Isolation of Murray Valley encephalitis virus from sentinel chickens

Sentinel chickens were established in 3 centres along the Murray Valley on 20 December 1973. The demonstration of antibody in the serum of chickens in the Mildura and Kerang areas indicated Sindbis virus activity late in December 1973 and early in January 1974. Tests for antibody to MVE virus were negative until blood collected from one chicken at Echuca on 27 February 1974 and several chickens at Mildura and Kerang on 14 March 1974, showed positive HI reactions. Murray Valley encephalitis virus was isolated from blood collected from chickens at Echuca and Kerang respectively on 31 January 1974 and 27 February 1974.

Countercurrent immunoelectrophoresis in the evaluation of childhood infections

Samples of CSF, serum, and urine from 162 children with a clinical diagnosis of possible bacterial infection were examined by CIE within 1 hr of admission to the hospital. Results obtained were compared to information derived from gram stain and bacterial cultures of these specimens. Thirty-eight of 59 patients with culturally proved bacterial infections had positive CIE determinations at the time of admission. Highest correlation between culture and CIE results was in patients with meningitis due to Hemophilus influenzae type b while poorest correlation was obtained in children with pneumococcal septicemia. PRP within serum or CSF was quantitated on 21 occasions in patients with H. influenzae meningitis. Patients who experienced sequelae of their meningitis had significantly (p less than 0.005-0.025) higher levels of PRP within CSF and serum than those whose recovery was uneventful.

Myasthenia gravis

Taken from the weekly Pediatric Grand Rounds held at the University Hospital of San Diego County, University of California, San Diego, School of Medicine, June 20, 1972

Preservation of immunological and biological activities of insulin by insulinase inhibitor in vitro

The relation of insulinase activity to the biological effect of insulin on isolated tissue was studied. Rat diaphragm in vitro caused the rapid disappearance of immunoreactive insulin (IRI) in physiological concentrations. IRI loss at time intervals was exponential. The fractional rate of loss of IRI was therefore independent of IRI concentration and was also approximately constant per milligram of tissue, the value being 0.0216%/mg∙mm. The value of the Michaelis constant (Km), obtained from initial velocities at five initial concentrations of IRI, was 1.85 × 10−8M, and of the maximal velocity (Vmax) was 2.32 × 10−11 mole/g∙min, based on insulin dimer. The addition of an insulinase inhibitor (a partial hydrolysate of insulin) to hemidiaphragm in vitro reduced the fractional rate of IRI loss by 60%. The increase in Km, without appreciable change in Vmax, indicated that the inhibition was competitive. The IRI preserved by means of the inhibitor was biologically active, since it increased the glycogen accumulation and the incorporation of 14C-U-glucose into glycogen in a second, fresh hemidiaphragm. In single incubation of hemidiaphragm with insulin, the gain in glycogen was correlated with the amount of inhibitor. The biological effect of insulin on diaphragm in vitro was therefore limited by tissue insulinase activity, and insulinase inhibitor potentiated to some extent the action of insulin.

A consideration of methods of insulin assay

The potency of “unknown” solutions of insulin has been determined by the U.S.P. rabbit method of assay. The same solutions have also been assayed by the mouse convulsion method, mouse hemidiaphragm method and by several immunoassay methods. The record shows reasonable agreement among the various methods which were used.

Pancreatic insulinase and its inhibition by the A and B chains and partial hydrolysate of insulin

Insulin was destroyed rapidly by insulinase of rabbit pancreatic extract. The activity was enhanced threefold by glutathione, and was inhibited by the sulfhydryl poisons, mercuric chloride, cupric sulfate, and p-chloromercuribenzoate. The insulinase was also strongly inhibited by low concentrations of acid hydrolysate of insulin and by the oxidized forms of the B and the A chains of insulin.

Elevation in serum insulin, albumin, and FFA, with gains in liver lipid and protein, induced by glucocorticoid treatment in dogs

Administration of methylprednisolone to dogs (4 mg/kg per day, intramuscularly for 17 days) had the following effects. Immunoreactive insulin (IRI) in serum (postabsorptive) rose threefold to a peak in 4 days and later returned to normal. Serum glucose was little altered. The rise in the IRI/glucose ratio suggests that the sensitivity of the insulin release mechanism of the pancreatic beta cells to glucose was increased. Serum albumin rose, concomitantly with IRI, then returned to normal at a slower rate than did IRI. Globulins were not appreciably altered. Free fatty acids (FFA) rose later, during days 7–14. Liver weight increased, owing to gains in total lipid and fat-free solids. The plasma volume percent increased, and polyuria occurred. In response to a glucose load (1 g/kg, intravenously) methylprednisolone caused an augmented rise in serum IRI on days 1 and 4, with a later return to or below normal, and an increase in the rate of disappearance and the apparent volume of distribution of glucose. Cortisone (5 mg/kg per day intramuscularly, for 6 days) exerted similar effects in the dog. The results suggest that an increased insulin secretion was induced by glucocorticoids, and that this effect was involved in enhanced synthesis of liver protein and albumin and in increased rate of uptake of glucose.

Exocrine pancreatic disease and the malabsorption syndrome in tropical Africa

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Augmented insulin secretion due to growth hormone. Stimulating effects of glucose and food in dogs

In iinanesthetized dogs, portal vein (PV) blood was repeatedly sampled by means of an indwelling cannula, simultaneously with blood from a superficial vein (SV), for determination of insulin by two-antibody immunoassay. Under control conditions, and in the postabsorptive state, mean serum insulin in the SV was 31 μU. per milliliter, and the PV/SV ratio was about 2. Following intravenous injection of 1 gm. of glucose per kilogram of body, serum insulin rose in 15 to 30 min. to peak values that were higher in the PV, and regressed to normal in 60 to 120 min. Growth hormone, 2 mg. per kilogram of body, injected daily for six to thirteen days, (1) increased PV and SV “fasting” serum insulin to the maximum of tenfold; the effect was found after one day of injection, was maintained during injection, and returned to normal within four days of ceasing injection; (2) caused a further increase in serum insulin, in 100 min. following a meal, to a greater extent in the PV than in the SV; and (3) enhanced the rises in serum insulin in PV and SV following intravenous injection of glucose, to maxima of nine- and sixfold, respectively; these rises were prolonged and the rates of regression regression of serum insulin from the peak values were reduced. Similar effects of growth hormone treatment were found in dogs under anesthesia at the time of glucose infusion. It is concluded that, during the treatment of several days, growth hormone caused continuously maintained increase in insulin secretion with enhanced secretion in response to a meal, and to the injection of a standard load of glucose.

Further effects of growth hormone on serum were: (a) free fatty acid levels rose promptly, and remained above normal; (b) glucose tended to increase; (c) the insulin/glucose ratio increased—the values were consistently reater in the PV than in the SV; and (d) in response to the glucose load, the rate of regression of serum glucose was reduced. The insulin/glucose ratio tended to remain stable at the particular “fasting” value, following glucose injection, both under the control conditions and during growth hormone treatment. This evidence indicates that growth hormone caused readjustment of the homeostatic control of the pancreatic islets such that, at any particular level of glucose in the blood, insulin was secreted at a higher rate.