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Biomedical subjects

K Katevuo

Publications and source records attributed to K Katevuo.

At least 19 recordsLinked to original sources
PubMed1999

ChT1, an Ig superfamily molecule required for T cell differentiation.

The thymus is colonized by circulating progenitor cells that differentiate into mature T cells under the influence of the thymic microenvironment. We report here the cloning and function of the avian thymocyte Ag ChT1, a member of the Ig superfamily with one V-like and one C2-like domain. ChT1-positive embryonic bone marrow cells coexpressing c-kit give rise to mature T cells upon intrathymic cell transfer. ChT1-specific Ab inhibits T cell differentiation in embryonic thymic organ cultures and in thymocyte precursor cocultures on stromal cells. Thus, we provide clear evidence that ChT1 is a novel Ag on early T cell progenitors that plays an important role in the early stages of T cell development.

Amino Acid Sequence↗
PubMed1998

CTX, a Xenopus thymocyte receptor, defines a molecular family conserved throughout vertebrates.

CTX, a cortical thymocyte marker in Xenopus, is an immunoglobulin superfamily (Igsf) member comprising one variable and one constant C2-type Igsf domain, a transmembrane segment and a cytoplasmic tail. Although resembling that of the TCR and immunoglobulins, the variable domain is not encoded by somatic rearrangement of the gene but by splicing of two half-domain exons. The C2 domain, also encoded by two exons, has an extra pair of cysteines. The transmembrane segment is free of charged residues, and the cytoplasmic tail (70 amino acids) contains one tyrosine and many glutamic acid residues. ChT1, a chicken homologue of CTX, has the same structural and genetic features, and both molecules are expressed on the thymocyte surface. We cloned new mouse (CTM) and human (CTH) cDNA and genes which are highly homologous to CTX/ChT1 but not lymphocyte specific. Similarity with recently described human cell surface molecules, A33 antigen and CAR (coxsackie and adenovirus 5 receptor), and a number of expressed sequence tags leads us to propose that CTX defines a novel subset of the Igsf, conserved throughout vertebrates and extending beyond the immune system. Strong homologies within vertebrate sequences suggest that the V and C2 CTX domains are scions of a very ancient lineage.

Amino Acid Sequence↗
PubMed1998

Antigenic phenotype of early intra-embryonic lymphoid progenitors in the chicken.

The stem cells for the definitive haematopoiesis are derived from intra-embryonic sources originally described in an avian model and later also in mammals. However, the molecular make-up of the early embryonic haematopoietic progenitors is not yet clearly defined. We have recently characterized the phenotype of prethymic intra-embryonic progenitors capable of thymic colonization. Here we studied the ontogeny of cell-surface antigens HEMCAM, alpha2beta1 integrin, thrombomucin, chL12 and c-kit and their co-expression on prethymic T-cell progenitors. The early intra-embryonic expression of avian B-cell antigen chB6 was also demonstrated on cells derived from the intra-embryonic areas. We suggest that in the chicken, embryonic B-cell progenitors segregate earlier than T-cell progenitors in the differentiation of multipotent haematopoietic stem cells to committed progenitors.

Animals↗
PubMed1996

Thymocyte emigration in the chicken: an over-representation of CD4+ cells over CD8+ in the periphery.

We have examined the emigration of chicken thymocytes after intrathymic fluorescein isothiocyanate (FITC) labelling in situ. In this paper we show that in young birds about 0.7% and 0.4% of thymocytes emigrate from the thymus to the blood and the spleen, respectively, per day. This suggests that, as in mammals, most thymocytes die within the thymus. At 3 weeks of age gamma delta and alpha beta T cells leave the thymus in comparable levels to their appearance in the blood. The phenotype of recent emigrants in peripheral tissues is similar to that of mature T cells. Interestingly, recent emigrants contain relatively much higher numbers of CD4+ and fewer CD8+ cells than is observed in peripheral tissues in a steady-state situation.

Animals↗
PubMed1994

MRI of the brain in muscle-eye-brain (MEB) disease.

Muscle-eye-brain (MEB) disease belongs to the spectrum of rare congenital syndromes with migration disorders of the brain and muscular dystrophy, along with the Walker-Warburg syndrome and Fukuyama congenital muscular dystrophy. Their features overlap, and differential diagnosis presents some difficulties. We examined the brain of 10 patients with MEB using high-field MRI and found a uniform pattern consisting of a pachygyria-type cortical migration disorder, septal and corpus callosum defects and severe hypoplasia of the pons in 7 of them.

Adolescent↗
PubMed1992

Operative treatment of unstable thoracolumbar fractures by the posterior approach with the use of Williams plates or Harrington rods.

Two similar groups of patients with unstable fractures and fracture dislocations of the thoracic or lumbar spine have been treated with the posterior application of Williams plates or Harrington distraction rods over a period of 10 years. The instrumentation was routinely removed from 13 to 19 months after insertion. The initial preoperative kyphotic angle was corrected by a mean of 4.5 and 6.9 degrees respectively. However, follow up after a minimum of four years has shown a loss of correction by a mean of 14.4 and 12.7 degrees to an angle of 21.9 degrees even in the Harrington rod cases. These results do not show the ability to maintain correction of deformity by either method with a dorsal approach. Reduction and stabilization of fractures of the spine should be directed to the anterior part of the vertebrae to overcome late deformity of the spine.

Adolescent↗
PubMed1992

T1 in subacute and chronic brain infarctions. Time-dependent development.

RATIONALE AND OBJECTIVES: Time-dependent behavior of T1 in brain infarcts and in brain tissue of the contralateral hemisphere was studied in the subacute and early chronic stages of stroke. METHODS: T1 was measured from magnetic resonance images (MRIs) of 29 patients as a function of infarct location and age. Another group of 11 patients was studied with consecutive MRI studies during the first 5 weeks after the onset of infarct, and the distribution of T1 in the infarctions was analyzed from T1 maps using a histographic method. RESULTS: During the first 2 months after a stroke, T1 was longer in the infarcted gray matter than in the infarcted white matter (P = .002), and prolonged linearly in both. The histographic analysis showed a component arising from tissue breakdown products that could be identified for up to 5 weeks. A transient lengthening in T1 of the contralateral hemisphere, reaching a maximum at 3 weeks, also was observed. CONCLUSIONS: These characteristics of recent infarctions differentiate them from older, gliotic lesions. The lengthening of T1 in the contralateral hemisphere may reflect remote flow and metabolic effects of brain infarctions.

Acute Disease↗
PubMed1991

Visual evoked potentials in Basedow's ophthalmopathy before and after orbital decompression or retrobulbar irradiation.

VEP are an objective and a more sensitive sign of optical neuropathy in Graves' ophthalmopathy than is visual acuity. A correlation exists between VEP and the changes in the external eye muscles as visualized on CT scans. VEP should always be registered if CT changes are present. Improvement of optic neuropathy as evaluated from VEP seems to be remarkably infrequent.

Evoked Potentials, Visual↗
PubMed1991

CT five years after myelographic diagnosis of lumbar disk herniation.

Fifty-seven patients were examined with CT 5 years after primary myelography for disabling sciatica and suspected herniated lumbar disk. Forty were in an operated group, 22 with good and 18 with poor results evaluated by occupational handicap (21) 5 years after surgery. Seventeen patients had myelography indicating disk herniation, but were treated conservatively, 9 with good and 8 with poor result. Various spinal dimensions measured at CT did not correlate with outcome. Operated patients had narrower canals than others, and male canals were broader than those in females. Increased amount of scar tissue at L4 level correlated with poor result (p = 0.008). Operated patients with poor result had more advanced lateral stenosis than those treated conservatively (p less than 0.001). Patients with good result after operation had more degeneration observed on CT of erector spinae muscle than those treated conservatively with good outcome. Only 9% of operated patients did not have muscle degeneration. A tendency for more frequent recurrent disk herniations could be seen for conservatively treated patients. The narrowing of the spinal canal 5 years after operation did not correlate with the 5-year outcome.

Adult↗
PubMed1991

Painful spine after stable fractures of the thoracic and lumbar spine. What benefit from the use of extension brace?

In a series of 126 patients with conservatively treated stable fractures of the thoracic and lumbar spine, the fracture occurred most often (56%) in the thoracolumbar junction. The mean follow-up time was 7.2 years (range 5.5-10.7) and the mean age was 45.9 years (range 14-83). The radiological measurement of vertebral deformity and evaluation of clinical outcome showed that the patients with poor outcome had significantly greater anterior wall compression and kyphosis on admission than the patients with good outcome, but the deformity worsened similarly in both groups. The use of extension brace seemed to decrease subjective symptoms during the mobilization phase but it could not prevent the development of kyphosis deformity during the follow-up period. The results favour the conception of more effective treatment concerning patients with kyphosis of greater than or equal to 13 degrees or anterior wall compression of greater than or equal to 30% on admission, respectively.

Adult↗
PubMed1990

Superparamagnetic particles as gastrointestinal contrast agent in magnetic resonance imaging of lower abdomen.

Negative gastrointestinal contrast enhancement can be achieved by oral administration of superparamagnetic particles. Their feasibility for the MR imaging of the female pelvis and lower abdomen was evaluated in studies on 32 follow-up patients with treated gynaecologic cancer. All the applied doses (0.2-1.0 mg particles/ml given in a volume of 600-800 ml) of contrast medium decreased the intraluminal signal. However, there was unpredictable individual variation in segmental distribution, and in some cases only a limited contrast effect was obtained. Image distortion was detected when the applied particle concentration exceeded 0.5 mg/ml, especially of the sagittal sections.

Abdomen↗
PubMed1989

Disc degeneration in Scheuermann disease.

Comparison of the radiographic signs of Scheuermann disease and the corresponding disc degeneration on thoracolumbar magnetic resonance (MR) images was made in 21 young patients. Marginal sclerosis, Schmorl nodes and narrowed disc spaces, but not irregular or wedge-shaped end-plates, were significantly associated with disc degeneration. Fifty-five percent of the discs in the patients with Scheuermann disease were abnormal on MRI, compared with 10% in asymptomatic controls. Our study confirms that thoracolumbar disc degeneration is enhanced in 20-year-old patients with low back pain who have radiological evidence of Scheuermann disease.

Adolescent↗
PubMed1989

Mediastinoscopy: not needed preoperatively in CT-negative lung carcinoma?

The objective was to investigate the necessity of mediastinoscopy in preoperative staging of lung carcinoma in 57 operable patients. Noninvasive radiology was compared to mediastinoscopy and thoracotomy. Computed tomography (CT-scan) and mediastinoscopy were in agreement in 40 cases (70%). CT-scan was negative in 26 patients, of which 4 were false negatives. Mediastinoscopy is therefore of no benefit preoperatively for 85% (22 out of 26) of patients. Consequently, we have changed our staging policy and only patients with positive CT-scan are now subjected to mediastinoscopy.

Adult↗
PubMed1988

X-linked myopathy with excessive autophagy: a new hereditary muscle disease.

We report on 3 brothers with a myopathy that also affected their maternal grandfather and great-uncle. Characteristic features are onset in early childhood, very slow progression, normal life expectancy, weakness of proximal limb muscles, especially in the legs, elevation of serum creatine kinase, and no cardiac or intellectual involvement. In biopsy material muscle fibers are almost never necrotic but show excessive autophagic activity and exocytosis of the phagocytosed material. We suggest that this family has an undescribed type of congenital myopathy, for which we propose the name X-linked myopathy with excessive autophagy.

Adult↗
PubMed1988

Reliability of CT in preoperative evaluation of bladder carcinoma.

Sixty patients with bladder carcinoma were examined by CT prior to radical cystectomy. CT indicated perivesical tumour growth or extension to neighbouring organs correctly in 68% of these cases. Overstaging was observed in 23% and understaging in 8% of the cases. Most of the difficulties concerned assessment of tumours in the anterior bladder wall and identification of the plane between the bladder and the seminal vesicle. In most instances CT provided no supplementary information to clinical staging, but was useful when obesity or previous irradiation impeded clinical staging.

Adult↗
PubMed1988

The utility of contrast media in MRI at 0.02 T. A preliminary report.

The effect of 0.1 mmol gadolinium-DTPA on ultralow field magnetic resonance (MR) images of intracranial neoplasms was studied on 20 patients. Tumors that characteristically were enhanced markedly on computed tomography (CT) (meningiomas, acoustic neuromas) demonstrated moderate to marked contrast enhancement with inversion recovery sequences and with saturation recovery sequences with a short repetition time. Standard spin-echo sequences failed to show any contrast effect. The enhancement of gliomas and metastases was weak and often absent. Contrast enhancement, when present, was helpful in delineating the tumor from surrounding edema but the differentiation of living from necrotic tumor was not successful because of low signal intensity. The low effect of gadolinium-DTPA at 0.02 T may be due to a relatively higher T2 weighting of available pulse sequences. The relaxing effect of macromolecules may also change the proportional effect of paramagnetic substances in an ultralow magnetic field.

Adult↗
PubMed1988

Examination of infant brain maturation using ultra low field MRI.

The brains of 42 newborn infants were examined with MRI at 0.02 T field, and regional variations of T1 relaxation time were measured from the images. There were three groups: 1. full term infants (9), 2. preterm infants (10) and 3. SGA (= small for gestational age) infants (20). Relaxation times showed a correlation to myelination of the brain. The brain of SGA infants showed a large variation in their T1 values.

Brain↗