Sarcoplasmic reticulum. IX. The permeability of sarcoplasmic reticulum membranes.

Fragmented sarcoplasmic reticulum (FSR) membranes isolated from rabbit skeletal muscle are impermeable to inulin-(14)C (mol wt 5,000), and dextran-(14)C (mol wt 15,000-90,000) at pH 7.0-9.0, yielding an excluded space of 4-5 microl/mg microsomal protein. In the same pH range urea and sucrose readily penetrate the FSR membrane. EDTA or EGTA (1 mM) increased the permeability of microsomes to inulin-(14)C or dextran-(14)C at pH 8-9, parallel with the lowering of the FSR-bound Ca(++) content from initial levels of 20 nmoles/mg protein to 1-3 nmoles/mg protein. EGTA was as effective as EDTA, although causing little change in the Mg(++) content of FSR. The permeability increase caused by chelating agents results from the combined effects of high pH and cation depletion. As inulin began to penetrate the membrane there was an abrupt fall in the rate of Ca(++) uptake and a simultaneous rise in ATPase activity. At 40 degrees C inulin penetration occurred at pH 7.0 with 1 mM EDTA and at pH 9.0 without EDTA, suggesting increased permeability of FSR membranes. This accords with the higher rate of Ca(++) release from FSR at temperatures over 30 degrees C. The penetration of microsomal membranes by anions is markedly influenced by charge effects. At low ionic strength and alkaline pH acetate and Cl are partially excluded from microsomes when applied in concentrations not exceeding 1 mM, presumably due to the Donnan effect. Penetration of microsomal water space by acetate and Cl occurs at ionic strengths sufficiently high to minimize charge repulsions.

Microalbuminuria in NIDDM.

OBJECTIVE: To determine an effective screening procedure for microalbuminuria. RESEARCH DESIGN AND METHODS: The prevalence of microalbuminuria in NIDDM patients whose urine was negative on routine Albustix testing was studied. Microalbuminuria was measured in overnight urine samples from 128 NIDDM patients on at least two of three occasions over a 6-mo period. Patients were tested with Micro-Bumintest or Micral-Test. RESULTS: Ten of 128 patients had albumin concentrations > or = 20 mg/L on two or more occasions, 14 patients had A-C ratios > or = 3 mg/M on two or more occasions, and 9 patients had both. CONCLUSIONS: Neither Micro-Bumintest nor Micral-Test is a useful or feasible screening procedure for microalbuminuria.

Elevated serum angiotensin converting enzyme levels in metastatic ovarian dysgerminoma.

A case of a 32-year-old XY genotype female is described, presenting with mediastinal and abdominal lymphadenopathy and associated with an elevated serum angiotensin I converting enzyme (SACE) level. Lymph node histology showed a malignant dysgerminoma of ovarian origin. Combined chemotherapy led to a radiological regression of the lymphadenopathy and coincided with a decrease in SACE concentration. The authors suggest that SACE may be a marker for disseminated germinoma tumours and may be useful for monitoring treatment.

Adapting the uricase/peroxidase procedure for plasma urate to reduce interference due to haemolysis, icterus or lipaemia.

The estimation of serum urate by uricase/peroxidase procedures involving single point bichromatic absorbance monitoring gives inaccurate results with samples which are haemolysed, icteric or lipaemic. These inaccuracies can be greatly minimized by reducing the rate of chromogen formation and applying the assay in a kinetic mode.

A robust procedure for the automated measurement of total serum bilirubin using potassium ferricyanide.

Bilirubin is oxidized to biliverdin by 1.0 mmol/L potassium ferricyanide in the presence of caffeine. The absorbance decline at 480 nm with blanking at 660 nm is proportional to bilirubin concentration. The assay is linear up to 1000 mumol/L and is suitable for the measurement of bilirubin in adult and neonatal patients. The assay is accurate and precise and is not significantly affected by haemolysis up to 5.0 g/L haemoglobin. Reagents and calibration are stable for at least 3 months.

Simple adaptation of the Technicon SMAC system to operate 18 channels with reduced volumes of plasma.

The Technicon SMAC system was adapted to function with much smaller volumes of plasma than those used in standard procedures. With only minimal operator-entered changes to the 7.6 computer program, and simple modifications of the glucose and alkaline phosphatase channels, the SMAC analyser performed equally well when the plasma volume was decreased from 235 microliter sequentially down through 176 microliter, 142 microliter, and 105 microliter. The basic principle employed was to maintain a constant flow rate of diluted sample plus diluent with decreasing sample size. The instrument proved to have the capability of operating successfully on all channels with lower signals than those encountered with the unmodified system.

Relation of angiographically defined coronary artery disease to serum lipoprotein levels.

The relationship of coronary artery disease to plasma lipoproteins was examined in 43 men admitted to our unit with suspected ischemic heart disease. Coronary arteriography was performed, and a score reflecting the severity of disease was assigned to the angiogram. Plasma, obtained after a 12-h overnight fast, was assayed for triglycerides, total cholesterol, high-density lipoprotein (HDL) cholesterol, and HDL-3 cholesterol. HDL-2 cholesterol was found by subtraction. The cholesterol contents of very low-density lipoprotein (VLDL) and low-density lipoprotein (LDL) were quantitated by the Freidwald equation. Men with high coronary scores tended to be older, and subjects with moderate coronary disease had significantly higher total and LDL cholesterol values than those with minimal disease. Age was the only factor to be significantly associated with coronary score and there was no significant association between coronary score and total LDL and HDL cholesterol or its subfractions when the age factor was taken into account.

Blood lead levels and free red blood cell protoporphyrin as measure of lead exposure in mute swans.

The use of blood lead levels in assessing lead exposure in mute swans, Cygnus olor (Gmelin) is investigated. 823 blood samples were taken from 456 uniquely ringed mute swans at a coarse-fish angling site over a period of 24 months. Blood lead values in individual swans monitored over several weeks were shown to conform to a recently reported kinetic model for blood lead values in birds. The highest median lead levels for flock birds were recorded in the winter and spring and the lowest during the summer moulting period. The use of Free Red Blood Cell Protoporphyrin for detecting lead exposure was examined. Whole blood lead detected 44% (n = 357) with elevated lead, while free red blood cell protoporphyrin detected 34.50%. In a large number of cases levels of protoporphyrin were above the normal level, while the corresponding lead levels were low. The value of both methods and the need to correct each value for haemoglobin is discussed.

Adaptation and validation of a radioimmunoassay kit for measuring plasma cortisol in turbot.

Levels of cortisol in fish blood provide quantitative information on the degree of stress induced by a variety of stressors. It is also useful in describing the social status of individual fish within groups. The commercial production of radioimmunoassay (RIA) kits, such as the DPC Coat-A-Count radioimmunoassay kit, has considerably reduced the effort required for cortisol measurement. These kits employ human plasma based cortisol standards which are not compatible for use with non mammalian species such as fish e.g. turbot, Scophthalmus maximus (Rafinesque), blood due to the interference effect of lipids and steroid binding proteins present in the plasma. In this study the DPC kit was used following the removal of these lipids and steroid binding proteins from the plasma using an ethanol-hexane extraction. Excessive variability in the cortisol values obtained using this method deemed it unsatisfactory in overcoming the problem of incompatibility. A second modification of this technique that was tested involved the preparation of turbot specific standards for use in the preparation of modified standard curves. Using this method, an accuracy of 93.4% was achieved, as opposed to 79.6% using the kit human plasma based standards, and 47.1% using samples following lipid removal using an ethanol-hexane extraction. Based on analysis of accuracy, precision and reproducibility it is concluded that commercially available cortisol kits are suitable for use with turbot plasma, but a number of minor modifications are necessary.

Perioperative creatine phosphokinase trends in elderly patients with hip fracture.

A prospective study of the serum levels of unfractionated creatine phosphokinase (CPK) in 69 consecutive elderly patients undergoing surgery for hip fracture is reported. Serum unfractionated CPK levels were measured on admission, on the evening following surgery and daily for the first five days post-operatively. All of the CPK levels measured on admission were within the normal range for this laboratory. A gradual rise in CPK levels followed surgery. On the evening following surgery 75% of values were greater than the upper limit of the normal reference range. The peak values were seen on day 1 post-operatively but 25% of values were still less than the reference maximum. A gradual decline was seen after this and at day 5 post operatively 50% of values were within the normal reference range. A single unfractionated CPK determination is not of diagnostic benefit in the post-operative period in elderly patients with hip fracture. However, patients with intracapsular and intertrochanteric fractures do not show elevation of unfractionated CPK levels prior to surgery.