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PubMed2002

The Distance to Which Wound Effects Influence the Structure of Secondary Xylem of Decapitated Pinus pinea.

Decapitation of stems of annuals and trees for the study of vascular and fiber differentiation with or without hormonal application is a common procedure. There is controversy about whether wound effects play a role in such experiments, and to what distance from the point of decapitation. To examine this question, the distance from the point of decapitation at which apparent wound effects are obvious developmentally, was studied in decapitated 4-year-old Pinus pinea plants. The wound effects just below the cut included differentiation of many traumatic resin ducts, a parenchyma band instead of tracheids, more tracheid files, and a higher proportion of late wood. The increase in the number of resin ducts was still considerable and statistically significant 10 cm below the point of decapitation compared with the nondecapitated control. These results indicate that in pines, wound effects in the first 5 cm below the decapitation point (a common point for tissue examination) cannot be ignored in experiments on the regulation of vascular differentiation.

Journal Article↗

PubMedDate not supplied

The use of decapitated insects to study lipid mobilization in adult Manduca sexta: effects of adipokinetic hormone and trehalose on fat body lipase activity.

In order to perform studies on lipid mobilization in adult M. sexta, it is necessary to overcome the effects of starvation and handling, which both provoke an increase in hemolymph lipid concentration. When trehalose was injected into intact insects, a 35% decrease in the content of the diacylglycerol (DG)-rich hemolymph lipoprotein, low density lipophorin (LDLp) was observed within 30 min, but the level of LDLp returned to control values after 1 h. Decapitated insects exhibited 60% reduction in LDLp concentration and the levels remained low for at least 24 h. In contrast to intact insects, injection of trehalose into decapitated animals did not alter the LDLp concentration. After decapitation, the response to adipokinetic hormone (AKH) and the ability of the fat body to release DG into the hemolymph was maintained for at least 24 h. In decapitated insects, 6 pmol of AKH-stimulated measurable lipid mobilization and a near maximum response was obtained with 100 pmol of the hormone. The action of trehalose and AKH on the fat body triacylglycerol (TG)-lipase activity in decapitated animals was studied. Fat body homogenates from trehalose-treated insects exhibited a TG-lipase activity 40% lower than the control insects. Activation of fat body triacylglycerol-lipase was observed after injection of AKH, with the extent of activation ranging between 97 and 380% ten min after AKH injection. A time course study showed that the activation of the fat body triacylglycerol lipase preceded the increase in hemolymph LDLp concentration, suggesting that activation of the lipase initiates lipid mobilization. It is concluded that decapitated insects injected with trehalose is a very useful system for investigating the hormonal regulation of lipid mobilization in adult M. sexta.

Animals↗

PubMed1981

Skeletal muscle development in the fetal pig after decapitation in utero.

The effect of fetal decapitation on skeletal muscle growth and development in utero was studied in the pig. Pig fetuses were decapitated at 45 days of gestation and the peroneus longus muscle was analyzed at 110 days of gestation. Muscle wet weight, length, minimum fiber diameter, DNA, RNA, protein content, and incidence of muscle fiber nuclei and satellite cell nuclei were determined in the decapitated fetus and in sham-decapitated control fetuses. Decapitation did not significantly influence (p greater than 0.05) any of the traits measured. Muscle and satellite cell ultrastructure was not altered by decapitation. Therefore, an intact brain and hypothalamic-hypophyseal axis are not critical to growth and development of fetal pig skeletal muscle as measured in this study.

Animals↗

PubMed2002

Increases in plasma dihydroxyphenylacetic acid levels in decapitated mice after exposure to various stresses.

This study investigated changes in plasma levels of the dopamine metabolite dihydroxyphenylacetic acid (DOPAC) in decapitated mice in response to the variable stresses of restraint, restraint and water immersion, and foot shock. DOPAC levels, but not norepinephrine (NE) and epinephrine (EPI) levels, increased upon exposure to these stresses. Plasma DOPAC levels measured using the decapitation method in rats were then compared with those measured using the catheter method. The NE and EPI levels in plasma measured using the decapitation method were much higher than those using the catheter method under basal conditions. In contrast, differences in the levels of DOPAC in plasma were smaller than those of NE and EPI under basal conditions using in both methods; furthermore parallel changes in plasma DOPAC levels occurred during restraint and water immersion stresses. These results indicate that the plasma DOPAC levels measured in mice using the decapitation method were clearly increased by the different stresses. Furthermore, in rats there were correlations between the decapitation and catheter methods for plasma levels of DOPAC. Thus the change in plasma DOPAC levels measured using the decapitation method is a good indicator of stress responses involving sympathoneural activity.

3,4-Dihydroxyphenylacetic Acid↗

PubMed1981

Adipose tissue development in the fetal pig after decapitation.

The effect of fetal decapitation on adipose tissue development in utero was studied in the pig. Pig fetuses were decapitated at 45 days of gestation, and dorsal subcutaneous adipose tissue was analyzed at 110 days of gestation. The histology, histochemistry, ultrastructure, size and lipoprotein lipase activity of adipocytes from decapitated and sham-decapitated control fetuses were determined. Decapitation resulted in a poorly developed dermis and epidermis, a poorly developed outer layer of adipose tissue and larger fat cells that were metabolically and structurally more mature. Fewer fat cell clusters in decapitated fetuses were associated with fewer blood vessels in the subcutaneous layers. The results of this study demonstrate that fat cell development in subcutaneous tissues may be an integral aspect of the development of skin and associated structures.

Adipose Tissue↗

PubMed1975

The effect of in utero decapitation on the morphological and physiological development of the fetal rabbit lung.

A study has been made of the consequences of in utero decapitation on the morphological and physiological development of the fetal lung. Fetal rabbits were decapitated in situ at 22 days, without losing any amniotic fluid, and allowed to continue their development with their undamaged littermates as controls. Such decapitation, of course, removes the pituitary and so interferes with adrenal cortical development. Morphological studies showed an interference with lung development in that, although the number of alveolar saccules increased normally, their walls failed to thin. In the decapitated fetuses, a reduction in the number of lamellated bodies per Type II pneumonocyte was found at each age studied; while dense, homogeneous bodies were more numerous. The normal disappearance of glycogen in the Type II pneumonocytes of the decapitated fetuses was retarded. Physiological studies supported these findings. In control fetuses allowed to breathe for a while the Bubble Stability Ratio increased rapidly from day 26 to reach a maximum at 28 days; whereas, in the decapitated ones, bubble stability was not apparent before day 28 and by the 29th day had reached a maximum which was lower than that of the controls. In the control fetuses, lecithin was detected in lung fluid from 26 days on, and in stomach fluid from 29 days. It is argued that lung development must be, at least in part, under the control of the fetus' own pituitary-adrenal axis.

Animals↗

PubMed1986

Bud induction in decapitated Hydra attenuata by 5-azacytidine: a morphological study.

The effect of 5-azacytidine (5-azaCR) on head regeneration and budding in hydra are reported. Hydra attenuata were exposed to various doses of 5-azaCR for 48 h and then decapitated and cultured. Head regeneration and bud formation were observed for 12 days after decapitation. Untreated control hydra regenerated heads within 7 to 8 days of decapitation with a budding index of 0.2. Buds invariably arose in the normal budding zone (below the gastric region). In the group treated with 0.8 mM-5-azaCR, 9 days after decapitation head regeneration was seen in only 13% of animals, and an average of two buds per hydra were formed, most of which were in the vicinity of the distal end. Induction of budding was also seen in the animals that regenerated heads. In animals exposed to 1 mM-5-azaCR three main types of responses were observed 9 days after decapitation. 44% of the animals regenerated normal heads; about half of them developed at least one bud and these buds originated in the budding zone. 17.5% of the animals developed abnormal, long hypostome-like structures with single or bifurcated tentacles at their tips. There were at least two buds per animal and they were invariably at abnormal sites. 32% of the animals failed to regenerate heads, although they developed two buds. 87% of these buds originated in abnormal sites of the body column and a large number (72%) did not detach even by the 12th day after decapitation. Both 5 and 10 mM of 5-azaCR were toxic to the animals; the survivors formed large globe-shaped heads. Bud induction was seen in 60% and 28% of animals in the 5 and 10 mM groups, respectively. These observations demonstrate that 5-azaCR induces bud formation in hydra at doses that inhibit head regeneration. This bud induction might be due to a specific expression of gene products responsible for bud formation.

Animals↗

PubMedDate not supplied

Comparative studies on the influence of decapitation, ketamine and thiopental anesthesia on rat heart mitochondria.

The influence of decapitation, ketamine and thiopental anesthesia on some properties of rat heart mitochondria was compared. Polarographic analysis were performed, oxygen consumption rates, respiratory control index, ADP : O ratio and oxidation of exogenous NADH were determined. Electronmicroscopic and gasometric examinations were also conducted. Mitochondrial fractions from hearts of decapitated rats oxidized at a generally faster rate and mitochondria from such hearts exhibited a significantly lower RCI value. These differences can be explained through the action of uncoupler(s) present in the decapitated group. A hypothesis linking decapitation with the uncoupling effect of fatty acids released intracellularly during catecholamine-stimulated lipolysis is discussed. No differences in the ADP : O ratio and electronmicroscopic details between the groups were found. Gasometric determinations in both anesthetized groups did not show any marked dysfunction of the respiratory system. It is concluded that decapitation leads to some changes in the functional integrity of rat heart mitochondria. Ketamine and thiopental anesthesia can be used with equal success for the isolation of mitochondria from the heart.

Adenosine Diphosphate↗

PubMed1986

Effects of new neuroleptics, isofloxythepin and zotepine, on post-decapitation convulsions and prolactin secretion in rats.

Oral administration of isofloxythepin (0.5-8.0 mg/kg) inhibited decapitation convulsions in a dose-dependent manner as shown by decreasing the incidence and shortening the convulsion's duration, the effects continuing until 24 hr after administration. Zotepine (8, 16 mg/kg, SC) also decreased the duration but not the incidence of the convulsion. However, the other neuroleptics such as haloperidol, spiperone, perphenazine, trifluoperazine, pimozide and sulpiride failed to affect decapitation convulsions. Reserpine (8 mg/kg, SC) inhibited decapitation convulsions, accompanied by decreasing levels of norepinephrine, dopamine and serotonin in the spinal cord. Isofloxythepin at doses of 4 and 8 mg/kg, PO which completely abolished decapitation convulsions, failed to change norepinephrine and dopamine levels but increased serotonin levels in the spinal cord. Isofloxythepin (0.5-8.0 mg/kg) increased serum prolactin levels in a dose-dependent manner and zotepine (16 mg/kg), haloperidol (1 mg/kg) and reserpine (8 mg/kg) also elevated the levels. The results imply that both isofloxythepin and zotepine, but not the other neuroleptics, inhibit convulsions without decreasing spinal levels of norepinephrine which appears to be the amine most directly involved in the occurrence of decapitation convulsions, although these neuroleptics enhance prolactin secretion by blocking dopamine receptors in the pituitary.

Animals↗

PubMed1988

Lateral bud outgrowth on decapitated shoots of low-pruned mulberry (Morus alba L.).

After decapitation, lateral shoot growth of mulberry coppice (Morus alba L. cv. Shin-ichinose) from 10-year-old stumps had an extremely acrotonic form compared with that of intact one-year-old stems of trees during the spring. When one dominant shoot from each stump was decapitated, only a few upper lateral buds grew out and elongated. Defoliation of the decapitated shoots resulted in an increase in the number of shoots sprouting and a decrease in the rate of elongation of the laterals. Further enhancement of laterals on decapitated dominant shoots resulted from the removal of competing intact coppice shoots from the stumps. 1-Naphthaleneacetic acid (NAA) applied as a spray reduced the number of lateral buds sprouting from both defoliated, decapitated erect shoots and intact horizontally trained shoots. The results suggest that management of mulberry coppice could increase the supply of leaves for commercial silk production.

Journal Article↗

PubMed1997

Restoration of phototropic responsiveness in decapitated maize coleoptiles.

The literature indicates that the tip of maize (Zea mays L.) coleoptiles has the localized functions of producing auxin for growth and perceiving unilateral light stimuli and translocating auxin laterally for phototropism. There is evidence that the auxinproducing function of the tip is restored in decapitated coleoptiles. We examined whether the functions for phototropism are also restored by using blue-light conditions that induced a first pulse-induced positive phototropism (fPIPP) and a time-dependent phototropism (TDP). When the apical 5 mm, in which photosensing predominantly takes place, was removed, no detectable fPIPP occurred even if indole-3-acetic acid (lanolin mixture) was applied to the cut end. However, when the blue-light stimulation was delayed after decapitation, fPIPP became inducible in the coleoptile stumps supplied with indole-3-acetic-acid/lanolin (0.01 mg g-1), indicating that phototropic responsiveness was restored. This restoration progressed 1 to 2 h after decapitation, and the curvature response became comparable to that of intact coleoptiles. The results for TDP were qualitatively similar, but some quantitative differences were observed. It appeared that the overall TDP was based on a major photosensing mechanism specific to the tip and on at least one additional mechanism not specific to the tip, and that the tip-specific TDP was restored in decapitated coleoptiles with kinetics similar to that for fPIPP. It is suggested that the photoreceptor system, which accounts for fPIPP and a substantial part of TDP, is regenerated in decapitated coleoptiles, perhaps together with the mechanism for lateral auxin translocation.

Cotyledon↗

PubMed2000

Auxin inhibition of decapitation-induced branching is dependent on graft-transmissible signals regulated by genes Rms1 and Rms2.

Decapitation-induced axillary bud outgrowth is a vital mechanism whereby shoots are able to continue normal growth and development. In many plants, including wild-type garden pea (Pisum sativum L.), this process can be inhibited by exogenous auxin. Using the ramosus (rms) increased branching mutants of pea, we present evidence that this response to auxin is dependent on graft-transmissible substance(s) regulated by the genes Rms1 and Rms2. The response to exogenous auxin is massively diminished in decapitated rms1 and rms2 mutant plants. However, basipetal auxin transport is not reduced in intact or decapitated mutants. Grafting rms1 or rms2 shoots onto wild-type rootstocks restored the auxin response, indicating that Rms1 and Rms2 gene action in the rootstock is sufficient to enable an auxin response in mutant shoots. We conclude that Rms1 and Rms2 act in the rootstock and shoot to control levels of mobile substance(s) that interact with exogenous auxin in the inhibition of bud outgrowth after decapitation. At least for rms1, the reduced auxin response is unlikely to be due to an inability of auxin to decrease xylem sap cytokinin content, as this is already low in intact rms1 plants. Consequently, we have genetic evidence that auxin action in decapitated plants depends on at least one novel long-distance signal.

Biological Transport↗

PubMed1984

IAA-Induced Growth Responses of Decapitated Corn Seedlings: Indications of Two Apparent Adaptations with a Possible Role in Gravitropism.

The vertical growth responses of corn seedlings (Zea mays L. Mo17 x B73) were determined over an 8-hour period. When seedlings were decapitated 3 millimeters from the coleoptile's tip and supplied with indole-3-acetic acid (IAA) in 1.5% agar blocks, the response was dependent both on time and IAA concentration. The dose-response curves changed in shape and magnitude depending on the total time of IAA application. High concentrations (>3.2 x 10(-6) molar) initially produced high relative growth rates that decreased back to the intact rate (0.03 millimeter per hour per millimeter) after 3 hours. Low concentrations (<1.0 x 10(-6) molar), or agar blocks without IAA, resulted in a rapid decrease from the intact rate to a level that stabilized at 0.01 millimeter per hour per millimeter until the growth rate began to recover after 3 to 4 hours. Intermediate concentrations produced responses similar to that of the intact organ, though some features of these responses were unique.The coleoptile curvature in response to gravity depended upon whether the coleoptiles were intact, decapitated, or decapitated and supplied with IAA. Coleoptiles decapitated and not supplied wth IAA showed little or no curvature for 3 hours after decapitation. By this time an adaptation, evoked by the low IAA level, had developed and the coleoptiles began to curve steadily. When 1.0 or 3.2 x 10(-6) molar IAA was supplied, curvature was initiated within the first 30 minutes and reached a maximum rate before decreasing and stopping after 3 to 4 hours. The sequence of events in response to these concentrations was similar to the intact sequence but the curvature rate was reduced to one-third to one-half. A model for the autotropic response involving an auxin concentration-dependent, growth-modulating mechanism capable of two modes of adaptation is described.

Journal Article↗

PubMed1985

Effects of fetal decapitation upon porcine placental metabolism. Evidence for a fetal influence in placental metabolism.

This experiment was performed to determine if the fetus can influence its placental metabolism. Fetal pigs were decapitated at 45 days of gestation and their placentas compared at 110 days to within litter controls. No histological or histochemical differences were observed. Glycogen levels were elevated in the fetal placenta of decapitated pigs by 107%. Fatty acid synthesis was increased in the fetal placenta of decapitated animals (12.9 +/- 1.5 vs. 3.4 +/- 0.7 nmol acetate units/100 mg/2 h). Fetal decapitation increased fetal placental fatty acid esterification by 43% and oxidation by 125%. The altered lipid metabolism of the fetal placenta was reflected in enzymes associated with substrate utilization (pyruvate kinase and lactate dehydrogenase). Maternal placenta lipogenesis was also altered by fetal manipulation. Leucine conversion to its alpha ketoacid was increased in the fetal placenta of the decapitated pigs (14.8 +/- 1.7 vs. 8.6 +/- 1.4 nmol/100 mg/2 h) indicating amino acid metabolism was affected by this treatment. The ability of an altered fetal endocrinology and metabolism to affect the placental metabolism supports the concept of a fetal influence on placental metabolism.

Animals↗

PubMed1979

Retention of plasma somatomedin activity in the foetal rabbit following decapitation in utero.

One rabbit foetus within each litter was decapitated in utero on day 24 of gestation. Plasma somatomedin activity and costal cartilage metabolism were studied 5 days later in the experimental foetuses and control litter-mates. Somatomedin was assayed by the uptake of [35S]sulphate in vitro into costal cartilage from intact foetuses. Uptake was proportional to logarithmic increases in the concentration of both foetal and maternal rabbit plasma. The mean (+/- 1 S.D.) somatomedin activity of four plasma pools, each pool being derived from the intact foetuses within each of four litters, was 1.3 +/- 0.3 compared with a potency of unity for the reference pool of maternal plasma. The plasma somatomedin activity of decapitated foetuses did not differ significantly from that of control litter-mates when analysed by rank test, but the costal cartilage of decapitated foetuses took up less [35S]-sulphate in basal medium when compared with that of intact litter-mates. The headless body weight of the decapitated foetueses did not rank in a position significantly different from the one expected. The concentration of plasma growth hormone in the decapitated foetuses was less than 5 ng/ml and that of the intact foetuses was more than 157 ng/ml. It is concluded that plasma somatomedin in the rabbit foetus is not dependent on foetal growth hormone.

Animals↗

PubMed1982

Semitendinosus muscle development in fetally decapitated pigs.

The effect of decapitation on semitendinosus muscle growth and development was studied in the fetal pig. Pig fetuses were decapitated at 45 d of gestation and histochemical and biochemical analyses conducted at 110 d of gestation. Decapitation prevented or delayed the conversion of secondary fibers from Type II to Type I histochemistry as is characteristic of the normal semitendinosus. Morphological analyses indicated either a prolonged stage of secondary myofiber formation or an inhibition of secondary myofiber hypertrophy in muscle from decapitated fetuses. Biochemical and histochemical analyses indicated that muscle from decapitated fetuses was biochemically and chemically immature compared with that from normal fetuses.

Adenosine Triphosphatases↗

PubMed1989

Histochemical studies of muscle development in decapitated and hypophysectomized pig fetuses: blood vessel development.

In Exp. 1, fetuses were decapitated in utero on d 45 of gestation and examined at 110 d of gestation; in Exp. 2, fetuses were hypophysectomized (hypox) in utero with a cauterizing needle at d 70 of gestation and examined at 110 d of gestation. Semitendinosus muscles were sampled and transverse cryostat sections were cut from the medial portion of the muscle. Quantitative analysis of lectin-stained sections showed that capillary:fiber ratios (C/F) were lower (P less than .01) for sections from decapitated and hypox fetuses than for sections from control fetuses. The superficial and deep aspects of muscle sections from control fetuses had markedly different C/F ratios (deep region, 24.1 +/- 2; superficial region, 11.2 +/- .5). Fetal decapitation and hypophysectomy abolished differences in C/F ratios between deep and superficial regions of muscle sections (hypox fetuses; deep region, 6.9 +/- 1; superficial region, 6.4 +/- .6). Capillaries in sections from control fetuses were reactive for several enzymes, whereas capillaries in sections from experimental fetuses (decapitated and hypox) were not reactive for these enzymes. The number of small arterioles was reduced in sections from experimental fetuses (decapitated and hypox) compared with sections from control fetuses. These studies demonstrate that lowering the levels of pituitary hormones in the fetus retards the development of blood vessels in muscle tissue both quantitatively and qualitatively.

Animals↗

PubMed1975

Effects of fetal decapitation on the structure and function of Leydig cells in rhesus monkeys (Macaca mulatta).

Fetal decapitation in utero has enabled us to study the role of fetal pituitary hormones in the development of the fetal testis. Testes from males decapitated near 80 days of gestational life and later delivered at 150 days were smaller than normal and about one-tenth the normal weight. The size of the seminiferous tubules was similar in both groups; however, the number of Leydig cells seemed reduced. In addition, the Leydig cells of the experimental group contained smaller mitochondria with reduced tubular cristae, fewer lipid droplets, and reduced agranular endoplasmic reticulum. Androgen production was inhibited. Measured by radioimmunoassay, the testosterone level in the umbilical vein was 329 +/- 82 pg/ml in six decapitates fetuses, 412 +/- 62 pg/ml in ten normal fetuses. The level in the umbilical artery was 328 +/- 56 pg/ml in five decapitated fetuses, 658 +/- 140 pg/ml in normal fetuses. These studies suggest that chronic deprivation of fetal pituitary hormones inhibits the growth and development of the testis in general and of the Leydig cells in particular.

Androgens↗