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Biomedical subjects

J Acevedo

Publications and source records attributed to J Acevedo.

13 recordsLinked to original sources
PubMed2004

Phenotype characterization and natural history of spondylothoracic dysplasia syndrome: a series of 27 new cases.

Spondylothoracic dysplasia (STD, MIM#277300) is an autosomal recessive disorder with high prevalence in the Puerto Rican population. It is generally regarded as a lethal condition. Since Jarcho and Levin described it in 1938, it has been referred to as spondylocostal dysplasia, costovertebral dysplasia, Jarcho-Levin syndrome and STD. We have prospectively characterized 27 patients with STD by detailed physical examination, pedigree analysis, thoracic CT scans, and pulmonary function tests (PFTs). Diagnoses were established using spinal radiographs and 3-D reconstructive CT scans to demonstrate fusion of the ribs at the costo-vertebral junction with a fan-like (crab-like) configuration of the thorax. Vertebral segmentation and formation defects were seen throughout the spine with a decrease in the number of vertebral bodies. Characteristic vertebral shape consisted of a decrease in antero-posterior diameter and an increase in lateral length, giving the vertebra a sickle shape. Eight out of 18 prospectively follow patients died within the first 6 months of life, a 44% mortality rate. Cause of death was respiratory insufficiency secondary to pneumonia and pulmonary restriction. This is an important finding since the vast majority of STD syndrome patients cited in the medical literature have died in the newborn and early childhood periods. Age of the remaining patients ranged from 4 months to 47 years. This represents the largest collection of patients with STD reported and it has allowed us to determine a detailed phenotype. Given 56% survival at 6 months, we show that STD is not a lethal syndrome.

Abnormalities, Multiple↗
PubMed2001

Stability and fixation techniques in first metatarsal osteotomies.

Osteotomy of the first metatarsal is a common procedure for correction of hallucal disease. Metatarsals are unique in that they are the only long bones in the human body that support load perpendicular to their longitudinal axis during standing. Thus, osteotomy of the first metatarsal may be complicated by loss of fixation, resulting in nonunion or malunion. The authors review the forces that must be resisted by the osteotomy of the first metatarsal as postoperative weight bearing is initiated, and explore the principles of osteotomy geometry and different fixation techniques to maximize stability of the final construct and to minimize the risk of displacement.

Biomechanical Phenomena↗
PubMed1993

[Transesophageal echocardiography in mitral prosthesis dysfunction: usefulness and limitations in the evaluation of mitral insufficiency].

This study was performed to test the usefulness of transesophageal echocardiography in the diagnosis and assessment of pathological mitral regurgitation in patients with mitral valve prostheses. Doppler color flow imaging by transesophageal echocardiography was compared to the transthoracic echocardiography and angiographic and surgical assessment. We analyzed the influence of the spatial configuration of the jet on the semiquantitative assessment of mitral regurgitation. We studied 71 patients with prostheses in mitral position which were submitted for transesophageal echocardiography examination. 51 of these patients were found to have a pathological prosthetic regurgitation that was confirmed in 21 cases by left ventriculography and in 4 during cardiac surgery. Transesophageal echocardiography Doppler color flow imaging identified a regurgitant jet in 31 patients (60.7%). There was complete agreement with the quantitative assessment of regurgitation by angiography or surgery in 36% of the cases. All patients with prosthetic insufficiency observed by angiography or during cardiac surgery were confirmed by transesophageal echocardiography. Complete agreement in grade of severity by transthoracic echocardiography was found in 84% of cases. There was a difference in grade of severity of mitral regurgitation in only 4 patients. Regurgitant jets were classified by transesophageal echocardiography color Doppler in two groups: free jets and impinging wall jets. 21 cases presented a free jet and 31 excentrically directed impinging wall jet of mitral regurgitation. There was complete agreement with hemodynamic assessment of severity in all patients with regurgitant free jets (11/11). In presence of jet wall there was understimation of mitral regurgitation in 28.5% (4/13).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Local T helper cell signals by lymphocytes infiltrating intraocular tumors.

Tumor-infiltrating lymphocytes from mice bearing minor histoincompatible tumor cells in the anterior chamber (AC) or subconjunctival (SCon) space of the eye have been shown to contain large numbers of tumor-specific precursor cytotoxic T cells. Because SCon tumors eventually acquire directly cytotoxic, tumor-specific T cells and are rejected by their hosts and because AC tumors never acquire cytotoxic effector cells and are not rejected, we have examined tumor-infiltrating lymphocytes from both types of ocular tumors for the capacity to secrete lymphokines in response to in vitro stimulation with tumor cells. The results indicate that T "helper" cells were able to infiltrate both SCon and AC tumors. In the former, T cells capable of secreting IL-2 and IL-4 were found whereas in the latter only IL-2-secreting T cells were detected. These findings implicate a defect in local delivery of appropriate T cell help as the reason why AC tumors are not rejected. The failure of AC tumor-bearing mice to destroy their tumors correlates not only with defective delivery of local help but with a systemic inability to produce tumor-specific T cells that can secrete IL-2 and IL-4. Because these mice also generate down-regulatory T cells that suppress the expression of tumor-specific delayed hypersensitivity, they appear to have an immunologically mediated block in T helper cell differentiation which renders them unable to generate either T helper 1 or T helper 2 cells. This immunologic abnormality is discussed in terms of tumor rejection and the phenomenon of immunologic privilege.

Animals↗
PubMed1991

Infiltration and accumulation of precursor cytotoxic T-cells increase with time in progressively growing ocular tumors.

Precursors of cytotoxic T-cells (pTc) infiltrate P815 tumors growing progressively within the immunologically privileged anterior chamber (AC) of BALB/c mouse eyes, but directly cytotoxic T-cells cannot be detected in these eyes. To determine if the failure to reject these tumors is due to a relative inability of tumor-specific pTc to gain access to, or be retained by, the tumor-containing eye, we have assayed through time the frequency of pTc in eyes that received P511 tumor cells in the AC or subconjunctival space (SC; a site where the tumors are rejected). P511 tumor cells, a hypoxanthine-amethopterin-thymine medium-sensitive derivative of P815 cells, were selected for these studies because P511 tumor cells can be eliminated from in vitro lymphocyte cultures containing hypoxanthine-amethopterin-thymine medium, permitting us to make accurate estimates of pTc frequencies. To ensure that P511 cells are similar biologically and immunologically to P815 tumor cells, we demonstrated that both P511 and P815 cells form progressively growing tumors when injected into the AC of BALB/c eyes and that recipients of both tumor cell lines develop DBA/2-specific anterior chamber-associated immune deviation. Using cell suspensions harvested from eyes of mice bearing AC or SC P511 tumors, we found that tumor-specific pTc appeared first (day 8) in SC tumor-bearing eyes, compared to their appearance in AC tumor-bearing eyes (day 11). Thereafter, however, the number of pTc detected was significantly greater in eyes bearing progressively growing AC tumors than in SC tumor-injected eyes. The number and frequency of pTc we found in these eyes appeared to correlate directly with the size of the ocular tumor burden. We conclude that failure to reject P511 tumor from the AC can be ascribed neither to a quantitative deficiency in infiltrating tumor-specific pTc nor to an inability to retain pTc at the site. Our findings suggest that immune acceptance of allogeneic ocular tumor grafts may result from failure of infiltrating pTc to differentiate terminally in situ into cytotoxic effector cells.

Animals↗
PubMed1981

Diurnal levels of immunoreactive erythropoietin in normal subjects and subjects with chronic lung disease.

Serum levels of immunoreactive erythropoietin (Ep) were measured in 48 normal male and female volunteers, ages 20-60 years, to establish a control value for Ep of 18.5 +/- 5.0 (mean +/- SD) mU/ml. Levels of the hormone were also measured sequentially over a 24 h period of time in an additional 17 'normal' volunteers with no diurnal variation. Diurnal levels of immunoreactive Ep were also measured in 30 subjects, with chronic lung disease. These patients, in contrast to normal subjects exhibited a diurnal variation in the level of immunoreactive Ep with peak levels occurring at midnight. The only variable measured which correlated with the serum immunoreactive Ep level in subjects with chronic lung disease was the level of carboxyhaemoglobin (P less than 0.02).

Adult↗
PubMed1977

Enzymatic basis for bioenergetic differences of alveolar versus peritoneal macrophages and enzyme regulation by molecular O2.

Alveolar macrophages (AM) and peritoneal macrophages (PM) originate from common precursor cells, but function in different O2 environments. In the present studies, the impact of different O2 tensions on cell metabolism has been quantitatively determined, an enzymatic basis for these differences established, and a mechanism which regulates enzymatic differences demonstrated. O2 consumption and lactate production were compared in rabbit AM and PM in air and nitrogen. In air, AM demonstrate significantly greater O2 utilization. In nitrogen, (where glycolysis is the major source of energy provision) lactate production is two- to threefold greater in the PM. A comparison of several enzymes of energy metabolism in AM and PM indicate that one basis for the differences in cell energetics is a difference in activity of key enzymes of both the oxidative phosphorlyative and the glycolytic sequences. Exposure of cultivated AM to hypoxic conditions results in changes in the activity of these enzymes such that the AM closely resembles the PM. A key enzyme in oxidative phosphorylation (cytochrome oxidase) shows decreased activity and reaches values similar to those found in the PM. A key enzyme in glycolysis (pyruvate kinase) shows increased activity to values resembling those found in the PM. These alterations in enzyme pattern occur in isolated cell systems, suggesting that molecular O2 modifies the intrinsic cellular regulation of some enzymes of energy metabolism. Alterations in O2 tension may lead to alterations of the rate of biosynthesis and (or) the rate of biodegradation of key enzymes involved in oxidative phosphorylation and glycolysis. In turn, the alteration of enzyme patterns leads to a more suitable bioenergetic pattern as a function of O2 availability.

Animals↗
PubMed1975

Transalveolar transport of large polar solutes (sucrose, inulin, and dextran).

The in vivo transalveolar transport of three large polar solutes, sucrose, inulin, and dextran (mol wt 60,000-90,00), was compared with the transport of urea in saline-filled dog lung. Apparent permeability coefficents (p', in cm X sec-1 X 10(6)) were as follows; urea: 2.4 +/- 0.28 (SD) greater than sucrose: 0.64 +/- 0.31 (P less than 0.001) greater than inulin: 0.12 +/- .05 (P less than 0.001)--not different from dextran (mol wt 60,000-90,000): 0.08 +/- .02 (P greater then .01). Calculation of the resistance of the alveolar epithelium compared to total barrier resistance for the various solutes indicates that approximately 90% of the total resistance resides in the alveolar epithelium. Comparison of the ratio of permeability coefficients to the ratio of free-diffusion coefficients in water shows similar values for the three large polar solutes, suggesting that permeation through the alveolar epithelium occurs by means of water-filled channels. The values for permeability coefficients of alveolar epithelium fit into the spectrum of values reported for other epithelial structures (including gall bladder, frog skin, and toad bladder); it seems to have a system of channels with a small number of wide "pores" (greater than 80 A) that permit permeation of large polar solutes and is not a relatively homogeneous structure.

Animals↗
PubMedDate not supplied

Fulminant amebic colitis.

Amebiasis is the acute and chronic disease produced by Entamoeba histolytica, an entity which occurs in endemic fashion in many of the tropical and subtropical areas of the world, capable of affecting diverse organs of the body, especially the colon. Amebiasis has different clinical forms of presentation, varying from the asymptomatic carrier state to severe, although not frequent, fulminant or necrotizing colitis, characteristically associated with high morbidity and mortality. We hereby report a series of 50 adult patients with fulminating amebic colitis managed at our institution between January, 1971 and July, 1989, with a global mortality of 60%. Early diagnosis, treatment with effective antiamebic agents--specifically metronidazole--and opportune aggressive surgical intervention have resulted in better survival rates. We had no survivors prior to 1970; our current survival rate is still a dismal 40%, indicating the very severe nature of the disease.

Adolescent↗