The impact of replacing barley by dehydrated orange pulp in finishing pig diets on performance, carcass quality, and gaseous emissions from slurry.

Using agricultural by-products such as dehydrated orange pulp (DOP) in animal feeds is of interest to increase pig sector sustainability. With this aim, an assay was carried out to assess the effects of increasing inclusion levels of DOP in pig diets regarding animal performance, carcass quality, and environmental impact. Four experimental diets were designed, a control diet (T1) and three more diets with increasing levels of DOP with 80, 160, and 240 g/kg of DOP for diets T2, T3, and T4, respectively. One hundred and sixty growing pigs were used in the experiment. Growth performance (average daily gain, ADG; average daily feed intake, ADFI and feed conversion ratio, FCR) and in vivo backfat thickness (BF) and loin depth (LD) gain were recorded during the finishing phase (from 70 to 130 kg BW). Faecal samples were incubated for bacteria enumeration. At slaughter, carcass characteristics and meat quality traits were measured, and subcutaneous fat was sampled to analyse the fatty acid (FA) profile. Additionally, the slurry excreted by the animals was measured, characterised and subjected to a gaseous emission assay during its storage. The final BW and overall ADFI, ADG and FCR were similar among treatments. In vivo final LD and BF gain decreased (P ≤ 0.10) as the inclusion level of DOP increased. No differences were observed in carcass characteristics with the inclusion of DOP, except carcass weight that decreased linearly (P = 0.05) with DOP. Regarding the FA profile of the subcutaneous fat, the ratio of total monounsaturated to saturated FA increased with the inclusion level of DOP. Neither slurry excretion and characterisation nor bacterial counts from faeces showed any significant difference among treatments. The inclusion of DOP led to greater CH4 emissions in mg per L of slurry and hour, whereas these differences disappeared when expressed in mg per animal and day. In all, it has been demonstrated that the inclusion of DOP up to 240 mg/kg in pig diets had minor effects on growth performance, carcass quality traits or gaseous emissions from slurry, favouring the circular economy strategy and pig sector sustainability.

Partially defatted olive cake in finishing pig diets: implications on performance, faecal microbiota, carcass quality, slurry composition and gas emission.

One of the key factors to improve swine production sustainability is the use of agro-industrial by-products in feeds, such as olive by-products. However, it is necessary to assess its effects on the overall production process, including the animal and the environment. With this aim, an experiment was conducted to determine the effects of including a partially defatted olive cake (PDOC) in pig diets on growth performance, faecal microbiota, carcass quality and gas emission from the slurry. Two finishing diets were formulated, a control (C) diet and a diet with PDOC included at 120 g/kg. Eighty finishing male pigs Duroc-Danbred × (Landrace × Large White) of 60.4 ± 7.00 kg BW were divided between these two treatments. During the finishing period (60 to 110 kg BW, 55 days) average daily gain, average daily feed intake and feed conversion ratio were recorded. Faecal samples from the rectum of 16 animals per treatment were incubated for bacteria enumeration. At the end of finishing period, backfat thickness and loin depth (LD) were measured. Animals were slaughtered to obtain carcass weight and carcass composition parameters, and subcutaneous fat was sampled to analyse the fatty acid (FA) profile. In addition greenhouse gas and ammonia emissions were measured during pig slurry storage using the methodology of dynamic flux chambers. An initial slurry characterisation and biochemical methane potential (B0) were also determined. No significant differences between treatments were found in performance, carcass quality and microbial counts with the exception of LD, which was lower in PDOC compared with C animals (45.5 v. 47.5 mm, SEM: 0.62; P = 0.020). The FA profile of the subcutaneous fat did not differ between treatments, but the monounsaturated FA (MUFA) concentration was higher and the polyunsaturated FA was lower in the animals fed PDOC (50.9 v. 48.3, SEM: 0.48, P < 0.001; 17.6 v. 19.3, SEM: 0.30, P < 0.001 in mg/100 g of Total FA, for PDOC and C animals, respectively). The initial pig slurry characterisation only showed differences in ADF concentration that was higher (P < 0.05) in the slurry from PDOC treatment. Regarding gas emission, slurries from both treatments emitted similar amounts of ammonia (NH3), carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O), as well as B0 values. The results obtained suggest that PDOC may be included in balanced pig diets at rates of up to 120 g/kg without negative effects on performance, carcass quality, gut microflora and slurry gas emission, while improving the MUFA concentration of subcutaneous fat.

Nitrogen use efficiency and nitrous oxide emissions from five UK fertilised grasslands.

Intensification of grasslands is necessary to meet the increasing demand of livestock products. The application of nitrogen (N) on grasslands affects the N balance therefore the nitrogen use efficiency (NUE). Emissions of nitrous oxide (N2O) are produced due to N fertilisation and low NUE. These emissions depend on the type and rates of N applied. In this study we have compiled data from 5 UK N fertilised grassland sites (Crichton, Drayton, North Wyke, Hillsborough and Pwllpeiran) covering a range of soil types and climates. The experiments evaluated the effect of increasing rates of inorganic N fertiliser provided as ammonium nitrate (AN) or calcium ammonium nitrate (CAN). The following fertiliser strategies were also explored for a rate of 320 kg N ha-1: using the nitrification inhibitor dicyandiamide (DCD), changing to urea as an N source and splitting fertiliser applications. We measured N2O emissions for a full year in each experiment, as well as soil mineral N, climate data, pasture yield and N offtake. N2O emissions were greater at Crichton and North Wyke whereas Drayton, Hillsborough and Pwllpeiran had the smallest emissions. The resulting average emission factor (EF) of 1.12% total N applied showed a range of values for all the sites between 0.6 and 2.08%. NUE depended on the site and for an application rate of 320 kg N ha-1, N surplus was on average higher than 80 kg N ha-1, which is proposed as a maximum by the EU Nitrogen Expert Panel. N2O emissions tended to be lower when urea was applied instead of AN or CAN, and were particularly reduced when using urea with DCD. Finally, correlations between the factors studied showed that total N input was related to Nofftake and Nexcess; while cumulative emissions and EF were related to yield scaled emissions.

Assessing ventilation rate measurements in a mechanically ventilated laying hen facility.

Gaseous emission in laying hen facilities affects animal production performance and the environment. Emission is ruled by gas concentration and ventilation rate (VR), which are the key parameters to estimate precise emission factors. In this work, VR were assessed in a mechanical ventilated laying hen facility under Mediterranean climate conditions. The study was performed during a complete production cycle from July 2015 to October 2016. Direct hot wire anemometer (HWA) and fan rotational speed methods, and indirect CO2 mass balance method were used to assess the VR. Mean VR was 5.3 ± 2.9 m3 h-1 hen-1 for the HWA method. The mean uncertainty of VR based on the HWA method was 8.5%, and it varied among ventilation stages from 2.3 to 12.8%. Uncertainty was higher in warm season (9.6%) than in cold season (5.4%). In relation to fan rotational speed method, mean VR was 5.9 ± 3.3 m3 h-1 hen-1, which accounts for 8.3% more than the HWA method. According to the results, the fan rotational speed method would be less sensitive than the HWA method for assessing VR. VR was 6.3 ± 2.1 m3 h-1 hen-1 for the CO2 balance method, which estimated lower VR values in warm season compared to the laser tachometer (LT) method (-5%) but higher values compared to the HWA method (+5%). In contrast, it estimated higher values in cold season compared to the HWA method (+23%) and LT method (+17%). Correlation analysis showed a strong correlation between the CO2 balance method and both direct methods (R = 0.85 and 0.86 for HWA and LT, respectively).

The influence of broiler activity, growth rate, and litter on carbon dioxide balances for the determination of ventilation flow rates in broiler production.

Carbon dioxide balances are useful in determining ventilation rates in livestock buildings. These balances need an accurate estimation of the CO(2) produced by animals and their litter to determine the ventilation flows. To estimate the daily variation in ventilation flow, it is necessary to precisely know the daily variation pattern of CO(2) production, which mainly depends on animal activity. The objective of this study was to explore the applicability of CO(2) balances for determining ventilation flows in broiler buildings. More specifically, this work aimed to quantify the amount of CO(2) produced by the litter, as well as the amount of CO(2) produced by the broilers, as a function of productive parameters, and to analyze the influence of broiler activity on CO(2) emissions. Gas concentrations and ventilation flows were simultaneously measured in 3 trials, with 1 under experimental conditions and the other 2 in a commercial broiler farm. In the experimental assay, broiler activity was also determined. At the end of the experimental trial, on the day after the removal of the broilers, the litter accounted for 20% of the total CO(2) produced, and the broilers produced 3.71 L/h of CO(2) per kg of metabolic weight. On the commercial farm, CO(2) production was the same for the 2 cycles (2.60 L/h per kg of metabolic weight, P > 0.05). However, substantial differences were found between CO(2) and broiler activity patterns after changes in light status. A regression model was used to explain these differences (R(2) = 0.52). Carbon dioxide increased with bird activity, being on average 3.02 L/h per kg of metabolic weight for inactive birds and 4.73 L/h per kg of metabolic weight when bird activity was highest. Overall, CO(2) balances are robust tools for determining the daily average ventilation flows in broiler farms. These balances could also be applied at more frequent intervals, but in this case, particular care is necessary after light status changes because of discrepancy between animal activity and CO(2) production.

Characterization of gas emissions from a Mediterranean broiler farm.

Gas emissions from broiler production have been the subject of intensive research. However, little experimental information exists for farms under the particular management and environmental conditions of the European Mediterranean area. In this study, ammonia, carbon dioxide, methane, and nitrous oxide concentrations and emissions were measured in a commercial broiler farm located in Spain. Gas concentrations were measured using a photoacoustic gas monitor, whereas the ventilation flow was evaluated by controlling the operation status of each fan. Two rearing periods were studied, one in summer and one in winter. All gas emissions increased with bird age. Ammonia emission rates averaged 19.7 and 18.1 mg/h per bird in the summer and winter, respectively, and increased with indoor temperature (r(2) = 0.51 in summer; r(2) = 0.42 in winter). Average CO(2) emission rates were 3.84 and 4.06 g/h per bird, CH(4) emission was 0.44 and 1.87 mg/h per bird, and N(2)O emission was 1.74 and 2.13 mg/h per bird in summer and winter, respectively. A sinusoidal daily variation pattern was observed in all emissions except for CH(4). These patterns were characterized in terms of time of maximum emission and amplitude of the daily variation.

The influence of the lighting program on broiler activity and dust production.

Among the factors influencing dust production on the farms, animal activity is probably the least studied. Animal activity is strongly affected by circadian rhythms and it is altered by the rearing conditions, especially the management of light and the feeding strategy. In this study, a broiler flock was evaluated until 35 d of age with the general objective of studying the factors influencing the production of dust, particularly the effect of animal activity, as affected by the lighting program. In an experimental room, 2 daily dark periods of 6 and 4 h with 158 birds divided in 12 groups, reared on wood shavings, were evaluated. A TEOM analyzer was used to measure dust concentrations, whereas animal activity was determined by observation of birds on video tapes. Animal activity was defined by an activity index, which was determined by direct evaluation of birds on video tapes. The animal activity index was closely related to the lighting program (0.084 and 0.556 during dark and light periods, respectively) and was maximum at wk 4 of the rearing period. The dust concentrations during light periods were on average 4 times higher than during dark periods, with a maximum average concentration of 2.82 mg x m(-3) during the last week of the cycle. Particulate matter emission was on average 2.08 mg x animal(-1) x hour(-1). Dust concentration increased linearly with bird weight and daily variations in dust production were characterized. As a result, a direct cause-effect relationship between animal activity and dust concentration was obtained (r(2) = 0.89).

[Acute precordial pain: 100 cases in 3 years]. / Dolor precordial agudo: 100 casos en 3 años.

OBJECTIVE: To find the effectiveness of diagnoses of acute precordial pain seen as an emergency at our centre. DESIGN: Observational, descriptive and retrospective study. SETTING: Urban primary care centre. PATIENTS: The 100 most recent patients who attended as an emergency with their first episode of acute precordial pain were included. STUDY PERIOD: December 1994 to March 1998. Home visits, patients without medical records and those seen on repeated attendance for precordialgia were excluded. MEASUREMENTS AND MAIN RESULTS: The emergency diagnosis and the diagnosis recorded afterwards in the clinical history of 100 people with acute precordialgia, aged 54.9 (16.7 years; 56% [n = 56] women), were gathered. Ischaemic cardiopathy (41%, n = 41) and mechanical precordialgia (36%, n = 36) were the most common initial diagnoses. We found 66.6% sensitivity and 81.4% specificity in the detection of ischaemic cardiopathy. The proportion of diagnostic errors was not linked to the pathological history of anxiety, ischaemic cardiopathy or oesophageal disease. CONCLUSIONS: 41% of precordialgias are diagnosed as presumably ischaemic and are potentially serious, although only 50% of them are confirmed as such. Our sensitivity in their diagnosis is comparable to that of other studies.

Dolor precordial agudo: 100 casos en 3 años / Acute precordial pain: 100 cases in three years

Objetivo.Conocer la efectividad diagnóstica frente al dolor precordial agudo atendido de urgencias en nuestro centro. Diseño. Estudio observacional, descriptivo y retrospectivo. Emplazamiento.Centro urbano de atención primaria. Pacientes. Se incluyeron los 100 últimos pacientes que acudieron de urgencias con el primer episodio de dolor precordial agudo. Período de estudio: diciembre de 1994 a marzo de 1998. Se excluyeron las visitas domiciliarias, los pacientes sin historia clínica y los atendidos en visitas sucesivas por precordialgia. Mediciones y resultados principales.Se recoge el diagnóstico en urgencias y el registrado a posteriori en la historia clínica de 100 sujetos con precordialgia aguda, de edad 54,9 ñ 16,7 años, 56 de ellos mujeres (56 por ciento). La cardiopatía isquémica y la precordialgia mecánica fueron los diagnósticos iniciales más frecuentes (41 por ciento [n = 41] y 36 por ciento [n = 36], respectivamente). Tenemos una sensibilidad del 66,6 por ciento y una especificidad del 81,4 por ciento para la detección de cardiopatía isquémica. La proporción de errores diagnósticos no se asociaba a los antecedentes patológicos de ansiedad, cardiopatía isquémica o esofágica. Conclusiones.Un 41 por ciento de las precordialgias son de presunto diagnóstico isquémico y potencialmente graves, aunque sólo llegan a confirmarse como tales el 50 por ciento de ellas. Nuestra sensibilidad para su diagnóstico es comparable a la de otros estudios (AU)

Identification of a signaling pathway activated specifically in the somatodendritic compartment by a heparan sulfate that regulates dendrite growth.

In two earlier reports we demonstrated that natural heparan sulfate, but not dermatan or chondroitin sulfate glycosaminoglycans, stimulate axonal elongation and inhibit dendrite growth in vitro (Lafont et al., 1992). The latter specific effect on dendrite elongation was reproduced by chemically synthesized heparan sulfates and by SR 80037A, a purified sulfated and hexanoylated heparin fragment (Lafont et al., 1994). Adding radioactive SR 80037A to purified neurons demonstrated the existence, at the neuronal surface, of heparan sulfate-specific and saturable binding sites, suggesting that SR 80037A activates specific signal transduction pathways. In the present study, using rat or mouse neurons from the embryonic cortex, we show that SR 80037A signaling involves one or several G-coupled receptor or receptors, small GTPases rhoA and/or rhoC, and one or several PKCs. We also demonstrate that the rapid soma rounding elicited by SR 80037A does not require protein synthesis but that the long-term effect on dendrite initiation requires protein synthesis in a short period after the addition of the heparan sulfate. Finally, by preparing membranes from the somatodendritic or axonal compartments we demonstrate that the identified signaling pathway is activated by SR 80037A primarily in the somatodendritic compartment and is not sensitive to the addition of a dermatan sulfate glycosaminoglycan that does not induce the axonal phenotype by impairing dendrite initiation and elongation.

Stimulation and recording from regenerated peripheral nerves through polyimide sieve electrodes.

This paper describes the use of a new polyimide sieve electrode as a chronic neural interface to stimulate and record signals from regenerated peripheral nerves. Flexible thin polyimide electrodes were placed in silicone chambers and implanted between the severed ends of the sciatic nerve in rats. The sieve part of the interface has 281 round via holes of 40 microns diameter, with seven integrated recording-stimulating electrodes arranged around via holes. Axonal regeneration through the via holes was demonstrated by histological and physiological methods over a two to six month post-implantation period in all the rats. The regenerated nerves were organized in fascicles corresponding to the grid pattern of the via holes. Longitudinal sections showed myelinated fibers, with normal appearance and well developed myelin sheath, crossing the via holes. Stimulation of the regenerated nerve through the polyimide electrode evoked distal muscle and nerve responses similar in amplitude to those evoked by nerve stimulation with hook metal electrodes. The polyimide electrodes were useful for recording nerve action potentials in response to electrical stimulation of the distal regenerated nerve, and in response to functional sensory stimulation of several modalities.

Association of Engrailed homeoproteins with vesicles presenting caveolae-like properties.

We report here that the homeoproteins Engrailed-1 and Engrailed-2 are present in specific non-nuclear subcellular compartments. Using electron microscopy, we observed that chick-Engrailed-2 expressed in COS-7 cells associates with membrane fractions that are characterized as caveolae. This characterization is based on morphological, biochemical and immunological criteria such as, in particular, the absence of clathrin coat and the presence of caveolin and cholera toxin-binding sites. These data are fully confirmed by subcellular fractionation experiments, which demonstrate that transfected chick-Engrailed-2 is present in low density membrane fractions that are resistant to Triton X-100, enriched in caveolin and solubilized by the addition of a cholesterol-binding detergent, a set of properties highly characteristic of caveolae. The association of Engrailed-2 with specific membrane fractions observed after transfection in COS-7 cells is also observed for endogenous Engrailed-1 and Engrailed-2 expressed at late embryonic stages in the cerebellum and posterior mesencephalon of the rodent. Indeed, the two proteins are present in membrane fractions that bear all the characteristics of microdomains or caveolae-like domains, i.e. Triton X-100 resistance, saponin solubilization, low density on sucrose gradients, enrichment in glycosphingolipid GM1, absence of transmembrane Neural Cell Adhesion Molecule, presence of the glypiated (GPI-anchored) glycoprotein F3/F11 and of the acylated growth-associated protein GAP-43. Finally we demonstrate that part of the membrane-associated Engrailed, either expressed in COS-7 cells or endogenously present in neural tissues, is not accessible to proteolytic enzymes unless the membranes have been permeabilized with detergent. This study suggests that, in addition to their well-known presence in the nucleus, Engrailed proteins are also associated with caveolae-like vesicles that are primarily transported anterogradely into the axon, and that they can get access to a compartment compatible with secretion.

Cell internalization of the third helix of the Antennapedia homeodomain is receptor-independent.

We have recently reported that a 16-amino acid long polypeptide corresponding to the third helix of the DNA binding domain (homeodomain) of Antennapedia, a Drosophila transcription factor, is internalized by cells in culture (Derossi, D., Joliot, A. H., Chassaing, G., and Prochiantz, A.(1994) J. Biol. Chem. 269, 10444-10450). The capture of the homeodomain and of its third helix at temperatures below 10 degrees C raised the problem of the mechanism of internalization. The present demonstration, that a reverse helix and a helix composed of D-enantiomers still translocate across biological membranes at 4 and 37 degrees C strongly suggests that the third helix of the homeodomain is internalized by a receptor-independent mechanism. The finding that introducing 1 or 3 prolines in the structure does not hamper internalization also demonstrates that the alpha-helical structure is not necessary. The data presented are compatible with a translocation process based on the establishment of direct interactions with the membrane phospholipids. The third helix of the homeodomain has been used successfully to address biologically active substances to the cytoplasm and nucleus of cells in culture (Théodore, L., Derossi, D., Chassaing, G., Llirbat, B., Kubes, M., Jordan, P., Chneiweiss, H., Godement, P., and Prochiantz, A.(1995) J. Neurosci. 15, 7158-7167). Therefore, in addition to their physiological implications (Prochiantz, A., and Théodore, L.(1995) BioEssays 17, 39-45), the present results open the way to the molecular design of cellular vectors.

Peripheral nerve regeneration through microelectrode arrays based on silicon technology.

This paper describes some developments, made to obtain a chronic neural interface to record signals from regenerated peripheral nerves. Microperforated silicon dices, fabricated by techniques compatible with CMOS processes, were coupled in silicone nerve chambers and implanted between the severed ends of peripheral nerves in rats. Three configurations of perforated dices with 25 via-holes of 100 µm diameter, 121 via-holes of 40 µm and 400 via-holes of 10 µm were assessed. The feasibility of axonal regeneration through the dices via-holes was proved by histological and physiological methods over 3 months post-implantation. The regenerated nerves were organized in fascicles corresponding to the grid pattern of the via-holes. However, nerve regeneration was difficult and distal re-innervation delayed with respect to simple tubulization repair. The size of the via-holes and the total open area are determinants of the degree and quality of regeneration. Further improvements are needed in both the microelectrode dice design and in neurobiological stimulation of regeneration.

[Methodological considerations concerning peripheral nerve morphometry]. / Consideraciones metodológicas acerca de la morfometría de nervio periférico.

Morphometric studies of the peripheral nerve often present widely varying results which, in part at least, may be attributed to the different methodologies used. Two questions may be of importance with regard to the reliability of such results: the preselection of fibres according to their morphology and the method used in quantifying observations. In this work a morphological study was carried out on the myelinated fibres of the sciatic nerve of a rat in order to evaluate fibre selection criteria. A morphometric analysis was also performed using manual measurements, image digitalisation and surveying, and automatic image analysis. It was shown that morphological variability of transverse section fibres is considerable and that, really, the proportion of circular fibres with homogeneous compact myelin is only 50 to 70%, from which we can conclude that the selection of fibres carried out in some studies wishing to eliminate abnormal fibres is somewhat exaggerated. By analysing the fibres using various methods significant differences appear, some due to the fact that distinct methods may be used to calculate the same parameters in a different way. The most reliable parameters would appear to be those which do not depend on the shape of the fibres and those which automatic or semiautomatic methods can calculate directly such as areas and perimeters. In any case quantifying methods seem hardly discriminatory and the differences between methods disappear if analyses are carried out using random samples. Preselection of fibres appears unnecessary in this context as in no case are the results altered. Finally we suggest finishing quantitative analyses with qualitative studies which would permit getting more information especially useful in cases of ageing, regeneration or pathological studies.

Enzymatic synthesis of X-Phe-Leu-NH2 in low water content systems: influence of the N-alpha protecting group and the reaction medium composition.

The influence of eight different N-terminal protecting groups (For, Ac, Boc, Fmoc, Mal, Pheac, Aloc and Z) on the alpha-chymotrypsin-catalyzed synthesis of the dipeptide derivative X-Phe-Leu-NH2 in organic media was studied. Groups such as Ac, For, Boc, Z, Mal, Pheac and Alloc always rendered good peptide yields (92% to 99%) either in acetonitrile or in ethyl acetate. Good correlations were found between molecular and physico-chemical characteristics of the N-alpha moiety such as the hydrophobicity (log P), ovality and dipole moment and the global reaction rate parameter k'. High k' values were obtained with the less hydrophobic groups, Ac, For and Mal, that have ovality values close to one and the highest dipole moments. Furthermore, it was found that the relative rate of hydrolysis and aminolysis of the acyl-enzyme intermediate expressed as the partition parameter p is affected by the N-alpha moiety of the acyl donor. Correlations between this parameter and the dipole moment of the protecting group were observed.

Racemization free coupling of peptide segments. Synthesis of an insect neuropeptide.

The total synthesis of the insect neuropeptide derivative Z-Gly-Gly-Ser-Leu-Tyr-Ser-Phe-Gly-Leu-NH2 has been carried out by a convergent solid phase strategy. For the coupling of the N-terminal pentapeptide to the C-terminal tetrapeptide, three different methods were assayed. Racemization of the acyl activated amino acid during the fragment condensation reaction was monitored by HPLC. Best results were obtained by enzymatic coupling in a low water containing media using adsorbed alpha-chymotrypsin. An optically pure product was obtained in 82% yield after 1 h of reaction. Chemical methods such as DIC/HOBt and BOP/HOBt/NMM always rendered highly optically impure products containing 10-20% of the D-epimer.

Application of empirical design methodologies to the study of the influence of reaction conditions and N-alpha-protecting group structure on the enzymatic X-Phe-Leu-NH(2) dipeptide synthesis in buffer/dimethylformamide solvents systems.

The influence of five different N-terminal protecting groups (For, Ac, Boc, Z, and Fmoc) and reaction conditions (temperature and dimethylformamide content) on the alpha-chymotrypsin-catalyzed synthesis of the dipeptide derivative X-Phe-Leu-NH(2) was studied. Groups such as For, Ac, Boc, and Z always rendered good peptide yields (82% to 85%) at low reaction temperatures and DMF concentrations, which depended on the N-alpha protection choice. Boc and Z were the most reactive N-alpha groups and, in addition, the most suitable for peptide synthesis. On the other hand, the use of empirical design methodologies allowed, with minimal experimentation and by multiple regression, to deduce an equation, which correlates the logarithm of the first order kinetic constant (log k') with reaction temperature, DMF concentration, and hydrophobicity (log P values) of the different protecting groups. The predictive value of the equation was tested by comparing the performance of another protective group, such as Aloc, with the performance predicted by said equation. Experimental and calculated k' values were found to be in good agreement.

Effects of L-asparaginase on rat embryonic development and yolk sac membrane in vitro.

A comparative analysis of the teratogenic effects of L-asparaginase on 10.5- and 11.5-day rat embryos after 24 and 48 hours of exposure in vitro, respectively, were performed. Several medium concentrations of L-asparaginase (0.05, 0.25, and 1.5 IU/ml) were tested in both embryo series. Resulting embryos were submitted to morphological studies in a search for a specific route of pathogenesis. Morphological alterations of the visceral yolk sac were also studied to investigate its contribution to L-asparaginase teratogenicity in rats. Main embryonic malformations (open truncal neural tube, open encephalic vesicles, anophthalmia, lack of inversion, abnormal frontolateral protrusions, great vascular dilations at the cephalic level) and developmental retardation were already generated after the first 24 hours of culture (embryos of 10.5 days) and presented a dose-response relationship. Vascular dilations and neurulation disturbances seemed to be related to an early mesenchyme deficiency. Reduced number of mesenchymal cells was more evident in embryos of 10.5 days than those of 11.5 days, suggesting the existence of a later compensatory mechanism of cellular proliferation in the older embryo. Visceral yolk-sac endodermal cells at both embryonic stages were greatly deformed and enlarged by an increase of the high electron-dense vacuolar system. Therefore, both a blockage of the processes of lysosomal digestion and derived trophic deficiencies probably existed. A double teratogenic mechanism for L-asparaginase is postulated: a direct action mainly in younger embryos (before invagination of the embryo into the yolk sac) and a yolk sac-mediated one.