Influence of forage source and forage inclusion level on growth performance, feeding behavior, and carcass characteristics in finishing steers.

Two experiments were conducted to determine the effects of forage source (Exp. 1) and forage inclusion level (Exp. 2) in finishing diets on growth performance and feeding behavior. In Exp. 1, sixty-four steers (394 ± 3.6 kg BW) were allotted by BW to 3 pens. Within each pen, steers were assigned randomly to 1 of 4 dietary treatments containing different forage sources: 1) alfalfa hay, 2) corn silage, 3) wheat straw, and 4) corn stover. Alfalfa hay was provided at 10% of the diet DM and the other forage sources were offered to provide the same percentage of NDF from forage. In Exp. 2, forty-four steers (451 ± 4.6 kg BW) were used in a completely randomized design and were fed dry-rolled corn-based diets containing a mixture of hay and corn silage as the forage source at 5%, 10%, 15%, or 20% forage (DM basis). Intake and feeding behavior traits were calculated from data generated by the Insentec feeding system. In Exp. 1, final BW, ADG, and G:F did not differ between treatments. Dry matter intake and feeding behavior traits responded differently depending on week (interaction ≤ 0.04) of the experiment with DMI generally greater in steers fed alfalfa or corn silage early in the experiment and time per meal generally greater and eating rate slower in steers fed diets containing wheat straw or corn stover. In Exp. 2, ADG and G:F decreased linearly ( < 0.001) with increasing forage inclusion. Quadratic effects ( ≤ 0.002) were observed for eating time (per visit, meal, and d) and DMI (per visit, meal, and min) with eating time greatest in the 10% forage treatment and DMI the least in the 20% forage treatment. Dry matter intake per d responded differently depending on week (interaction = 0.01) with some weeks exhibiting linear and other quadratic effects that were primarily the result of the largest decrease in DMI in the 20% forage inclusion treatment. These data indicate that growth performance was not influenced by forage source, when fed at a similar NDF inclusion level, but was negatively impacted by increasing forage inclusion in high-concentrate finishing diets. However, both forage source and inclusion level impacted feeding behavior as cattle consuming bulkier forages (wheat straw or corn stover) or at greater inclusion levels typically had a slower eating rate and took longer to consume a meal. Additionally, DMI may decrease at greater forage inclusion levels (> 15%).

Influence of limit-feeding and time of day of feed availability to growing calves on growth performance and feeding behavior in cold weather.

Objective swere to determine the effects of limit-feeding and time of feed access in cold weather on growth performance and feeding behavior of growing calves fed a corn silage-based diet. Sixty-six steers (BW = 317 ± 5.3 kg) and 30 heifers (BW = 239 ± 7.6 kg) were assigned randomly to dietary treatment: 1) ad libitum feed intake (AL), 2) limit-fed to 80% of the average DMI of the AL group on a BW basis in the daytime (0601-1759 h; LF-D), 3) limit-fed to 80% of the average DMI of the AL group on a BW basis in the nighttime (1800-0559 h; LF-N), and 4) limit-fed to 80% of the average DMI of the AL group on a BW basis, split 1/2 in the daytime and 1/2 in the nighttime (LF-S). Feed intake and feeding behavior were monitored over 84 d using the Insentec feeding system. Average daily gain, DMI, and G:F were greater ( ≤ 0.002) in the AL group compared with others. Dry matter intake was not different ( = 0.17) when comparing the LF-D with the LF-N groups. Average daily gain and G:F were greater ( ≤ 0.05) when comparing the LF-N group to the LF-D group, and were not different ( ≥ 0.51) when comparing the LF-S group with the mean of the LF-D and LF-N groups. Number of visits and meals per d was greater ( ≤ 0.001) in the LF-N than the LF-D group. Feed intake per visit was not different ( = 0.55) when comparing the AL group and others, and tended to be greater ( = 0.06) in the LF-D than the LF-N group. Feed intake per meal was greater ( < 0.001) when comparing the AL group with others, and the LF-D with the LF-N group. Feed intake per minute (eating rate) was not influenced by treatment. In conclusion, limit-feeding at 80% of ad libitum intake decreased ADG and G:F. Limit-feeding in the nighttime as compared to limit-feeding in the daytime improves growth performance and increases feeding activity (number of visits and meals per d) which could be because of increased heat production to help maintain body temperature and thus reduce maintenance energy requirements.

Modulation of the transient outward current (Ito) in rat cardiac myocytes and human Kv4.3 channels by mefloquine.

The antimalarial drug mefloquine, is known to be a potassium channel blocker, although its mechanism of action has not being elucidated and its effects on the transient outward current (Ito) and the molecular correlate, the Kv4.3 channel has not being studied. Here, we describe the mefloquine-induced inhibition of the rat ventricular Ito and of CHO cells co-transfected with human Kv4.3 and its accessory subunit hKChIP2C by whole-cell voltage-clamp. Mefloquine inhibited rat Ito and hKv4.3+KChIP2C currents in a concentration-dependent manner with a limited voltage dependence and similar potencies (IC50=8.9µM and 10.5µM for cardiac myocytes and Kv4.3 channels, respectively). In addition, mefloquine did not affect the activation of either current but significantly modified the hKv4.3 steady-state inactivation and recovery from inactivation. The effects of this drug was compared with that of 4-aminopyridine (4-AP), a well-known potassium channel blocker and its binding site does not seem to overlap with that of 4-AP.

Effects of alternate-day feeding of dried distiller's grain plus solubles to forage-fed beef cows in mid- to late gestation.

Forty-six nonlactating beef cows were used to examine effects of dried distiller's grains plus solubles (DG) supplementation strategies to cows fed grass hay during mid- to late gestation on BW, ultrasound body composition characteristics, concentrations of serum NEFA and urea, feeding behavior, and calf birth weight. Cows were assigned to dietary treatments in a completely randomized design: 1) control, where hay was fed each day of the week (CON), 2) both hay and DG fed daily during the week (DG7), 3) hay fed daily but DG fed 3 d of the week (DG3), and 4) hay fed 4 d of the week alternating with DG fed on the remaining 3 d (DGA). Hay was offered ad libitum on days it was fed. The DG were fed at 0.40% of BW when offered daily and 0.93% of BW when offered 3 d per week (Monday, Wednesday, and Friday). Feed intake was monitored continuously over the 84-d feeding period. Hay intake and total DMI were reduced (P < 0.05) in DGA compared with DG7 and DG3. Gain and G:F were decreased (P < 0.05) for CON compared with other treatments. No differences (P > 0.05) were observed among treatments for change in BCS, intramuscular fat, rib fat, or rump fat from d 1 to 84. On a day when DG7, DG3, and DGA all received DG (Friday), DGA had reduced (P < 0.05) concentrations of urea compared with DG3 and DG7. On a day when only DG7 received DG (Saturday), urea was greater (P < 0.01) for DG3 and DGA compared with DG7, and concentrations of NEFA were greater (P < 0.01) in CON and DGA compared with DG7. On the second consecutive day when only DG7 received DG (Sunday), concentrations of NEFA were less (P < 0.001) for DG7 compared with other treatments. On days when all cows received hay, DGA spent more time eating (P < 0.05) compared with DG7 and DG3. Cows fed DGA had greater (P < 0.05) hay intake per meal and time per meal compared with other treatments. On days when DG7, DG3, and DGA all received DG, cows in the DG3 and DGA treatments had greater (P < 0.05) number of DG meals, time spent eating, intake per meal, and time per meal but a slower (P < 0.05) rate of DG intake compared with DG7. No differences (P > 0.05) were observed in calf birth weights among treatments. The alternate-day feeding strategy reduced hay and total intake, altered concentrations of serum urea and NEFA, and altered feeding behavior compared with other supplementation methods.

Influence of dry-rolled corn processing and increasing dried corn distillers grains plus solubles inclusion for finishing cattle on growth performance and feeding behavior.

Sixty-four yearling steers (345 ± 4.2 kg BW) were used to study the effects of degree of dry-rolled corn processing and corn dried distillers grains plus solubles (DDGS) inclusion on feeding and ruminating behavior, G:F, and carcass characteristics. Steers were assigned randomly to 1 of 4 experimental treatments (n = 16 per treatment): 1) coarse-rolled (2.68 mm) corn and 20% DDGS, 2) coarse-rolled corn and 40% DDGS, 3) fine-rolled (1.46 mm) corn and 20% DDGS, and 4) fine-rolled corn and 40% DDGS. Final BW and ADG were not affected by corn processing or DDGS. Dry matter intake (kg/d and % of BW) decreased (P < 0.001) and G:F increased (P < 0.001) with increasing inclusion of DDGS. Meal number increased (P ≤ 0.05) and meal size decreased (P < 0.001) with finer dry-roll corn processing and with increasing inclusion of DDGS. Drinking time decreased (P = 0.03) with finer dry-rolled corn processing and tended to increase (P = 0.06) with increased inclusion of DDGS. Rumination time while standing decreased (P = 0.03) with increased inclusion of DDGS. Increasing inclusion of DDGS from 20 to 40% decreased intake, increased G:F, and altered feeding behavior of finishing steers consuming a 90% concentrate diet without affecting carcass quality. Increasing the degree of dry-roll corn processing did not impact growth performance and did not interact with increasing inclusion of DDGS in finishing diets.

Influence of supplementation with corn dried distillers grains plus solubles to growing calves fed medium-quality hay on growth performance and feeding behavior.

To determine the effect of increasing supplementation of corn dried distillers grains plus solubles (DDGS) on growth performance and feeding behavior, 70 steer calves (287 ± 10 kg of BW) were blocked by BW to 3 pens equipped with Insentec feeders. For 84 d, calves were fed medium-quality grass/legume hay offered for ad libitum intake and provided 1 of 3 dietary supplemental treatments (n = 7 or 8 steers per treatment within each pen; n = 23 or 24 per treatment): 1) nothing, 2) DDGS at 0.5% of BW daily (DM basis), and 3) DDGS at 1% of BW daily (DM basis). Hay intake (kg/d and % of BW daily) decreased linearly (P < 0.001) as DDGS supplementation increased. Total DMI (kg/d and % of BW) increased linearly (P < 0.001) with DDGS supplementation. Average daily gain and gain efficiency (G:F) responded quadratically (P ≤ 0.006) as G:F increased to a lesser extent when DDGS supplementation increased from 0.5 to 1% than from 0 to 0.5%. Meals (number per day) and time eating per meal for hay and total diet decreased linearly (P ≤ 0.006) with increasing DDGS supplementation. Time eating per day for hay responded quadratically (P < 0.001) and decreased to a greater extent when increasing from 0 to 0.5% DDGS supplementation than from 0.5 to 1% DDGS. Feed intake per minute (eating rate) for hay and total diet increased linearly (P ≤ 0.05) with increasing DDGS supplementation. On d 84, LM area, back fat thickness, and rump fat thickness increased linearly (P ≤ 0.006) with increasing DDGS supplementation. There were significant day × treatment interactions (P < 0.001) for plasma glucose and urea-N concentrations. Glucose did not change over the feeding period in control steers but increased in both supplemented groups. Urea-N decreased for control steers over the feeding period whereas urea-N increased in supplemented steers. In conclusion, supplementation of DDGS in amounts of 0.5 or 1% of BW daily can be used to reduce hay intake and improve ADG and G:F in growing steers fed medium-quality hay. Additionally, DDGS supplementation alters feeding behavior.

Effect of corn dry distiller grains plus solubles supplementation level on performance and digestion characteristics of steers grazing native range during forage growing season.

Two experiments were conducted to evaluate effects of corn dry distiller grains plus condensed solubles (DDGS) supplementation level on performance digestion characteristics of steers grazing native range during the forage growing season. In the performance study, 72 (206 ± 23.6 kg; 2008) and 60 (230 ± 11.3 kg; 2009) English crossbred steer calves were used in a randomized complete block design replicated over 2 yr. The grazing periods lasted 56 and 58 d and started on August 11 and 18 for 2008 and 2009, respectively. Each year, steers were blocked by BW (light, medium, and heavy), stratified by BW within blocks, and randomly assigned to 1 of 4 grazing groups. Each grazing group (6 steers in 2008 and 5 in 2009) was assigned to a DDGS supplementation levels (0, 0.2, 0.4, and 0.6% BW). Grazing group served as the experimental unit with 12 groups per year receiving 1 of 4 treatments for 2 yr (n = 6). In the metabolism study, 16 English crossbred steers (360 ± 28.9 kg) fitted with ruminal cannulas grazing native range during the summer growing season were used in a completely randomized design to evaluate treatment effects on forage intake and digestion. The experiment was conducted during the first and second weeks of October 2008. Steers were randomly assigned to supplement level (0, 0.2, 0.4, and 0.6% BW; n = 4) and grazed a single native range pasture with supplements offered individually once daily at 0700 h. In the performance study, ADG (0.64, 0.75, 0.80, and 0.86 ± 0.03 kg/d for 0, 0.2, 0.4, and 0.6% BW, respectively) increased linearly (P = 0.01) with increasing DDGS supplementation level. In the metabolism study, forage OM, NDF, CP, and ether extract (EE) intake decreased (P ≤ 0.05) linearly with increasing DDGS supplementation level. Total CP and EE intake increased (P ≤ 0.002) with increasing DDGS supplementation level. Digestibility of OM, NDF, and EE increased (linear; P ≤ 0.008) whereas the soluble CP fraction of forage masticate sample linearly increased (P = 0.01) and slowly degradable CP fraction linearly decreased (P = 0.05) with increasing DDGS supplementation level. Forage in situ masticate DM and NDF disappearance rate decreased (quadratic; P ≤ 0.05) and DDGS in situ DM disappearance rate increased (linear; P = 0.03) with increasing supplementation levels. These results indicate that DDGS supplementation enhanced grazing performance and total-tract digestion of steers grazing native range during the forage growing season.

Effect of supplementation of dried distillers grains with solubles on forage intake and characteristics of digestion of beef heifers grazing small-grain pasture.

Sixteen ruminally cannulated, English-crossbred heifers (378 ± 28.4 kg) grazing small-grain pasture (SGP) were used in a completely randomized design to evaluate effects of supplementing different amounts of corn dried distillers grains with solubles (DDGS; 0, 0.2, 0.4, and 0.6% of BW; as-fed basis) on forage intake, digestibility, and rumen fermentation characteristics. The experiment was conducted from April 6 through April 20, 2007. Heifers grazed in a single SGP with supplements offered individually, once daily at 0700 h. Forage and total OM, CP, and NDF intake were not affected (P ≥ 0.21) by DDGS amount. Digestibility of NDF and ether extract (EE) increased linearly (P < 0.001) when heifers consumed more DDGS. Intake of DM (kg/d and g/kg of BW), ruminal volume (L), fluid dilution rate (%/h), fluid flow rate (L/h) turnover time (h), and particle dilution rate (SGP and DDGS) were not affected (P ≥ 0.32) by increasing DDGS supplementation amount. In situ DDGS CP kinetic parameters were not affected (P ≥ 0.25) by increasing DDGS supplementation amount. Forage masticate in situ soluble CP fraction and CP effective degradability increased quadratically (P = 0.01) with increasing DDGS supplementation amount. However, amount of DDGS did not affect forage masticate CP slowly degradable fraction (%; P = 0.39) or degradation rate (%/h; P = 0.63). Rate of in situ disappearance (%/h) for DDGS DM (P = 0.94), forage masticate DM (P = 0.89), and NDF (P = 0.89) were not affected by DDGS supplementation amount, nor was rumen undegradable intake protein (% of CP) for DDGS (P = 0.28) and forage masticate samples (P = 0.93). Ruminal concentration of VFA and ammonia and ruminal pH were not affected (P ≥ 0.21) by increasing DDGS amount. Results indicated that DDGS can be used in SGP supplements without negatively affecting forage intake, digestibility, or ruminal fermentation.

Seroprevalence of and risk factors for infectious bovine rhinotracheitis in beef cattle herds of Yucatan, Mexico.

The main objective of this cross-sectional study was to estimate the seroprevalence of infectious bovine rhinotracheitis (IBR) in a population of non-vaccinated beef cattle in the livestock region of Yucatan, Mexico and to determine potential risk factors related to the seroprevalence. Also, we estimated the intraherd correlation (r(e)) and design effect (D) of IBR seropositivity. Cattle were selected by two-stage cluster sampling. Blood samples were collected from 564 animals from 35 herds. Sera were tested for antibodies against IBR using the serum-neutralisation test. Information regarding the herd and each animal sampled were recorded through a personal interview with the farmer or farm manager. The data were analysed using fixed-effects logistic multiple regression. Thirty-four of the 35 herds had at least one seropositive animal. The animal true seroprevalence was 54.4%. Animals in large herds or in production had higher odds of seropositivity than those in small herds or growing. The r(e) and D were 0.17 and 3.62, respectively.

Characterization of lesions caused by a South American virulent isolate ('Quillota') of the hog cholera virus.

In this study, macroscopic and histopathological lesions produced by a virulent South American isolate ('Quillota') of hog cholera virus were studied. The virus was inoculated in doses of 10(5)TCID50 in each of 35 pigs of 20 kg live weight. The animals were slaughtered from 4 to 18 days post-inoculation. The presence of virus antigens in lymphatic tissue was confirmed by both direct immunofluorescence and Avidin-Biotin-Peroxidase techniques in formalin-embedded tissue samples. Histological sections were stained with haematoxylin-eosin and Mallory's phosphotungstic acid haematoxylin methods. The 'Quillota' isolate used in this study caused a disease characterized by vascular lesions (splenic infarcts, haemorrhages in the lymph nodes and the urinary system and disseminated microthrombosis), and necrosis of lymphocytes, particularly in the B-areas of the lymphoid organs, lesions that are characteristic of the acute form of the disease. Other lesions observed were a non-purulent meningoencephalitis, the necrosis of the epithelial cells of tonsils, the presence of fibrin nets in the red pulp and a marked thickening of the alveolar septa.

Effects of winter supplementation and antiparasite treatment on the productive performance of milk herd in the central-south region of Chile.

During the winter of 1994, a survey of productive and reproductive parameters was undertaken in the south-central part of Chile (8th Region) on 71 cows provided by four small farms with low production (< 3000 l/year). A low food intake was recorded (8.6 +/- 0.2-12.4 +/- 0.2 kg DM/day) and, as a result, the cows calved with poor body condition score (1.9 +/- 0.04 points on the scale of one-to-five, had milk production between 10.5 +/- 0.4 and 12.8 +/- 0.6 l/day, had a delayed start of ovulatory activity (78.2 +/- 4.6 days) and an interval between calving and conception of 120.3 +/- 4.6 days. In addition, low levels of packed cell volume (PCV) and hemoglobin (HEM) were found, which were considered to be a combined effect of low feed ingestion and parastic infection by Fasciola hepatica. To improve the productive and reproductive parameters, treatments were undertaken in three of the four small farms; a parasiticide treatment was used against the F. hepatica at the beginning of the winter and the availability of forage was increased via the use of supplementary green oats. Spring crops were also cultivated: corn for silage and oats with peas to make hay. The antiparasite treatment and supplementation of forage was associated with better body condition score at calving, improved hematological parameters, increased milk production (17%), reduced number of days to conception (120 vs. 91) and increased conception rate at first service (36 vs. 60%). In the fourth small farm where no interventions were undertaken, the parameters obtained during 1994 remained unchanged.

Bioterapia del hepatoma de Novikoff con DNA politimidílico / Biotherapy of Novikoff's hepatoma with thymidilic DNA

Con el propósito de investigar una nueva forma de bioterapia nosotros exploramos el tratamiento del hepatoma de Novikoff con DNA que sintetiza RNA mensajero (mRNA). Para trasmitir permanentemente esta información en las células de hepatoma de Novikoff, se decidió usar DNA politimidílico (DNA poli T). La extracción de DNA poli T y de mRNA de hígado y de bazo de ratas normales o inmunizadas con células de hepatoma de Novikoff no viables se llevó a cabo por medio de cromatografía de afinidad con una columna de celulosa-ácido oliodenílico y de celulosa-ácido oligotimidílico, respectivamente. Las células de hepatoma de Novikoff viables fueron inoculadas intraperitonealmente en roedores machos Sprague Dawley, después de haber sido incubadas 30 minutos a 37 ºC con: a) solución salina, b) solución salina con 100 µgde mRNA de hígado normal de rata, c) 100 µg de mRNA de bazo normal de rata, d) 100 µg de mRNA de bazo de ratas inmunizadas con células no viables de hepatoma de Novikoff, e) 100 µg de DNA poli T de hígado normal de rata y f) 100 µg de DNA poli T de bazo normal de rata. La supervivencia de las ratas se evaluó hasta 200 días después de la inoculación de las células tumorales. El análisis de varianza mostró una supervivencia más larga, estadísticamente significativa, de las ratas inoculadas con células de hepatoma de Novikoff tratadas con DNA poli T bazo normal de rata. Estos resultados sugieren que la administración de DNA poli T podría ser usada como poligenoterapia del cáncer y que su efectividad podría ser mayor en las células neoplásicas en suspensión y probablemente la incorporación del DNA poli T en el material genética sería más fácil. Es aconsejable la administración de estas macromoléculas, como una forma de poligenoterapia en neoplasias experimentales, para evaluar su posible utilización en el ser humano

Comparación de dos métodos de ELISA para el diagnóstico de hepatitis C / Comparison of two ELISA methods for diagnosis of hepatitis C

Con objeto de comparar dos métodos de Elisa (Ensyme-linked immunosorbent assay), el UBI HCB (Organon Teknika) que emplea péptidos sintéticos y el de Ortho HCV 2.0 (Ortho Diagnostics) que utiliza antígenos recombinanates; se analizaron los sueros de 397 pacientes del Hospital de Especialidades del Centro Médico Nacional Siglo XXI, 222 mujeres y 175 hombres con promedio de edad de 42.5 años. Se incluyeron pacientes con sospecha de hapatopatía crónica y se analizaron los antecedentes de hemotransfusión, cirugía y nefropatías. 212 pacientes tuvieron elevación de aninotransferasas. 84 fueron positivos para la prueba UBI HCV (39.6 por ciento) y 83 (39.1 por ciento) también positivos para la prueba Ortho HCV 2.0. La sensibilidad fue de 65.1 y 64.8 por ciento y la especificidad de 92.7 y 90.5 por ciento respectivamente. Los resultados confirman que la prueba de ELISA para detectar anticuerpos con el virus de la hepatitis C es útil como prueba de escrutinio y que la confiabilidad de ambas pruebas es semejante, segura y accesible a los laboratorios de análisis clínicos

DNA repair in the MYC and FMS proto-oncogenes in ultraviolet light-irradiated human HL60 promyelocytic cells during differentiation.

In order to better understand the role of transcription in cellular processing of damage in specific DNA sequences, we have used an in vitro differentiation system to modulate the activity of the MYC gene. When human HL60 promyelocytic cells differentiate in vitro, the transcriptional activity of the MYC gene is down-regulated. We have shown that in the expressed MYC gene, 56% of UV-induced cyclobutane pyrimidine dimers (CPDs) are removed within 18 h and the transcribed strand is selectively repaired. However, late in differentiation, when the MYC gene is maximally down-regulated, only 15% of the CPDs are removed within the same period. During early differentiation, the MYC gene is regulated by a block to transcription elongation at the 5' end of the first intron. Our results reveal no significant difference in the rate of CPD removal between the restriction fragments upstream and downstream of this elongation block. Furthermore, both strands of each fragment exhibit similar repair characteristics. In contrast, the constitutively expressed FMS gene exhibits proficient removal of CPD in both the differentiated and undifferentiated cells. Furthermore, the repair appears to be more proficient at the 5' end (exon 1) than in the 3' end of the gene about 35 kilobases downstream from exon 1. Since efficient repair of the active FMS gene is maintained in the differentiated cells the loss of repair competence seen in MYC is more likely associated with its reduced transcriptional activity than with a decrease in the overall repair capacity of the terminally differentiated cells.

Transcription-coupled repair of psoralen cross-links but not monoadducts in Chinese hamster ovary cells.

We have examined the rate and extent of removal of 4'-(hydroxymethyl)-4,5',8-trimethylpsoralen (HMT) cross-linkable monoadducts and interstrand cross-links from restriction fragments within the amplicon containing the dihydrofolate reductase (DHFR) gene in the Chinese hamster ovary (CHO) cell line B11. The rate and extent of removal of HMT cross-links was significantly greater in an actively transcribed fragment than in a nontranscribed extragenic fragment of similar size. For the 5' half of the DHFR gene, approximately 80% of the HMT cross-links were removed in 8 h, in agreement with results reported by Vos and Wauthier [Vos, J. M., & Wauthier, E. L. (1991) Mol. Cell Biol. 11, 2245-2252, 1991]. However, few cross-links were removed in that period from the nontranscribed fragments, whose 5' end is approximately 7 kb downstream from the DHFR transcription unit and which includes a putative replication initiation site. Even after 24 h, only about 50% of the cross-links had been removed from this fragment. In contrast, both the rate and the extent of removal of cross-linkable HMT monoadducts were similar in the two fragments with 50% of the cross-linkable monoadducts removed in 24 h. Moreover, monoadducts formed in the bulk of the genome were removed in 24 h. Moreover, monoadducts formed in the bulk of the genome were removed at a slightly slower rate and to a lesser extent (30% in 24 hours) than those from either of these specific sequences.(ABSTRACT TRUNCATED AT 250 WORDS)

The mechanism of V(D)J recombination: site-specificity, reaction fidelity and immunologic diversity.

Site-specific recombination reactions in higher eukaryotes are uncommon, perhaps because of the potential genomic instability that they may create. We focus this review on the issues of site-specificity, reaction fidelity and immunologic diversity in the V(D)J recombination reaction.

Psychometric analysis in children with mental retardation due to perinatal hypoxia treated with fibroblast growth factor (FGF) and showing improvement in mental development.

Basic fibroblast growth factor (bFGF) has shown a neurotrophic effect in the neurons of several CNS areas. In vivo, it contributes to restore neurochemical and morphological deficits in different rodent models of brain damage, including rats with brain damage induced by hypoxia/ischemia when FGF was intramuscularly (i.m.) administered. Toxicological and immunological studies performed in rats, mice and volunteers showed no evidence of side-effects. Bovine FGF was i.m. administered in children with mental retardation caused by perinatal hypoxia, aged 1-15 years, at dosages of 0.4 or 0.28 microgram kg-1, once or twice a month, over 7-12 months. Group A [n = 12; 6 treated (T), 6 controls (Ct)], group B (n = 16; 8 T, 8 Ct) and group C (n = 67; 45 T, 22 Ct) were evaluated with the P. A. R. scale, the WISC-RM and the Gesell scale, respectively. Development increased significantly in treated children from groups A (P < 0.02) and C (P < 0.001), and IQ rose by more than 10 points (P < 0.001) in group B patients.

Differential introduction and repair of psoralen photoadducts to DNA in specific human genes.

We have developed a novel procedure to measure interstrand DNA cross-linking in specific DNA sequences. After alkaline denaturation, CsCl gradient equilibrium sedimentation at pH 10.8 is used to resolve cross-linked double-stranded DNA from un-cross-linked single-stranded DNA. The DNA in gradient fractions is slot-blotted and hybridized with 32P-labeled DNA probes for the sequences of interest. After densitometric quantitation of the autoradiograms, the fraction of DNA cross-linked is determined by the ratio of cross-linked DNA to total DNA (the sum of cross-linked and un-cross-linked DNA). We have used this approach to measure the initial levels of production and extent of repair of the photoadducts of 4'-hydroxymethyl-4,5',8-trimethylpsoralen, i.e., both interstrand cross-links and cross-linkable monoadducts, in specific DNA sequences in cultured human cells. Under conditions in which DNA fragments carrying the expressed dihydrofolate reductase gene were extensively modified, with approximately 92% of the fragments cross-linked, only 37% of the fragments containing the unexpressed fms protooncogene were cross-linked. The overall level of cross-linking for bulk DNA was 74%. Within 24 h, 90% of the cross-linking had been removed from the dihydrofolate reductase gene, whereas little removal was detected in fms, and the bulk DNA showed 31% removal. From this study, we conclude that both the introduction and removal of 4'-hydroxymethyl-4,5',8-trimethylpsoralen adducts are dependent upon the target DNA sequence and its transcriptional activity. The implications for DNA repair of chromatin structure and active transcription are discussed in relation to our results.

Avocado.

EDITOR'S NOTE Journals teach and stimulate in many ways. They present new information. They raise questions. They emphasize. They also may affect patient care by affecting physicians' feelings. This paper has affected reviewers not necessarily by presenting new information but by edging into their consciousness, by stirring their sense of humanity, by giving a new approach to hopelessness and handicaps. It is about teaching and about caring."Avocado" is an adaptation of an address given at the Stanford University Class Day, June 1990. It is an excerpt from an unpublished novel, La Mollie and the King of Tears. Dr Islas is Professor of English at Stanford. He has dealt with his own chronic illness for 30 years.