Papovaviral sialoadenitis in athymic nude rats

A wasting disease was found in 32 athymic nude rats. The rats had parotid sialoadenitis with intranuclear inclusion bodies in ductal and acinar epithelial cells. Other common lesions included bronchitis, bronchiolitis and secondary bacterial pneumonia. Less commonly, rhinitis and Harderian adenitis were seen. Intranuclear inclusions were also seen in bronchial epithelium of 1 rat, Harderian gland acini of 1 rat and laryngeal glands of 2 rats. Viral particles, averaging 45 nm in diameter, sometimes in crystalline arrays, were found in the nucleus of parotid epithelial cells. By the use of the avidin-biotin-peroxidase complex (ABC) immunoperoxidase technique, antibodies to disrupted SV40 virus (the group specific antigen of the polyomavirus (miopapovavirus) genus of the papovavirus family) reacted with intranuclear inclusions and cytoplasm of parotid epithelium and inclusions in lung and Harderian gland. The viral antigen did not cross react with antibodies to mouse polyoma, mouse K or disrupted bovine papilloma viruses.     

Homologous and heterologous mitogenic desensitization of Swiss 3T3 cells to phorbol esters and vasopressin: role of receptor and postreceptor steps

Prolonged treatment of Swiss 3T3 cells with phorbol 12,13 dibutyrate (PDB) rendered the cells refractory to subsequent mitogenic stimulation by both PDB and vasopressin. In contrast, the cells retained full responsiveness to a wide variety of other mitogens. An early response to vasopressin and phorbol esters, inhibition of (125I)-labeled epidermal growth factor [(125I)-EGF] binding, was also substantially decreased in PDB pretreated cells. The cross desensitization was not produced by vasopressin; this ligand induced homologous but not heterologous desensitization. Exposure of Swiss 3T3 cells to PDB caused a down regulation of (3H)-PDB receptors but did not reduce the binding of vasopressin to refractory cells. The time-course (t1/2 = 7 h) and dependence on PDB concentration (half maximal at 20 nM) for this phorbol ester receptor loss paralleled the induction of the mitogenic desensitizations to both PDB and vasopressin. However, the time-course of recovery revealed an important dissociation between receptor presence and mitogenic response. When Swiss 3T3 cultures, which had been pretreated with PDB, were washed to remove this ligand and incubated in its absence for 24 h, both (3H)-PDB receptors and PDB or vasopressin inhibition of (125I)-EGF binding were almost completely restored to control levels. However the homologous and heterologous mitogenic desensitizations showed a very different reversal time. After a 24-h recovery period PDB-treated refractory cells were still unable to synthesize DNA in response to PDB or vasopressin. The mitogenic desensitizations were however completely reversible; after a 48-h incubation in the absence of PDB the cells responded fully to the mitogenic actions of PDB or vasopressin. This finding suggests that a further postreceptor step was also desensitized by prolonged PDB treatment. The presence of a low level of cycloheximide during the PDB pretreatment blocked induction of this postreceptor refractoriness. We propose that this refractory postreceptor step selectively blocks both PDB and vasopressin stimulation of DNA synthesis and may represent the point at which the mitogenic pathways of phorbol esters and vasopressin converge.     

The 110,000-dalton actin- and calmodulin-binding protein from intestinal brush border is a myosin-like ATPase

A 110-kDa protein present in chicken intestinal brush-border microvilli is believed to laterally link the actin filament bundle that forms the structural core of the microvilli with the microvillar plasma membrane. We have purified a 110-kDa protein to greater than 95% homogeneity by extraction of brush borders with solution containing 0.6 M KCl and 5 mM ATP, followed by gel filtration chromatography, sedimentation as a complex with exogenous actin, and hydroxylapatite chromatography. The 110-kDa protein-calmodulin complex bound F-actin in the absence but not the presence of ATP and had K+,EDTA-ATPase (0.2 mumol/min/mg) and Ca2+-ATPase (0.2 mumol/min/mg) activities and Mg2+-ATPase activity (0.03 mumol/min/mg) that was not activated by F-actin. The actin-binding and ATPase activities of the complex were similar to those of purified brush-border myosin. However, immunoblot analysis showed no reactivity between the 110-kDa protein and polyclonal antibody against purified chicken brush-border myosin. Also, peptide maps of 110-kDa protein and myosin obtained by limited proteolysis with chymotrypsin and Staphylococcus aureus V8 protease had few, if any, peptides in common. Immunoblot analysis also showed that myosin heavy chain was stable under the conditions of the preparation.     

Dihydroorotase from Escherichia coli. Purification and characterization

Dihydroorotase (4,5-L-dihydroorotate amidohydrolase (EC 3.5.2.3], which catalyzes the reversible cyclization of N-carbamyl-L-aspartate to dihydro-L-orotate, has been purified to homogeneity from an over-producing strain of Escherichia coli. Treatment of 70 g of frozen cell paste produces about 7 mg of pure enzyme, a yield of about 35%. The native molecular weight, determined by equilibrium sedimentation, is 80,900 +/- 4,300. The subunit molecular weight, determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis is 38,400 +/- 2,600, and by amino acid analysis is 41,000. The enzyme is thus a dimer and contains 0.95 +/- 0.08 tightly bound zinc atoms per subunit when isolated by the described procedure, which would remove any loosely bound metal ions. Isoelectric focusing under native conditions yields a major species at isoelectric point 4.97 +/- 0.27 and a minor species at 5.26 +/- 0.27; dihydroorotase activity is proportionately associated with both bands. The enzyme has a partial specific volume of 0.737 ml/g calculated from the amino acid composition and a specific absorption at 278 nm of 0.638 for a 1 mg/ml solution. At 30 degrees C, the Michaelis constant and kcat for dihydro-DL-orotate (at pH 8.0) are 0.0756 mM and 127 s-1, respectively; for N-carbamyl-DL-aspartate (at pH 5.80), they are 1.07 mM and 195 s-1.     

Amino acid sequence of rabbit ventricular myosin light chain-2: Identity with the slow skeletal muscle isoform

Many studies have established a correlation of differences in the activities of various muscle types with differences in the expression of myosin isoforms. In this paper we report the sequence determination of myosin light chain-2 from rabbit slow skeletal (LC2s) and ventricular (LC2v) nmscles. We sequenced tryptic peptides from LC2v which account for all except a few terminal amino acid residues. The major part (87 residues) of the rabbit LC2s sequence, obtained from tryptic and cyanogen bromide (CNBr) peptides, was found to be identical to rabbit LC2v. Our results provide the first sequence information on LC2s from any species, and lend strong support to the hypothesis that LC2s and LC2v are identical. Comparisons of rabbit LC2v and LC2s with rabbit LC2f (from fast skeletal muscle), and also with chicken LC2f and LC2v, show clearly that LC2s and LC2v from mammalian and avian species are more closely related to each other than they are to LC2f isoforms from the same species.     

Primary productivity of the River Ely,South Wales,U.K.

The present study was carried out on the non-tidal reaches of the River Ely, South Wales, from October 1979 to October 1980. The seasonal variations of the chlorophyll-a content of the phytoplankton was unimodal with one maximum in May and a minimum in December. The chlorophyll-a content varied from 0.277 to 41.259 mg m^?3. The primary productivity showed a bimodal seasonal distribution with two maxima in May and September and lower values throughout the remainder of the year, particularly in winter. The value for the primary productivity varied from 0.269 to 24.302 mg C m^?3 h^?1. A positive correlation was obtained between chlorophyll-a content and primary productivity. The seasonal distribution of the dominant algal species and the saprobity of the River Ely were also studied. The diatom species almost showed a similar seasonal periodicity. Their concentrations were low during the winter months and high during most of the spring and summer months. Many of the dominant diatom species found in the phytoplankton populations were either considered by the other authors as saprobic (Nitzchia palea) or as inhabitants of eutrophic waters (Gomphonema parvulum, Navicula cryptocephala and Synedra ulna). Chlamydomonas spp. were the most abundant green algae followed by Chlorella vulgaris. The effect of sewage effluent disposal and cattle excreta at three of the sampling sites might partly explain the presence of high Chlamydomonas spp. populations at those sites. Physical factors (low flow rates, high transparency and water temperature) and organic pollution at some sampling sites seemed to play an important role in increasing the number of algal species during spring and summer. The non-tidal reaches of the River Ely were found to be β-mesosaprobic above and below Station 5 and α-mesosaprobic at the latter station and therefore, the river can be considered as polluted at Station 5 and mildly polluted at the others.     

Studies on the Indochina I/CDC strain of Plasmodium falciparum in Colombian and Bolivian Aotus monkeys and different anophelines

The Indochina I/CDC strain of Plasmodium falciparum was isolated from a physician returning to the United States after working in the refugee camps along the Thailand-Kampuchean border. The strain was established in splenectomized Aotus monkeys from Colombia after being grown in vitro for 50 days. During the first three passages in Colombian monkeys, the parasites were not infective to Bolivian Aotus monkeys. After six intervening passages in Saimiri sciureus monkeys, the parasites produced high parasitemias in both Colombian and Bolivian Aotus, but gametocytes were no longer produced. Mosquito infections were obtained only during the first three passages in the Colombian monkeys. The most susceptible mosquito was Anopheles freeborni, followed by An. dirus, An. stephensi, An. maculatus, An. culicifacies, and, rarely, An. gambiae. Sporozoites were found in the salivary glands of the An. freeborni, An. dirus, An. stephensi, and An. maculatus.     

Studies of the Sal I strain of Plasmodium vivax in the squirrel monkey (Saimiri sciureus)

The Sal I strain of Plasmodium vivax was successfully adapted to three phenotypes of the squirrel monkey, Saimiri sciureus. Through five linear blood passages, parasitemias in excess of 200,000/mm3 blood were attained; Bolivian phenotype Saimiri appear to develop higher peak parasitemias. Sporozoites of the Sal I strain inoculated intravenously produced patent parasitemias in all five squirrel monkeys challenged, with prepatent periods ranging from 21 to 38 days. Anopheles freeborni and An. gambiae were the most susceptible of eight anopheline species fed on infected squirrel monkeys. As a model for in vivo studies of P. vivax the Sal I strain in Saimiri has great potential.