Cat Interferon inhibits Feline Leukaemia Virus Infection in Cell Culture

TRANSMISSION of feline leukaemia can be accomplished with tissue extracts from cases which occur naturally¹. Virus particles which are morphologically indistinguishable from the murine and avian C-type viruses are present in cats with the transmitted disease². Feline leukaemia virus (FeLV) replicates in cat cell cultures³ and infected cells are demonstrable by the indirect immunofiuorescent antibody test which detects FeLV group-specific antigen as granular punctate fluorescence in the cytoplasm of acetone fixed cells⁴; this method allows easy quantitation of the antiviral effect of interferon. We report the production and assay of feline interferon using the fluorescent antibody test with FeLV infected cat cell cultures.     

Control of Ovarian Function in Domestic Animals

Plasma hormone levels during the estrous cycle of the cow, ewe,and sow have been measured, and the patterns of secretion ofestrogens, progesterone, and luteinizing hormone during thecycle have been related to ovarian changes and other informationconcerning the cycle for each species. Peripheral plasma progesteroneand LH levels are generally inversely related during the cyclein each species, and it seems clear that progesterone exertsa negative feedback on LH secretion in all three species, atleast insofar as the cyclic release of preovulatory amountsof LH is concerned. Peak plasma progesterone levels are highestin the sow, lowest in the ewe, and intermediate in the cow.Plasma LH levels at estrus are highest in the ewe, lowest inthe sow, and intermediate in the cow. Sharp peaks in plasmaLH occur at the onset of estrus in the cow, and a few hoursafter the onset of estrus in the ewe and sow; these peaks areof about 6–8 hr duration. LH exerts a luteotrophic actionon the corpora lutea of all three species, and verylow levelsof LH secretion appear capable of maintaining the corpus luteumin the ewe and cow. There is no good evidence that prolactinis luteotrophic in any of these species. Three peaks of plasmaestrogen levels are seen in the ewe and the cow and these appearrelated to periods of accelerated follicle growth. One peakoccurs early in the cycle and before plasma progesterone levelsrise appreciably and another occurs during the luteal phasejust prior to corpus luteum regression. The third peak occursafter plasma progesterone levels decline and is associated withgrowth of the ovulating follicle. The luteal phase estrogenpeak has not been found in the sow. The rapid rise in bloodestrogens after the corpus luteum regresses facilitates thepreovulatorysurge of LH in all three species. Cyclical regressionof the corpus luteum in all three speciesappears to be underlocal control of the adjacent horn of the uterus. Exogenousestrogens are luteolytic in the cow and ewe, but luteotrophicin the sow. The ovaries of all three species contain very poorlydeveloped interstitial tissue probably because of the neailycomplete dedifftrentiation of the thecal cells during atresia.Thus, these animals lack an important source ofsteroid hormonespresent in the lodents and certain other species.     

Periodic Nocturnal Stomatal Opening of Citrus in a Steady Environment

In a steady environment, leaf stomates of sour orange (Citrus aurantium L.) remained closed in the dark, whereas those of rough lemon (Citrus jambhiri Lush) underwent several 20-minute periods of pronounced opening at intervals of 60–85 minutes. Peak nocturnal opening occurred about 10 minutes after the cycle began, as shown by a change in leaf diffusion resistance from 60 s cm^?1 (closed) to 2 s cm^minus;1 (open). This minimal leaf resistance equals that obtainable in rough lemon in strong illumination (26 kilolux). The transitory stomatal opening detected by leaf resistance measurements was corroborated by measurements of leaf temperature and leaf thickness. During nocturnal opening, leaf temperature was 2°C below the value representing non-cycling periods. Also, minimal leaf thickness coincided with maximal stomatal opening. The triggering mechanism for nocturnal stomatal opening appears to originate within the plant, since the environmental factors of air temperature, humidity, carbon dioxide concentration, and substrate (aerated water culture) were held steady.     

Nucleic Acid Precursor Incorporation by Eimeria nieschulzi (Protozoa: Apicomplexa) and Jejunal Villus Epithelium*

Autoradiography was used to investigate incorporation of tritiated adenine, adenosine, guanosine and thymidine by Eimeria nieschulzi and rat jejunal villus epithelial cells. At 2 1/2 days postinoculation, parasitized and control tissues were incubated for 20 min in oxygenated Tyrode's solution (37 C, pH 7.5) containing 30 μCi/ml of each nucleic acid precursor. Treatment of tissues with ribonuclease revealed that E. nieschulzi incorporated label from [³H]adenine primarily into RNA while that from [³H]adenosine and [³H]guanosine was present mainly in DNA. Label from [³H]thymidine was not utilized by parasites. Host villus epithelial cells incorporated label from [³H]purines primarily into RNA. Labeled cytoplasmic RNA was significantly increased in parasitized cells after incubation in [³H]adenine. Tritiated nuclear RNA and cytoplasmic RNA were significantly decreased in parasitized cells after incubation in [³H]adenosine. Incorporation of label from [³H]guanosine was similar for parasitized and control cells. A small quantity of label from each [³H]precursor was incorporated into DNA of villus epithelial cell nuclei.     

Play Between Adult Male and Infant Rhesus Monkeys

Play among four pairs of adult male and infant rhesus monkeysis described and compared to mother-infant and peer play. Datawere collected while the adult males reared the infants fora period of 7 months in the absence of mothers and peers. Typesof play were categorized as solitary, parallel, and interactive.Sex differences in play patterns are described, as are antecedentand consequent events. Adult male-infant play was found to beof much greater intensity and mean duration than mother-infantplay.     

BUOYANCY CONTROL IN AMMONOIDS

A specimen of Buchiceras bilobatum is shown to have been able to maintain neutral buoyancy in water despite the ever increasing weight of epifaunal oysters which it carried on its shell. It is deduced that before settlement of the oyster spat, the camerae of the ammonite contained several grammes of water and that this was slowly pumped out as the oysters grew. Revised calculations on the densities of other ammonoids suggest that the presence of large quantities of liquid in cephalopod camerae was a common occurrence. The significance of this liquid in the growth, mode of life, and evolution of ammonoids is discussed.     

Apparent Indispensability of Bacteria in Foraminiferan Nutrition

SYNOPSIS. Bacteria were required for the sustained reproduction of 4 species of foraminifera in gnotobiotic culture. None of the species of algae tested, singly or in combination, supported continuous reproduction of the foraminifera in bacteria-free gnotobiotic culture. It is inferred that bacteria have some nutritional factor required by the foraminifera that is either unavailable or unavailable in sufficient quantity in an exclusively algal diet.
Gnotobiotic clones of Quinqueloculina lata, Spiroloculina hyalina, Rosalina leei , and Allogromia laticollaris were established on bacteria + algae (usually 1 or 2 species). In balanced gnotobiotic cultures neither light nor foraminiferan density (organisms/ml) were limiting. As cultures aged, pH shifted and limited growth. When waste products were removed by washing, reproductive rates were higher.     

Structure and Respiration of Sporulating Eimeria stiedae and E. tenella Oocysts*

SYNOPSIS. The structure and respiration of sporulating Eimeria tenella and E. stiedae oocysts was compared. Oocysts were purified by Clorox digestion and incubated at 29 C. The sporulation events were similar for both species, except for the spindle stage, altho sporulation took longer in E. stiedae. Sporulating oocysts go thru the process with some degree of synchrony. Oocyst respiration was measured polarographically. An early increase in respiratory rate in both species was followed by a depression in rate that correlated with the appearance of the early spindle stage. The rate again increased and then decreased toward a base rate during and after completion of sporulation. E. tenella oocysts incubated in air remained viable 4 times longer than those incubated in nitrogen. E. tenella sporozoites excysted and remained motile in the presence of sodium cyanide. These facts suggest that E. tenella sporozoites are facultative anaerobes.     

Ultrastructure of the Amoeboflagellate Tetramitus rostratus1

The life-cycle of the amoeboflagellate Tetramitus rostratus includes amoeboid, cyst, and flagellate stages. The ultrastructure of these three stages is illustrated, with particular emphasis on flagellate morphology. Amoeba morphology is typical of that of limax amoebas. Cysts, forming from trophic amoebas, are enclosed by a wall made up of two layers: ectocyst (ca. 70 nm), and endocyst (200 nm). The wall apparently forms from precursor material present in vesicles in the pre-cyst stage cytoplasm. Flagellate morphology is characterized by a well-defined top-shaped profile, maintained by microtubules under the plasma membrane. The flagellar apparatus or mastigont consists of four flagella, their basal bodies, sheaves of microtubules associated with two of the basal bodies, and several rhizoplasts (periodicity 20 nm). A deep, microtubule-supported, ventral invagination appears to function as a gullet. A small number of mitotic stages observed in amoeboid and flagellate individuals suggests similarity in the division process in both stages: intranuclear mitotic apparatus, nucleolus persisting through mitosis, no centrioles or basal bodies functioning as centrioles, difficulty in resolving chromosomes. The text compares ultrastructures of several amoeboflagellate organisms and evaluates the phylogenetic significance of those features common to different species. On the basis of this study, Tetramitus most closely resembles Naegleria spp.