Anatomic dissection of the tibialis posterior muscle and its correlation to medial tibial stress syndrome

The authors attempt to redefine the anatomic origin of the tibialis posterior muscle, and correlate it with the location of medial tibial stress syndrome that occurs in the lower third of the tibia. Contrary to what is commonly described, the authors show on all ten dissected specimens, that the origin of the tibialis posterior does include a portion of the lower third of the tibia. The mean distance from tibialis posterior's origin to the medial malleolus was only 7.77 cm. In addition, to further explain lower leg pain, the authors investigated the crossing point of tibialis posterior and flexor digitorum longus; a mean distance for this to occur in the same ten specimens was 8.16 cm. proximal to the medial malleolus. These findings provide insight to anatomic reasons behind biomechanical factors responsible for medial tibial stress syndrome. This is also important to consider when performing surgery for a deep compartment syndrome.

Purification and characterization of the extracellular C3d-binding protein of Candida albicans

A C3d-binding glycoprotein was purified from the culture filtrate of Candida albicans by preparative isoelectric focusing. The protein possessed a pI of 3.9 to 4.1 and could inhibit rosetting of EAC3d (sheep erythrocytes conjugated to C3d) by pseudohyphae of C. albicans. When analyzed by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate and mercaptoethanol, the protein migrated as a doublet with apparent molecular masses of 55 and 60 kilodaltons (kDa) and as a 50-kDa band in nonreducing gels. These results were observed with Aurodye stain for proteins. Western immunoblot, and concanavalin A stain, which indicates that both bands contain carbohydrate as well as antigenic determinants. The treatment of purified glycoprotein with endoglycosidase F but not endoglycosidases H, N, and O resulted in a complete conversion of the doublet into a faster-migrating broad band with an apparent molecular mass of 45 kDa. When the amino acid analysis of the C3d-binding protein was compared with that of the CR2 from B lymphocytes, significant differences were observed. These data indicate that C. albicans secretes a C3d-binding protein during growth in vitro which appears to be different from the mammalian C3d receptor.

Interactions of macrophages from in vivo stimulated guineapigs & the trophozoites of Entamoeba histolytica

The interactions between peritoneal macrophages obtained from guineapigs immunized with a Sephadex chromatographed fraction (FI) of crude amoebic extract proteins and trophozoites of axenic E. histolytica (NIH:200) were studied in vitro in the presence or absence of anti FI antiamoebic antibodies. Unstimulated macrophages killed trophozoites to some extent. Incorporation of anti FI antiamoebic antibodies or IgG of FI antibodies in the amoebae macrophages mixture significantly enhanced the cytotoxic potentials of both unstimulated and in vivo stimulated peritoneal macrophages. Transmission electron microscopy revealed a close contact between macrophages and E. histolytica trophozoites. A large number of lysosomal vacuoles were seen accumulating near the contact areas. The contact between peritoneal macrophages and amoebic trophozoites in the presence of anti FI antibodies led to extensive degeneration of amoebic trophozoites. The antiamoebic antibodies induced cytotoxicity by macrophages in an opsonic manner. The data suggest that antiamoebic IgG binding to the trophozoites by its Fab portion and to the macrophages by its Fc portion initiated the cytotoxic mechanism(s) of macrophages.

Doppler echocardiographic assessment of transmitral gradients and mitral valve area before and after mitral valve balloon dilatation

This is a comparative study of 60 sets of observations of mitral valve end-diastolic gradient, mean diastolic gradient, and mitral valve area obtained by Doppler echocardiography and cardiac catheterization. The studies were performed in 28 patients, 16 of whom underwent mitral valve balloon valvuloplasty. These 16 patients had studies performed before, immediately after valvuloplasty, and one week later. Thus 28 studies were performed before or without valvuloplasty (Group I) and 32 after valvuloplasty (Group II). The time interval between Doppler echocardiography and cardiac catheterization was less than 24 hours in 44 studies and 24 to 72 hours in 16 studies. In Doppler echocardiography the gradients were obtained by simplified Bernoulli's equation and the mitral valve area by pressure half-time method. There was excellent correlation between end-diastolic gradients (r = 0.96, p less than 0.001) and mean diastolic gradients (r = 0.92, p less than 0.001) measured by the two techniques. A statistically significant correlation also existed in the mitral valve area values (r = 0.53, p less than 0.005). On separate analysis Group I showed excellent correlation for all three variables (r values of 0.90, 0.87, and 0.82 for end-diastolic gradients, mean-diastolic gradients, and mitral valve area, respectively). Group II also showed excellent correlation of end-diastolic gradients (r = 0.80) and mean diastolic gradients (r = 0.87), but poor correlation of the mitral valve areas (r = 0.17; p = NS) by the two techniques. Doppler echocardiography can accurately measure transmitral gradients both before and after valvuloplasty.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparative Doppler evaluation of the monostrut and older convexo-concave Björk-Shiley mitral prosthetic valve

Doppler echocardiography was performed in 104 patients with a Björk-Shiley prosthetic valve in the mitral position. Valves of size 25 mm and 27 mm were inserted in 39 and 65 patients, respectively. Each valve had two models; the older convexo-concave model (22 and 40, of 25 and 27 mm size, respectively). Inflow velocities were recorded using Doppler techniques and the gradients calculated using the Bernoulli principle. The area of the mitral valve was determined by the T1/2 method. Comparison of the two models for both sizes did not reveal any significant differences in either the gradients across the valves or the area of the valve. Trivial mitral regurgitation was detected in a higher percentage of monostrut valves (18% and 20% for the 25 and 27 mm older convexo-concave models and 59.9% and 52% for the 25 and 27 mm monostrut valve). We conclude that the newer monostrut model of the Björk-Shiley valve in the mitral position does not offer any additional haemodynamic benefit.

Bronchogenic carcinoma. A study of 109 cases

The clinical profile of 109 cases of bronchogenic carcinoma has been studied. Definite histopathological typing of malignancy was possible in 61 patients, squamous cell carcinoma being the commonest tumour in 27 followed by small cell carcinoma in 16, adenocarcinoma in 11 and large cell carcinoma in 7. Another 23 patients showed changes suggestive of malignancy on histological/cytological examination. Definitive diagnosis was obtained in half of the patients by bronchial biopsy, in 16% by bronchial aspiration fluid cytology, in 13% by pleural biopsy, in 11% by lymph node biopsy and in others by pleural fluid cytology, lung biopsy and skin biopsy. Commonest radiological involvement among different cell types was hilar involvement in small cell carcinoma in 62%, evidence of bronchial obstruction (collapse/consolidation) in squamous cell carcinoma in 56%, peripheral mass in adenocarcinoma in 54% and cavitation in a mass in squamous cell carcinoma in 15% cases.

Isolation and sequencing of cDNA clones encoding Drosophila chromosomal protein D1. A repeating motif in proteins which recognize at DNA

Drosophila melanogaster D1 is a satellite DNA-associated protein which preferentially binds DNA sequences containing runs of AT base pairs. Clones encoding this polypeptide have been isolated from a lambda gt11 cDNA library by immunological screening with a D1 antiserum. The deduced sequence of the D1 polypeptide is 355 amino acids long and contains 10 copies of a repeating motif consisting of a glycine-arginine-proline (GRP) tripeptide located within a cluster of basic amino acids. Three copies of a similar motif have previously been observed in a mammalian satellite DNA-binding protein, high mobility group protein I (Lund, T., Dahl, K. H., Mork, E., Holtlund, J., and Laland, S. G. (1987) Biochem. Biophys. Res. Commun. 146, 725-730), suggesting that this motif may be a general feature of proteins which bind AT-rich satellite DNA and perhaps other AT-containing DNA as well.

New radiographic angle to assess intra-articular calcaneal fractures

The authors' describe a new radiographic angle, the calcaneal compression angle, to assess intra-articular calcaneus fractures. Pre- and postreduction values of eight subjects sustaining intra-articular calcaneus fractures using the new angle were compared to Boehler's angle values. A higher percentage of immediate postreduction value of the calcaneal compression angle was retained when compared to Boehler's angle. The new angle may be more beneficial for evaluating these type of calcaneal fractures and their subsequent reduction.

Echocardiographic assessment of infants born to diabetic mothers

Echocardiography was carried out in 31 neonates (group 1) born to diabetic mothers and 37 control infants (group 2) matched for weight and gestational age. The interventricular septum was significantly thicker in group 1 babies (mean (SD) 4.77 (1.4) mm) compared with those in group 2 (2.5 (0.7) mm); in eight it was more than 5 mm, but had regressed in six over a period of three months. There was no significant difference between the two groups in the left ventricular internal dimension, right ventricular outflow tract, or size of the left atrium or the aorta. The left ventricular mass was significantly greater in infants born to diabetic mothers. The left ventricular contractility (judged by the percentage of shortening of the internal dimension and the ejection fraction) was significantly greater in group 1. No evidence of left ventricular outflow obstruction was found on pulse Doppler echocardiography in group 1.

Echocardiographic--angiocardiographic correlation in persistent truncus arteriosus

Four cases of persistent truncus arteriosus (PTA) type 1 are presented where echocardiography was helpful in making the diagnosis. The diagnosis was later confirmed by cardiac catheterisation and angiocardiography.

Intracranial aneurysms in India--microsurgical approach

This is a retrospective study of 100 cases of intracranial aneurysms, treated in an Indian hospital, reflecting the special situation and experiences in our country. The incidence of subarachnoid haemorrhage due to ruptured aneurysm has been more or less the same as is reported from other parts of the world. The cases of recurrent haemorrhage resulting in poor clinical status are more common in our situation. Delayed referral and diagnosis were responsible for recurrent haemorrhage, increased morbidity and mortality. Forty two percent developed cerebral vasospasm within two weeks after the bleed. The use of a temporary clip on the parent vessel prevented the intraoperative rupture of the aneurysm while dissecting round about the aneurysm. Operative mortality was eight percent in the present series.

Analysis of mannans of two relatively avirulent mutant strains of Candida albicans

We previously reported the isolation of two cerulenin-resistant mutant strains of Candida albicans 4918 that differ in adherence properties and are less virulent than the parental strain. In addition, biochemical characterization demonstrated significant differences in both protein and polysaccharide composition of cell wall material between the mutant and wild-type strains. These observations prompted studies concerning the chemical structure of mannans in these strains. After extraction and subsequent purification by ion-exchange chromatography, mannan fractions were subjected to either mild acid hydrolysis, alkali hydrolysis, or acetylation followed by acetolysis. Acid- and alkali-modified mannans were studied by proton magnetic resonance spectroscopy, and released products were analyzed by high-performance liquid chromatography on an Aminex HPX-42A column. The results demonstrated quantitative and qualitative differences between mannooligosaccharides of the wild-type and mutant strains in the identity of released oligosaccharides as well as in linkage of the oligosaccharides to the protein backbone.

Ethylene biosynthesis-inducing protein from cellulysin is an endoxylanase

The proteinaceous ethylene biosynthesis-inducing factor (EIF) that was purified from Cellulysin was also shown to contain a xylanase activity. In all nondenaturing protein separation methods employed (Sephacryl S-200 chromatography, and preparative isoelectric focusing and agarose electrophoresis), xylanase activity copurified with the ethylene biosynthesis-inducing activity. Treatment with heat (60 degrees C) or proteases in 8 molar urea inhibited both ethylene-inducing and xylanase activities. Antibodies raised against purified EIF, which contains three polypeptides of 18, 14, and 10 kilodaltons, immunoprecipitated both ethylene biosynthesis-inducing and xylanase activities. The purified EIF contained no detectable cellulase, polygalacturonase, or protease activity. Other hydrolytic activities as estimated by using p-nitrophenyl derivatives of several sugars as substrates also were not detected. Different commercially available hydrolytic enzyme preparations were tested for both ethylene biosynthesis-inducing and xylanase activities. All enzymes tested contained xylanase activity, but only a few induced ethylene biosynthesis. Western blots of proteins separated by SDS-PAGE, using antibodies prepared against the non-denatured purified EIF, revealed two major bands of about 18 and 14 kilodaltons in EIF. These antibodies seem to be specific for these proteins from Trichoderma viride, because there was little cross-reactivity with the other proteins in Cellulysin and other commercial enzyme preparations. Based on these data, we suggest that EIF contains a specific xylanase activity which is involved in inducing ethylene biosynthesis.

Myocardial involvement and its response to immunosuppressive therapy in nonspecific aortoarteritis (Takayasu's disease)--a study by endomyocardial biopsy

Myocardial involvement in nonspecific aortoarteritis was evaluated in 16 patients (age 7-37 years, 2 males, 14 females) with the help of endomyocardial biopsy obtained from the right ventricle using the Cordis bioptome introduced from the right femoral vein. Morphological features of myocarditis were present in 8, endocardial thickening in 2, mild to moderate myofibre hypertrophy in 11, and a normal biopsy in 3 patients. Myocarditis was present in 8/11 cases with active disease and in none with inactive disease. Five of the 8 patients with myocarditis presented with congestive cardiac failure with 3 of them having no associated hypertension or valvar involvement to account for it. Immunosuppressive therapy was given to all patients with myocarditis. Serial studies (ongoing) showed clinical, haemodynamic and morphological improvement. Myocarditis appears to occur commonly in nonspecific aortoarteritis during the acute phase of the disease and may precipitate congestive cardiac failure in some patients. Immunosuppressive therapy shows promise and merits further evaluation.

Metabolism of the 18O-methoxy substituent of 3-methoxybenzoic acid and other unlabeled methoxybenzoic acids by anaerobic bacteria

O-methyl substituents of aromatic compounds can provide C1 growth substrates for facultative and strict anaerobic bacteria isolated from diverse environments. The mechanism of the bioconversion of methoxylated benzoic acids to the hydroxylated derivatives was investigated with a model substrate and cultures of one anaerobic consortium, eight strict anaerobic bacteria, and one facultative anaerobic microorganism. Using high-pressure liquid chromatography and gas chromatography-mass spectral analysis, we found that a haloaromatic dehalogenating consortium, a dehalogenating isolate from that consortium, Eubacterium limosum, and a strain of Acetobacterium woodii metabolized 3-[methoxy-18O]methoxybenzoic acid (3-anisic acid) to 3-[hydroxy-18O]hydroxybenzoic acid stoichiometrically at rates of 1.5, 3.2, 52.4, and 36.7 nmol/min per mg of protein, respectively. A different strain of Acetobacterium and strains of Syntrophococcus, Clostridium, Desulfotomaculum, Enterobacter, and an anaerobic bacterium, strain TH-001, were unable to transform this compound. The O-demethylating ability of E. limosum was induced only with appropriate methoxylated benzoates but not with D-glucose, lactate, isoleucine, or methanol. Cross-acclimation and growth experiments with E. limosum showed a rate of metabolism that was an order of magnitude slower and showed no growth with either 4-methoxysalicylic acid (2-hydroxy-4-methoxybenzoic acid) or 4-anisic acid (4-methoxybenzoic acid) when adapted to 3-anisic acid. However, A. woodii NZva-16 showed slower rates and no growth with 3- or 4-methoxysalicylic acid when adapted to 3-anisic acid in similar experiments. The results clearly indicate a methyl rather than methoxy group removal mechanism for such reactions.

Footwear and ankle stability in the basketball player

Ankle stability in basketball players is affected by footwear. Athletic shoe manufacturers have introduced specialized lacing systems and high-top performance shoes to improve ankle stability. These performance shoes not only aid in preventing ankle injuries, but also protect injured ankles.

Immunoprotective behaviour of plasma-membrane-associated antigens of axenic Entamoeba histolytica

Immunisation of golden hamsters with plasma-membrane-associated antigens of a virulent subline of axenic Entamoeba histolytica strain NIH 200 V, entrapped in multilamellar phosphatidylcholine liposomes (MPL) or Freund's complete adjuvant (FCA), afforded protection against intrahepatic challenge with axenic amoebic trophozoites of the same strain. Amoebic liver abscess developed in 86% and 80% of the animals that received empty liposomes or buffer emulsified in FCA but in none of the animals that received plasma-membrane-antigen vaccines. All the immunised animals had significantly higher levels (p less than 0.001) of antibodies to plasma-membrane components and significantly higher levels (p less than 0.001) of cellular sensitisation. Antibody-dependent macrophage-mediated cytotoxicity against trophozoites was also found to be significantly greater (p less than 0.001) in immunised animals. Liposome-entrapped antigens stimulated the immune system of the host as well as, or better than, antigens administered with FCA.

Low susceptibility of trophozoites of virulent Entamoeba histolytica to cellular and antibody-dependent cellular cytotoxicity by guinea-pig effector cells

Cytotoxic potentialities of lymphocytes and macrophages were determined against trophozoites of virulent and avirulent sublines of Entamoeba histolytica in vitro. Guinea-pigs were immunized with antigens of both sublines to obtain stimulated effector cells and antiamoebic antibodies. Trophozoites of an avirulent/attenuated subline of E. histolytica (NIH200) were significantly more susceptible to killing by lymphocytes and macrophages through cellular and antibody-dependent cellular cytotoxic mechanisms. The resistance of virulent trophozoites to killing was attributed to their higher phagocytic ability and virulence characteristics. Electron microscopic studies of the interactions showed that contact between the effector cells and the trophozoites was essential for the cytolytic event which resulted in disintegration of the trophozoites. Antigens of trophozoites of the virulence subline of E. histolytica (NIH200 V) were effective in inducing cytotoxicity against both virulent and avirulent trophozoites: however, the reverse was not true.

Isolation and sequencing of cDNA clones encoding alpha and beta subunits of Drosophila melanogaster casein kinase II

Cloned cDNAs encoding both subunits of Drosophila melanogaster casein kinase II have been isolated by immunological screening of lambda gt11 expression libraries, and the complete amino acid sequence of both polypeptides has been deduced by DNA sequencing. The alpha cDNA contained an open reading frame of 336 amino acid residues, yielding a predicted molecular weight for the alpha polypeptide of 39,833. The alpha sequence contained the expected semi-invariant residues present in the catalytic domain of previously sequenced protein kinases, confirming that it is the catalytic subunit of the enzyme. Pairwise homology comparisons between the alpha sequence and the sequences of a variety of vertebrate protein kinase suggested that casein kinase II is a distantly related member of the protein kinase family. The beta subunit was derived from an open reading frame of 215 amino acid residues and was predicted to have a molecular weight of 24,700. The beta subunit exhibited no extensive homology to other proteins whose sequences are currently known.

Alterations of humoral, cell mediated and antibody dependent cell mediated cytotoxic responses during the course of amoebic infection in guinea pigs

The cellular and antibody dependent cellular cytotoxic (ADCC) responses of splenic lymphocytes and peritoneal macrophages obtained from animals at variable intervals after inoculation were studied against trophozoites of axenic E histolytica (NIH:200). Cytotoxic responses of effector cells from infected animals were compared with those of effector cells from vaccine stimulated and unstimulated uninfected control animals. Cellular and antibody-dependent cellular cytotoxic responses of the effector cells from animals during the establishment and acute phase of infection were significantly suppressed, compared with unstimulated uninfected and vaccinated (FI amoebic proteins stimulated) effector cells. The effector cells from animals recovered from infection showed enhanced cytotoxic responses against trophozoites of E histolytica. The suppressed cytotoxic response was accompanied by impairment of cytotoxic cell activities and lack, or very low level of anti-FI antibodies in the sera of animals during the establishment phase of infection. With the rise in anti-FI antibodies in the sera of animals ADCC could be induced effectively against trophozoites of E histolytica, which seem to result in clearance of amoebic infection.

Effect of Plasmodium yoelii nigeriensis infection and chloroquine on the hepatic mixed function oxidase system of mice

Plasmodium yoelii nigeriensis infection in albino mice significantly altered the hepatic microsomal mixed function oxidase system. Cytochrome P-450 (the terminal monooxygenase) and other monooxygenases, viz. aniline hydroxylase, aminopyrine-N-demethylase and benzo(a)pyrene hydroxylase were significantly lowered while microsomal heme showed 4-fold increase at 80% parasitaemia. Noticeable impairment in the other components like NADH:cytochrome b5 reductase, NADPH:cytochrome c reductase, cytochrome b5 and glucose-6-phosphatase was also observed. Oral treatment of normal and P. y. nigeriensis infected mice with chloroquine (64 mg per kg body weight for 4 days) caused lowering of mixed function oxidase activities which however showed a recovering trend, a week after cessation of treatment.

Microorganisms capable of metabolizing the herbicide metolachlor

We screened several strains of microorganisms and microbial populations for their ability to mineralize or transform the herbicide metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)-acetami de] because such cultures would potentially be useful in the cleanup of contaminated sites. Although we used various inocula and enrichment culture techniques, we were not able to isolate microorganisms that could mineralize metolachlor. However, strains of Bacillus circulans, Bacillus megaterium, Fusarium sp., Mucor racemosus, and an actinomycete were found to transform metolachlor. Several metabolites could be determined with high-performance liquid chromatography. The tolerance of the strains to high concentrations of metolachlor was also evaluated for the usefulness of the strains for decontamination. Tolerance of the actinomycete to metolachlor concentrations over 200 ppm (200 micrograms/ml) was low and could not be increased by doubling the sucrose concentration in the growth medium or by using a large biomass as inoculum. However, a Fusarium sp. could grow and transform metolachlor up to a concentration of 300 ppm.

Antibody-dependent macrophage-mediated cytotoxicity against Entamoeba histolytica

Interactions between trophozoites of Entamoeba histolytica and peritoneal exudate macrophages from unsensitised and antigen-sensitised animals were studied in vitro. Normal macrophages killed trophozoites to some extent. This killing capacity was enhanced by prior sensitisation of the animals with specific antigen. Incorporation of anti-amoebic antiserum in the amoeba-macrophage mixture greatly enhanced the killing capacity of macrophages. Fraction one (F-I) of a crude amoebic extract was most effective in enhancing the cytotoxicity of macrophages by prior sensitisation and anti-F-I serum was the most effective antiserum. The cytotoxicity-inducing capacity of the immune serum resided in the IgG but not in the IgM fraction.

Elucidation of cellular population and nature of anti-amoebic antibodies in cytotoxicity to Entamoeba histolytica (NIH:200)

Interactions between trophozoites of Entamoeba histolytica and cells of the immune system were studied in vitro by mixing effector cells obtained from normal and immunized guinea pigs with trophozoites in a ratio of 10:1. Crude amoebic extract (CAE) and its highest molecular weight (MW 650,000) fraction (F-I) were used for priming the effector cells in vivo. The effector cells were collected from the spleens of normal and immunized animals. Lymphocytes were prepared by allowing splenic mononuclear cells to adhere to plastic, followed by passage through nylon wool column. There was no significant difference between the killing capacity of mononuclear cells, monocyte depleted mononuclear cells or nylon wool fractionated lymphocytes, indicating that probably monocytes and B-cells were not involved in the cytotoxicity against E. histolytica. The data suggest that effector cells probably belonged to the T-cytotoxic and K-cell category. Both CAE and F-I sensitization could induce cytotoxicity of lymphocytes against trophozoites. Similarly, anti-CAE and anti-F-I sera were found to enhance the killing capacity of effector cells in vitro. The ability of anti-amoebic serum to induce cytotoxicity was found to be independent of complement involvement and resided in IgG but not in IgM.

The pH-dependent subunit dissociation and catalytic activity of bovine dopamine beta-hydroxylase

The soluble form of dopamine beta-hydroxylase from bovine adrenal medulla has previously been shown to exist as a tetrameric species of Mr = 290,000 composed of two disulfide-linked dimers. Here we report that this enzyme can also undergo a reversible tetramerdimer dissociation which is dependent on pH. Gel permeation chromatography of dopamine beta-hydroxylase at pH 5.0 demonstrates a Stokes radius of 5.8 nm. When the pH is shifted to 5.7, the Stokes radius changes to 6.9 nm. Sedimentation equilibrium analysis of the purified enzyme demonstrates that this change in molecular size is due to a change in molecular weight. At low protein concentration, the estimated Mr of the enzyme is 145,000 at pH 5.0 and at high protein concentration approaches 290,000 at pH 5.7. This change in Mr is consistent with the existence of a tetramer-dimer dissociation and a change in the equilibrium constant from 1.8 X 10(-6) M to 1.16 X 10(-9) M when the pH is increased from 5.0 to 5.7. This pH-dependent subunit dissociation is correlated with pH-dependent changes in enzyme activity. Purified bovine-soluble dopamine beta-hydroxylase activity is a hyperbolic function of tyramine concentration at pH 5.0. However, the hydroxylase activity displays non-hyperbolic kinetics at pH 6.0. The kinetic data obtained at pH 6.0 can be accounted for by fitting to a model containing two nonidentical catalytic forms of enzyme generated by the pH-dependent partial dissociation of tetrameric enzyme to dimeric subunits. The two catalytic forms have apparently identical maximal velocities; however, they differ in their Michaelis constants for the substrate; the dimeric form having a low Km and the tetrameric form having a high Km. Since the pH inside bovine adrenal medullary chromaffin granules is approximately 5.5, we conclude that the subunits of dopamine beta-hydroxylase are in dynamic dissociation in a physiologically important pH range.

Interactions between trophozoites of Entamoeba histolytica and cells of the immune system

The interaction between Entamoeba histolytica trophozoites and cells of the immune system was studied in vitro. Both immune as well as non-immune mononuclear cells (MNC) to some extent were capable of exerting a cytotoxic effect on E. histolytica trophozoites. Incorporation of immune serum directed against the trophozoites in the reaction mixture resulted in a marked increase in the killing capacity of MNC. Highest killing was observed (96.7 +/- 1.04%) with MNC obtained from animals immunized with fraction-I(F-I) of the crude amoebic extract in association with anti-F-I serum. This cytotoxic event was found to be independent of complement involvement and required very low antibody concentrations. This antibody-dependent cellular cytotoxicity against E. histolytica in vitro was found to correlate well with the results of experiments reported earlier by us and others where a high degree of protection has been shown after vaccination of animals with F-I followed by challenge with highly virulent strains of E. histolytica.

Testicular changes in rats after administration of organotin complex

Intratesticular administration of di-n-butyltin (o-hydroxyacetophenone S-methyldithiocarbazate) has been shown to induce marked degenerative changes in the testes of adult rats. The possible mechanism of its action is discussed. In particular, an atrophy of seminiferous tubules with complete arrest of spermatogenesis has been noted.

Effect of raised portal venous pressure on blood pressure, urine output and body fluids

Acute rise of portal venous pressure resulted in a fall of blood pressure and subsequent anuria which could be either due to the state of shock or may be reflex in origin. There also occurred an increase in extra-cellular fluid volume with an initial increase in both plasma volume and interstitial fluid volume. Subsequently the extra-cellular fluid volume remained at a high steady value whereas the plasma volume increased at the expense of interstitial fluid volume which decreased. It is further postulated that the rise of extra-cellular fluid volume is due to the shift of fluid from intra-cellular compartment of the extra-cellular compartment, as a defence mechanism to combat the state of shock.