Neonatal rat hepatocytes in primary tissue culture free from density-dependent regulation of growth

Summary Studies employing [³H]thymidine and radioautography as well as colchicine and Feulgen staining of DNA showed that up to 19-fold increases in the degree of cell crowding in vitro, i.e. from 1.45 to 27.55×10⁴ cells per specimen, did not change the rates of entry into DNA synthesis and mitosis of cultivated primary neonatal rat hepatocytes.     

The restoration of the T-lymphoid system of nude mice: lower efficiency of nonlymphoid, epithelial thymus grafts.

The T-cell deficiency of nude mice is due to an abnormal differentiation of the thymus epithelium; it can be persistently corrected by grafting a neonatal thymus. However, grafted adult thymuses or epithelial thymuses are not repopulated by large numbers of host-derived lymphocytes, as is the case when a whole neonatal thymus is grafted. Furthermore, the repopulation of the spleen and lymph nodes by T cells is less pronounced than after whole neonatal thymus transplantation, and the restoration of the reactivity to T-cell mitogens is irregular. Therefore, the integrity and the age of the thymus graft are important for a good restoration of the T-lymphoid system of congenitally athymic animals.     

Factors controlling the rhythmic contraction of collagen gels by neonatal heart cells

Summary A floating collagen matrix culture of neonatal rat heart myocardial cells shows rhythmic contractions which are dependent on localization of cells, cell density, and collagen concentration. The rhythmic contractions of the collagen matrix can be registered by a device scanning the optical density at the edge of the gel and have been observed over a temperature range from 9° to 40° C. The results of the present study underline the usefulness of myocardial cell populated collagen matrixes for studies on coherent contractions of heart cell cultures.     

Ixodes dammini: Induced skin lesions in guinea pigs and rabbits compared to erythema chronicum migrans in patients with lyme arthritis

Erythematous skin lesions occurred in rabbits 2 days after being fed upon by larvae or nymphs of the tick, Ixodes dammini. Similar lesions occurred in guinea pigs 7 days after a primary infestation with either larvae or nymphs. Host resistance to secondary feeding by larvae was demonstrated in guinea pigs and rabbits. Host resistance to secondary feeding by nymphs was seen in guinea pigs, but not in rabbits. Guinea pigs developed resistance to nymphs after being previously fed upon twice by larvae. All skin lesions in resistant guinea pigs contained large accumulations of basophils (49–76% of cells) with smaller (20–33%), but significant, numbers of eosinophils. These responses were characteristic of strong cutaneous basophil hypersensitivity reactions. Primary and secondary lesions in rabbits fed upon by larvae contained mostly mononuclear cells (46–52%) and moderate numbers (16–30%) of basophils and eosinophils. Primary and secondary lesions in rabbits fed upon by nymphs had few (3–11%) basophils and eosinophils and were dominated by mononuclear cells (73–86%). Thus, acquired resistance in guinea pigs and rabbits was associated with cutaneous basophil and eosinophil responses and the lack of resistance of rabbits to nymphs was associated with erythematous lesions dominated by mononuclear cells. The mononuclear nature of rabbit lesions induced by nymphal feeding was similar to that seen in erythema chronicum migrans in Lyme arthritis patients who are thought to have been fed upon by I. dammini nymphs. This study confirms the cutaneous basophil hypersensitivity characteristics of lesions in guinea pigs resistant to ticks and demonstrates a relationship between the mononuclear cell response of rabbits to nymphal I. dammini and the cellular response seen in patients with erythema chronicum migrans and Lyme arthritis.     

Boophilus microplus: characterization of larval phosphomonoesterases and isolation of subcellular fractions with high phosphatase activity.

Phosphomonoesterase activity was determined for a 115,000g pellet and soluble fractions resulting from a subcellular fractioning of a homogenate of larval Boophilus microplus. Both fractions showed maximum phosphatase activity at pH 5.5 and 10. Acid phosphatase (EC 3.1.3.2) activity was found to be greatest in the soluble fraction. When the reaction rate was plotted against homogenate concentration, the soluble acid phosphatase deviated from the linear relationship. For both fractions different thermostability patterns were obtained, inactlvation beginning for the alkaline phosphatase (EC 3.1.3.1) at 45–55 C. When the effect of substrate concentration on activity was studied, deviations from the typical hyperbolic behavior were observed. Homogenization of larvae with 5 mm EDTA buffer failed to yield a low-speed pellet with high alkaline phosphatase activity, as it is expected if absorptive structures sediment. Moreover, total alkaline phosphatase activity recovered by this method is significantly lower than activity recovered when homogenization is carried out without EDTA. Alternately, homogenization with 10 mM Tris buffer and 0.25 M sucrose gave 27,000g and 115,000g fractions with high phosphatase activity when fractioned by centrifugation. Alkaline treatment of the 115,000g fraction with 10 mM Tris buffer, pH 7.8, failed to separate endoplasmic reticulum contaminants without loss of phosphatase activity. When the 115,000g fraction was centrifuged in a sucrose density gradient, two activity peaks, coincident for both acid and alkaline phosphatases, were obtained. Antigenic analysis showed the existence of similar antigenic determinants in both peaks “immunologically” presented in different ways.     

Predatory behaviour of lutzia on Culex fatigans

The carnivorous mosquito Lutzia (= Culex) raptor devours 20 to 50 larvae (third instar) of Culex fatigans in a day. The predatory capacity of L. raptor is not influenced by changes in volume of water, but significantly influenced by changes in prey density. With increasing prey density, the percentage of prey killed and left unconsumed increases. The duration required to subdue and consume a single larva is 15 min for L. raptor previously deprived of food for 3 to 24 hrs; the handling duration of prey increases to 20 min for the predator previously deprived food for 1 hr. The duration increases with increasing prey size; L. raptor requires 1, 6, 62 or 113 min to handle a single II, III, IV or mini pupa of Culex fatigans weighing 0.2,1.2,4.2 and 4.0 mg respectively.     

The occurrence of the second moult of Ascaris lumbricoides and Ascaris suum

Maung M. 1978. The occurrence of the second moult of Ascaris lumbricoides and Ascaris suum. International Journal for Parasitology 8: 371–378. Eggs of Ascaris lumbricoides and A. suum were cultured at 28°C and observed daily. Larvae were released by pressure, by artificial hatching with CO₂, and by natural hatching after infection of laboratory mice. The early stages of development in the egg were observed to comprise two moults, one occurring immediately after the other. Both moults were initiated within the egg, but the time of completion of the second moult varied considerably, and in some instances was not completed until the larvae reached the liver of experimentally infected animals.     

Satiation time and predatory behaviour of the dragonfly nymph Mesogomphus lineatus

Summary The dragonfly nymph Mesogomphus lineatus satiated predating 21 larvae of Culex fatigans in 50 minutes; number of attack and predatory efficiency decreased precipitously from 2 attacks/min and 70% during the first 10 minutes of feeding to 0.04 attack/min and 0.01% efficiency respectively during the sixth 10 minutes interval. The nymphs fed after 6, 12, 18, 24, 36 or 42 hours of deprivation consumed 4, 13, 15, 20, 21 or 21 larvae; apparently, the maximum appetite is returned after about 36 hours of deprivation. Satiation time, which was 50 minutes at the density of 15 larvae/aquarium, decreased to 30 minutes in aquaria containing 200 larvae. The nymphs predated increased the number of prey when they were exposed to higher densities of C. fatigans and Anopheles stephansi larvae, and pupa of C. fatigans. They consumed equal weight (but different number) of Culex and Anopheles larvae at all the tested prey densities and selectively selected Culex larva over the pupa or Anopheles larva. Comparative analyses suggest that the dragonfly nymphs deserve serious consideration as larvivorous predators.     

Stimuli for cuticle formation and ecdysis in vitro of the infective larva of Anisakis sp. (Nematoda: Ascaridoidea)

Third-stage larvae of the genus Anisakis from the fish Leionura atun (Trichiuroidei: Perciformes) form a new cuticle and moult in vitro in about 72 h. If the culture medium is Krebs-Ringer under 5% carbon dioxide in air at 37°C, relatively few moult and survival is poor. But more moult and survival is enhanced if worms are incubated in tissue culture medium 199, even if the gas phase is air, although they moult more quickly if it contains 5% carbon dioxide. In both Krebs-Ringer and 199 the benefits of high concentrations of carbon dioxide only accrue if the gas is present during the first 40 h of incubation. Worms do not feed in these media until they have moulted.