Application of a new method of antibody-enzyme conjugation with maleimide derivative for immunohistochemistry: hepatocellular production, interstitial tissue distribution, and renal cell reabsorption of plasma albumin in guinea pig

A new sophisticated method for enzyme-antibody conjugation developed in quantitative solid-phase enzyme immunoassay was revealed to be an applicable method for immunohistochemistry; one that offered several advantages over present methods. Using a new maleimide derivative as a coupling reagent, monomeric conjugate of horseradish peroxidase and Fab' antibody was easily prepared with high efficiency and reproducibility. Nonspecific staining was greatly reduced in the presence of this monomeric conjugate. Since the enzyme activity and antigen-binding activity were well preserved in the conjugate, the reaction was strong enough to analyze the antigen localization in intracellular organelles or in interstitial tissue space by both light and electron microscopy. The fate of plasma albumin was investigated in liver, skin, and kidney using the new method with rabbit anti-guinea pig albumin antibody, and satisfactory results were obtained. In the liver, the reaction products were observed in the rough and smooth endoplasmic reticulum and the Golgi apparatus in hepatocytes, which confirmed the synthesis of plasma albumin in hepatocytes of guinea pig. In a study of the distribution of albumin, reaction products were seen in the intercellular space of the epidermis, along the basement membranes of epidermis and of proximal convoluted tubules in kidney, and among the collagen fibers in interstitial tissue, particularly at papillary dermis, suggesting the wide distribution of plasma albumin in interstitial extravascular tissue spaces. In addition, positive reaction was obtained in the apical vesicles and the lysosomes of the proximal convoluted tubules and in the pinocytotic vesicles of the basal cells of epidermis, suggesting the reabsorption and destruction of albumin in the kidney and the skin.     

Ca2+-sensitizing effects of the mutations at Ile-79 and Arg-92 of troponin T in hypertrophic cardiomyopathy

Several mutationsin human cardiac troponin T (TnT) gene have been reported to causehypertrophic cardiomyopathy (HCM). To explore the effects of themutations on cardiac muscle contractile function under physiologicalconditions, human cardiac TnT mutants, Ile79Asn and Arg92Gln, as wellas wild type, were expressed in Escherichiacoli and exchanged into permeabilized rabbit cardiac muscle fibers, and Ca²⁺-activatedforce was determined. The freeCa²⁺ concentrations required fortension generation were found to be significantly lower in the mutantTnT-exchanged fibers than in the wild-type TnT-exchanged fibers,whereas no significant differences were found in tension-generatingcapability under maximal activating conditions and in cooperativity.These results suggest that a heightenedCa²⁺ sensitivity of cardiac musclecontraction is one of the factors to cause HCM associated with theseTnT mutations.

     

Rapid and sensitive method for detection of Salmonella strains using a combination of polymerase chain reaction and reverse dot-blot hybridization

Abstract Cell-free extracts of Thiobacillus acidophilus catalysed the stoichiometric conversion of tetrathionate to thiosulphate, sulphur and two protons. The pH optimum of the enzyme activity was 3.0 and its temperature optimum 40°C. The enzyme was unstable at 30 and 40°C, at which its activity decreased to zero within 100 and 20 h, respectively. Enzyme activity was not affected by incubation for 1 week on ice or by freezing and thawing of the extract. The K _m for tetrathionate was 0.3 mM. Enzyme activity was stimulated by ammonium sulphate up to a concentration of 1M. The results indicate that trithionate hydrolase cannot account for the observed conversion of tetrathionate.