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Biomedical subjects

D Katz

Publications and source records attributed to D Katz.

At least 163 records · Page 9Linked to original sources
PubMed1985

Measurement of lumbar spine bone mineral: a comparison of dual photon absorptiometry and computed tomography.

A comparison of computed tomography (CT) and dual photon absorptiometry (DPA) in the measurement of spinal bone mineral was made in 44 subjects of whom 26 had vertebral crush fractures. Although CT measures only trabecular bone within the vertebral body whilst DPA measures the whole vertebral segment, a good correlation was observed (r = 0.80) when these quantities were expressed in dimensionally similar units. Trabecular bone in the distal radius measured by CT correlated less well with vertebral CT (r = 0.65). Cortical bone in the radius correlated poorly with the spinal DPA measurement (r = 0.38).

Adult↗
PubMed1985

(T,G)-A-L specific immune response potential and HLA typing of Israeli patients with systemic lupus erythematosus.

Thirty-three Israeli patients with systemic lupus erythematosus (SLE) were studied for their ability to respond to the synthetic polypeptide poly (Tyr,Glu)-poly (DLAla)-poly(Lys) [( T,G]-A-L) as measured by the production of a T cell helper factor by their antigen activated T cells. Twenty-seven of the patients were typed for their HLA phenotypes. Nineteen patients were with more active disease and 14 with a milder non-active disease. All the patients of the two groups responded to (T,G)-A-L by the production of an antigen specific helper T cell factor, in contrast to only 50% responders among healthy donors. Thus, lack of normal regulation of T cell helper function was observed among all patients with SLE, independently of their disease activity and/or treatment. A higher frequency of DR5 (75%) was observed in patients with a milder non-active disease (vs 46.6% in normal healthy control individuals) while 53.3% of patients with active disease possessed DR7 (21.8% in controls). These findings may suggest a possible association between the severity of the disease and a specific DR determinant.

Antibody Formation↗
PubMed1985

Autoreactive T-cell lines specific for mouse thyroglobulin.

Autoreactive T-cell specific for mouse thyroglobulin have been established and characterized. These Lyt 1+ T cells proliferated specifically in response to thyroglobulin presented by syngeneic irradiated spleen cells. The antigen-presenting cell requirements of these autoreactive T cells appeared to be the same as those for foreign antigen (PPD) reactive T cells. All lines tested required antigen-presenting cells compatible at the I-A subregion of the H-2 complex. Both T-cell types responded to antigen presented by peritoneal cells and splenic dendritic cells, but only gave optimal responses when whole spleen cells were used. The cross-reactivity patterns of responses to mouse, rat, pig and human thyroglobulins indicated that at least two different epitopes could be recognized by the autoreactive T cells. Furthermore, these epitopes appeared to be different from those recognized by the majority of serum autoantibodies to mouse thyroglobulin.

Animals↗
PubMed1985

Use of monoclonal antibodies to sialylated Lewisx and sialylated Lewisa for serological tests of cancer.

A new monoclonal antibody, CSLEX1, directed against sialylated Lewisx was tested in parallel with a monoclonal antibody, CSLEA1, directed against sialylated Lewisa antigen. In tests with a solid-phase radioimmune sandwich assay, the sialylated Lewisx monoclonal antibody detected sera from certain cancer patients that were negative with the sialylated Lewisa monoclonal antibody. Some sera from cancer patients showed the reverse reaction. We conclude that the combined use of these two monoclonal antibodies detects a wider range of sera from cancer patients than the use of a single antibody alone. It should be possible in the future to use multiple monoclonal antibodies to increase detection.

Antibodies, Monoclonal↗
PubMed1984

Absorption of 5-methyltetrahydrofolate in rat jejunum with intact blood and lymphatic vessels.

UNLABELLED: Transport results from in vitro studies may not be applicable to in vivo situations. In this study, we extended our previous in vitro observations regarding the intestinal transport of 5-methyltetrahydrofolate to in vivo studies in the unanesthetized rat and examined the effect of the unstirred water layer on the absorption process. We used a well defined intestinal perfusion technique. Absorption of 0.5 and 5 microM 5-methyltetrahydrofolate proceeded in a linear manner for 40 min of perfusion at 0.31 and 1.74 nmol/100 cm per min, respectively. Absorption of 0.5 microM 5-methyltetrahydrofolate increased with increasing perfusate flow-rate from 0.5 to 2 to 4 ml/min, indicating an unstirred water layer influence on the absorption rate. Absorption of the substrate was saturable with an apparent Kt of 5.7 microM and Vmax of 3.45 nmol/100 cm per min. Absorption was pH-dependent, and was inhibited by structural analogues. In contrast to the in vitro data, addition of glucose (20 mM) to the perfusate was unnecessary for in vivo absorption to proceed. Unconjugated cholic (5 mM) and deoxycholic (1 mM) acids and the organic anion rose bengal (0.1 mM) inhibited the absorption of 0.5 microM 5-methyltetrahydrofolate when added to the perfusate. CONCLUSIONS: the results of previous in vitro studies of 5-methyltetrahydrofolate intestinal transport are applicable to in vivo situations, except that luminal glucose was found to be unnecessary in the latter. The unstirred water layer modulated the absorption of 5-methyltetrahydrofolate, while unconjugated bile acids and rose bengal inhibited it.

Animals↗
PubMed1984

An exponential formula for heart rate dependence of QT interval during exercise and cardiac pacing in humans: reevaluation of Bazett's formula.

A new exponential formula to characterize the human RR-QT relation was evaluated in comparison with Bazett's formula in 16 subjects: 10 healthy, normal men (ages 18 to 30 years) who exercised on a stationary bicycle, and 6 patients (ages 50 to 80 years; 2 women and 4 men) with rate-programmable VVI pacemakers whose rates were changed by an external programmer. The RR and QT intervals for heart rate in the range of 50 to 180 beats/min were measured from electrocardiographic tracings recorded at a paper speed of 100 mm/s. The data from each subject were fitted separately by 4 formulas by an appropriate regression analysis using a statistical package program: (F1) QT = A1 - B1*Exp(-k1*RR); (F2) QT = A2[1-Exp-(-k2*RR)]; (F3) QT = A3* square root (RR) + B3; and (F4) QT = A4* square root (RR), where all A, B, and k are regression parameters. The relative goodness of fit of data by the 4 formulas was assessed by the mean-squared residual and the Akaike Information Criterion using Wilcoxon signed-ranks tests. This analysis confirmed that F1 is the best model among the formulas tested and F4 (Bazett's formula) is the least acceptable for both exercised and paced groups. The deviations from Bazett's formula were more striking for the paced group than for the exercised group, as reflected by the mean-squared residual values for F4 (715 +/- 86 for the paced group vs 384 +/- 41 for the exercised group, p less than 0.005).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1984

Evaluation of immunoadsorbent electron microscopic techniques for detection of Sindbis virus.

Two immunosorbent electron microscopic techniques (ISEM), the protein A coated grid technique (PA-CGT) and the antibody coated grid technique (AB-CGT) were applied and evaluated for the detection of Sindbis virus from infected tissue culture fluids. At optimal conditions, the efficiency of trapping the virions was only about 1.5 higher with the PA-CGT as compared to the AB-CGT, but the PA-CGT was less dependent on the antiserum dilution used in the test. Both methods were suitable for quantitation experiments, since the number of virions trapped was proportional to the virus concentration. The influence of virus incubation time and temperatures, staining solutions, buffers and washing procedures on the trapping efficiency and specificity was further studied with the PA-CGT. Maximal trapping on coated grids was obtained after 3 h incubation of the virus. At room temperature, less debris was found on the grids, as compared to 37 degrees C, and the numbers of virions counted were only slightly lower. The optimal staining solution was alcohol uranyl acetate. The specificity of the PA-CGT was dependent on washing steps with phosphate buffered saline containing bovine serum albumin. With the standard procedure, at room temperature around 3 X 10(7) virions/ml (1 X 10(6) PFU/ml) were specifically detected in about 1.5 h.

Animals↗
PubMed1984

A simplified microwell pseudoreplica for the detection of viruses by electron microscopy and immunoelectron microscopy.

Simplified procedures for immunoelectron microscopy (IEM) and electron microscopy (EM) are described. The procedures employ the principle of agar filtration and pseudoreplication. The modification consisted of the use of microwells for storage of gels with or without antiserum (for IEM or EM, respectively) and an array of containers in which pseudoreplication and negative staining were performed. The containers were prepared from 5 ml syringes from which the needle holding parts were cut. This device enabled simultaneous and rapid handling of specimens. With Sindbis virus as a model, our microwell pseudoreplica IEM (MW-PR-IEM) was compared to six other IEM techniques and was found to be the most rapid and sensitive technique. With the MW-PR-IEM technique, the specific minimal detection limit (detection of clumps) was 1.5 x 10(7) virus particles per ml, and the non-specific detection limit (detection of single virions) was 1.8 x 10(6) virus particles per ml.

Antibodies, Viral↗
PubMed1983

Sampling strategies for noncompartmental estimation of mean residence time.

An optimization procedure is presented for selecting sample times for estimating mean residence time using noncompartmental data analysis. Performance of this experimental design strategy is evaluated using Monte Carlo simulations of a model for digoxin kinetics. The contribution of measurement error to the overall expected error in MRT estimates is examined and its importance emphasized. Also, the sensitivity of the proposed experimental design strategy to required assumptions is investigated using the digoxin model, and the importance of accurate estimates of extrapolated areas is noted.

Humans↗
PubMed1983

Computed tomography in the diagnosis of extramedullary plasmacytoma.

Extramedullary plasmacytomas involving the retroperitoneum are rare. Review of the literature reveals only one case in which computed tomography (CT) findings were illustrated, and this case involved the pancreas. Described here is unusual case in which pancreatic and renal plasmacytomas occurred in a patient who 18 months previously had presented with a solitary plasmacytoma of bone. The clinically unsuspected renal masses was diagnosed by CT, allowing easy biopsy and radiotherapy planning.

Bone Neoplasms↗
PubMed1983

Genetically regulated human (T,G)-A-L specific helper T cell replacing factors possess HLA-DR and VH determinants.

Human (T,G)-A-L specific T cell helper factors secreted by in vitro activated peripheral blood lymphocytes of normal donors were characterized. Factors were passed through columns of Sepharose coupled either to antibodies against human immunoglobulin or antibodies against the variable region of the heavy (VH) and light (VL) chains of human immunoglobulin. In addition, the same factors were applied to columns of Sepharose coupled to anti-HLA-DR antibodies or to monoclonal antibodies against human Ia or beta 2-microglobulin. The activity of the antigen specific factors was removed by the anti-VH antibodies and not by anti-VL or anti-human immunoglobulin antibodies. The factors passed through Sepharose coupled to anti-DR antibodies could be removed and eluted from columns of anti-DR antibodies relevant to the donors' DR antigens. The same factors were also removed by a monoclonal antibody (anti-Ia) which recognizes a monomorphic determinant on HLA-DR, but not by monoclonal anti-beta 2-microglobulin. The results suggest that the genetically regulated (T,G)-A-L specific helper factors possess HLA-DR as well as VH determinants in their active moiety.

Animals↗
PubMed1983

CT findings in obstructed upper moieties of duplex kidneys.

Obstructed upper moiety of a duplex kidney is an uncommon diagnostic problem in adults. This is a report on two cases examined by computed tomography (CT) for suspected abdominal and suprarenal masses, respectively. Although CT is not the primary investigative tool for this condition, the unusual presentations allowed us the opportunity of studying the CT appearance.

Humans↗
PubMed1983

Prolonged heparin therapy in pregnancy causes bone demineralization.

The relation of heparin therapy to osteoporosis was assessed in a retrospective analysis of 20 women treated during and after pregnancy with subcutaneous heparin for thromboembolism prophylaxis. The phalangeal cortical area ratio was significantly less after long term therapy (greater than 25 weeks) compared with that after short term therapy (less than 7 weeks). The same trend was found in the metacarpal area ratio, although this did not reach statistical significance. The changes were most marked in a woman who had received heparin also in a previous pregnancy. No correlations were found between duration of therapy and back pain, conventional radiology of lumbar spine or the Singh index of femoral trabecular pattern which were within the normal range in all patients. The findings indicate a dose-related demineralization process associated with prophylactic heparin therapy in pregnancy. The correct methods of and criteria for thromboembolism prophylaxis in pregnancy need critical re-examination.

Adult↗
PubMed1983

Experimental design for estimating integrals by numerical quadrature, with applications to pharmacokinetic studies.

Many experimental situations, including bioavailability studies, require the estimation of integrals by numerical quadrature applied to dependent variable observations with measurement error. A strategy is described for selecting values for the independent variable (e.g. time). The strategy minimizes the expectation of the square of the difference between the exact integral and the quadrature approximation. This approach was applied to simulated pharmacokinetic problems, including the estimation of bioavailability. Results indicate that the procedure is potentially useful in reducing the variance of resulting estimates and that it appears to be robust with respect to prior assumptions about model parameter values.

Biological Availability↗
PubMed1982

Comparison of two methods of virus detection by immunosorbent electron microscopy (ISEM) using protein A.

The efficiency of two methods of immunosorbent electron microscopy has been compared. The first method consists in trapping virus particles by means of Staphylococcus aureus cells coated with a layer of viral antibodies; the second method consists in trapping virus particles o electron microscope grids coated with specific antibody. A suspension containing 107 antibody-coated bacteria trapped the total number of virions present in 1 ml of a 500 ng/ml virus preparation; the cells were then fully saturated with virions, and approximately 100 virions (of 30 nm diameter) were visible at the periphery of each cell. When 107 cells/ml were used the minimum virus concentration needed to see one virion at the cell periphery was 5 ng/ml. Antibody-coated grids allowed for the detection of approximately the same quantity of virus, but the data obtained with the method were more reproducible and suitable for quantitation.

Antibodies, Viral↗