Species differences in the negative inotropic effect of acetylcholine and soman in rat, guinea pig, and rabbit hearts.

1. Acetylcholine reduced atrial contractions by 82.5% in guinea pig, 50.8% in rat, and 41.5% in rabbit. 2. The EC50 values for the negative inotropic effect of acetylcholine were 3.3 x 10(-7) M in rat and guinea pig atria and 4.1 x 10(-6) M in rabbit atria. 3. There was no correlation between the species differences in the negative inotropic effect of acetylcholine in atria and the density or affinity of acetylcholinesterase or muscarinic receptors. 4. Inhibition of atrial acetylcholinesterase with soman reduced the EC50 of acetylcholine three-fold in all species, but did not change the maximal inotropic effect of acetylcholine. 5. Species differences in the negative inotropic effect of acetylcholine may be caused by differences in the coupling between myocardial muscarinic receptors and the ion channels that mediate negative inotropy.     

In vitro proteolytic cleavage of Gazdar murine sarcoma virus p65gag.

Moloney murine leukemia virus, disrupted in concentrations of 0.1 to 0.5% Nonidet P-40, catalyzed the cleavage of p65, the gag gene polyprotein of the Gazdar strain of murine sarcoma virus, into polypeptides with sizes and antigenic determinants of murine leukemia virus-specified p30, p15, pp12, and p10. Cleavage performed in the presence of 0.15% Nonidet P-40 in water yielded polypeptides of approximately 40,000 (P40) and 25,000 (P25) Mr. In vitro cleavage performed in a buffered solution containing dithiothreitol in addition to 0.1% Nonidet P-40 allowed the efficient processing of P40 to p30 and a band migrating with p10. Immunoprecipitation with monospecific sera indicated that P40 contained p30 and p10, whereas P25 contained p15 and pp12 determinants. P40 and P25 are similar in size and antigenic properties to Pr40gag and Pr25gag observed in infected cells (Naso et al, J. Virol. 32:187-198, 1979).     

Vitamin D supplements in pregnant Asian women: effects on calcium status and fetal growth.

In a double-blind trial of vitamin D supplements in pregnant Asian women calciferol (ergocalciferol, 1000 IU/day) was administered to 59 women and placebo to 67 controls during the last trimester. The two groups had similar distributions of maternal age, height, parity, number of vegetarians, countries of origin, and sex and gestation of the infants. At entry to the trial maternal serum 25-hydroxy vitamin D (25-OHD) concentrations were low in both treatment and control groups and significantly lower in vegetarians than non-vegetarians. Mothers in the treatment group gained weight faster in the last trimester than those in the control group, and at term they and their infants all had adequate plasma 25-OHD concentrations, Mothers and infants in the control group, however, had low plasma concentrations of 25-OHD and calcium and raised plasma alkaline phosphatase (bone isoenzyme) activity. Five of these infants developed symptomatic hypocalcaemia. Almost twice as many infants in the control group were small for gestational age (29% v 15%), but there were no significant differences between the two groups of infants in antropometric measurements. Infants in the control group, however, had larger fontanelles, suggesting impaired ossification of the skull. Because of the benefits to mothers and infants in the treatment group and the absence of side effects, vitamin D supplements should be given to all pregnant Asian women in the United Kingdom.     

Lack of ''acid reversal'' of myofibrillar adenosine triphosphatase in masticatory muscle fibres of rhesus monkeys

Summary Myofibrillar adenosine triphosphatase (ATPase) activity was demonstrated in sections of masseter and temporalis muscles and of selected limb muscles of adult rhesus monkeys. Incubations were performed either with no pre-treatment or after prior incubation in alkaline media (pH 10.2–10.4) or acidic media (pH 3.8–4.6). Without pre-treatment, fibres having high or low ATPase activity were observed in limb and masticatory muscles. Following alkaline pre-incubation the difference between high and low ATPase of limb muscle fibres is accentuated, whereas pre-incubation in acidic media (pH 4.3) results in inhibition of high and potentiation of low ATPase activities (acid reversal). While pre-incubation of masticatory muscle sections at pH 10.2 accentuates differences in ATPase activity, pre-incubation at pH 10.4 abolishes ATPase activity. In contrast, masticatory muscle fibres showed no reversal of ATPase activity following acidic pre-incubation (pH 4.3). Pre-incubation at pH 3.8 abolished the ATPase activity of both limb and masticatory muscle fibres. The biochemical basis for the differences in ATPase histochemistry between masticatory and limb muscles is not known.     

Skeletal muscle fiber regeneration following heterotopic autotransplantation in cats.

Whole 3 g extensor digitorum longus (EDL) muscles of cats were autotransplanted. The EDL muscles were either transplanted without denervation prior to transplantation (normal transplants) or denervated 3 to 4 weeks prior to transplantation (pre-denervated transplants). A few peripheral skeletal muscle fibers survived transplantation but most fibers degenerated and then regenerated as the transplant became revascularized. Both normal and pre-denervated muscles regenerated successfully and by 50 days after transplantation fibers which had reinnervated showed high and low myofibrillar ATPase activity. Compared to controls, the smaller mean fiber cross-sectional area of the transplants was due to the large number of small fibers, but some fibers in the transplant were larger than any fibers observed in the controls. Transplants regained 57 percent of the muscle mass of the controls. Contraction and half relaxation times of transplanted muscles were slower than controls, but peak isometric tetanus tension per cm² of muscle was nearly normal. Fifty to 170 days after transplantation, muscles showed low oxidative capacity and fatigued rapidly.     

An infrared study of NO bonding to heme B and hemoglobin A. Evidence for inositol hexaphosphate induced cleavage of proximal histidine to iron bonds.

Five- and six-coordinate nitrosyl hemes have been prepared and their infrared, electron paramagnetic resonance (EPR), and visible-Soret spectra compared with the corresponding spectra for nitrosyl hemoglobin A (Hba-NO) determined both in the presence and the absence of inositol hexaphosphate (IHP). The five- and six-coordinate NO complexes prepared from either dipyridine or pyridine carbonyl protoheme dimethyl ester had N-O stretch bands (nuno) near 1675 and 1625 cm-1, respectively. These frequencies are sensitive to change in solvent (nuno decreased as the dipole moment of the solvent increased) and, with six-coordinate species, to changes in trans ligand. However, these solvent and trans ligand effects were small compared with the difference (ca. 50 cm-11) between five- and six -coordinate species. The nature of the trans ligand affected the relative proportions of the two...     

The study of rous sarcoma virus-transformed baby hamster kidney cells using fluorescent probes

The fluorescent probes pyrene, pyrene butyric acid and $\text{N-}\text{phenyl}$ 1-naphthylamine have been used to investigate the changes that accompany in vitro transformation of a baby hamster kidney cell line using Rous sarcoma virus. The fluorescent probes which reside in the membrane were used to compare the changes in microviscosity and polarity of the membranes of normal cells with two transformed cell lines. The spectrofluorimetric data indicate that following transformation the probe $\text{N-}\text{phenyl}$ 1-naphthylamine resides in a more polar environment. However, using the probe pyrene, the yield of excimer indicates decreased mobility of this probe in the membrane of transformed cells. The data also indicate differences between the two transformed cell lines. Laser photolysis was used to study the lifetime of the pyrne probes and the quenching of the pyrene fluorescence in the membrane by several different quenching molecules. The data indicate differences between the three cell lines and suggest that transformation decreases movement within the membrane.     

Properties of biologically active messenger RNA from human placenta. Cell-free synthesis of two immunoreactive forms of placental lactogen.

In order to understand better the regulation of human placental proteins the activity of placental lactogen messenger RNA has been examined. Total RNA was extracted from normal term placentas and purified by chromatography on oligo(dT)-cellulose. The poly(A)-containing fraction stimulated amino acid incorporation 5- to 10-fold in wheat germ cell-free extracts, and immunoprecipitation of the translation products with antiserum directed against human placental lactogen (hPL) suggests that about 2% of the peptides contain hPL determinants. Analysis of the material precipitated with hPL antiserum by electrophoresis on sodium dodecyl sulfate-polyacrylamide gels revealed two major species, one co-migrating with hPL and the other migrating slightly slower than hPL. On DEAE-cellulose chromatography the former material eluted close to authentic hPL while the latter material eluted at higher ionic strength than hPL, indicating a difference in net charge of these two species. Tryptic peptide analysis of the large material and authentic hPL shows marked similarities in the primary structure of these two proteins. The slower migrating peptide has an apparent molecular weight about 3000 larger than hPL and thus may represent a precursor molecule. Both cell-free products could be competed out of immunoprecipitates by a large excess of authentic hPL, confirming their immunologic similarities. Centrifugation of the placental poly(A)-containing RNA through aqueous glycerol gradients indicates that the hPL mRNA sediments at about 14 S.     

Demonstration of acid phosphatase-containing vacuoles in hyphal tip cells of Sclerotium rolfsii.

A lysosomal system was demonstrated in hyphal tip cells of Sclerotium rolfsii by light and electron microscopy observations of the sites of acid phosphatase activity visualized by a modified Gomori lead nitrate method. The cytochemical reaction product was found to be present in numerous vacuoles, each aout 0.5 mum in diameter, which were seen as chains of spheres when viewed with the light microscope. They usually did not occur in the first 30 to 40 mum of the hyphal tip cell, but were concentrated in a zone extending from 30 to 200 mum from the hyphal apex. As shown by the electron microscope, the vacuoles were sometimes interconnected by narrow channels. Acid phosphatase reaction product was also occasionally localized in vacuoles of the older hyphal cells, but never in apical vesicles, lipid bodies, or microbodies. It is proposed that this vacuolar system may orginate from the endoplasmic reticulum.