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Biomedical subjects

A C Hsu

Publications and source records attributed to A C Hsu.

11 recordsLinked to original sources
PubMed2000

Accuracy of 1H and 31P MRS analyses of lactate in skeletal muscle.

As the end product of anaerobic metabolism and a source of H(+), lactic acid is important in metabolism and pH regulation. Several methods have been introduced to calculate changes in the lactate anion (Lac(-)) concentration in exercising skeletal muscle from information derived from the (31)P spectrum. Alternatively, Lac-may be observed directly with (1)H MRS. Both (1)H and (31)P spectroscopy have potential problems, which could prevent accurate determination of [Lac(-)]. It is demonstrated that quantitatively accurate (1)H MRS measurements of changes in [Lac(-)] due to exercise are possible in isolated muscle. In general, calculation by (31)P MRS overestimates Lac-production. An analysis is presented of possible sources of errors in the (1)H and (31)P MRS methods.

Animals↗
PubMed1998

Offset-dependent partial saturation in binomial solvent suppression sequences.

In vivo spectroscopic experiments are commonly done under partially T1 saturated conditions and saturation factors (observed signal intensity divided by fully relaxed intensity) used for quantitative analysis of absolute and relative metabolite concentrations. The conventional calculation of the saturation factor assumes uniform excitation across the spectrum. This assumption is violated when selective-excitation solvent peak suppression techniques, such as binomial sequences, are used. In this case, the degree of partial saturation, and hence the saturation factor, is dependent on the resonance offset. This has implications for the frequency offset of maximum excitation, solvent suppression effectiveness, absolute and relative quantitative measurements, and progressive saturation T1 measurements. In this paper, the jump and return (JR) and jump and return echo (JRE) sequences are examined in detail with regard to these implications. It is shown that offset-dependent partial saturation depends on the sequence used and can become significant. A saturation factor which is a function of offset can be used to correct for this effect and allow for proper quantitative interpretation of experimental results under partially saturated conditions.

Algorithms↗
PubMed1982

Renal osteodystrophy in children with chronic renal failure: an unexpectedly common and incapactating complication.

The incidence, age at onset, and progression of the biochemical, radiographic, and histologic characteristics of renal osteodystrophy were studied in 50 children in whom chronic renal failure had been recently diagnosed. During a ten-year observation period, 19 patients progressed to end-stage renal failure and radiographic signs of renal osteodystrophy developed in 15 of these (79%). Renal osteodystrophy developed in all nine patients whose chronic renal failure was diagnosed before 3 years of age and in six of the ten children with later onset of failure. The mean interval from diagnosis of renal failure to development of osteodystrophy was 1.4 years. Radiographically, growth zone lesions predominated in the younger children, whereas cortical erosions were more prevalent in the older children. Histologic examination, performed in 38 patients, showed both defective mineralization and excessive resorption and was a more sensitive diagnostic index than radiography. Noticeable deformities developed in one third of the patients with osteodystrophy, despite medical treatment including vitamin D2 therapy. Deformities were particularly frequent and severe in patients whose renal failure developed in infancy. In all 13 patients whose growth patterns were studied before and after osteodystrophy developed, the onset of bone lesions was associated with a deterioration of growth, indicating that osteodystrophy plays a major role in causing the growth retardation commonly observed in children with chronic renal failure.

Adolescent↗
PubMed1979

Gonadal function in males treated with cyclophosphamide for nephrotic syndrome.

Analysis of semen from 16 patients treated with cyclophosphamide for nephrotic syndrome showed azoospermia in three and oligospermia in seven. Analysis was normal in the other six. Prolonged treatment, particularly with larger total dosage, was associated with a higher incidence of gonadal dysfunction. Recovery was not evident at follow-up, 2 years and 9 months to 9 years and 1 month after cessation of the therapy. Limitation of treatment with cyclophosphamide to 8 weeks/course (2.5 mg/kg/day) minimizes this side effect without greatly increasing the rate of relapse of the nephrotic syndrome in the first 2 years after therapy.

Adolescent↗
PubMed1978

Allograft renal-artery stenosis: increased peripheral plasma renin activity as an early indicator of uncontrollable hypertension.

We measured indices of the renin-aldosterone system and body-fluid spaces in 11 adolescents who had received a renal transplant after removal of their own diseased kidneys. None had hypervolemia but 6 had hypertension. Renal angiography revealed greater than 50% luminal occlusion by allograft renal-artery stenosis (RAS) in only the 3 patients who had severe hypertension refractory to conventional medical therapy. Excessive peripheral plasma renin activity (PRA) distinguished these patients from those who had less severe stenosis or normal angiogram, and diuretic stimulation heightened the PRA differences. We conclude that significant allograft RAS does not necessarily act like a typical single-kidney Goldblatt model until after volume depletion. Our findings indicate that peripheral PRA values can be used to assess the degree of graft ischemia clinically. This permits early identification of patients who have severe RAS that probably will be difficult to control medically, and, therefore, should be followed closely with a view of reconstructive vascular surgery before further deterioration of renal function.

Adolescent↗
PubMed1976

Renal allograft biopsy: a satisfactory adjunct for predicting renal function after graft rejection.

Forty-four biopsies of transplanted kidneys undergoing rejection were examined by light microscopy without knowledge of the eventual clinical outcome. All patients received extensive antirejection medication. A scoring system based on nine histopathologic criteria was formulated to predict whether the serum creatinine would be less than 1.8 mg/dl (good prognosis), 1.8 to 2.5 mg/dl (fair), or greater than 2.5 mg/dl (poor), two months after biopsy. Predictions were accurate in 37 of the 44 cases. In some cases with relatively minimal vascular changes the prognosis was poor, whereas heavy cellular infiltreate without vessel damage did not necessarily preclude functional recovery. It was concluded that specific histopathologic pictures should enable the physician to decide whether to institute extensive antirejection therapy or adopt alternative measures.

Acute Disease↗
PubMed1975

Effect of chronic renal failure, dialysis and transplantation on motor nerve conduction velocity in children.

Ulnar and peroneal motor nerve conduction volocities (MNCVs) were measured in 47 children in a dialysis-transplantation program. Mean peroneal MNCV was significantly decreased from normal in children with mild renal failure (serum creatinine concentration, 1.5 to 2.9 mg/dl), whereas ulnar MNCV was significantly decreased only when the serum creatinine value was at least 9 mg/dl. Both ulnar and peroneal MNCVs remained unchanged during long-term hemodialysis or peritoneal dialysis; however, after individual dialyses ulnar MNCV increased. After renal transplantation ulnar MNCV returned to normal within a year and peroneal MNCV within 3 years. Before dialysis was required and during long-term dialysis most plasma magnesium values were elevated; ionized calcium activity was decreased in about 50% of determinations. After transplantation and the concentration of divalent cations rapidly returned to normal. These children differed from adults studied in that (a) there was no correlation between severity of renal failure and MNCV, (b) long-term dialysis did not improve MNCV and (c) peroneal velocities did not recover for 3 years after transplantation.

Adolescent↗