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Biomedical subjects

R D Howard

Publications and source records attributed to R D Howard.

At least 19 recordsLinked to original sources
PubMed2005

Modulation of equine articular chondrocyte messenger RNA levels following brief exposures to recombinant equine interleukin-1beta.

The effect of recombinant equine IL-1beta (EqIL-1beta) on steady-state mRNA levels of equine articular chondrocytes in high-density monolayer culture was investigated using a customized cDNA array analysis. Total RNA samples isolated from chondrocytes cultured in media alone or with the addition of 1 ng/ml EqIL-1beta for 1-, 3-, and 6-h durations of exposure were reverse transcribed, radiolabeled, and hybridized to a customized 380-target cDNA array. Means of duplicate log base 2 transformed hybridization signals were normalized to equine glyceraldehyde 3-phosphate dehydrogenase (GAPDH) mean signal intensities. Differentially expressed transcripts were identified using a two-stage mixed linear analysis of variance model (Statistical Analysis Software, Cary, NC). A time-dependent pattern was observed in the number of transcripts increased > or =two-fold in response to EqIL-1beta after 1, 3 and 6h (1, 2 and 109 transcripts, respectively). At 6 h of EqIL-1beta stimulation, signal intensities for 88 cDNA targets with purported function in processes related to cell cycle, intracellular signaling, transcription, translation, extracellular matrix turnover, and inflammation, as well as a number of cDNAs lacking homology to previously reported cDNA sequences, were increased >two-fold and were associated with p<0.05. Principal component analysis identified a vector component ( approximately 10% of the total variation) corresponding to a potential EqIL-1beta co-regulation of cell cycle associated gene transcription. These results support and expand our existing comprehension of the complex role of IL-1 in modulated chondrocyte gene expression and suggest the involvement of specific target gene up-regulation and activation of downstream inflammatory cascade mediators. This study adds to the current understanding of the molecular events associated with an IL-1 induced inflammation and pathobiologic processes that may be associated with the development of equine osteoarthritis.

Animals↗
PubMed2005

Detection of differentially regulated genes in ischaemic equine intestinal mucosa.

REASONS FOR PERFORMING STUDY: Colic is a serious disease syndrome in horses. Much of the mortality is associated with ischaemic-injured intestine during strangulating obstruction, yet there is limited understanding of the associated molecular events. Identification of differentially expressed genes during ischaemic injury should expand our understanding of colic and may lead to novel targeted therapeutic approaches in the future. OBJECTIVE: To isolate and identify differentially expressed genes in equine jejunum following a 2 h ischaemic event compared to normally perfused jejunum. METHODS: Suppressive subtractive hybridisation was used to clone genes that are differentially expressed in equine jejunum injured by 2 h of complete ischaemia as compared to time-matched control jejunal tissues. Expression of selected clones was further evaluated by northern blot analysis. RESULTS: Of the 384 clones selected, 157 were confirmed to possess cDNAs corresponding differentially expressed genes by dot blot analysis. Two genes, fatty acid binding protein 2 and calcium-activated chloride channel 4 were further confirmed to be differentially expressed by northern blot analysis. CONCLUSIONS: Suppressive subtractive hybridisation can be used to detect changes in expression of a broad array of genes, as confirmed by northern blot analysis of selected genes. POTENTIAL RELEVANCE: These initial results have identified a pool of equine intestinal epithelial genes that are differentially expressed following a 2 h ischaemic event. In particular, genes indicative of deranged metabolic activity and those potentially involved in early repair events were identified and may ultimately provide clues as to the nature of epithelial ischaemic injury in horses.

Animals↗
PubMed2003

Interactions between the ovary and the local IGF-I axis modulate mammary development in prepubertal heifers.

The objective was to determine the effects of ovariectomy and epithelial-stromal interactions on mammary development and local expression of IGF-I and IGF-binding protein (IGFBP) mRNA in prepubertal heifers. An epithelium-free ('cleared') fat pad (CFP) was prepared in two glands in each of 14 Holstein heifers, aged 1-3 Months. Eight of the calves were also ovariectomized. Serum concentrations of GH, IGF-I and prolactin were not affected by ovariectomy. At 6 Months of age, calves were killed to provide mammary samples of parenchyma, CFP and intact fat pad (MFP). Total mammary mass was reduced in ovariectomized calves (130+/-21 g vs 304+/- 25 g; P<0.001), and in several cases parenchymal tIssue was essentially absent. Uterus weight was also reduced by ovariectomy (14.5+/-3.8 g vs 30.4+/-4.5 g; P<0.05). In support of our hypothesis that local IGF-I mediates prepubertal mammary development, mRNA expression of IGF-I was lower in ovariectomized than in control calves (62.1+/-7.8 vs 91.6+/-7.8 arbitrary units; P<0.05). Specific binding of IGF-I to mammary parenchymal microsomes was also reduced by ovariectomy (377+/-142 vs 868+/-82 c.p.m.; P<0.01), suggesting decreased sensitivity to IGF-I. Expression of IGFBP-3 and IGFBP-5 mRNA were not influenced by ovariectomy. Expression of IGF-I, IGFBP-3 and IGFBP-5 mRNA did not differ between CFP and MFP, suggesting that expression of these factors was not influenced by interactions between stroma and developing epithelium. Overall, the data suggested that interactions between the ovary and the local IGF-I axis act to optimize the availability and effectiveness of IGF-I within the gland to stimulate mammary growth.

Animals↗
PubMed2003

Mammary epithelial proliferation and estrogen receptor alpha expression in prepubertal heifers: effects of ovariectomy and growth hormone.

The objectives of this study were to determine the effects of ovariectomy and growth hormone on mammary epithelial cell proliferation and estrogen receptor alpha (ER alpha) expression within the bovine mammary gland. Two experiments were performed. In the first experiment, eight Holstein heifer calves aged between 1 and 3 mo were ovariectomized, while six calves served as controls. At 6 mo of age, calves were treated with bromodeoxyuridine (BrdU) to label proliferating cells and sacrificed 2 h later. Coinciding with reduced mammary mass (304 +/- 25 vs. 130 +/- 21 g), proliferation of mammary epithelial cells was significantly lower in ovariectomized heifers compared to control heifers (2.24 vs. 0.25%). ER alpha expression was restricted to mammary epithelial cells and was not observed within intra-lobular stroma of parenchymal tissue. The proportion of ER alpha positive cells was significantly higher in ovariectomized heifers than in controls (36.1% +/- 2.2 vs. 46.7% +/- 2.4). In the second experiment, mammary biopsies were taken from five 6-mo-old heifers, immediately preceding and 7 d following a single injection of bovine growth hormone. Mammary epithelial cell proliferation (assessed by incorporation of 3H-thymidine) was increased by growth hormone. The proportion of ER alpha positive mammary epithelial cells was not increased by growth hormone. In conclusion, reduced mammary epithelial cell proliferation following ovariectomy was associated with an increase in ER alpha expression, whereas increased proliferation caused by bovine growth hormone was not associated with changes in the proportion of ER alpha positive cells.

Animals↗
PubMed2003

Mammary localization and abundance of laminin, fibronectin, and collagen IV proteins in prepubertal heifers.

The objective was to determine localization and abundance of extracellular matrix proteins fibronectin, laminin, and collagen in mammary tissues from ovariectomized or intact prepubertal heifers. Mammary parenchyma and fat pad tissues were collected from 14 6-mo-old heifers: eight were ovariectomized between 1 to 3 mo of age, and six were used as intact controls. Distribution of total collagen was assessed by Sirius Red staining of tissue sections. Fibronectin, laminin, and type IV collagen were assessed by immunohistochemistry. Abundance of fibronectin and laminin was also analyzed by western blotting. Total mammary mass was much less in ovariectomized animals (130 +/- 21 vs. 304 +/- 25 g). Histological structure differed as parenchyma from intact animals contained abundant, complex branching epithelial terminal ductular units, whereas terminal ductular units from ovariectomized animals were mostly major ductal structures with little or no branching. Collagen fibers were abundant and densely packed throughout interlobular stroma and were less abundant and more diffuse within intralobular stroma. Type IV collagen was primarily in basal lamina of mature ducts, whereas fibronectin and laminin staining were present throughout parenchymal stroma, in both intact and ovariectomized animals. Using western blotting, fibronectin was more abundant within parenchyma than in the fat pad and significantly higher in parenchyma from ovariectomized heifers. Laminin was more abundant in parenchyma from intact than ovariectomized animals (30 vs. 17 densitometric units/mg of tissue), but laminin was similar between parenchyma and fat pad. These results provide initial evidence that fibronectin, laminin, and collagen participate in regulation of heifer prepubertal mammary development.

Adipose Tissue↗
PubMed2001

Failure of holmium:yttrium-aluminum-garnet laser lithotripsy in two horses with calculi in the urinary bladder.

Holmium:yttrium-aluminum-garnet (Ho:YAG) laser lithotripsy was attempted in a mare and a gelding with calculi in the urinary bladder. The procedure was unsuccessful in producing adequate fragmentation of the calculi. In the gelding, pulsed dye laser lithotripsy was subsequently used to fragment the urolith. Manual removal of the urolith via the urethra was performed in the mare.

Animals↗
PubMed1999

Possible ecological risks of transgenic organism release when transgenes affect mating success: sexual selection and the Trojan gene hypothesis.

Widespread interest in producing transgenic organisms is balanced by concern over ecological hazards, such as species extinction if such organisms were to be released into nature. An ecological risk associated with the introduction of a transgenic organism is that the transgene, though rare, can spread in a natural population. An increase in transgene frequency is often assumed to be unlikely because transgenic organisms typically have some viability disadvantage. Reduced viability is assumed to be common because transgenic individuals are best viewed as macromutants that lack any history of selection that could reduce negative fitness effects. However, these arguments ignore the potential advantageous effects of transgenes on some aspect of fitness such as mating success. Here, we examine the risk to a natural population after release of a few transgenic individuals when the transgene trait simultaneously increases transgenic male mating success and lowers the viability of transgenic offspring. We obtained relevant life history data by using the small cyprinodont fish, Japanese medaka (Oryzias latipes) as a model. Our deterministic equations predict that a transgene introduced into a natural population by a small number of transgenic fish will spread as a result of enhanced mating advantage, but the reduced viability of offspring will cause eventual local extinction of both populations. Such risks should be evaluated with each new transgenic animal before release.

Animals↗
PubMed1999

Small intestine strangulation by components of the spermatic cord in two geldings.

Two adult Quarter Horse geldings were evaluated for signs of abdominal pain. Both horses had signs of depression and distended small intestines on abdominal palpation per rectum. Abdominal exploratory surgery was performed on both horses. In each instance, small intestine was found to be strangulated by components of the spermatic cord. Both horses were euthanatized because of a poor prognosis. Although not commonly observed, incarceration of intestine by components of the spermatic cord should be considered as a cause of small intestine strangulation in male horses. Early recognition of this condition would have increased these horses' chances of survival.

Animals↗
PubMed1998

Pulsed dye laser lithotripsy for treatment of urolithiasis in two geldings.

Transendoscopic pulsed dye laser lithotripsy was effective in the treatment of calcium carbonate urothlithiasis in 2 adult geldings. Perineal urethrotomy provided convenient access for standing transendoscopic lithotripsy and evacuation of a large cystic calculus in one gelding. In the second horse, an obstructive urethral calculus was fragmented and removed by a transurethroscopic approach. Pulsed dye laser lithotriptor is effective in fragmentation of the most common form (calcium carbonate) of uroliths in horses and may be performed in standing horses with reduced surgical invasiveness and trauma to the urinary tract, compared with conventional approaches. The principle disadvantages include cost of the procedure, which is comparable to laparocystotomy, and the time delay required to make arrangements for use of the pulsed dye laser lithotriptor.

Animals↗
PubMed1998

CLoning of equine interleukin 1 alpha and equine interleukin 1 beta and determination of their full-length cDNA sequences.

OBJECTIVES: To clone equine interleukin 1 alpha (IL-1 alpha) and equine interleukin 1 beta (IL-1 beta) and determine their full-length cDNA sequences. PROCEDURES: The mRNA isolated from lipopolysaccharide-stimulated cultured equine monocytes was reverse transcribed, and a cDNA library was constructed in a lambda phage. The cDNA library was screened by means of plaque hybridization with radiolabeled human IL-1 alpha and IL-1 beta cDNA probes. The cDNA nucleotide sequences for equine IL-1 alpha and equine IL-1 beta were determined by use of the dideoxy chain termination technique. The cDNA sequences were analyzed, using computer software, for sequence characteristics and compared with sequences reported for other species. RESULTS: The cDNA for equine IL-1 alpha was 1,728 base pairs in length with an ORF encoding a peptide of 270 amino acids with a predicted molecular mass of 30.823 kd. The cDNA for equine IL-1 beta was 1,473 base pairs in length with an ORF encoding a peptide of 268 amino acids with a predicted molecular mass of 30.342 kd. Similarity between amino acid sequence of equine IL-1 alpha and sequences for IL-1 alpha of other species ranged from 62.5 to 82.2%; similarity between amino acid sequence of equine IL-1 beta and sequences for IL-1 beta of other species ranged from 62.5 to 82.2%; similarity between amino acid sequences of equine IL-1 alpha and equine IL-1 beta was 26%. CONCLUSIONS AND CLINICAL RELEVANCE: Results establish a basis for studying the roles of interleukin 1 in healthy and diseased joints in horses.

Amino Acid Sequence↗
PubMed1998

Cloning of equine interleukin 1 receptor antagonist and determination of its full-length cDNA sequence.

OBJECTIVES: To clone equine interleukin 1 receptor antagonist (IL-1ra) and determine its full-length cDNA sequence. PROCEDURE: A cDNA library derived from lipopolysaccharide-stimulated equine monocytes was screened by means of plaque hybridization to radiolabeled equine IL-1ra DNA probes generated by means of the polymerase chain reaction. The cDNA nucleotide sequence for equine IL-1ra was determined by use of the dideoxy chain termination technique, analyzed by use of computer software for sequence characteristics, and compared with sequences reported for IL-1ra of other species. RESULTS: The cDNA of equine IL-1ra was 1,614 base pairs in length with an ORF encoding a peptide of 177 amino acids with a predicted molecular mass of 20.427 kd. Similarity between the amino acid sequence of equine IL-1ra and sequences for human, murine, rat, and lapine IL-1ra was 76%. Similarity between sequence for equine IL-1ra and sequences for equine interleukin-1 alpha and equine interleukin-1 beta were 22.6 and 24.6%, respectively. CONCLUSION: Comparison of the sequence for equine IL-1ra with sequences for IL-1ra of other species indicated a high degree of conservation. CLINICAL RELEVANCE: Results establish a basis for studying the roles of interleukin-1 in healthy and diseased joints in horses.

Amino Acid Sequence↗
PubMed1998

Evaluation of mild lameness in horses trotting on a treadmill by clinicians and interns or residents and correlation of their assessments with kinematic gait analysis.

OBJECTIVE: To estimate sensitivity and accuracy of subjective evaluation of mild lameness in horses during treadmill locomotion and to correlate subjective evaluation with kinematic analysis. ANIMALS: 19 lame and 5 clinically normal horses. PROCEDURE: Lameness was evaluated by subjective score and kinematic analysis before and after palmar digital nerve block (PDNB). Evaluations were made by 6 clinicians and 7 interns or residents. Within- and between-observer agreement analyses (kappa values) were calculated and compared, using a Student's t-test. Pearson's product-moment correlation coefficients were calculated between clinician's change in score and the change in kinematic variables after PDNB. RESULTS: Within-observer agreement was within the range expected for conditions of moderate diagnostic difficulty. Within-observer agreement was higher for clinicians than for interns or residents. Between-observer agreement was acceptable for scores within 1 value of each other. Between-observer agreement of change in lameness score after PDNB was poor. When kinematic variables were ranked with each clinician's subjective change in score, only 2 were among the top 3 for the majority of clinicians. Asymmetry of vertical head movement between contralateral forelimb stance phases and the point of maximum hoof height during swing decreased as lameness subjectively improved. CONCLUSION: Mild lameness may be difficult to evaluate during treadmill locomotion. Although clinicians were more repeatable in their subjective evaluation of lameness than interns or residents, they were not more reliable at detecting the true state of lameness. CLINICAL RELEVANCE: Lack of agreement between clinician scoring of mild lameness emphasizes the need to use more objective measures for quantifying lameness.

Animals↗
PubMed1995

Arthroscopic surgery for subchondral cystic lesions of the medial femoral condyle in horses: 41 cases (1988-1991).

Clinical signs, radiographic and arthroscopic findings, and outcome for 41 horses with subchondral cystic lesions of the medial femoral condyle treated by arthroscopic surgery were reviewed. There were 17. Quarter Horses, 15 Arabians, 8 Thoroughbreds, and 1 Holsteiner, with 28 (68%) of the horses being 1 to 3 years old. For all horses, the owners' complaint was mild to moderate hind limb lameness or an altered gait. Bilateral radiographic abnormalities of the medial femoral condyle were detected in 27 horses. Nineteen of the 27 horses had lesions identified bilaterally at arthroscopic surgery. In addition to the subchondral cystic lesion, 13 joints in 11 horses had an osteochondritis dissecans lesion on the articular surface of the medial femoral condyle that extended from the opening of the subchondral cystic lesion. Surgical debridement performed via arthroscopy was the only treatment for 37 lesions of 23 horses. Debridement followed by drilling of the defect bed was performed in 23 lesions of 18 horses. Complete follow-up information was obtained for 39 horses; 22 (56%) had a successful result and 17 (44%) had an unsuccessful result. In a separate analysis excluding horses with unsuccessful results because of factors not directly attributable to the subchondral cystic lesion of the medial femoral condyle, 23 of 31 (74%) horses had a successful result and 8 of 31 (26%) horses had an unsuccessful result.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Long-term fate and effects of exercise on sternal cartilage autografts used for repair of large osteochondral defects in horses.

Bilateral osteochondral defects (10 mm2 x 3 mm deep) were created on the distal articular surface of the radial carpal bone of ten, 2- to 3-year-old horses. One defect of each horse was repaired, using a sternal cartilage autograft (treated), and the other was left untreated (control). The horses were exercised on a high-speed treadmill at incrementally increased speed and duration over the course of 12 months. Horses were evaluated arthroscopically at 6 to 7 weeks, and clinical examinations were conducted weekly at exercise. Twelve months after surgery, carpuses of each horse were radiographed and clinically examined prior to euthanasia. A gross pathologic evaluation of each joint was conducted, and samples were collected for histologic, histochemical, histomorphometric, and biochemical evaluation. Radiographically, the grafted joints had more extensive evidence of arthropathy, and clinically, 8 of the 10 horses were more lame in the grafted limb. On the basis of histomorphometry, the repair tissue of the grafted defects contained a greater median percentage of hyaline cartilage (45%) than that of control defects (4.5%), and the control defects contained a greater percentage of fibrocartilage (82%) than did grafted defects (28.5%). A greater median percentage of repair tissue stained with safranin-O in the grafted defects (24.5%) than in the control defects (3.5%). On gross pathologic and histologic evaluation, repair tissue of the control defects had better continuity and was more firmly attached to the subchondral bone than was repair tissue of the grafted defects. Repair tissue of the grafted defects had extensive fissure and flap formation. Histologically, subchondral bone reactivity and fibroplasia was extensive in grafted joints. Repair tissue of grafted defects had a greater percentage of type II collagen (mean +/- SEM, 83.5 +/- 2.95%) than did controls (mean, 79.4 +/- 3.87%) that was not statistically significant. Hexosamine content was significantly higher (P < 0.05) in repair tissue of the grafted defect (mean, 28.9 +/- 3.00 mg/g of dry weight) vs control (mean, 20.6 +/- 1.85 mg/g of dry weight). On the basis of this experimental model, sternal cartilage autografts cannot be recommended at this time for repair of osteochondral defects in athletic horses.

Animals↗
PubMed1993

Reconstructive surgery of selected injuries of the head.

Traumatic injuries to the head region of the horse are a common presenting complaint. Because of a copious blood supply, these wounds typically exhibit a tremendous capability for healing. By following the basic principles of wound management and employing a few techniques unique for specific injuries, the healing of these wounds can result in a satisfactory outcome.

Animals↗
PubMed1993

Evaluation of occlusive dressings for management of full-thickness excisional wounds on the distal portion of the limbs of horses.

Two 2.5-cm2 full-thickness skin wounds were created surgically over the lateral aspect of the cannon bone of each limb of 6 horses (n = 48 wounds). Dressings evaluated were a nonadherent gauze pad (group 1); a synthetic semiocclusive dressing, (group 2); equine amnion (group 3); and a synthetic fully occlusive dressing (group 4). Wounds were assessed subjectively at each dressing change, and total wound area, area of granulation tissue, and area of epithelium in each wound were determined by computerized digital analysis of photographs of the wounds. Complete healing time (wound covered by epithelium) also was determined for each wound. Statistical comparisons were made, using Kruskal-Wallis analysis and a Mann-Whitney U test. Median time to complete healing was: group 1, 53 days; group 2, 71 days; group 3, 63 days; and group 4, 113 days. Time to complete healing was significantly longer for wounds of group-4 horses than all other groups, and wounds of group-1 horses healed faster than did those of group-2 horses (P < 0.05). Wounds in group-4 horses required significantly (P < or = 0.05) more excisions of granulation tissue (median, 11.5 times) than did those in group-1 (median, 3.5), group-2 (median, 5.5) or group-3 (median, 2.5) horses. Epithelial tissue was detected later in wounds of group-4 horses (median, 27 days) than in wounds of horses in groups 1, 2 or 3 (median, 17 days); however, this difference was not statistically significant.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Premarital contraceptive use: a discriminant analysis approach.

The ability of seven independent variables to predict accurately, from a sample of unmarried, sexually active students, which ones use reliable contraceptives and which ones use unreliable contraceptives, was investigated. Using discriminant analysis, the seven independent variables were age individuals started engaging in coitus, frequency of coitus, frequency of dating, length of time sex partners knew each other, number of sex partners, having anticipated coitus to occur, and the number of close friends who were thought to use birth control. The results indicated that these variables were accurate in predicting which students were users of contraceptives, with more than 80% of males and females being correctly classified. The number of close friends thought to use contraceptives was the most influential variable for both sexes, followed by length of time the partners knew each other.

Adult↗