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Biomedical subjects

C Diaz

Publications and source records attributed to C Diaz.

At least 55 records · Page 3Linked to original sources
PubMed1998

Stability of the peritoneal membrane in long-term peritoneal dialysis patients.

One of main challenges of peritoneal dialysis (PD) is the functional and vital long-term stability of the peritoneal membrane. Few longitudinal and controlled studies on peritoneal function have been published, and the results are somewhat contradictory. We have performed a longitudinal study with 90 patients. The overall analysis has shown that creatinine mass transfer coefficient (MTC) significantly increases and ultrafiltration (UF) capacity decreases over time. Nevertheless, urea MTC remained unaltered and MTC ratios significantly decreased after the third year. Subsequently, we examined the clinical outcomes and identified 19 patients who required peritoneal resting periods for Type I UF failure and 71 patients who did not require such a procedure. The latter patients did not show any significant functional change over time, whereas the former 19 patients showed an increase of peritoneal creatinine transport and a loss of UF capacity. These data corroborate changes in long-term peritoneal function in approximately 20% of PD patients. These changes consist of an increase in effective exchange area, peritoneal permeability, or both, accompanied by signs suggestive of mesothelial regenerative capacity loss. Infectious peritoneal injuries, especially appearing during late PD periods, are deleterious to the peritoneum. The remainder of the functional-structural changes are related to the effects of currently used dialysate. Early diagnosis, preemptive, and therapeutic measures should permit better management of long-term PD patients. The particular response to these injuries has individual characteristics that when addressed permit PD to be used long-term.

Analysis of Variance↗
PubMed1998

Perinatal transmission of hepatitis C virus from human immunodeficiency virus type 1-infected mothers. Women and Infants Transmission Study.

Antepartum plasma hepatitis C virus (HCV) RNA was quantified in 155 mothers coinfected with HCV and human immunodeficiency virus type 1 (HIV-1), and HCV RNA was serially assessed in their infants. Of 155 singleton infants born to HCV antibody-positive mothers, 13 (8.4%) were HCV infected. The risk of HCV infection was 3.2-fold greater in HIV-1-infected infants compared with HIV-1-uninfected infants (17.1% of 41 vs. 5.4% of 112, P = .04). The median concentration of plasma HCV RNA was higher among the 13 mothers with HCV-infected infants (2.0 x 10(6) copies/mL) than among the 142 mothers with HCV-negative infants (3.5 x 10(5) copies/mL; P < .001), and there were no instances of HCV transmission from 40 mothers with HCV RNA concentrations of < 10(5) copies/mL. Women dually infected with HIV-1 and HCV but with little or no detectable HCV RNA should be reassured that the risk of perinatal transmission of HCV is exceedingly low.

Adult↗
PubMed1998

Anorexigen (TNF-alpha, cholecystokinin) and orexigen (neuropeptide Y) plasma levels in peritoneal dialysis (PD) patients: their relationship with nutritional parameters.

BACKGROUND: Malnutrition has definitely been related to mortality among dialysis patients. Persistent loss of appetite is one of the major symptoms found in these patients. It is also well recognized that several substances produce anorexia or disorders of the hunger-satiety cycle in several diseases. The aim of this study was to identify the role of anorexigen substances (TNF-alpha and cholecystokinin or CCK) and an orexigen substance (neuropeptide Y or NPY) in anorexia and malnutrition among 55 clinically stable peritoneal dialysis (PD) patients. RESULTS: High TNF-alpha plasma levels were found in 41 of 42 patients (97.6%) with a mean of 70.5+/-32.3 pg/ml. Patients with anorexia (n=11) or anorexia with nausea or vomiting (n=5) had higher TNF-alpha values than patients without these symptoms (75.9+/-34 vs 52.1 +/-24.5 pg/ml, P<0.05). Eight patients with a prior diagnosis of acid pylori disease showed higher TNF-alpha values (87.2+/-24.3) than 30 unaffected patients (63.6+/-30.5, P<0.05). TNF-alpha showed a significant negative linear correlation with retinol binding protein (RBP) (r=-0.37, n=34, P<0.05), and venous pH (r=-0.4, n=42, P<0.01); also, TNF-alpha values higher than 65 pg/ml were inversely associated with transferrin, cholesterol, blood urea nitrogen (BUN) and CCK. Patients with prealbumin levels lower than 30 mg/dl, a BMI lower than 30 kg/m2, nPCR lower than 1.1 g/kg/day and urea KT/V lower than 2.2 showed higher serum TNF-alpha levels. Patients who had been on CAPD treatment for longer periods showed higher TNF-alpha values. High plasma CCK levels were found in 38 of 45 patients (84%), mean 45.9+/-32.3 pg/ml. Patients with anorexia had no difference in CCK values compared with those without. A direct association was found between CCK levels and some nutritional markers (albumin, fibronectin, triglycerides, folic acid and nPCR in non diabetic patients). Although CCK has a recognized anorectic effect, this direct association might be because of an abnormal stimulation of CCK glucose feedback (trypsin) due to continuous peritoneal glucose absorption. This suggests that CCK could be an immediate food intake marker in PD patients. The NPY plasma levels were normal in 33 patients, high in 6 and low in 11. Patients with anorexia showed lower NPY levels than those without. NPY values greater than 50 pg/ml were directly associated with higher transferrin, prealbumin, RBP, nPCR and urea KT/V values. Importantly, a negative linear correlation between NPY and TNF-alpha was found (r=-0.42, n= 41, P<0.01). There was no significant relationship between residual renal clearance and the serum levels of the three peptides. CONCLUSION: In conclusion, our data suggest that high TNF-alpha and low NPY serum levels are associated with anorexia. High TNF-alpha, low CCK and low NPY serum levels are also related to a poor nutritional status. Further research on these circulating substances is required.

Adult↗
PubMed1998

The immunogenicity of Haemophilus influenzae type b conjugate vaccines in children born to human immunodeficiency virus-infected women. Women and Infants Transmission Study Group.

BACKGROUND: Immunocompromise caused by HIV-1 infection increases the importance of receipt of routine childhood vaccines to prevent infections such as invasive Haemophilus influenzae type B (Hib) disease. The objectives of the study were to evaluate the immunogenicity of Hib conjugate vaccines among HIV-infected children according to clinical and immunologic disease progression as well as viral load. METHODS: The concentration of antibody to polyribosylribitol phosphate (PRP) was measured at approximately 9 and 24 months of age in plasma specimens from children of HIV-infected women enrolled in the Women and Infants Transmission Study. RESULTS: Among 227 children (35 HIV-infected, 192 uninfected) at the 9-month study visit who were known to have received age-appropriate immunization with CRM197 mutant Corynebacterium diphtheriae protein-conjugated Hib vaccine, geometric mean antibody concentrations were lower among HIV-infected children (1.64 microg/ml) than among uninfected children (2.70 microg/ml), although the difference was not statistically significant. Anti-PRP antibody concentrations did not vary significantly among these HIV-infected children with predominantly mild-moderate disease progression according to clinical category, immunologic stage or viral load (P > or = 0.48). The proportion of children with antibody concentrations > or = 1.0 microg/ml did not vary significantly according to HIV infection status (73% uninfected, 74% infected) or, if infected, clinical or immunologic disease progression or viral load. Similar results were obtained among 127 children (17 HIV-infected, 110 uninfected) eligible for analysis at the 24-month study visit. Changes in antibody concentrations over time (between 9 and 24 months of age) did not differ significantly among 10 HIV-infected as compared with 72 uninfected children (P=0.81). CONCLUSIONS: These results suggest that HIV-infected children with predominantly mild-moderate disease progression respond reasonably well in terms of a quantitative antibody response to Hib conjugate vaccines during the first 2 years of life. Research to further characterize the immune response to Hib conjugate vaccines and to further delineate the "durability" of anti-PRP antibody concentrations beyond 2 years of life should be pursued.

Antibodies, Bacterial↗
PubMed1997

Immune complex-dissociated p24 antigen in congenital or perinatal HIV infection: role in the diagnosis and assessment of risk of infection in infants.

Immune complex-dissociated (ICD) HIV-1 p24 antigen assay is a rapid technique for assessing the presence of HIV gag or core protein in plasma or serum. In this study, ICD p24 antigen detection in HIV-1 infected mothers and their infants enrolled in the Women and Infants Transmission Study (WITS) was evaluated primarily as a diagnostic assay for HIV-1 detection in young infants and for its association with perinatal transmission. Plasma from 47 infected infants and 160 uninfected infants was examined, along with plasma from 197 of their mothers who had a delivery or close-to-delivery specimen. ICD p24 antigen was detected in plasma of 27.3% of infected infants at birth and in 70% to 81% at 1 to 6 months. The diagnostic specificity at birth was 90% and 98% to 100.0% at 1 to 6 months. The ICD p24 antigen concentration correlated with concurrent quantitative HIV culture results. The risk of transmission from mother to infant was higher if the mother had detectable ICD p24 antigen at or near the time of delivery (p = 0.002), but its presence did not accurately predict transmission (positive predictive value of 36%, negative predictive values of 85%). The relative ease of performing the ICD p24 antigen assay and the low cost compared with that of HIV culture or DNA PCR makes this test a useful adjunct for the diagnosis of perinatal HIV infection and for enhancing understanding of its pathogenesis, particularly where cost and availability limit access to more sensitive assays.

Antigen-Antibody Complex↗
PubMed1997

Viral load and disease progression in infants infected with human immunodeficiency virus type 1. Women and Infants Transmission Study Group.

BACKGROUND: There are only limited data on human immunodeficiency virus type 1 (HIV-1) RNA in perinatally infected infants. Understanding the dynamics of HIV-1 infection and its relation to disease progression may help identify opportunities for effective antiviral treatment in infected infants. METHODS: We obtained plasma samples from 106 HIV-infected infants at birth; at 1, 2, 4, 6, 9, 12, 15, and 18 months of age; and subsequently every 6 months. HIV-1 RNA was assayed by means of a reverse-transcription polymerase chain reaction. The infants were born between 1990 and 1993, and only 21 percent of the infants' mothers received any treatment with zidovudine during pregnancy. RESULTS: Plasma HIV-1 RNA levels increased rapidly after birth, peaked at 1 to 2 months of age (median values at 1 and 2 months, 318,000 and 256,000 copies per milliliter, respectively), and then slowly declined to a median of 34,000 copies per milliliter at 24 months. Newborns with a first positive HIV-1 culture within 48 hours after birth had significantly higher HIV-1 RNA levels, although only during the first two months of life, than those with a first positive culture seven or more days after birth. Infants with a rapid progression of disease had higher peak HIV-1 RNA levels in the first two months of life than those without rapid progression (median value, 724,000 vs. 219,000 copies per milliliter; P=0.006), as well as a higher geometric mean value during the first year of life (median value, 330,000 vs. 158,000 copies per milliliter, P=0.001). CONCLUSIONS: In perinatally infected infants, HIV-1 RNA levels are high and decline only slowly during the first two years of life. Infants with very high viral loads in the first months of life are at increased risk for a rapid progression of disease, which suggests that early treatment with antiretroviral agents may be indicated for these infants.

Child, Preschool↗
PubMed1997

Tumours of the posterior pharyngeal wall: the use of the platysma flap.

Posterior pharyngeal will tumours are infrequent neoplasms with a very poor prognosis. The 5 year survival rate range from 3% to 32%. Most authors agree that the treatment of choice is surgery with post-operative radiotherapy. The results of treatment of 36 patients (tumour excision plus bilateral neck dissection and post-operative radiotherapy) in which the posterior pharyngeal wall defect was closed with a platysma myocutaneous flap were compared with other forms of repair (13 patients). The 5 year survival rate was 17.2% in the whole group. Laryngeal voice was achieved in 79% of patients having a platysma flap reconstruction. The platysma myocutaneous flap is very satisfactory for the repair of the posterior pharyngeal wall as it is easy to perform, it is oncologically safe and its functional results match well with other forms of reconstruction, with the advantage of laryngeal preservation.

Actuarial Analysis↗
PubMed1997

Defining the time of fetal or perinatal acquisition of human immunodeficiency virus type 1 infection on the basis of age at first positive culture. Women and Infants Transmission Study (WITS).

It has been suggested that a positive diagnostic test for human immunodeficiency virus type 1 (HIV-1) during the first 48 h of life is indicative of intrauterine transmission, whereas negative tests during the first week with positive tests later indicate intrapartum transmission. On the basis of data from all 140 infected infants in the Women and Infants Transmission Study (WITS), the probability was estimated that an HIV-1 culture would be positive for the first time at each day of life if cultures were performed daily. The estimated probabilities (+/-SE) by days 0, 2, 4, 7, 9, 16, and 30 of life are 27.4% (+/-6.4%), 27.4% (+/-13.0%), 45.3% (+/-20.5%), 45.3% (+/-22.5%), 65.3% (+/-20.0%), 88.4% (+/-7.8%), and 89.3% (+/-7.0%), respectively. The initial 27% probability is consistent with the hypothesis that transmission usually occurs during the intrapartum period. However, the distribution of age at first positive culture does not separate clearly into two distinct intervals. More definitive methods for determining the timing of transmission are needed.

Age Factors↗
PubMed1997

Trichoblastoma and basal cell carcinoma are neoplasms with follicular differentiation sharing the same profile of cytokeratin intermediate filaments.

Trichoblastoma and nodular basal cell carcinoma are generally held to be distinctive epithelial neoplasms with some overlapping features. We investigated 30 trichoblastomas in which the basaloid cells expressed cytokeratins (CK) CK5/6, CK14, CK17, CK19, and, in a few cells, vimentin. The cells of the periphery of small and large cysts showed the same profile. Cells lining the lumen of small cysts expressed CK14, CK17, and involucrin, and those in larger cysts showed a positivity for CK1, CK4, CK10, CK14, CK17, and involucrin. The remaining tested antibodies (CK7, CK8, CK13, CK18, CK20, alpha-smooth-muscle actin) were negative in all cases. The cells of the stroma expressed vimentin and in 22 cases, the CD34 antigen. Seventeen nodular basal cell carcinomas showed exactly the same staining pattern. Furthermore, there are striking immunohistochemical similarities between the neoplastic basaloid cells of both neoplasms and the cells of the hair germ. Therefore, trichoblastoma and nodular basal cell carcinoma cannot be distinguished by their pattern of cytokeratin expression in paraffin sections. The virtually identical cytokeratin pattern seen in trichoblastoma, basal cell carcinoma, and the developing fetal hair follicle is compelling evidence for common differentiation pathway.

Actins↗
PubMed1997

The clinical management of children perinatally exposed to HIV.

The spread of the HIV/AIDS epidemic to children has become one of the most serious public health problems in the United States. This article presents the clinician with an overview of the epidemiology of HIV/AIDS among infants and children, discusses major issues about the prevention of perinatal HIV transmission (including ZDV prophylaxis), and presents the management and treatment issues of HIV infection among children.

Anti-HIV Agents↗
PubMed1997

Frequent recurrence of secondary hyperparathyroidism after pulse oral calcitriol withdrawal in PD patients.

The aim of this study was to evaluate the role of pulse oral calcitriol in the control of secondary hyperparathyroidism in peritoneal dialysis (PD) patients, addressing the effects after withdrawal. We studied 15 patients with intact parathyroid hormone (iPTH) plasma levels above 250 pg/mL. The initial calcitriol dose was 8 or 4 micrograms/week, administered in two doses, according to whether the iPTH plasma levels were above or below 400 pg/mL. This dose was modified during the follow-up according to the response. Serum iPTH levels decreased in all patients after the first month (559 +/- 243 to 212 +/- 94 pg/mL, p < 0.001). Serum calcium levels significantly increased during therapy, while serum phosphorus levels did not change. The mean duration of the treatment was 95 +/- 57 days. Nine patients reached the target iPTH levels without complications, and in 6 patients the treatment was interrupted because of hypercalcemia. One month after finishing pulse therapy, a significant decrease in serum calcium levels and an increase in iPTH levels were observed. These values were similar to baseline data and were significantly higher than those found during the pulse calcitriol period. Pulse oral calcitriol administration seems to be a short-term, efficient therapy for secondary hyper-parathyroidism in PD patients. However, after the end of pulse therapy, iPTH serum levels return to baseline values, suggesting long-term therapeutic failure.

Administration, Oral↗
PubMed1996

A receptor in pituitary and hypothalamus that functions in growth hormone release.

Small synthetic molecules termed growth hormone secretagogues (GHSs) act on the pituitary gland and the hypothalamus to stimulate and amplify pulsatile growth hormone (GH) release. A heterotrimeric GTP-binding protein (G protein)-coupled receptor (GPC-R) of the pituitary and arcuate ventro-medial and infundibular hypothalamus of swine and humans was cloned and was shown to be the target of the GHSs. On the basis of its pharmacological and molecular characterization, this GPC-R defines a neuroendocrine pathway for the control of pulsatile GH release and supports the notion that the GHSs mimic an undiscovered hormone.

Amino Acid Sequence↗
PubMed1996

Generation of phenotypically aged phosphatidylserine-expressing erythrocytes by dilauroylphosphatidylcholine-induced vesiculation.

In vitro stored red blood cells (RBC) and RBC artificially induced to vesiculate by incubation with dilauroylphosphatidyl-choline were monitored for age- and vesiculation-dependent changes in cell density, membrane lipid asymmetry, and their ability to be recognized and cleared by reticuloendothelial cells. RBC demonstrated a progressive increase in density on self-forming Percoll gradients upon vesiculation and in vitro "aging." Uptake of vesiculated RBC by in vitro cultivated macrophages was increased threefold over non-vesiculated control RBC. The clearance rate of dense vesiculated RBC was biphasic and contained a rapid component and a slower second component consistent with the clearance rates of normal control populations. Determination of phosphatidylserine (PS) in the outer leaflet of RBC by the PS-dependent prothrombinase assay revealed that PS redistributed to the cell's outer leaflet upon in vitro storage and vesiculation. Inhibition of PS movement by oxidation of membrane sulfhydryls with pyridyldithioethylamine resulted in higher prothrombinase levels and enhanced clearance of vesiculated RBC. These experiments suggest that vesiculation contributes to alterations in membrane lipid asymmetry and cell density characteristic of the aged RBC phenotype.

Animals↗
PubMed1996

The utility of IgA antibody to human immunodeficiency virus type 1 in early diagnosis of vertically transmitted infection. National Institute of Allergy and Infectious Diseases and National Institute of Child Health and Human Development Women and Infants Transmission Study Group.

OBJECTIVE: To determine the sensitivity and specificity of anti-human immunodeficiency virus (HIV) IgA in identifying infected infants at or before 6 months of age among the offspring of HIV-infected mothers. DESIGN: Prospective comparison of anti-HIV IgA measurement performed in 2 different laboratories by 2 different methods with the criterion standard of blood culture. SETTING: Five centers in the United States and Puerto Rico. PATIENTS: Population-based sample of 156 infants of HIV-infected mothers in the Women and Infants Transmission Study. MAIN OUTCOME MEASURES: Results of anti-HIV IgA test in relation to the infection status of the infants as measured by blood culture. RESULTS: Six-month plasma or serum samples were first tested in the 2 laboratories. The sensitivity and specificity of anti-HIV IgA in detecting infected infants at this age by laboratories 1 and 2 were 69% and 63% and 100% and 99%, respectively. A look-back study of samples obtained at birth, 1, 2, and 4 months was then performed on all infected children and a matched set of uninfected children. The performance of the test at birth was unsatisfactory in both laboratories (sensitivity 44% and 33%, specificity 43% and 60%), whether peripheral or cord blood was examined. At 1, 2, and 4 months, the sensitivity of the test was lower than at 6 months, but specificity was high. A modest correlation of absent anti-HIV IgA antibody and low percentage of CD4 cells in peripheral blood was seen at 6 months of age. CONCLUSIONS: The anti-HIV IgA test has moderate sensitivity and high specificity for the diagnosis of HIV infection at 6 months of age in the offspring of infected mothers.

Female↗
PubMed1996

Lymphoblastoid interferon alfa with or without steroid pretreatment in children with chronic hepatitis B: a multicenter controlled trial.

The comparative efficacy of prednisolone followed by interferon alfa (IFN-alpha) versus IFN-alpha alone in enhancing the rate of antibody to hepatitis B e antigen (anti-HBe) seroconversion has not been evaluated in a large cohort of white children. To determine this, a multicenter-controlled trial was conducted in 95 hepatitis B virus (HBV)-DNA/hepatitis B e antigen (HBeAg)-positive children (median age, 9 years [range, 2-16 years]; 56 boys; 84 [89 percent] white), all having inflammatory changes on liver biopsy. Patients were randomized to receive either prednisolone followed by IFN-alpha (n = 34); placebo followed by IFN-alpha (n = 30); or no treatment (n = 31). The prednisolone/placebo was given on a double-blind basis. Lymphoblastoid IFN-alpha was given at 5 MU/m(2) three times a week for 12 weeks. Baseline clinical, biochemical, and histological features were similar for the three groups. The majority (85 percent) had a baseline aspartate aminotransferase (AST) level < or = 100 IU/L. On follow-up between 12 and 18 months (median, 15 months) after treatment, the loss of HBeAg with anti-HBe seroconversion was more common in patients pretreated with steroids (12 of 34 [35 percent]) or placebo [12 of 30 (40 percent)] as against controls (4 of 31 [13 percent], P< .05). Factors predictive of anti-HBe seroconversion were baseline HBV-DNA concentration of < or = 1,000 pg/mL and a greater degree of portal tract inflammation on pretrial biopsy. Our results show that in white children treatment with IFN-alpha, at the dose and duration used in this study, improves the rate of anti-HBe seroconversion. Steroid priming does not potentiate the effect of IFN-alpha.

Adolescent↗
PubMed1996

Intradiploic epidermoid cysts.

We studied 37 intradiploic epidermoid cysts, reviewing typical and atypical radiological features and the differential diagnosis. The most common clinical feature was a long standing lump in the scalp, occurring in 25 patients (67.7%). Plain films were the most cost-effective radiological technique in diagnosis. The typical finding was a well-defined lytic lesion with sclerotic border, seen in 29 cases (78%). Atypical lesions were those larger than 5 cm and/or with an ill-defined edge, being observed in 8 cases (22%). CT and MRI were the best methods for assessing atypical ones. In all cases with typical radiological findings a preoperative diagnosis of intradiploic epidermoid cyst was suggested.

Adolescent↗
PubMed1996

Natural history of somatic growth in infants born to women infected by human immunodeficiency virus. Women and Infants Transmission Study Group.

OBJECTIVE: To evaluate the nature and magnitude of the effect of congenitally or perinatally acquired human immunodeficiency virus (HIV) infection on somatic growth from birth through 18 months of age. STUDY DESIGN: Anthropometry was performed serially in 282 term infants born to HIV-infected women in a multicenter prospective natural history cohort study. Repeated measures analysis was used to compare z-score anthropometric indexes of weight-for-age, length-for-age, weight-for-length, and head circumference-for-age between infected and uninfected infants, with adjustment for covariates including infant gender; maternal education; prenatal alcohol, tobacco, and/or illicit drug exposure; and mean prenatal CD4+ T-lymphocyte count. A separate repeated measures model was used to assess the effect of infant zidovudine treatment on growth. RESULTS: Infants infected with HIV were an estimated average 0.28 kg lighter and 1.64 cm shorter than uninfected infants at birth, were 0.71 kg lighter and 2.25 cm shorter by 18 months of age, and had a sustained estimated average decrement of 0.70 to 0.75 cm in head circumference. Patterns of growth were similar in male and female infants. Infected infants had a progressive decrement in body mass index from birth through 6 months of age. Infection with HIV was associated with significant decrements across all standardized growth outcome measures after adjustment for covariates. Mean z scores were lower for weight by 0.612 (p < 0.001), for length by 0.735 (p < 0.001), for weight-for-length by 0.255 (p = 0.02), and for head circumference by 0.563 (p < 0.001) SD units compared with uninfected infants. Zidovudine treatment was not associated with improved growth. CONCLUSION: The effect of congenitally or perinatally acquired HIV infection on infant growth is one of early and progressive decrements in attained linear growth and growth in mass, early and sustained decrements in head growth, and marked early decrements in body mass index.

Body Height↗