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Biomedical subjects

R L Larson

Publications and source records attributed to R L Larson.

At least 19 recordsLinked to original sources
PubMed1998

Economic evaluation of neonatal health protection programs for cattle.

OBJECTIVE: To develop an economic tool that can be used to help cattle producers evaluate benefits of neonatal health programs. DESIGN: Computer simulation of a multiple-year spreadsheet model, using economic and production variables. SAMPLE POPULATION: Records for a university research farm beef herd. PROCEDURE: Data from the university research farm beef herd for each year from 1990 to 1995 were evaluated to determine economic benefits for the cow-calf enterprise that would result from a decrease in morbidity and mortality. A baseline economic evaluation of returns to variable costs was performed, using actual production and marketing information. Actual economic performance was contrasted with a projected simulation in which morbidity and mortality were decreased. Sensitivity analysis for the simulation model assessment of a neonatal health program was also performed. RESULTS: Mean-per-cow increase in net income for the herd during the 6-year period for morbidity and mortality reductions of 20, 40, and 60% was $7.44, $14.93, and $22.42, respectively. Sensitivity analysis revealed that net income per cow was not sensitive to errors in projections of morbidity and mortality. CLINICAL IMPLICATIONS: Identifying potential economic benefits for implementing a neonatal health plan and quantifying the costs to implement each component of the plan can be used by veterinarians and their clients when formulating a proactive strategy to provide the greatest potential for economic reward.

Animals↗
PubMed1996

Synchronization of estrus in yearling beef heifers with the melengestrol acetate/prostaglandin F(2alpha) system: efficiency of timed insemination 72 hours after prostaglandin treatment.

Two experiments were conducted to determine the conception rates of heifers time-inseminated following melengestrol acetate/prostaglandin F(2alpha) (MGA/PG) estrous synchronization treatment. In Experiment 1, timed insemination of heifers at 72 h after the PG injection, without regard for behavioral estrus, tended to improve (P < 0.15) the percentage of heifers pregnant to artificial insemination (AI) compared with that of synchronized heifers bred 12 h after they were first detected in estrus. In the timed-insemination treatment, heifers exhibiting behavioral estrus 48 to 72 h after PG tended to have an increased (P < 0.15) conception rate to AI compared with heifers exhibiting estrus within 48 h of PG administration. In Experiment 2, the number of heifers conceiving to AI following the MGA/PG estrous synchronization regimen was increased by mass insemination of all heifers not exhibiting estrus by 72 h after PG. The pregnancy rate to AI was higher in heifers with serum progesterone (P(4)) concentrations higher than 1 ng/ml compared with that of heifers with concentrations lower than 1 ng/ml. Of heifers with serum P(4) greater than 1 ng/ml, the pregnancy rate to AI tended to be higher when concentrations exceeded 2 ng/ml than when concentrations were 1 to 2 ng/ml. In cyclic heifers, timed insemination can increase the percentage of heifers pregnant after being synchronized with MGA/PG.

Journal Article↗
PubMed1995

Estrus after treatment with Syncro-Mate B* in ovariectomized heifers is dependent on the injected estradiol valerate.

A series of experiments was conducted to determine why ovariectomized heifers exhibit estrus after they are treated with the estrus synchronization product, Syncro-Mate B(*) (SMB). In Experiment 1, 23 of 40 (58%) ovariectomized heifers exhibited estrus after treatment with SMB. The mean concentration of estradiol-17beta (E(2)) in serum was lower (P < 0.001) before treatment than after implant removal in ovariectomized heifers treated with SMB. Six of 10 heifers from which serum was collected to determine concentrations of LH exhibited estrus and 5 of 6 had a surge of LH in serum after implant removal. In Experiment 2, when no estradiol valerate (EV) was given or when the norgestomet implant period was extended from 9 to 18 d, no heifer exhibited estrus after implant removal. The mean concentration of E(2) for 3 d after implant removal was lower (P < 0.001) in ovariectomized heifers with implants for 18 d versus those with implants for 9 d and was also lower (P < 0.001) in ovariectomized heifers treated only with norgestomet compared with those receiving the standard SMB treatment. When estradiol-17beta was substituted for EV in the SMB treatment, serum E(2) was lower (P < 0.001) after implant removal than in heifers receiving the standard SMB treatment. Experiment 3 demonstrated that combining a norgestomet implant or implant plus a 3-mg injection of norgestomet with EV did not alter concentrations of E(2) in serum on the days when synchronized estrus would be expected following SMB treatment. The results indicate that the SMB-induced estrus in ovariectomized heifers is dependent upon EV in the SMB treatment. Apparently, EV elevates the concentration of E(2) in serum, and the E(2) remains sufficiently high to induce estrus after implant removal.

Journal Article↗
PubMed1995

Effect of treatment with ivermectin on reproductive performance of yearling beef heifers.

To determine the effect of treatment with ivermectin on reproductive parameters, 78 fall-born, yearling heifers were allotted to either an ivermectin treatment group or to the control, non-treatment group. The heifers were treated in June and October when they were approximately 7 and 11 mo old, respectively. Ivermectin effectively lowered fecal egg counts in the treated heifers compared with that of the controls. In heifers that were maintained on a marginal plane of nutrition, treatment with ivermectin not only improved weight gains during each recording period but also hastened the onset of puberty and improved the pregnancy rate during a 60-d breeding season. The positive effect of ivermectin on these reproductive characteristics could not be explained by increased weight gain alone, because the correlation between weight gain and puberty was not significant. Treatment with ivermectin positively affected pelvic area but not uterine score when compared with those of the controls.

Journal Article↗
PubMed1993

Molecular analysis of allelic polymorphism at the AAT2 locus of alfalfa.

Aspartate aminotransferase (AAT) plays a key enzymatic role in the assimilation of symbiotically fixed nitrogen in legume root nodules. In alfalfa, two distinct genetic loci encode dimeric AAT enzymes: AAT1, which predominates in roots, and AAT2, which is expressed at high levels in nodules. Three allozymes of AAT2 (AAT2a, -2b and -2c), differing in net charge, result from the expression of two alleles, AAT2A and AAT2C, at this locus. Utilizing antiserum to alfalfa AAT2, we have previously isolated from an expression library one AAT2 cDNA clone. This clone was used as a hybridization probe to screen cDNA libraries for additional AAT2 cDNAs. Four different clones were obtained, two each that encode the AAT2a and AAT2c enzyme subunits. These two sets of cDNAs encode polypeptides that differ in net charge depending upon the amino acid at position 296 (valine or glutamic acid). Within each set of alleles, the two members differ from each other by the presence or absence of a 30 bp (ten amino acid) sequence. The presence or absence of this ten amino acid sequence has no effect on the size or charge of the mature AAT2 protein because it is located within the region encoding the protein's transit peptide, which is proteolytically removed upon transport into plastids. The data suggest that a deletion event has occurred independently in two AAT2 progenitor alleles, resulting in the four allelic cDNA variants observed. The deletion of this ten amino acid sequence does not appear to impair the normal maturation of the enzyme.

Alleles↗
PubMed1993

Prolonged postpartum anovulation in mastectomized cows requires tactile stimulation by the calf.

Association of the calf with its dam prolongs the postpartum interval to first ovulation in intact and mastectomized cows indicating that tactile stimulus of the teat and (or) udder is not necessary. Therefore, we conducted the following experiment to determine whether individual calves allowed restricted contact with their mastectomized dam would delay the onset of first postpartum ovulation. Mastectomized cows (n = 21) were allotted randomly and equally to three groups in which cows were 1) allowed unrestricted access to their calves, with unlimited tactile, olfactory, visual, and auditory stimuli (calf present); 2) removed permanently from their calves 24 h after parturition and provided no further association with their calves (calf removed); and 3) remained with their calves for 24 h and then the cow-calf pair was restricted to a pen where tactile contact of the calf was limited to the head and neck region of its dam (calf restricted). Seven udder-intact cows (control) remained with their calves and were allowed to nurse ad libitum. Postpartum intervals to ovulation and first estrus for the calf-restricted cows and calf-removed cows were similar but shorter (P < .05) than those for the calf-present and udder-intact groups. We conclude that restricting tactile stimuli of the calf to the head and neck area of its dam failed to prolong postpartum anovulation in the mastectomized dam and that a cow-calf nursing orientation with tactile stimuli to the inguinal area, but not limited to the teat and(or) udder, was sufficient to prolong anovulation.

Animals↗
PubMed1991

Maize microsomal benzoxazinone N-monooxygenase.

The benzoxazinones occur in hydroxamic acid and lactam forms in maize (Zea mays L.) tissue. The hydroxamic acid forms which possess a N-hydroxyl group are found in the highest concentration while the lactam members which lack the N-hydroxyl group occur in lower concentrations. The hydroxamic acid 2,4-dihydroxy-1,4-benzoxazin-3-one (DIBOA) has as its lactam counterpart 2-hydroxy-1,4-benzoxazin-3-one (HBOA). An enzyme has been identified in maize microsomal preparations which catalyzes the N-hydroxylation of HBOA to form DIBOA. The enzyme is initially observed in seedlings 2 days after imbibition which coincides with the onset of hydroxamic acid accumulation. The enzyme requires NADPH and is inhibited by sulfhydryl reagents, NADP, cytochrome c, cations, carbon monoxide, and nitrogen gas. The effect of nitrogen can be reversed by exposing the enzyme to air, while the effect of carbon monoxide can be reversed by exposing the enzyme to 450 nanometer light during the incubation period. The apparent K(m) values for HBOA and NADPH are 13 and 5 micromolar, respectively. The pH optimum is 7.5 and the temperature optimum for the enzyme is 35 degrees C. A 450 nanometer absorbance peak is observed when reduced microsomal preparations are exposed to carbon monoxide which in combination with other data presented supports the hypothesis that the enzyme is a cytochrome P-450 dependent N-monooxygenase.

Journal Article↗
PubMed1991

Synthetic materials for the replacement of knee ligaments.

The augmentation of autogenous tissue should be considered in failed autogenous grafts or when inadequate tissue is present which does not allow adequate tissue length, provide enough tensile strength, or insufficient fixation. Multiply failed anterior cruciate ligament surgical procedures should be considered candidates for a true prosthetic replacement. In certain patients with degenerative changes and functional instability, the use of a true prosthesis might also be considered in combination with other types of degenerative joint surgery. With all of our attempts at ligamentous reconstruction about the knee, we are seeking the ideal solution--the ultimate surgical technique for the anterior cruciate loss--minimal morbidity, rapid rehabilitation, return to full function, and reliable results. The intra-articular notch is not the ideal area to create a new ligament whether it be by autogenous or artificial means.

Humans↗
PubMed1990

Syncro-mate B induces estrus in ovariectomized cows and heifers.

Eleven ovariectomized Hereford x Simmental cows and 10 ovariectomized crossbred heifers (primarily Angus and Hereford) were given the Syncro-Mate B (SMB) estrous synchronization treatment. The SMB treatment consisted of a 2 ml i.m. injection containing 5 mg of estradiol valerate and 3 mg of norgestomet plus a hydron ear implant containing 6 mg of norgestomet. The ear implant was removed 9 d later. Cows and heifers were considered in estrus only if they stood for mounting by a herdmate or a bull. Observations for estrus were made four or six times each day for 3 d after implant removal. The 21 animals were used in eight trials. Each trial involved 9 or 11 cows or 5 or 10 heifers. Four days to three weeks elapsed between implant removal and implant insertion for the next trial. No ovariectomized cow or heifer was observed in estrus for 21 d before treatment with SMB. In the eight trials, 3 of 9, 7 of 9 and 6 of 11 cows exhibited estrus, whereas 5 of 10, 1 of 5, 3 of 5, 3 of 5 and 5 of 5 heifers exhibited estrus after treatment. When data were pooled, 16 of 29 (55.2%) cows and 17 of 30 (56.7%) heifers exhibited estrus after treatment. Our data indicate that the SMB treatment can induce estrus in cows and heifers, independently of the ovaries.

Journal Article↗
PubMed1989

Hydroxamic Acid glucosyltransferases from maize seedlings.

Hydroxamic acids occur in several forms in maize (Zea mays L.) with 2,4-dihydroxy-7-methoxy-2H-1,4-benzoxazin-3(4H)-one (DIMBOA) being the predominant form and others including 2,4-dihydroxy-1,4-benzoxazin-3-one (DIBOA) being found at lower concentrations. Two enzymes capable of glucosylating hydroxamic acids were identified in maize protein extracts and partially purified and characterized. The total enzyme activity per seedling increased during the first 4 days of germination and was concurrent with the accumulation of DIMBOA. Purification of the enzymes by ammonium sulfate precipitation followed by Sephadex G-200 and Q-Sepharose gel chromatography resulted in a 13-fold increase in specific activity. The enzymes are initially separated into two peaks (peak 1 and peak 2) of activity by Q-Sepharose gel chromatography. The peak 1 glucosyltransferase had 3.6% of the DIMBOA glucosylating activity when DIBOA was used as substrate, whereas this percentage increased to 57% for the peak 2 enzyme. The enzyme in peak 2 has a K(m) of 174 micromolar for DIMBOA and a K(m) of 638 micromolar for DIBOA; the enzyme in peak 1 has a K(m) of 217 micromolar for DIMBOA and its activity on DIBOA was too low to determine a K(m). The identification of two glucosyltransferases capable of glucosylating hydroxamic acids in vitro serves as an initial step in the characterization of the enzymes involved in production of hydroxamic acids in maize.

Journal Article↗
PubMed1988

Achieving order entry by physicians in a computerized medical record.

When Community Memorial Hospital selected a computerized Medical Information System (MIS), it was recognized that physician use and acceptance was paramount to success. To achieve this, active participation from the medical-dental staff via an advisory committee, system education and emphasis on physician benefits was sought. Advance preparation included selection of light pen technology, field trips by selected physicians to other hospitals with the same system, and strategic placement and availability of terminals. During implementation, training was scheduled at the convenience of the physician. This training continues to be offered immediately to new physicians as they join the staff. System upgrades and added functions prompt scheduling of demonstrations for interested physicians. Many developmental ideas come from physicians using MIS indicating their interest in maintaining the system. New approaches that will make order entry easier for physicians so that everyone can benefit from their cooperation and participation are continually being looked for.

Computer User Training↗
PubMed1988

Proximal tibial osteotomy in patients who are fifty years old or less. A long-term follow-up study.

Proximal tibial valgus osteotomy was performed for unicompartmental osteoarthritis in forty-five patients (fifty-one knees). The average age of the patients was forty-one years (range, twenty-three to fifty years), and the average length of follow-up was ten years. At follow-up, 70 per cent (thirty-six knees) were rated as good or excellent and 30 per cent (fifteen knees) were rated as fair or poor. There was no clear correlation between the quality of the result and the radiographic evidence of the severity of the arthritis preoperatively, the age of the patient at osteotomy, or the length of follow-up. There was a correlation between an improved result and an increased angle of correction after osteotomy, but the values were not statistically significant. The most important factor influencing the quality of results was the over-all level of disease in the knee as reflected in the preoperative knee score. Deficiency of the anterior cruciate ligament at the time of the osteotomy did not prevent a good result. We believe that proximal tibial osteotomy for unicompartmental arthritis of the knee is a good and effective procedure for patients who are less than fifty years old and who have an active life-style, and that lasting results can be achieved if the procedure is done early in the course of the disease.

Adult↗
PubMed1986

Microsomal flavonoid 3'-monooxygenase from maize seedlings.

Identification of flavonoid 3'-monooxygenase establishes another reaction in the biosynthesis of flavonoid compounds in maize (Zea mays L.). The flavonoid 3'-hydroxylase was obtained as a microsomal enzyme preparation by buffer extraction of 5 day old maize seedlings and ultracentrifugation. Seedlings were exposed to light 24 hours prior to enzyme extraction. The extraction buffer required the addition of sucrose or glycerin and dithiothreitol to obtain an active hydroxylase that retained its activity on storage at -70 degrees C. Enzymic activity required O(2) and NADPH, was optimum at pH 8.5 and 30 degrees C, and could be inhibited 79% by carbon monoxide. Carbon monoxide inhibition could be reduced to 21% by irradiation of the samples with 450 nanometer light during incubation. Kaempferol, a flavonol; naringenin, a flavanone; and apigenin, a flavone, all served as substrates for the hydroxylase. Treatment of the microsomal enzyme preparation, previously reduced with sodium dithionite, with carbon monoxide gave a 455 nanometer absorption peak which disappeared on oxidation of the preparation with the formation of a 420 nanometer peak. These results suggest a cytochrome P-450 type monooxygenase enzyme. The concentration of cytochrome P-450 was 0.21 nanomoles per milligram protein. Identification of the monooxygenase provides further biochemical information about a biosynthetic sequence for which the genetics have been studied intensely.

Journal Article↗
PubMed1985

Overview and philosophy of knee injuries.

The problem of the injured knee has attracted thoughtful discussion over the years. A current review of changes in thinking and treatment relative to the meniscus, ligament injuries, the extensor mechanism, prosthetic ligaments, and rehabilitation is presented.

Humans↗
PubMed1985

Augmentation of acute rupture of the anterior cruciate ligament.

Acute repair and augmentation of anterior cruciate ligament rupture is indicated in the active individual who is going to place excessive demands on the knee. Repair of any other ligament injury with the addition of augmentation of the anterior cruciate ligament repair provides a better chance for functional stability and lessens the incidence of secondary meniscal injury.

Humans↗