Evaluation of the ability of intact platelets to accumulate acridine orange

A new approach to the evaluation of the uptake of fluorescent probes by intact cells is described. Acridine orange (AO) was used because it can be selectively accumulated by serotonin-containing granules of platelets. Analysis of the fluorescence signal allows the estimation of the relative volume of the granules and the equilibrium coefficients for AO transport across the cytoplasm and granule membranes. The following results were obtained for human and rabbit platelets: the relative volumes of the granules were 14 +/- 1% and 29 +/- 2%, the ratios of intragranular-extracellular probe concentration were 2260 +/- 382 and 30,000 +/- 5550, and the cytoplasm-extracellular medium concentration ratios were 375 +/- 60 and 225 +/- 60, respectively.     

Mechanical parameters determined in dispersed ventricular heart cells

A high-resolution laser diffraction system suitable for studying the basic mechanical properties of small contractile single cells has been developed. This method was used to establish the mechanical behavior of 95 ventricular cells isolated from adult guinea pig hearts. During contraction, the sarcomere length shortened from 1828 +/- 43 nm (mean +/- SD) to 1518 +/- 99 nm. The maximal velocities were 1.98 +/- 0.64 micron/s for shortening and 1.93 +/- 0.54 micron/s for re-lengthening. The twitch duration from 20% shortening to 80% re-lengthening was 622 +/- 120 ms.     

Dopamine and octopamine in whole body extracts of the bulb mite

Summary Using high performance liquid chromatography with electrochemical detection, whole body extracts of the bulb mite,Rhizoglyphus echinopus (Fumouze and Robin), were found to contain the biogenic amines dopamine and octopamine at concentrations of 4.3±0.6 and 2.3±1.4 ng g^–1 wet weight, respectively. Adrenaline, noradrenaline, tyramine,N-methyldopamine,N-acetyldopamine, and 5-hydroxytryptamine, if present, were below the limits of detectability. This is the initial demonstration of the presence of octopamine in a mite species.     

Seasonal fluctuations of population densities of the fish-miteSeudacia medanensis independent of atmospheric temperature and humidity

Summary Seudacia medanensis is a species of mite which reaches pest proportions on dried stored fishery products in the warm conditions of the tropics. Studies extending for a period of 2 years have shown that the seasonal variation in the population intensity of the mite is not influenced by atmospheric humidity or temperature.     

Plasma estrogens in Pleurodeles waltlii. Comparison between diploid and triploid females]

Estrogens have been examined in the plasma of diploid and triploid newts Pleurodeles waltlii. Estradiol-17 beta (E2) and estrone (E1) were determined by radioimmunoassay, before and after enzymatic hydrolysis of the conjugates. Total (t) and unconjugated (u) E2 levels were positively correlated (E2u = 0.478 35 E2t + 0.579 98; r = 0.883), but no correlation was detected between E1 levels. No statistical difference was found for the estrogen levels between the different experimental lots of diploid newts (E2t = 7.5 +/- 0.37 ng/ml, E2u = 4.3 +/- 0.20 ng/ml, E1t = 2.19 +/- 0.08 ng/ml, E1t = 0.41 +/- 0.02 ng/ml) but every estrogen level was lower in the triploid group (E2t = 1.8 +/- 0.60, E2u = 1.0 +/- 0.18, E1t = 1.4 +/- 0.13, E1u = 0.3 +/- 0.04 ng/ml). This difference is discussed in relation to lower fertility of the triploid females.     

The influence of different nutrients on plasma cholecystokinin levels in the rat

Isocaloric and isovolemic amounts of protein (casein), fat (intralipid) and carbohydrate (saccharose) and an isovolemic control solution of water were administered intragastrically to conscious rats. The plasma CCK levels, determined by a sensitive and specific radioimmunoassay, showed an increment of 6.3 +/- 0.6, 2.7 +/- 0.5, 1.7 +/- 0.4 and -0.9 +/- 0.4 pM, respectively (basal value 2.5 +/- 0.3 pM). The threshold increment of plasma CCK to stimulate pancreatic enzyme secretion by exogenous CCK was found to be 1.5 pM. It is therefore concluded that casein is a potent stimulus for CCK secretion and pancreatic secretion, but that fat and even carbohydrate, although less potent, also produce a CCK increment above the threshold for pancreatic secretion.     

Satellite cells in the regenerated and regrafted skeletal muscles of rats

Soleus (SOL) muscles were grafted into extensor digitorum longus (EDL) muscle beds (EDL-first-graft). Sixty days later, some mature EDL-first-grafts were regrafted into their own beds (EDL-second-grafts). Fully regenerated muscle fibers and satellite cells were observed in both types of mature grafts. The ratios of satellite cell nuclei per total nuclei (myonuclei and satellite cell nuclei) were 4.81 +/- 0.47% for EDL-2nd graft, 4.26 +/- 0.51% for EDL-1st-graft, 4.30 +/- 0.33% for control SOL, and 3.30 +/- 0.18% for control EDL. It is thought that satellite cells are required for the repeated activity of muscle fiber regeneration. The persistance of satellite cells in EDL-second-grafts suggests that satellite cells are not depleted during the first grafting, making second-grafts possible.     

4-Proline and 4-hydroxyproline analogs of arginine vasopressin: role of the proline substitution in the two beta-turns of vasopressin

[4-L-Proline]arginine vasopressin, [4-D-proline]arginine vasopressin, [4-hydroxyproline]arginine vasopressin and [4-proline, 7-hydroxyproline] arginine vasopressin were synthesized and found to have antidiuretic activities of 91 +/- 4, 1.7 +/- 0.2, 1.0 +/- 0.1 and 4.4 +/- 1.0 units/mg, respectively. None of these analogs exhibited a significant level of rat pressor activity. The observed activities of these and other analogs with substitutions at position 4 and/or 7 are discussed on the basis of hypotheses and data bearing on the solution conformation of vasopressins.     

Hemodynamic studies in a parabiotic model of portal hypertension

Splanchnic and systemic hemodynamic studies were performed in a rat model of parabiosis and portal hypertension. A portal hypertensive and a normal rat were surgically united side to side. A hyperdynamic circulation, characterized by increased cardiac index (413 +/- 26 vs 318 +/- 23 ml X min-1 X kg-1; p less than 0.05) and portal venous inflow (9.61 +/- 1.29 vs 6.33 +/- 0.36 ml X min-1 X 100 g b.wt-1; p less than 0.05), was found in all the portal hypertensive rats but not in the normal parabiotic partners. These results do not support the existence of a transferable humoral factor mediating the hyperdynamic circulatory state of chronic portal hypertension.     

Comparison of X-prolyl dipeptidyl-aminopeptidase activity in human cerebrospinal fluid with that in serum.

X-Prolyl dipeptidyl-aminopeptidase activities in cerebrospinal fluid and serum from the same patients without neurological diseases, undergoing surgery under lumbar anesthesia, were assayed fluorometrically with a newly synthesized fluorogenic substrate, 7-glycylproline-4-methylcoumarinamide; the values were 129.1 +/- 19.5 nmoles/min/l and 54.17 +/- 3.11 mumoles/min/l (mean +/- SEM, n = 23), respectively, and there was no correlation between both activities (r = 0.0894).     

Neuropeptide Y in the guinea-pig biliary tract

High concentrations of neuropeptide Y (NPY) have been demonstrated in the gall bladder (16.7 +/- 5.4 pmol/g), cystic duct (25.4 +/- 9.2 pmol/g) and common bile duct (54.7 +/- 11.5 pmol/g) of the guinea-pig using a recently developed radioimmunoassay. Immunoreactive NPY containing nerves were demonstrated in all layers of the biliary tree using immunocytochemistry, being particularly dense in the myenteric and mucosal plexuses.     

Probing the penicillin sidechain selectivity of recombinant deacetoxycephalosporin C synthase

Deacetoxycephalosporin C synthase from Streptomyces clavuligerus catalyses the conversion of the five-membered penicillin ring to the unsaturated six-membered cephem ring of deacetoxycephalosporin C. The effects on enzyme activity of the penicillin substrate sidechain and various cofactors were investigated using a continuous spectrophotometric assay. The conversion of penicillin G to phenylacetyl-7-aminodeacetoxycephalo sporanic acid (G-7-ADCA) was confirmed, and further details of the reaction were elucidated. The conversion of ampicillin to cephalexin was faster than that of acetyl-6-APA to acetyl-7-ADCA kcat = 0.120 +/- 0.001 s(-1) versus 0.035 +/- 0.001 s(-1), but they had similar Km values: 4.86 +/- 0.12 and 3.28 +/- 0.26 mM, respectively. Amoxycillin and penicillin V were also converted at low levels. Conversion was not detected for penicillanate, 6-aminopenicillanate, carbenicillin, temocillin, ticarcillin or benzylpenicilloic acid, suggesting that the enzyme has a relatively strict selectivity for the sidechain of the penicillin substrate.     

Isolation of a potent allergen from house dust mite by interaction with the lectin tridacnin

Summary Tridacnin, the lectin from the clamTridacna maxima, precipitates with house dust mite extracts and provides a simple procedure for obtaining a potent, purified mite allergen. Allergenic activity was investigated using the radioallergosorbent test (RAST).We thankKarin Williams, Jill Butler, Elizabeth Quinn andGisela Steinhausen for technical help. This work was supported by the Princess Margaret Children's Medical Research Foundation, the Asthma Foundation of Western Australia, the National Health and Medical Research Council and the Deutsche Forschungsgemeinschaft.     

Transmembrane potential of J774.2 mouse macrophage cells measured by microelectrode and ion distribution methods

The transmembrane potential (Em) of J774.2 macrophage cells measured by microelectrodes was -24.1 +/- 0.7 mV (mean +/- SEM). Em measured by lipophilic ion distribution was -35 +/- 2 mV or -40 +/- 2 mV, using a cation or anion, respectively. By any method, colchicine reduced Em by approximately 3 mV.     

Denaturation map of the ribosomal DNA of Lytechinus variegatus sperm.

Electron microscopy of the partially heat denatured ribosomal DNA (rDNA) from sea urchin (Lytechinus variegatus) sperm has demonstrated that it consists of repeating units of 3.6 +/- 0.2 micron, corresponding to a mol.wt of 7.2 +/- 0.4 x 10(6). Based on differential denaturability, each repeat unit is divided into 2 regions. The larger region of 2.47 +/- 0.11 micron (mol.wt 4.9 +/- 0.22 x 10(6)) corresponds in length to the ribosomal precursor RNA of sea urchins and the smaller, GC-rich, subunit of 1.16 +/- 0.09 micrometer (mol.wt 2.3 +/- 0.18 x 10(6)) is presumed to contain non-transcribed spacer sequences.     

Bombesin-like immunoreactivity in the pituitary gland

Bombesin has been shown to stimulate release of anterior pituitary hormones both in vivo and in vitro. The aim of this study was to determine whether bombesin-like immunoreactivity could be detected in the human pituitary. Significant concentrations were found in the human anterior gland (4.6 +/- 1.5 pmoles/g), posterior gland (1.5 +/- 0.4 pmoles/g) and stalk (8.1 +/- 0.8 pmoles/g). Significant amounts were also observed in the guinea-pig pituitary. Gel permeation chromatography revealed the presence of 2 major molecular forms of bombesin-like immunoreactivity, one co-eluting with porcine gastrin-releasing peptide and the other with amphibian bombesin.     

Effects of 18-hydroxydeoxycorticosterone on central nervous system excitability

The effects of 18-hydroxydeoxycorticosterone (18-OH-DOC) on central nervous system excitability were studied in adrenalectomized rats. Sixty-four evoked potentials (EP) recorded from the pontine reticular formation were averaged before and after the injection of vehicle and hormone. 750 micrograms of 18-OH-DOC dissolved in 0.5 ml of a 4:1 saline Cremophor-EL solution were injected i.v. A decrease of 55.7 +/- 6.1% in the amplitude of the EPs was observed with the hormone 16.3 min +/- 2.7 (SE) after injection. Amplitude values returned to baseline levels 38 min +/- 6.8 (SE) after injection. The secretion of 18-OH-DOC is greatly increased by ACTH and might modulate central nervous system function.     

Role of calcium in the histamine release induced by D-galactosamine from rat mast cells

Rat peritoneal mast cells were isolated and purified by differential centrifugation in Ficoll. Cells pooled from three to four rats were suspended at approximately 10(6) cells/ml in a buffered salt solution and incubated for 1 h at 37 degrees C in 300 microliter volumes in the absence or presence (9 X 10(-4) M) of calcium chloride. Addition of D-galactosamine hydrochloride (DGM; 2.8 X 10(-4)M) caused (in addition to basal release) a mean +/- SEM percent histamine release of 15.7 +/- 5.2 in the presence of Ca++ and 19 +/- 4.9 in the absence of Ca++ (p greater than 0.05). It is suggested that D-galactosamine does not require extracellular Ca++ for the release of histamine from the rat mast cell.     

Serum cholesterol levels in a Nigerian population sample

Serum cholesterol was determined in 104 healthy Nigerians (57 males and 47 females). The average cholesterol concentration was 187 +/- 72.8 mg/100 ml (mean +/- SD) with a range of 60-480 mg/100 ml. Cholesterol levels were higher in males than in females and increased with age. Distribution of cholesterol level was generally skew to the left.     

Reduction of efferent renal nerve activity by propranolol in rabbits]

During intravenous infusion of propranolol (0.3--0.8 mg/kg) in the Rabbit, systolic arterial pressure is decreased (-6.5 +/- 4.2 mmHg) and electrical activity recorded from central end of the renal nerve is reduced significantly (-8.7 +/- 14.-%) with regard to the activity obtained, at the same pressure levels, by hemorrhage (+7.9 +/- 6.4%; p less than 0.25) or by intravenous infusion of the peripheral vasodilator sodium nitroprusside (+14.1 +/- 9.9%; p less than 0.01).