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Biomedical subjects

P Lang

Publications and source records attributed to P Lang.

At least 253 records · Page 14Linked to original sources
PubMed1992

Imaging of the hip joint. Computed tomography versus magnetic resonance imaging.

The authors reviewed the applications and limitations of computed tomography (CT) and magnetic resonance (MR) imaging in the assessment of the most common hip disorders. Magnetic resonance imaging is the most sensitive technique in detecting osteonecrosis of the femoral head. Magnetic resonance reflects the histologic changes associated with osteonecrosis very well, which may ultimately help to improve staging. Computed tomography can more accurately identify subchondral fractures than MR imaging and thus remains important for staging. In congenital dysplasia of the hip, the position of the nonossified femoral head in children less than six months of age can only be inferred by indirect signs on CT. Magnetic resonance imaging demonstrates the cartilaginous femoral head directly without ionizing radiation. Computed tomography remains the imaging modality of choice for evaluating fractures of the hip joint. In some patients, MR imaging demonstrates the fracture even when it is not apparent on radiography. In neoplasm, CT provides better assessment of calcification, ossification, and periosteal reaction than MR imaging. Magnetic resonance imaging, however, represents the most accurate imaging modality for evaluating intramedullary and soft-tissue extent of the tumor and identifying involvement of neurovascular bundles. Magnetic resonance imaging can also be used to monitor response to chemotherapy. In osteoarthrosis and rheumatoid arthritis of the hip, both CT and MR provide more detailed assessment of the severity of disease than conventional radiography because of their tomographic nature. Magnetic resonance imaging is unique in evaluating cartilage degeneration and loss, and in demonstrating soft-tissue alterations such as inflammatory synovial proliferation.

Arthritis↗
PubMed1991

[Immune deficiency associated with experimental graft-versus-host reaction. Lack of correlation with T-cell cytotoxic activity].

Graft-versus-host reactions (GvHR) are initiated by T lymphocytes. In mice, the T cell subset involved depends on the incompatibility for minor or major histocompatibility antigens between donor and host. However, the correlation between phenotype and function is not absolute, and anti-host cytotoxic T cells can be detected in recipients without GvHR. We have presently investigated in a P----F1 model differing at the MHC, whether GvH associated immunosuppression was correlated with donor cytotoxic T cell activity. The immunodeficiency was tested by the ability of the F1 mice to generate a cytotoxic T cell response against TNP self or an alloantigen. F1 specific parental cytotoxic T cells generated in vitro induced less immunosuppression than naive parental spleen cells. Specific in vivo priming increased the cytotoxicity of parental spleen cells, but decreased their capacity to induce GvH associated immunosuppression. In contrast, non specific priming resulted the usual immunodeficiency. Spleens of the F1 mice injected with specific cytotoxic T cells were very enlarged, suggesting that these cells remained capable of inducing a GvHR without generating immunosuppression.

Animals↗
PubMed1991

[Monoclonal immunoglobulins in kidney transplantation. Characterisation, evolution and risk factors].

Sera from 192 consecutive HIV negative renal transplant patients with more than 6 months follow-up were investigated for monoclonal or oligoclonal immunoglobulins (mIg) by immunoelectrophoresis or immunofixation. Gammapathy was present in 25 patients (13 percent). Eleven patients had only one monoclonal band, whereas 14 had two or more bands. Sixty percent were IgG K, 29 percent IgG lambda and 11 percent IgM lambda or K. Ninety percent of these mIg did not exceed 2 g/l; mIg appeared within 2-27 months following the transplantation (mean time-lag 8 +/- 6.4 months). The mIg were often transient: 20 disappeared within 1-33 months, most of them (14) being absent after 1 year of follow-up. Some risk factors for mIg could be identified: the patient's age (a risk factor only in women); the duration of dialysis; the occurrence of prior CMV infection; treatment with cyclosporine. The persistence of mIg was characterised by one or more of the followings: high titer of mIg, EBV infection or reactivation, inability to switch from IgM to IgG CMV antibodies. No significant association was found with the hepatitis B surface antigenemia, previous infection with hepatitis C or the number of rejection episodes. In 6 patients, the clinical course was characterised by severe infection or tumours. Although long-term follow ups are not yet available, patients in whom one or more mIg have been demonstrated should be carefully followed.

Adult↗
PubMed1991

Structure and solution properties of tamarind-seed polysaccharide.

The major polysaccharide in tamarind seed is a galactoxyloglucan for which the ratios galactose:xylose:glucose are 1:2:25:2.8. A minor polysaccharide (2-3%) contains branched (1----5)-alpha-L-arabinofuranan and unbranched (1----4)-beta-D-galactopyranan features. Small-angle X-ray scattering experiments gave values for the cross-sectional radius of the polymer in aqueous solution that were typical of single-stranded molecules. Marked stiffness of the chain (C infinity 110) was deduced from static light-scattering studies and is ascribed partially to the restriction of the motion of the (1----4)-beta-D-glucan backbone by its extensive (approximately 80%) glycosylation. The rigidity of the polymer caused significant draining effects which heavily influenced the hydrodynamic behaviour. The dependence of "zero-shear" viscosity on concentration was used to characterise "dilute" and "semi-dilute" concentration regimes. The marked dependence on concentration in the "semi-dilute" region was similar to that for other stiff neutral polysaccharide systems, ascribed to "hyper-entanglements", and it is suggested that these may have arisen through a tenuous alignment of stiffened chains.

Carbohydrate Conformation↗
PubMed1991

Immunoglobulin heavy-chain joining genes in the rat: comparison with mouse and human.

We have cloned by the polymerase chain reaction a 2.1-kb fragment carrying heavy-chain joining (JH) gene segments and a part of the JH-C mu intron of the rat. Sequencing showed that the rat genome has four functional JH segments and that only a slight divergence has occurred after the separation of rat and mouse. A systematic sequence comparison between the two species and human revealed an additional JH pseudogene in rat and mouse 5' of JH1 which has not been described so far. The implications in evolutionary terms are discussed. In addition, we give an assessment of the misincorporation rate of the Taq polymerase.

Amino Acid Sequence↗
PubMed1991

[Transmission of nephrotic syndrome to two neonates. Spontaneous regression].

We report a transient neonatal nephrotic syndrome in two infants born to a mother with idiopathic nephrotic syndromes (INS). The mother, born in Mali in 1966, had a normal first pregnancy, with a normal live child. Six months later a nephrotic syndrome appeared with normal renal function; renal biopsy disclosed slight lesions of focal and segmental glomerulosclerosis. Prednisone and ciclosporin were totally ineffective. In 1986 and 1988 two pregnancies occurred with normal gestation outcome; however, the two births were premature (35 weeks) with hypotrophic infantas (2.160 and 2.080 kg). In both cases urine analysis revealed neonatal heavy proteinuria, with low serum protein and hypoalbuminemia; proteinuria decreased and disappeared within 2 and 3 weeks respectively; simultaneously protidemia and albuminemia were normalized. Thus, a transitory nephrotic syndrome, resolving spontaneously, occurred in two successive offsprings of a patient with INS. These cases are in keeping with the hypothesis that heavy proteinuria in nephrotic syndrome might be linked to a circulating humoral factor and that INS is a disorder linked to T-lymphocyte function with enhanced production of a lymphokine acting on vascular permeability.

Blood Proteins↗
PubMed1991

Differentiation between vascular permeability factor and IL-2 in lymphocyte supernatants from patients with minimal-change nephrotic syndrome.

Immunotherapy of cancers with recombinant IL-2 induces a vascular leak syndrome which is mainly due to an increase in vascular permeability. A lymphokine, the vascular permeability factor (VPF), which increases vascular permeability, has been characterized in minimal-change nephrotic syndrome (MCNS) and appeared very similar to IL-2. Here we have undertaken a further characterization of VPF in order to determine how closely related this factor was to human IL-2. Both the IL-2 bioassay and Western blot analysis of the MCNS lymphocyte concentrated supernatants with high VPF activity revealed the presence of low quantities of IL-2. Preparative isoelectrofocusing (IEF) of concentrated supernatants resolved each lymphokine in a separate peak, with apparent pIs of 5.2 for VPF and 7.5-10.1 for IL-2. Since a sensitive IL-2 ELISA failed to exhibit any significant antigenic presence of IL-2 in the IEF fractions with the highest VPF activity, we conclude that VPF activity of the concentrated supernatants is not related to IL-2 nor to a biologically inactive form of IL-2. When concentrated supernatants were subjected to preparative SDS-PAGE, VPF activity was recovered within low mol. wt material (1-12 kD). Immunoadsorption experiments gave definite proof since the complete removal of IL-2 from concentrated supernatants did not affect the VPF activity. Although high amounts of IL-2 increased vascular permeability, our experiments clearly demonstrate that VPF is a lymphokine distinct from IL-2.

Animals↗
PubMed1991

Mucosal immunity in primary glomerulonephritis: II. Study of the serum IgA subclass repertoire to food and airborne antigens.

IgA specific for 7 food and 6 airborne antigens were sought in the serum of 30 adult patients with IgA mesangial nephropathy (IgA GN), 23 with membranous nephropathy (MGN), 20 with idiopathic nephrotic syndrome (INS), 11 with membranoproliferative GN (MPGN) and 22 healthy controls by means of an enzyme-linked immunoassay. The IgA subclass was determined using monoclonal antibodies. Increased levels of IgA specific for gliadin, bovine serum albumin (BSA), ovalbumin, lysozyme and alpha-lactalbumin were found in IgA GN, while increased levels of IgA to BSA, ovalbumin, lysozyme and alpha-lactalbumin were observed in MGN; IgA specific for alpha-lactalbumin were increased in INS, and MPGN patients had reduced levels of IgA to BSA and increased levels of IgA to beta-lactoglobulin and alpha-lactalbumin. These specific IgA to food antigens were restricted to the IgA1 subclass. Patients with IgA GN had significantly increased levels of IgA specific for Dermatophagoides pteronyssinus (DP) and Dactil while the MGN group showed increased levels of IgA specific for DP, feathers, Dactil and mold. INS patients had increased levels of IgA specific for DP, feathers, Dactil, mold and dog hairs, while MPGN patients had increased levels of IgA specific for feathers, Dactil, dog hairs and mold. All these specific IgA to airborne antigens were restricted to the IgA1 subclass. Patients with the four types of primary glomerulonephritis had decreased IgA specific for cat hairs which were of both the IgA1 and IgA2 subclasses. We conclude that anomalies of the IgA repertoire to environmental antigens are also encountered in primary glomerulonephritis other than IgA GN.

Adult↗
PubMed1991

Osteoarthritis of the knee: comparison of radiography, CT, and MR imaging to assess extent and severity.

Although conventional radiography is the method most frequently used for monitoring progression of osteoarthritis, it may not show osteoarthritic changes of the knee until late in the disease, and it may show involvement of only one or two compartments in patients who have tricompartmental disease. We compared radiography, CT, and MR imaging for assessing the extent and severity of osteoarthritis of the knee in 20 patients. Radiography included posteroanterior weight-bearing, true lateral, and sunrise patellar projections. Axial CT scans were reformatted in sagittal and coronal planes. MR imaging consisted of spin-echo (600-800/20; 2000/60, 120 [TR/TE]), and gradient-echo (600/30, theta = 30 degrees) sequences. The severity of osteoarthritic changes was graded from 0 to 3. MR frequently showed tricompartmental cartilage loss when radiography and CT showed only bicompartmental involvement in the medial and patellofemoral compartments. In the lateral compartment, MR showed a higher prevalence of cartilage loss (60%) than radiography (35%) and CT (25%) did. In the medial compartment, CT and MR showed osteophytes in 100% of the knees, whereas radiography showed osteophytes in only 60%. Notably, radiography often failed to show osteophytes in the posterior medial femoral condyle. On MR images, meniscal degeneration or tears were found in all 20 knees studied. Partial and complete tears of the anterior cruciate ligament were found in three and seven patients, respectively. MR is more sensitive than radiography and CT for assessing the extent and severity of osteoarthritic changes and frequently shows tricompartmental disease in patients in whom radiography and CT show only bicompartmental involvement. MR imaging is unique for evaluating meniscal and ligamentous disease related to osteoarthritis.

Adult↗
PubMed1991

Noninvasive measurements of bone mass, structure, and strength: current methods and experimental techniques.

Current methods for assessing osteoporotic fracture risk involve measuring the content and/or density of bone at a number of skeletal sites and relating the measurement to that in either age-matched or young control subjects measured at the same site with the same technique. These densitometric methods have been used to predict several types of fractures; however, engineering principles verify that the bone structure and loading conditions also affect skeletal strength. Many densitometric measurements inherently contain information about skeletal structure and bone distribution, yet this information is not clinically used. In this paper, the currently available techniques for assessing bone content and density, namely, single-photon absorptiometry, dual-photon absorptiometry, dual-energy X-ray absorptiometry, and quantitative CT, and their usefulness in assessing fracture risk and distinguishing between patients with and without osteoporosis are reviewed. Extensions of conventional densitometry that have been developed by several researchers to include information in addition to bone mass also are presented. Results from recent studies using new applications of ultrasound techniques and MR imaging are reviewed. Preliminary studies show the value of these new techniques in noninvasive measurement of bone structure in order to estimate bone strength and assess fracture risk more accurately. However, to become clinically useful, many of these methods require further investigation to increase their ease of use and decrease their cost.

Absorptiometry, Photon↗
PubMed1991

Three-dimensional imaging of the musculoskeletal system: an overview.

The clinical applications of three-dimensional computed tomography (3-D CT) reconstruction continue to expand rapidly. Recently, the field of three-dimensional magnetic resonance (3-D MR) reconstruction has also been developing. Three dimensional imaging offers a new approach to the analysis of complex anatomic relationships. The spatial configuration of an object can be directly displayed without observers requiring mental integration of a series of two-dimensional images. The easily interpretable images of 3-D CT have proven to be useful for surgical planning. Three-dimensional CT displays have used widely in the preoperative planning of craniofacial surgery, dysplastic hips in children, and complex fractures of skeletal systems. However, 3-D MR displays are technically more difficult than those of CT scans, and 3-D MR displays of the musculaskeletal system are still in a developing stage. Recently, we explored the feasibility of 3-D MR displays. This article provides an overview of those areas of the musculoskeletal system where the use of 3-D MR has proven valuable. The current techniques and ongoing applications are also presented. We believe that this exciting development will expand our ability to visualize pathologic anatomy in the near future.

Algorithms↗
PubMed1991

[Nodular regenerative hyperplasia of the liver associated with azathioprine therapy].

Three cases of nodular regenerative hyperplasia of the liver associated with azathioprine therapy are reported. The indication of azathioprine differed in each of the 3 cases including kidney transplantation, graft-versus-host disease following bone marrow transplantation, and suspicion of bowel inflammatory disease, respectively. In all three patients, nodular regenerative hyperplasia was discovered after a prolonged administration of azathioprine (24 to 40 months), with a cumulative dose of 52 to 120 g. Under light microscopy, vascular lesions were associated with nodular regenerative hyperplasia in the 3 cases and consisted of sinusoidal dilatation (2 cases), perisinusoidal fibrosis (2 cases), and peliosis (1 case). In two patients, nodular regenerative hyperplasia was responsible for severe portal hypertension which was treated by portacaval shunt. These findings are strongly suggestive of a role of azathioprine in the occurrence of nodular regenerative hyperplasia. The mechanism of azathioprine-induced nodular regenerative hyperplasia could be related to sinusoidal lesions caused by azathioprine and responsible for liver hypoperfusion, with regenerative hyperplasia in the areas remaining normally perfused. Patients receiving long-term therapy with azathioprine should be followed-up regularly and liver biopsy should be performed when clinical or biochemical liver abnormalities are observed.

Adult↗
PubMed1991

Osteoporosis. Current techniques and recent developments in quantitative bone densitometry.

Knowledge about the proper use and interpretation of bone densitometry studies and an understanding of appropriate medical interventions are not universal among physicians, nor are instrumentation and technical performance of bone density studies of uniformly high quality. Indeed, this deficiency of medical and technical expertise is the principal deterrent to widespread implementation of our recommended clinical applications at this time. Nonetheless, given the current impetus to disseminate information about osteoporosis, to make newer instrumentation more readily available, and to limit the cost of these techniques, we anticipate that our recommendations may soon become standard medical practice.

Absorptiometry, Photon↗
PubMed1991

Neonatal repair of tetralogy of Fallot with and without pulmonary atresia.

Our experience with the arterial switch operation for transposition of the great arteries has confirmed the attainability of excellent results with elective neonatal surgery. Up to this time, we have repaired tetralogy of Fallot during the neonatal period only when symptoms, either severe persistent cyanosis or cyanotic spells, have been present. This review assesses the results of such nonelective neonatal correction of tetralogy between 1973 and 1988. Twenty-seven neonates with either symptomatic tetralogy of Fallot or symptomatic tetralogy of Fallot with valvar pulmonary atresia underwent repair. Mean age at repair was 8 +/- 8.4 days and mean weight was 3.0 +/- 0.7 kg. Unsatisfactory palliative shunts had previously been placed elsewhere in four patients. Twenty-five transannular patches and two conduits were used for reconstruction of the right ventricular outflow tract. There were five deaths in the hospital, three of which were due to avoidable technical problems. All deaths occurred in patients with pulmonary artery (Nakata) index less than 150 mm2/m2. One premature child weighing 2.3 kg displayed an absent pulmonary valve-like syndrome after repair and died late of respiratory complications caused by aneurysmal branch pulmonary arteries. Actuarial survival at 5 years was 74%. There was a single rapidly declining hazard phase for death, with the hazard approaching zero at 1 1/2 years after repair. Actuarial freedom from need for reoperation was 76% at 5 years. Postoperative catheterization of 15 long-term survivors showed right ventricular pressure less than 70% systemic in 13 cases. All patients are symptomatically well and functioning in sinus rhythm 1 to 15 years after repair (mean, 5 +/- 4 years). This experience with neonates with symptoms suggests that, if mortality is lower in the absence of symptoms, elective repair of tetralogy of Fallot could be reasonably undertaken during the first months of life.

Abnormalities, Multiple↗