst to the aqueduct. The mass may compress the tectum and distort the proximal aqueduct; occasionally a large cyst may occlude the aqueduct. All patients with obstructive hydrocephalus had cysts greater than 2.0 cm in A-P diameter. Nine patients had suboccipital craniotomy. In all of them, the cysts contained clear fluid and were easily removed. We advocate conservative management with clinical observation of these benign lesions that may be developmental variants of normal pineal gland.

Adolescent↗
PubMed1990

Sporadic cerebral amyloid angiopathy with giant cell reaction.

We report a case of intracerebral hemorrhages due to sporadic cerebral amyloid angiopathy in a 43-year-old male with a luxuriant giant cell reaction. The amyloid was resistant to potassium permanganate-sulfuric acid oxidation and reacted with an antiserum to synthetic beta-protein. The distribution and histologic characteristics of the multinucleated giant cell reaction suggest that it represents a foreign-body reaction rather than giant cell arteritis.

Adult↗
PubMed1990

GC balance in the internal transcribed spacers ITS 1 and ITS 2 of nuclear ribosomal RNA genes.

The internal transcribed spacer (ITS) 1 and 2, the 5.8S rRNA gene, and adjacent 18S rRNA and 25S rRNA coding regions of two Cucurbitaceae (Cucurbita pepo, zucchini, ITS 1: 187 bp, and ITS 2: 252 bp in length, and Cucumis sativus, cucumber, ITS 1: 229 bp, and ITS 2: 245 bp in length) have been sequenced. The evolutionary pattern shown by the ITSs of these plants is different from that found in vertebrates. Deletions, insertions, and base substitutions have occurred in both spacers; however, it is obvious that some selection pressure is responsible for the preservation of stem-loop structures. The dissimilarity of the 5' region of ITS 2 found in higher plants has consequences for proposed models on U3 snRNA-ITS 2 interaction in higher eukaryotes. The two investigated Cucurbitaceae species show a G + C content of ITS 1 that nearly equals that of ITS 2. An analysis of the ITS sequences reveals that in 19 out of 20 organisms published, the G + C content of ITS 1 nearly equals that of ITS 2, although it ranges from 20% to 90% in different organisms (GC balance). Moreover, the balanced G + C content of the ITSs in a given species seems to be similar to that of so-called expansion segments (ESs) in the 25/28S rRNA coding region. Thus, ITSs show a phenomenon called molecular coevolution with respect to each other and to the ESs. In the ITSs of Cucurbitaceae the balanced G + C composition is at least partly achieved by C to T transitions, via deamination of 5-methylcytosine. Other mutational events must be taken into account. The appearance of this phenomenon is discussed in terms of functional constraints linked to the structures of these spacers.

Animals↗
PubMed1990

Human immunodeficiency virus infection among homeless men in a New York City shelter. Association with Mycobacterium tuberculosis infection.

The human immunodeficiency virus (HIV) seroprevalence among a selected sample of 169 high-risk homeless men residing in a congregate shelter in New York City, NY, was 62%. Seropositivity for HIV correlated significantly with intravenous drug use (odds ratio, 3.3; 95% confidence interval, 1.4 to 4.4) and active tuberculosis (odds ratio, 7.0; 95% confidence interval, 3.4 to 13.5). Most cases of active tuberculosis were among homeless men with acquired immunodeficiency syndrome (AIDS) or AIDS-related complex; and significant CD4 lymphocyte depletion was associated with active tuberculosis. Total time homeless correlated positively with active and latent tuberculosis infection. Compliance rates with return for HIV antibody test results, medications, and follow-up visits were 70%, suggesting a significant degree of knowledge, awareness, and personal concern regarding HIV infection among homeless men; yet 28% of homeless intravenous drug users continue active drug injection, despite HIV infection. Cohabitation in overcrowded congregate dormitories creates a risk of airborne transmission of tuberculosis, which is a common reactivation infection in HIV-seropositive homeless men. Medically appropriate housing should be provided to such homeless persons, and expanded HIV antibody testing, counseling, and medical services on site should be offered to residents of shelters.

Acquired Immunodeficiency Syndrome↗
PubMed1990

[Guidelines for management of genital herpes infection in the experience of a health care center for sexually transmitted diseases in Buenos Aires (Argentina)].

During two years all clinical genital lesions compatible with herpes simplex virus (HSV) etiology were studied systematically through intent of virus isolation in BHK cells. Isolation of virus was confirmed in 85% of the 206 cases studied. All seems to indicate that around the 20% of the isolations belong to the type HSV1 and the rest to the type HSV2. Viral Antigen demonstration, by direct and/or indirect technics with antibodies poly or monoclonals shows to be less sensitive than the virus isolation. The systematic study of these sexually transmitted disease revealed two indicative results: 5.32 cases of Gonococia per each case of HSV were confirmed. It seems to be a possibly relation for the actual epidemiology moment of our country. The other is the need, specially in younger people, to explore systematically syphilis, not only in all the genital ulcers, also in presence of a typical clinical of HSV.

Adult↗