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Biomedical subjects

K Cha

Publications and source records attributed to K Cha.

15 recordsLinked to original sources
PubMed1998

The clinical features of immunoglobulin light-chain (AL) amyloidosis with heart involvement.

We reviewed clinical presentation, investigations, therapy, prognosis and outcome of 232 patients with primary (AL) cardiac amyloidosis. There were 142 men and 90 women. Median age at presentation was 59 years (range 29-85). AL heart disease was unusual both in patients under the age of 40 (3.0%) and in non-Caucasians (6.5%). Fatigue and weakness were the commonest presenting symptoms. Hallmark features of periorbital ecchymoses and macroglossia were present in 12.5% and 27.2%, respectively. AL cardiac amyloidosis was unusual in isolation (3.9%), and most frequently patients had features of multiorgan dysfunction; heavy proteinuria and features of malabsorption predominating in this respect. Heart involvement represents the worst prognostic indicator, with a median survival from diagnosis of 1.08 years, falling to 0.75 years with the onset of heart failure. Current therapeutic procedures appear to prolong survival, with left ventricular wall thickness, mass and ejection fraction on echocardiography and late potentials on signal averaged electrocardiography of use in prognostic stratification. Cardiac involvement from AL amyloidosis is rapidly fatal. It should be suspected in all patients with heart failure who have wall thickening on echo, normal chamber sizes, low EKG voltages and evidence suggesting a multisystem disease.

Adult↗
PubMed1997

Rhodopsin kinase: expression in baculovirus-infected insect cells, and characterization of post-translational modifications.

Structure-function studies of rhodopsin kinase (RK; EC 2.7.1.125) require a variety of mutants. Therefore, there is need for a suitable system for the expression of RK mutant genes. Here we report on a study of expression of the RK gene in baculovirus-infected Sf21 cells and characterization of the enzyme produced as purified to near homogeneity. Particular attention has been paid to the post-translational modifications, autophosphorylation and isoprenylation, found in the native bovine RK. The protein produced has been purified using, successively, heparin-Sepharose, Mono Q, and Mono S FPLC (fast protein liquid chromatography) and was obtained in amounts of about 2 mg from 1 liter of cell culture. The enzyme from the last step of purification was obtained in two main fractions that differ in the level of phosphorylation. The protein peak eluted first carries two phosphate groups per protein, whereas the second protein peak is monophosphorylated. Further, while both peaks are isoprenylated, the isoprenyl groups consist of mixtures of C5, C10, C15, and C20 isoprenyl moieties. From these results, we conclude that the above expression system is suitable for some but not all aspects of structure-function studies.

Animals↗
PubMed1997

Mania in children with pervasive developmental disorder revisited.

OBJECTIVE: Although a small literature of case reports suggests that mania co-occurs with pervasive developmental disorder (PDD), little is known about this overlap. The authors systematically investigated the overlap between mania and PDD in a consecutive sample of referred youths, examining its prevalence and correlates. It was hypothesized that children with PDD plus manic features have both disorders. METHOD: Subjects were consecutively referred children meeting diagnostic criteria on structured interview for PDD without mania (n = 52), the comorbid condition PDD + mania (n = 14), and mania without PDD (n = 114). All subjects were evaluated using a comprehensive diagnostic battery that included assessment of psychopathology (structured diagnostic interview and Child Behavior Checklist), cognition, and functioning. RESULTS: Of the 727 referred children, 52 met criteria for PDD, 114 met criteria for mania, and 14 met criteria for both. The 14 children with both PDD + mania represented 21% of the PDD subjects and 11% of all manic subjects. Clinical characteristics of PDD were similar in PDD subjects with and without mania, and manic features were similar in manic children with and without PDD. CONCLUSIONS: Children with PDD and mania may suffer from two disorders. Comorbid mania among patients with PDD may be more common than previously thought. Identification of the comorbid condition may have important therapeutic and scientific implications.

Bipolar Disorder↗
PubMed1997

Familial and primary (AL) cardiac amyloidosis: echocardiographically similar diseases with distinctly different clinical outcomes.

OBJECTIVE: To determine whether patients with myocardial amyloidosis due either to AL (primary) amyloid or familial amyloid have distinguishing echocardiographic or electrocardiographic features; and to compare the prevalence of heart failure and survival in the two types of amyloidosis in relation to echocardiographic findings. DESIGN: Blinded group comparison of randomly selected cases of cardiac amyloidosis. SETTING: International referral centre for amyloid research and treatment. PATIENTS: 36 patients with cardiac amyloid heart disease, of whom 12 had familial and 24 had primary AL amyloidosis. RESULTS: Familial and AL echocardiograms were morphologically indistinguishable, with similar left ventricular wall thickness, mean (SD) 15.4 (2.3) nu 15.8 (2.5) mm, respectively; right ventricular wall thickness was also similar between amyloid types: 9.6 (2.8) nu 9.7 (6.5) mm, respectively. Doppler indices of left and right ventricular function, left ventricular volume, and ejection fraction were also similar. Low voltage electrocardiograms (< 0.5 mV) were more common in the AL (16/24, 67%) than in the familial group (4/12, 25%), P < 0.05. The one year survival for familial and AL forms was 92% (11/12) nu 38% (6/24), respectively, with virtually all deaths due to cardiac causes. CONCLUSIONS: Although cardiac involvement is echocardiographically indistinguishable, cardiac mortality is very different between the two forms of amyloidosis. Preservation of electrocardiographic voltage in familial amyloidosis suggests that the particular biochemical characteristics of distinct types of amyloid fibril have different pathological effects on the myocardium. This distinction becomes critical in the evaluation, treatment, and management of patients who have a diagnosis within the spectrum of the protein deposition diseases.

Amyloidosis↗
PubMed1996

Electrocardiography and Doppler echocardiography in secondary (AA) amyloidosis.

The fibrils in AL and AA amyloidosis, although similar in appearance, have different biochemical composition and staining characteristics. Whereas electrocardiographic and echocardiographic features of heart involvement in AA amyloidosis resemble those for AL amyloidosis, our findings support the concept that the constituent amyloid fibrils may play a decisive role in the clinical pattern and significance of heart infiltration.

Adult↗
PubMed1995

Multifrequency bioelectrical impedance fails to quantify sequestration of abdominal fluid.

Multifrequency bioelectrical impedance analysis (MFBIA) was used to determine the intracellular (ICW) and extracellular water (ECW) compartments in rats. Resistance and reactance were measured on various body segments with frequencies ranging from 1 KHz to 1 MHz. After initial measurements, 0.9% NaCl was injected intravenously or intraperitoneally, and changes in ECW and ICW were estimated by MFBIA. Important differences were found between segments. In the leg, estimated ECW increased in proportion to the volume of intravenous fluid infused, whereas estimated ICW changed minimally. However, in the trunk region, both estimated ECW and ICW were increased with intravenous and intraperitoneal injections. Our findings indicate that MFBIA has important limitations for quantifying fluid compartments in the trunk and thus in whole body, especially when applied to ill patients in whom sequestration of fluid in the trunk region frequently occurs.

Abdomen↗
PubMed1995

Multifrequency bioelectrical impedance estimates the distribution of body water.

Multifrequency bioelectrical impedance analysis was used to estimate the ratio of extracellular water (ECW) to total body water in subjects with end-stage renal disease. The body's resistance was measured at frequencies ranging from 1 kHz to 1 MHz. The impedance index (height2/resistance) determined at low frequency (5 kHz) correlated most closely with ECW (r = 0.886) using sodium bromide dilution as the standard of comparison. In contrast, the ratio of height squared to resistance determined at high frequency (500 kHz) correlated most closely with total body water (r = 0.974) using deuterium oxide dilution as the standard of comparison. The ratio of resistance at 500 kHz to resistance at 5 kHz was directly correlated (r = 0.767) with the ratio of ECW to total body water. Multifrequency bioelectrical impedance analysis may assist in the evaluation of body water distribution in endstage renal disease and other clinical disorders of fluid volume and/or distribution.

Body Composition↗
PubMed1994

An electronic method for rapid measurement of haematocrit in blood samples.

The bioelectrical impedance method was used to determine the haematocrit in patient blood samples. The resistance (R) and reactance (X) of a constant volume of blood were measured at a low (50 kHz) and high (1 MHz) frequency. These dual-frequency impedance measurements were then used to determine the intracellular and extracellular (plasma) fluid volume of the blood and thus the haematocrit in 308 blood samples. The values compared favourably with the microhaematocrit determined on the same samples, giving a correlation coefficient of 0.989 and a standard error estimation of 1.41%. Reactance at 1 MHz was a better parameter for predicting haematocrit than resistances. Factors affecting the resistivity of plasma, such as electrolyte and protein concentrations, were the error sources in the impedance technique. Our technique reduced such errors significantly. In conclusion, this electronic method can be used to measure haematocrit accurately and may be more desirable than conventional methods in certain clinical situations.

Electric Impedance↗
PubMed1994

A new bioelectrical impedance method for measurement of the erythrocyte sedimentation rate.

A new bioelectrical impedance method was developed to determine the erythrocyte sedimentation rate (ESR) by measuring the settling velocity of red blood cells. A sample of blood was collected in a plastic tube with two electrodes, one positioned above the other. Measurements of electrical resistance were made in the upper region of the blood column. As the red blood cells settled towards the bottom of the container, the resistance decreased continuously. The velocity of settling red blood cells was calculated in 45 samples. The values obtained compared favourably with the ESR determined by the standard Westergren method, giving a correlation coefficient of 0.96 and a standard error estimation of 7.0 mmh-1. We conclude that bioelectrical impedance can be used to measure ESR accurately and that this method has important advantages over existing methods.

Blood Sedimentation↗
PubMed1992

Simulation of a phosphene-based visual field: visual acuity in a pixelized vision system.

A visual prosthesis for the blind using electrical stimulation of the visual cortex will require the development of an array of electrodes. Passage of current through these electrodes is expected to create a visual image made up of a matrix of discrete phosphenes. The quality of the visual sense thus provided will be a function of many parameters, particularly the number of electrodes and their spacing. We are conducting a series of psychophysical experiments with a portable "phosphene" simulator to obtain estimates of suitable values for electrode number and spacing. The simulator consists of a small video camera and monitor worn by a normally sighted human subject. To simulate a discrete phosphene field, the monitor is masked by an opaque perforated film. The visual angle subtended by images from the masked monitor is 1.7 degrees or less, depending on the mask, and falls within the fovea of the subject. In the study presented here, we measured visual acuity as a function of the number of pixels and their spacing in the mask. Visual acuity was inversely proportional to pixel density, and trained subjects could achieve about 20/26 visual acuity with a 1024 pixel image. We conclude that 625 electrodes implanted in a 1 cm by 1 cm area near the foveal representation of the visual cortex should produce a phosphene image with a visual acuity of approximately 20/30. Such an acuity could provide useful restoration of functional vision for the profoundly blind.

Blindness↗
PubMed1992

Mobility performance with a pixelized vision system.

A visual prosthesis, based on electrical stimulation of the visual cortex, has been suggested as a means for partially restoring functional vision in the blind. The prosthesis would create a pixelized visual sense consisting of punctate spots of light (phosphenes). The present study investigated the feasibility of achieving visually-guided mobility with such a visual sense. Psychophysical experiments were conducted on normally sighted human subjects, who were required to walk through a maze which included a series of obstacles, while their visual input was restricted to information from a pixelized vision simulator. Walking speed and number of body contacts with obstacles and walls were measured as a function of pixel number, pixel spacing, object minification, and field of view. The results indicate that a 25 x 25 array of pixels distributed within the foveal visual area could provide useful visually guided mobility in environments not requiring a high degree of pattern recognition.

Blindness↗
PubMed1992

Reading speed with a pixelized vision system.

A visual prosthesis based on electrical stimulation of the visual cortex with an array of penetrating electrodes is expected to produce pixelized visual images consisting of punctate spots of light (phosphenes). We measured reading speed in subjects viewing text with optically simulated phosphene fields in order to obtain estimates of the following design parameters for such an electrode array: pixel number, pixel spacing, and visual-field size. Comparisons were made between scanning the text with eye movements and scanning the text with head movements. The results indicate that a 25 x 25 array of pixels representing four letters of text projected on a foveal visual field of 1.7 degrees is sufficient to provide reading rates near 170 words/min with scrolled text and near 100 words/min with fixed text.

Humans↗