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Biomedical subjects

R K Johnson

Publications and source records attributed to R K Johnson.

At least 199 records · Page 11Linked to original sources
PubMed1983

Cerebral arterial spasm--a controlled trial of nimodipine in patients with subarachnoid hemorrhage.

We enrolled 125 neurologically normal patients with intracranial aneurysms in a multi-institution, prospective, double-blind, randomized, placebo-controlled trial within 96 hours of their subarachnoid hemorrhage, to determine whether treatment with the calcium blocker nimodipine would prevent or reduce the severity of ischemic neurologic deficits from arterial spasm. A deficit from cerebral arterial spasm that persisted and was severe or caused death by the end of the 21-day treatment period occurred in 8 of 60 patients given placebo and in 1 of 56 given nimodipine (P = 0.03, Fisher's exact test). Analysis of the amount of basal subarachnoid blood on pre-entry CAT scans in patients with deficits from spasm showed that an increase in subarachnoid blood was not associated with a worse neurologic outcome among patients who received nimodipine, unlike the situation in patients given a placebo. There were no side effects from nimodipine. We conclude that nimodipine should be given to patients who are neurologically normal after subarachnoid hemorrhage in order to reduce the occurrence of severe neurologic deficits due to cerebral arterial spasm.

Adolescent↗
PubMed1983

Testicular growth in boars of different genetic lines and its relationship to reproductive performance.

Testicular growth of 377 boars was compared by obtaining in situ measurements of testes width and length and excised tissue weights. Two experiments involved a line selected nine generations for ovulation rate (OR) and a control line (CL), and two experiments contained boars of the OR line and two other lines; WL, a Large White-Landrace cross, and a line founded by crossing lines OR and CL and selected six generations for increased average daily gain and decreased backfat (LG line). In situ testes measurements were similar for the OR and CL lines and were curvilinearly related to age. The LG line had smaller in situ measurements than the OR line (P less than .05) when both unadjusted means and means adjusted for body weight were compared. The OR line had 10.5% heavier testes than the CL line at 90.8 kg and a 9 to 15% advantage at 120, 141, 162 and 183 d of age. The OR line had more rapid testicular development from 120 to 183 d of age (P less than .05) than the CL line. The LG line had significantly lower excised testes weights (17 to 50% less), a lower percentage of tubules that showed active spermatogenesis and lower mean diameter of the seminiferous tubules (P less than .05) than the OR line. The relative differences between lines OR, CL and LG suggest that selection for lean growth rate has resulted in less rapid testicular development and increased age at puberty. The correlations of testes weights and in situ testes measurements taken at the time of castration were between .76 and .93. The correlations of testes width and testes length with epididymides weights were slightly lower, and correlations of body weight and testes weight ranged from .51 to .70. Mean diameter of the seminiferous tubules and percentage of tubules with active spermatogenesis were correlated with measurements of testes size (r = .50 to .61) and body weight at the time of castration (r = .29 to .36). Correlations of excised testes weights with number born in the boar's contemporary litter and ovulation rate of full sibs were uniformly positive. The correlations of measurements of testes size and backfat (r = -.09 to .20) suggest that the phenotypic relationship between testes growth and body composition is small. However, the response found in the LG line suggests a negative genetic relationship between lean growth rate and testicular growth rate.

Animals↗
PubMed1983

Genetic and phenotypic parameters estimated from Nebraska specific-pathogen-free swine field records.

Records collected during 1971 through 1979 from 101,606 hogs raised in 18 Nebraska Specific Pathogen Free herds were analyzed. Traits considered were backfat at 100 kg (BF), weight at 140 d of age (WT) and, in some analyses, number of live pigs/litter at birth (NBA). The phenotypic correlation of BF and WT, averaged across herds, was -.07. The correlations between BF and NBA and between WT and NBA were .04 and -.05, respectively. Average phenotypic standard deviations for BF, WT and NBA were 2.6 mm, 8.8 kg and 2.0 pigs. Estimates of the heritability of BF and WT were lower than most estimates reported from university research herds. Within breed, herd and sex estimates of heritability ranged from -.22 and .51 (unweighted mean = .16 +/- .025) for BF and ranged from -.28 to .49 (mean = .16 +/- .016) for WT. Estimates of the genetic correlation between BF and WT were extremely variable (mean = -.62 +/- 14.3, range = -9.42 to 1.30) among breed-herd-sex subclasses.

Adipose Tissue↗
PubMed1983

Reciprocal recurrent selection for 21-day litter weight of crossbred gilts. I. Selection applied and genetic change in reproduction of crossbred gilts.

Six cycles of reciprocal recurrent selection (RRS) between Line 8 (Duroc) and Line 9 (Beltsville No. 1) were completed at the Fort Reno Livestock Research Center, El Reno, Oklahoma. A randomly mated control line was maintained. Each cycle of selection required three seasons. Selection of purebred pigs (born in the second season) was based on the mean 21-d litter weight of their maternal and paternal half-sib crossbred gilts that were born in the first season and farrowed in the third season (XB21DLWT). On the average, 5.8 maternal and paternal half-sib gilts contributed to the mean XB21DLWT for each purebred individual. The average potential selection differential for XB21DLWT was 5.64 kg, but only 70.2% of this value was realized in the initial selection (3.95 kg). Disease problems and unsoundness were the primary reasons for this discrepancy. The potential, initial, final and weighted final standardized selection differentials for females averaged 61, 60, 55 and 47%, respectively, of the corresponding differentials for males. Standardized selection differentials were similar for Line 8 and Line 9. The estimate of realized heritability for XB21DLWT was .076 +/- .319 for the average of 8 X 9 and 9 X 8 gilts. Environmental trends, estimated from control data, were not significant for any of the traits evaluated. The genetic change in reproductive ability of 8 X 9, 9 X 8 and their unweighted average was estimated by regressing the deviation of the line mean from the control mean on generation number. In general, estimates of genetic change for litter size, litter weight and average pig weight/litter at 0, 21 and 42 d of age were not significant, but all estimates were favorable. The estimated genetic change for 21-d litter weight was 1.04 +/- 1.25 kg/cycle of selection. Based on these results and considering the complexity of RRS, the increase in generation interval and the expected decline in purebred performance that theoretically should accompany successful RRS, it seems doubtful that RRS can be more beneficial than selection based on purebred performance as a method to improve productivity of crossbred gilts.

Animals↗
PubMed1983

Reciprocal recurrent selection for 21-day litter weight of crossbred gilts. II. Reproductive performance of purebred females producing purebred and two-way cross litters and performance of purebred and crossbred pigs.

This paper reports estimates of correlated genetic change in reproductive performance of purebred gilts producing two-way cross litters and purebred sows producing purebred litters as well as postweaning performance of two-way cross and purebred pigs produced during reciprocal recurrent selection (RRS) between Line 8 (Duroc) and Line 9 (Beltsville No. 1) for 21-d litter weight production of crossbred gilts. A randomly mated control line developed from a crossbred foundation was maintained to monitor environmental change. Data were adjusted for age of dam, inbreeding of dam, inbreeding of litter (or pig) and linear and quadratic effects of day born within season. The traits evaluated were: litter size, litter weight and average pig weight/litter at birth and weaning (42 d); postweaning average daily gain; age at 90.7 kg and backfat thickness at 90.7 kg. Two data sets were analyzed; the first set included seven seasons of data with purebred gilts producing two-way cross litters, and the second set included seven seasons of data with purebred sows producing purebred litters. No estimates of environmental trend were significant in either set of data. In the first data set, only the estimate of genetic change in backfat thickness of two-way cross pigs was significant and it was in the desired direction. All other estimates were small and did not approach significance. In the second data set, estimates of genetic trend were greater in Line 9 than in Line 8.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1983

Collateral sensitivity to N-(phosphonacetyl)-L-aspartic acid in a line of P388 leukemia cells selected for resistance to L-(alpha S, 5S)-alpha-amino-3- chloro-4,5-dihydro-5-isoxazoleacetic acid (acivicin).

Administration of N-(phosphonacetyl)-L-aspartic acid (PALA) is ineffective in treating mice bearing the parent P388 leukemia line; however, such treatment becomes highly effective when a cell line, P388/ACIA, derived from P388/0 was selected for resistance to another antimetabolite, acivicin. The observed phenomenon of collateral sensitivity is associated with a significantly higher inhibition of the specific activity of carbamyl phosphate synthetase II, pyrimidine nucleoside kinases, adenine phosphoribosyl transferase, and hypoxanthine phosphoribosyl transferase in the PALA-sensitive line, P388/ACIA. Twenty-four hr following administration of PALA, 200 mg/kg, the 10% lethal dose i.p. to tumor-bearing mice, the intracellular concentrations of uridine triphosphate and cytidine triphosphate were decreased in the P388/ACIA, PALA-sensitive cells, whereas no significant change in the corresponding nucleotide pool sizes was observed in P388/0, PALA-resistant line. Moreover, the purine nucleotide pool demonstrated a significant expansion of adenosine triphosphate and guanosine triphosphate only in the P388/ACIA line following a similar treatment with PALA. It is proposed that the imbalance in the generation of pyrimidine and purine nucleoside triphosphate pools may explain the observed collateral sensitivity to PALA in P388/ACIA leukemia line.

Adenine Phosphoribosyltransferase↗
PubMed1982

Carboxyimamidate, a low-molecular-weight polyelectrolyte with antitumor properties and low toxicity.

A new polyelectrolyte was synthesized and evaluated for antitumor activity. The product is a derivative of ethylene/maleic anhydride copolymer of low molecular weight (Mn approximately equal to 1100). The anhydride groups were first converted to the half-amide, half-ammonium salt by reaction with ammonia. A percentage (14-25 wt %) of these groups was further converted to the imide by heating. The product, carboxyimamidate (Carbethimer, N-137) inhibited the growth of a number of solid tumors in vivo. Sensitive tumor models included Lewis lung carcinoma, Madison 109 lung carcinoma, M5076 ovarian tumor, colon carcinoma 26, B16 melanoma, and P815 mastocytoma. Activity was dose related between nontoxic dose levels of 300 and 2000 mg/kg ip.

Animals↗
PubMed1982

Effect of tallow and choline chloride addition to the diet of sows milk composition, milk yield and preweaning pig performance.

Four trials were conducted with a total of 188 crossbred sows to determine the effect of feeding diets supplemented with tallow (0 or 8%) and choline chloride (220 or 770 mg/kg diet) prior to parturition and during lactation on preweaning pig performance. On d 100 of gestation, sows were allotted to four factorially arranged dietary treatments: 0% tallow-220 mg/kg choline chloride, 0% tallow-770 mg/kg choline chloride, 8% tallow-220 mg/kg choline chloride, 8% tallow-770 mg/kg choline chloride. Diets without tallow were fed at the rate of 1.82 kg/d with an additional .18 kg/d of cornstarch, whereas sows receiving diets supplemented with tallow were fed 1.82 kg/d. Daily metabolizable energy intake was constant for all diets (approximately 6,240 kcal). Following parturition, the diets were fed ad libitum for a 21-d lactation period. Pig survival to 21 d, in relation to the number of pigs born alive/litter, did not differ significantly between litters from sows receiving tallow (94.0%) and litters from sows receiving the control diet (92.5%). Although not significantly different, there was a trend toward slightly heavier pigs (6.35 vs 6.11 kg) and litters (53.97 vs 51.94 kg) after the 21-d lactation period in the groups nursing sows receiving tallow-supplemented diets. Litter performance was not improved by the addition of choline to sows' diets. A second study was conducted to measure the effect of energy source on milk yield and composition. Twelve crossbred sows was allotted to two dietary treatments (0 and 8% tallow), each supplemented with 770 mg choline chloride/kg of diet. The composition of colostrum and milk was determined on d 0, 9 and 18, and milk yield was measured on d 12 and 19. Throughout the lactation period, sows fed the tallow supplemented diet produced higher concentrations of total milk solids (22.15%, P less than .10) and fat (14.9%, P less than .01) than the control group (21.37 and 12.0%, respectively). Milk protein content, averaged over the lactation period, was lower (P less than .10) for sows receiving tallow (8.60 vs 9.22%); however, the depression appeared to be related to the colostrum samples, because values for the two treatment groups were similar on d 9 and 18. The mean milk yield was 9.44 kg/d for sows receiving tallow and 8.72 kg/d for those fed the control diet. Therefore, not only did sows in the tallow group produce a greater concentration of milk solids and fat, but the total quantity of the milk constituents available to the offspring was increased.

Animals↗
PubMed1982

Oxidation rates of major fatty acids in fasting neonatal pigs.

Thirty-two pigs were used to compare the oxidation rates of uniformly labeled (U-14C) palmitic (16:0), stearic (18:0), oleic (18:1) and linoleic (18:2) acids in fasting neonatal pigs. The pigs were allowed to nurse the sow for 24 to 48 h following birth. Subsequently, they were removed, an indwelling catheter was surgically placed in the external iliac vein and the pigs were fasted for 12 h to attain a postabsorptive state. The 14C fatty acids were administered as a single infusion (10 microCi) via the catheter, and recovery of the label as expired 14CO2 was determined at 45-min intervals for a 6-h period. Blood samples were taken following the infusion (15, 60, 120, 240, 360 min) to monitor activity maintained within the free fatty acid (FFA) fraction of the plasma pool. The oxidation rate of each fatty acid was corrected for the difference in dose dilution using a uniform factor based on plasma concentration of 18:1. The cumulative 6-h 14CO2 recovery rates (percentage of dose) were 19.1, 6.6, 30.1 and 13.1% for 16:0, 18:0, 18:1 and 18:2, respectively. Oleic acid was oxidized at a more (P less than .05) rapid rate than the other fatty acids. Palmitic acid and 18:2 were oxidized more rapidly than 18:0, although the difference between 18:0 and 18:2 was not significant. Plasma FFA pools differed with respect to the proportion of infused activity remaining at various times after administration. At 60 and 120 min postinfusion, the greatest (P less than .05) proportion of activity was maintained in the 18:1 pool (11.9 and 6.6%, respectively, vs 7.7 and 4.3% for 16:0, 6.9 and 3.9% for 18:2 and 3.6 and 2.2% for 18:0). Palmitic acid and 18:2 had a greater (P less than .05) level of activity in the plasma FFA pool at 60 min than did 18:0. This same pattern was observed through 2 h, but by 240 min postinfusion, the proportion of activity remaining in each of the plasma pools was similar. Rate of oxidation appeared to corrrespond with plasma concentration and proportion of activity remaining in the plasma FFA pool.

Animals↗
PubMed1981

Comparison of three-breed and backcross swine for litter productivity and postweaning performance.

Duroc, Hampshire and Yorkshire boars were mated with crossbred gilts of Duroc-Hampshire, Duroc-Yorkshire and Hampshire-Yorkshire breeding to produce 133 three-breed and 259 backcross litters that were farrowed during four seasons beginning in the fall of 1975. Three-breed cross litters were .31 +/- .27, .57 +/- .24 and .50 +/- .24 pigs larger than backcross litters at birth, 21 and 42 days, respectively, and .6 +/- .34, 2.3 +/- 1.2 and 5.4 +/- 2.4 kg heavier at these ages. The differences in average pig weight and survival percentage were small. Three-breed cross litters gained faster (.024 +/- .007 kg/day) and were younger (-4.7 +/- 1.5 days) at 100 kilograms. Three-breed cross pigs were about 3% more efficient than backcross pigs. The differences in average backfat probe and average daily feed intake were small and not significant. Breed of sire contrasts for litter traits were small and not significant. However, significant differences between sire breeds existed for postweaning performance. Also, few differences between crossbred dam groups were significant for litter size or litter weight, but significant differences in postweaning performance existed between progeny of crossbred dam groups. In general, pigs with Duroc breeding had the fastest growth rate and those with Hampshire breeding were the leanest.

Animals↗