Effect of diisopropylfluorophosphate on muscarinic and gamma-aminobutyric acid receptors in visual cortex of cats.

Administration of diisopropylfluorophosphate (DFP), an organophosphorus (OP) compound, irreversibly inhibits acetylcholinesterase (AChE) and results in cholinergic hyperactivity. This study investigated muscarinic and gamma-aminobutyric acid (GABA) receptor changes in visual cortex of cats following an acute exposure to DFP. A single acute administration of DFP (4 mg/kg) decreased the number of muscarinic receptors at 2, 10, and 20 hours after treatment. GABA receptors were elevated at 2 and 10 hours but returned to within control levels at 20 hours. No significant alteration in muscarinic or GABA receptor affinity was noted. In all cases cortical AChE activity was inhibited 60-90%. These findings show a down regulation of muscarinic receptors after DFP associated with low AChE activity. GABA receptors also are altered, and may be part of a compensatory mechanism to counteract excess cholinergic stimulation.     

Proteolytic studies on the structure of bovine von Willebrand factor

Bovine von Willebrand factor (vWF) was digested with protease I (P-I), a metalloprotease isolated from rattlesnake venom. Digestion of vWF for 24 h with P-I yielded a terminal digest consisting of an equimolar mixture of two major fragments (apparent Mr 250K and 200K). The 250-kilodalton (kDa) fragment consists of a 125-kDa chain from one subunit and a 45- and 78-kDa polypeptide chain from an adjacent subunit. The 200-kDa fragment consists of a 97-kDa chain from one subunit and a 35- and 61-kDa polypeptide chain from an adjacent subunit. The 200-kDa fragment binds to heparin, and the heparin binding domain is located on the 97-kDa polypeptide chain. This fragment also competes with labeled, native vWF for binding to formalin-fixed human platelets, with an IC50 of 12.5 micrograms/mL (65 nM). However, native vWF has an IC50 of 2.5 micrograms/mL, indicating that the affinity of the 200-kDa fragment for platelets is approximately one-fifth that of vWF. The 200-kDa fragment agglutinates platelets, but its agglutinating ability is only 5% that of the native molecule. Only the 200-kDa fragment is recognized by monoclonal antibodies 2 and H-9, which are directed against vWF and inhibit vWF binding to platelet glycoprotein Ib (GPIb). Immunological studies, using nine monoclonal antibodies directed against vWF, and the demonstration that the heparin and GPIb binding domains are located on only one fragment suggest that the two fragments are composed of different regions of the vWF subunit. Analysis of the P-I cleavage pattern suggests that all vWF subunits are not cleaved in the same fashion. The first cleavage on half of the subunits generates the 45-kDa terminal and 175-kDa intermediate digest products. The 175-kDa chain is again cleaved, producing the 97- and 78-kDa terminal polypeptide chains. However, the first cleavage of the other subunits generates the 35-kDa terminal and the 186-kDa intermediate digest product, which upon cleavage produces the 125- and 61-kDa terminal polypeptide chains. Immunological data support the asymmetric cleavage pattern. An epitope for a monoclonal antibody is present on both the 186- and 175-kDa intermediate digest products but is only found on one terminal digest fragment, the 78-kDa polypeptide chain, suggesting that the 186- and 175-kDa polypeptides are cleaved at different sites.(ABSTRACT TRUNCATED AT 400 WORDS)     

Total lung capacity does not change during methacholine-stimulated airway narrowing

The accurate measurement of changes in flow rates from partial flow-volume curves depends on their measurement at the same lung volume. This lung volume can be standardized from total lung capacity (TLC) if this does not change at the same time. We examined the effect of methacholine-stimulated maximal airway narrowing [change in mean forced expiratory volume in 1 s (delta FEV1) = 26.4%] on TLC, measured by whole-body plethysmography, in 10 normal subjects and of moderate airway narrowing (mean delta FEV1 = 34.9%) in 10 asthmatics. The TLC changed from 5.88 to 6.03 liters in normal subjects (P greater than 0.05) and from 6.92 to 6.95 liters (P greater than 0.5) in asthmatics. The results of this study suggest that TLC does not change significantly after methacholine-stimulated maximal airway narrowing in normal subjects and after moderate narrowing in asthmatics.     

The isolation and restriction mapping of a miniplasmid from the Actinomycete Nocardia corallina

Abstract A variety of plasmids has been identified as covalently closed circular and linear DNA in certain Actinomycetes, such as Streptomyces . This paper describes the first isolation and characterisation of a plasmid from the genus Nocardia . The plasmid pKU100 isolated from Nocardia corallina is a cccDNA molecule, 2.7 kb in length. This plasmid has been mapped with a wide variety of restriction enzymes and contains a number of unique restriction sites making it suitable for development as a cloning vector.     

Progesterone and estrogens in the pregnant and nonpregnant dolphin, Tursiops truncatus, and the effects of induced ovulation

Baseline serum levels of progesterone and total immunoreactive estrogens were determined for intact and ovariectomized captive female Atlantic bottlenose dolphins (Tursiops truncatus), as well as newly captured wild adult females. Stimulation of ovarian follicular growth and ovulation was attempted by intramuscular injection of pregnant mare's serum gonadotropin (PMSG). High doses of PMSG were required to increase serum estrogen levels. When PMSG was followed by an injection of human chorionic gonadotropin (hCG), ovulation was presumed to have occurred as indicated by subsequent high levels of serum progesterone. From these observations, it appears that 1) females with progesterone levels greater than 3000 pg/ml over an extended period are pregnant, 2) Tursiops truncatus is capable of spontaneous ovulation in captivity without gonadotropin therapy, 3) captive female dolphins, although relatively resistant to PMSG, can be induced to ovulate using a combination of high intramuscular-injected doses of PMSG followed by hCG, and 4) spontaneous ovulation is likely to follow an induced ovulation.     

Studies in rapidly labelled ribonucleic acid in cell fractions and in tumour tissues

1. Twenty minutes after injection of [(3)H]orotic acid into rats the rapidly labelled RNA from the liver is mainly associated with the nuclear fraction and little with the ribosomal cytoplasmic fraction. 2. The thermal denaturation of RNA from the fractions was not as reversible as that of the RNA extracted from whole liver. 3. Rapidly labelled RNA is synthesized by cells from a transplantable hepatoma when incubated in the presence of [(3)H]uridine and, after extraction and centrifugation, the label is present in three main fractions: one which sediments to the bottom of a gradient and is associated with DNA, a second which sediments to the heavy side of the 28s RNA, and a third which has a peak of activity between 28s RNA and 18s RNA and is associated with DNA. 4. After labelling and extraction of the RNA from Ehrlich ascites cells the distribution of radioactive components is similar to that of the material from the hepatoma cells. 5. The difference between the tumour cells and liver is due to some extent to the method of homogenizing the tissues and the nature of the components is discussed.     

Rapidly labelled ribonucleic acid from rat liver. Studies in the attachment to ribosomes and stimulation of the incorporation of amino acids into polypeptides in cell-free systems

1. Rapidly labelled RNA from rat liver, either as a complex with DNA (m-RNA-DNA) or with ribosomal RNA (m-RNA-RNA) binds to ribosomes in the polysome region. No binding could be demonstrated with ribosomal RNA or native DNA from Bacillus subtilis. 2. With ribosomes from rat liver, Escherichia coli or hepatoma the m-RNA-DNA stimulated incorporation of amino acids with rat-liver ribosomes only, whereas the m-RNA-RNA complex was effective with ribosomes from E. coli or the hepatoma. 3. Polyuridylic acid was effective as messenger RNA with all three ribosomes but much greater stimulation was obtained with ribosomes from E. coli and the hepatoma. 4. The degree of incorporation of phenylalanine with polyuridylic acid and ribosomes from a hepatoma was decreased by about 50% when ribosomal RNA was present.     

Inactivation of cephalothin and cephaloridine by Staphylococcus aureus

Benner, Ernest J. (University of Washington School of Medicine, Seattle), John V. Bennett, Jean L. Brodie, and William M. M. Kirby. Inactivation of cephalothin and cephaloridine by Staphylococcus aureus. J. Bacteriol. 90:1599-1604. 1965.-Marked differences were observed in the susceptibility of penicillinase-producing staphylococci to cephalothin and cephaloridine. All of 100 strains of penicillin G-resistant Staphylococcus aureus, with the use of a large inoculum, were found to be susceptible to 2 mug/ml of cephalothin, whereas only 50% were susceptible to this concentration of cephaloridine, and 15% required 15 mug/ml or more for inhibition. In contrast, penicillin G-sensitive strains were more susceptible to cephaloridine and did not show the marked inoculum effect observed with the cephaloridine-resistant strains. These differences were due to a much greater destruction of cephaloridine than of cephalothin by staphylococcal penicillinase. Cephaloridine-resistant staphyloccoci were stronger penicillinase producers than were susceptible strains, and the resistant strains were found to inactivate cephaloridine by hydrolysis of the beta-lactam ring. In population studies, cephaloridine-resistant cells differed from methicillin-resistant cells in that they decreased in numbers as the drug concentration was increased, and the survivors in higher drug concentrations were no more resistant than was the parent strain. Treatment with acriflavine eliminated resistance of the cells to both penicillin G and cephaloridine. It was concluded that cephaloridine resistance was due to hydrolysis by penicillinase, and that this was related to the pyridine ring substitution in the cephalosporanic acid nucleus.