Calcium-sodium antagonism on the frog's heart: a voltage-clamp study

1. In double sucrose-gap voltage-clamped frog atrial fibres the influence of [Ca]o and [Na]o on membrane current and contraction was investigated. 2. The slow (secondary) inward current varied with [Ca]o but was almost insensitive to changes in [Na]o. In contrast, the phasic (transient) contraction initiated by the slow inward current was affected by both [Ca]o and [Na]o. 3. With moderate changes of [Ca]o and [Na]o from normal, the strength of phasic contraction at a given depolarization followed the [Ca]o/[Na]2o ratio approximately. This was best seen at membrane potentials near zero level. 4. Under the same conditions, tonic (sustained) contractions associated with prolonged depolarizations were strictly correlated to the [Ca]o/[Na]2o ratio at any potential. No interrelation between tonic tension and steady-state current was found. 5. With extensive changes in [Ca]o and [Na]o, the sensitivity of both phasic and tonic tension to the [Ca]o/[Na]2o ratio declined, the negative effect of [Na]o becoming smaller than was expected from this ratio. 6. In Na-free choline-Ringer, a strong contracture developed followed by a spontaneous relaxation. Starting from the relaxed state, application of depolarizing clamps gave rise to phasic contractions with a very slow relaxation while tonic contractions were apparently lacking. 7. The results are interpreted in terms of an energy-dependent carrier mechanism exchanging one Ca for two Na ions across the cell membrane. The model implies a strong asymmetry in the rate constants governing the chemical reactions on both sides of the membrane. The system is thought to operate close to equilibrium at any potential, thereby determining the steady level of myoplasmic Ca. The equilibrium itself is considered to shift upon depolarization. Assuming that [Na]i is constant, the steady level of [Ca]i is expected to be proportional to the [Ca]o/[Na]2o ratio, the scale factor being a function of membrane potential. 8. The carrier model suggests the occurrence of a depolarization-induced inward transfer of Ca which might be involved in the generation of tonic contractions. 9. The apparent lack of tonic contractions in the absence of external Na ions may be explained by a suppression of carrier-mediated Ca influx normally occurring upon depolarization. 10. The antagonistic effects of [Ca]o and [Na]o on phasic contraction are understood as being due to alterations of the Ca pumping system rather than changes in slow inward current.     

Medical and surgical therapy in diverticular disease: a comparative study

The course of 132 patients with documented acute diverticulitis was analyzed: 99 patients treated medically and 33 patients treated surgically were followed for an average of 9.2 years. Seventy-three per cent of the medical group and 79% of the surgical group had no further symptoms or hospital admissions as a result of their diverticular disease once they were recovered from the acute episode. For three-quarters of the patients, therefore, acute diverticulitis occurred as a single episode that responded to either medical or surgical management. Considering the morbidity and cost to the patient, the treatment of the patient recovered from acute diverticulitis should be medical, with operation reserved for complications.     

Hemoglobin M equon beta 41 (C7) phenylalanine leads to tyrosine

A severe hemolytic crisis was observed in a 34-yr-old female of English-Irish extraction following a viral illness treated with acetaminophen. Heinz bodies and heat instability were present only during a transient hemolytic event. A challenge dose of acetaminophen caused no detectable hematologic abnormality. Structural studies of the hemoglobin during hemolysis and again after complete recovery localized the abnormality to tryptic peptide beta Tp-5, and automated sequencing of I 125-labeled beta chains indicated a replacement of phenylalanine (C7) beta 41 by tyrosine. Substitution of the next residue, phenylalanine (CD1) beta 42 by serine (Hb Hammersmith), has resulted in chronic severe Heinz body hemolytic anemia. The lack of chronic anemia in the present disorder may reflect the different relationships of beta41 and beta 42 and/or the similarities in volume and hydrophobicity of tyrosine and phenylalanine. It is suggested that substitution of tyrosine for phenylalanine in Hb Mequon may disturb the critical environment around the heme group and render it susceptible to oxidative denaturation in the presence of infections and/or drugs.     

An approach to general oncology: principles and procedures

53 patients clinically suspected of having a cerebellopontine angle (CPA) lesion were examined by computer tomography (CT) with 160 X 160 matrix EMI scanner. 17 cases (32%) had tumour positive CT, of which 12 were neurinomas and 1 meningioma. 1 CT suggestive of a CPA lesion was false positive and 1 unoperated case is probably a false negative CT. Three of the eleven verified neurinomas (27%) were of the medial type originating in the angle cistern. One neurinoma protruding 1 cm into the cistern showed no contrast enhancement. 2 CT scans (3.8%) were unsatisfactory due to movements and the large size of the head. CT is valuable for the investigation of CPA pathology and the diagnostic efficiency compares favourably to other neuroradiological procedures.     

A classification of endocervical curettings

The influence of inborn errors of metabolism on the amino acid content, the structure and growth of human hair has been studied in patients suffering from Phenylketonuria, Cystinosis, Homocystinuria and Tyrosinosis. Examiniation of hairs under the scanning electron microscope reveals defects and abnormalities such as a plicated pattern of the cuticula in patients with Phenylketonuria and Cystinosis. The amino acid content of the hydrolized hair keratin of all patients was within normal range and did not reveal significant changes of phenylalanine, cystine, homocystine, methionine or tyrosine. Disturbance in hair growth was determined by evaluation of standardized hair root samples. The results indicate an increase in hair root atrophy with increasing severity of the disorder of amino acid metabolism.     

Acute liver injury in rats by praseodymium nitrate (author''s transl)

After acute intoxication with praseodymium nitrate (10 mg/kg body weight i.v.), time functions of enzyme activities of GOT, GPT, ChE, AP and of free fatty acids concentration in rat serum were analysed and the results subjected to significance and correlation analysis. Time functions of free fatty acids concentration corresponded with those of enzyme activities of GOT and GPT. In the early state of intoxication serum concentrations of palmitoleinic and oleic acid were more increased than those of stearinic acid. There seems to be an alteration in the correlations of analysed measures with regard to their temporal changes parallel to the progress of intoxication.     

Lactate metabolism in the dog during shock from hemorrhage, cardiac tamponade or endotoxin

Serum IgE concentrations of patients with paragonimiasis were determined by a radioimmunosorbent test. The mean concentration was 3,462.3 IU/ml in a group of 13 cases of paragonimiasis miyazakii in which patients showed clinical symptoms and/or positive immunological diagnostic tests, and 1,026.6 IU/ml in a control group of 13 individuals who had eaten uncooked freshwater crabs, Potamon dehaani, but had been found to be free from the infection. Moreover, the IgE level of the pleural exudates obtained from four patients with paragonimiasis miyazakii on the day of bleeding or within several days after was significantly higher than that of their sera, ranging between 4,200 IU/ml and 10,000 IU/ml. This was true also in a case of paragonimiasis westermani. Sera and pleural exudates of patients with both forms of paragonimiasis were applied to immunosorbent columns of Sepharose 4B beads coupled with saline extracts of Paragonimus miyazakii, P. weetermani, or P. ohirai. IgE eluted from the corresponding column was considered to be specific, being around 5% to 10% of the total IgE.     

In vitro effects of urease inhibitors on rate of urea hydrolysis in soils

We studied the effect of urease inhibitors on the urea hydrolysis in some Sundanese soils belonging to the orders of Vertisol and Entisol. The hydrolysis showed a lag period of about 3 days and its rate (Y) per unit time (t) could be described by a two constants exponential equation of the general form Y = K₁t^K ₂. Statistical analysis showed that the intercept K₁ (rate of urea hydrolysis) was significantly affected by soil type rather than treatment. It seems that K₁ is associated with the soils' initial urease activity as it closely correlates with the Michaelis constant (km).The gradient, K₂, being significantly affected by soil type as well as treatment is probably associated with the induced urease activity with time and it, therefore, varied with variations in soils and treatments. Of the so-called urease inhibitors used in this study Ca(OH)₂, p-benzoquinone (PBQ) and orthophosphoric acid (OP) only PBQ reduced urea hydrolysis while the other chemicals have effects possibly related to modifying the soil pH. Inhibitor treated soils had substantial amounts of unacounted for N which was believed to be present, presumably, in the form of carbamate.Contribution from the Department of Biochemistry and Soil Science, Faculty of Agriculture, Shambat, Sudan.