The response of the brachial ventral horn or Xenopus laevis to forelimb amputation during development. (25/8915)

The normal development of the brachial ventral horn of the frog Xenopus laevis and the response of the brachial ventral horn to complete forelimb extirpation at five developmental stages were assessed histologically. Differentiation of brachial ventral horn neurons occurred in pre-metamorphic tadpoles between stages 52/53 and 57. Mean cell number in the brachial ventral horn reached a peak of 2576 (S.E.M. equals +/- 269, N equals 2) per side of the spinal cord at stage 55 and decreased to 1070 (S.E.M. equals +/- 35, n equals 7) by the end of metamorphosis. Cell degeneration was presumed to be the mode of cell loss since it was most prevalent during the period of rapid decrease in cell numbers. The response of the ventral horn to forelimb removal varied with the stage of the animal at amputation. Following amputation at stage 52/53 or 54 the ipsilateral ventral horn neurons appeared less differentiated than those on the control side and a rapid cell loss of about 80% occurred on the operated side. These effects occurred more rapidly after ablation at stage 54 than at stage 52/53. Amputation at stage 58, 61, or 66 caused chromatolysis in the ventral horn, a period of relative cell excess on the operated side, and a delayed neuronal loss of 32-66%. It was concluded that excess cell degeneration accounted for cell loss and that suppression of normal neuronal degeneration caused the relative cell excess on the operated side. The data indicate that the brachial ventral horn was indifferent to the periphery before stage 54, was quickly affected by limb removal between stages 54 and 58, and by stage 58 had entered a phase in which a delay preceded cell death. No forelimb regeneration occurred.  (+info)

Scanning electron microscopy of lithium-induced exogastrulae of Xenopus laevis. (26/8915)

Lithium-induced exogastrulae are abnormal embryos which fail to complete gastrulation and do not form normal neural structures. Scanning electron microscopy has been used to compare the surface structure of the ectoderm cells of exogastrulae with that of the ectoderm cells of normal embryos and has shown that the appearance of ciliated cells is delayed in exogastrulae. In addition, the structure of endoderm cells, which remain exposed in these embryos, has been studied.  (+info)

Isolation and characterization of RNA polymerase B from the larval fat body of the tobacco hornworm, Manduca sexta. (27/8915)

DNA-dependent RNA polymerase B has been extensively purified from the larval fat body of the tobacco hornworm (Manduca sexta) by employing chromatography on ion-exchange columns of DEAE-Sephadex, DEAE-cellulose and phosphocellulose and centrifugation on glycerol gradients. The isolated enzyme after electrophoresis on acrylamide gels shows one main band and one minor band, both having enzyme activity sensitive to alpha-amanitin. The catalytic and physicochemical properties of the enzyme are similar to those of other eucaryotic B-type RNA polymerases. The enzyme has an apparent molecular weight of 530000, is inhibited 50% by alpha-amanitin at 0.04 microgram/ml and shows maximum activity on denatured DNA at 5 mM Mn2+ and 100 mM ammonium sulfate. An antibody was obtained that cross-reacts with the pure enzyme and forms a precipitin line. This antibody does not cross react with either Escherichia coli RNA polymerase or with wheat germ RNA polymerase but does react with one of the B polymerases isolated from wing tissue of the silkmoth, Antheraea pernyi.  (+info)

Ocular development and involution in the European cave salamander, Proteus anguinus laurenti. (28/8915)

The anatomy and development of the eye of Proteus anguinus are described. The relationships between organogenesis of the eye in embryos and larva and its involution in the young and the adult are discussed. The availability (in breeding cultures) of a significant number of Proteus embryos (which are normally rare) allowed experimental analysis of the effects of light, xenoplastic differentiation and thyroid hormones on the development of the eye. The results of this study suggest that development and involution of the eye of Proteus are controlled by genetic factors which are not greatly influenced by environment, and one can, therefore, consider the microphthalmy of Proteus as a relict characteristic which is the result of a specific development with disturbance of the normal ontogenic process.  (+info)

Passive exchanges during water vapour absorption in mealworms (Tenebrio molitor): a new approach to studying the phenomenon. (29/8915)

The weights of single mealworms were continuously recorded at 20 degrees C during exposure to periods of constant humidity and to abrupt changes in atmospheric vapour pressure. Two exchange stages were recognized in each animal. Weight changes were either limited to slow losses, suggesting transpiration through the external cuticle, or showed more rapid humidity-dependent gains as well as losses. Rapid exchanges indicated that water was gained or lost through permeable barriers, from a fluid compartmet of significantly lower vapour pressure than the haemolymph, equivalent to about 90% R.H. Weight gains and losses during humidity changes provided evidence of a significant, passively exchanging fluid compartment located between the exchange surface and absorbing mechanism. Weight changes in faecal pellets following their elimination provide further support for a rectal site of atmospheric absorption.  (+info)

Effects of in vitro culture methods on morphological development and infectivity of Strongyloides venezuelensis filariform larvae. (30/8915)

The effects of in vitro culture methods on morphological development and infectivity of Strongyloides venezuelensis filariform larvae (L3) to rats were investigated. A significantly higher body length was observed in L3 from filter paper culture (597.3 +/- 32.2 microns) than those in fecal (509.9 +/- 35.0 microns) and nutrient broth culture (503.3 +/- 31.0 microns) (P < 0.05). Larval infectivity was assessed by exposing rats to 1,000 L3 from each culture and worms were recovered from the lungs and small intestines. Recovery rate of these worms did not show any significant difference. A significantly greater body length of adults was recorded in those corresponding to the L3 harvested from filter paper (2,777.5 +/- 204.4 microns) and nutrient broth culture (2,732.5 +/- 169.8 microns) than those corresponding to the L3 obtained from fecal culture (2,600.5 +/- 172.4 microns) (P < 0.05). Although worm fecundity and EPG counts differed among culture methods but worm burdens and course of infection did not. These findings suggest that the methods of cultures have a significant effect on the morphological development of the larvae to the L3 stage, but do not influence the infectivity to rats.  (+info)

A case of gastric pseudoterranoviasis in a 43-year-old man in Korea. (31/8915)

A case of Pseudoterranova decipiens infection was found in a 43-year-old man by gastroendoscopic examination on August 20, 1996. On August 6, 1996, he visited a local clinic, complaining of epigastric pain two days after eating raw marine fishes. Although the symptoms were relieved soon, endoscopic examination was done for differential diagnosis. A white, live nematode larva was removed from the fundus of the stomach. The larva was 38.3 x 1.0 mm in size and had a cecum reaching to the mid-level of the ventriculus. A lot of transverse striations were regularly arranged on the cuticle of its body surface, but the boring tooth and mucron were not observed at both ends of the worm. The worm was identified as the 4th stage larva of P. decipiens.  (+info)

An aural myiasis case in a 54-year-old male farmer in Korea. (32/8915)

A 54-year-old male farmer residing in Chunchon, Korea, complaining of blood tinged discharge and tinnitus in the left ear for two days, was examined in August 16, 1996. Otoscopic examination revealed live maggots from the ear canal. The patient did not complain of any symptoms after removal of maggots. Five maggots recovered were identified as the third stage larvae of Lucilia sericata (Diptera: Calliphoridae). This is the first record of aural myiasis in Korea.  (+info)