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Biomedical subjects

C A Leonard

Publications and source records attributed to C A Leonard.

12 recordsLinked to original sources
PubMed2001

Feline lameness.

Feline lameness is an increasingly recognized clinical problem. Today's veterinary practitioner must be comfortable with his/her ability to diagnose the various conditions responsible for lameness in the cat and be able to discuss the significance of their findings with the client. Disease of the feline musculoskeletal system can be grouped into broad categories, including: trauma, arthritis, infectious causes, developmental disorders, neoplasia, and muscular problems. Specific diseases from each of these categories will be discussed, particularly those that differ in their presentation or clinical behavior from that same disease in the canine patient.

Animals↗
PubMed2001

Vascular response of the meniscus to injury: effects of immobilization.

Failed meniscal healing may lead to degenerative osteoarthritis of the knee. Healing is thought to be dependent upon an adequate blood supply, yet "normal" vascular changes during healing are not well understood. In this study we have quantified vasoactive and angiogenic responses to medial meniscal injury in a rabbit model under clinically relevant conditions, and related these to histological criteria of healing. Twenty-six adult rabbits were given a standardized meniscal injury; 12 of these had the hind limb immobilized by pinning. Eight normal controls and 12 sham-operated animals were also studied. After 4 weeks, animals underwent either vascular volume (vascular index) determination, or blood flow measurement using coloured microspheres. Histological analysis was also performed to assess meniscal healing. In injured animals, blood flow to the menisci was increased fivefold 4 weeks post-operative; this increase was prevented by immobilization. The vascular index of the menisci was also increased threefold by injury, but not significantly reduced by immobilization. Histological examination of injured menisci showed examples of healing and non-healing tears in both mobile and immobile groups. Meniscal injuries are associated with characteristic changes in vascularity and perfusion, and these changes likely play a significant role in the healing process. Characterization of the vascular responses to meniscal injury may lead to techniques that can promote reliable healing of meniscal tears and thereby improve clinical outcomes.

Animals↗
PubMed2000

Adaptation of post-traumatic angiogenesis in the rabbit knee by apposition of torn ligament ends.

Apposition of torn ligament ends has been shown to have a beneficial effect on healing of the medial collateral ligament; however, the mechanism underlying this improved recovery is unclear. Excessive post-traumatic angiogenesis, an inherent component of soft-tissue regeneration, may be functionally detrimental in relatively hypovascular tissues such as ligaments. The present study therefore examined the relationship between contact of transected ligament ends and vascular remodeling. Female New Zealand White rabbits were subjected to a gap injury, Z-plasty apposition, or sham operation to the midsubstance of the medial collateral ligament. Six weeks after treatment, the volume of vessels supplying the healing zone of the medial collateral ligament, as well as the ipsilateral lateral collateral ligament, posterior cruciate ligament. menisci, and medial capsule, was quantified by carmine red vascular casting. The volume of vessels supplying the neoligamentous scar formed by gap injury to the medial collateral ligament was found to be twice that of ligaments that had undergone the sham operation, and lateral collateral ligament and meniscal vascularity was also augmented in the injured joint. The medial collateral ligaments that underwent Z-plasty apposition exhibited a level of vascularity comparable with that of the control ligaments that had undergone the sham procedure, whereas meniscal and lateral collateral ligament vascularities remained elevated in this group. Capsular and posterior cruciate ligament vascularities were unaffected by gap injury or Z-plasty to the ipsilateral medial collateral ligament. These findings indicate that injury to the medial collateral ligament not only stimulates angiogenesis in the healing ligament, but other ipsilateral soft tissues also undergo vascular remodeling. Furthermore, apposition of an injured medial collateral ligament modifies these pro-angiogenic events, and this may partly explain why contact of torn ligament ends is beneficial for post-traumatic recovery of an injured joint.

Adaptation, Physiological↗
PubMed2000

A role for calcitonin gene-related peptide in rabbit knee joint ligament healing.

Knee joint ligament healing has been shown to be improved when the torn ligament ends remain in contact, however, the rationale for these effects is unknown. The sensory neuropeptide calcitonin gene related peptide (CGRP) has potent trophic and vasodilatatory properties and as such is thought to be advantageous in wound repair. In ascertaining a role for CGRP in rabbit medial collateral ligament healing, the present study examined changes in CGRP-like immunoreactivity (CGRP-LI) and CGRP-mediated vasomotor responses in gap injured (non-contact), Z-plasty apposed (contact), and sham operated control medial collateral ligaments. At 6 weeks post-trauma, CGRP-LI decreased in the healing zone of gap injured and Z-plasty apposed medial collateral ligaments compared with controls, and non-contact ligament nerve fibres exhibited an abnormal morphology. Topical administration of CGRP (10(-13) to 10(-9) mol) caused a dose-dependent increase in ligament perfusion in each experimental group of knees. The CGRP-mediated vasodilatation associated with gap injured ligaments was not significantly different from controls (P = 0.06), whereas apposed medial collateral ligaments showed an augmented response to the peptide (P < 0.0005). These findings indicate that the beneficial effects of ligament interposition post-trauma may be related to an enhanced responsiveness to CGRP in conjunction with a more typical re-innervation profile. Conversely, the aberrant characteristics of CGRP-LI nerves occurring in gap injured tissue is suggestive of impaired CGRP release which may explain the poor functional recovery associated with these ligaments.

Animals↗
PubMed1989

Rocastine (AHR-11325), a rapid acting, nonsedating antihistamine.

Rocastine [AHR-11325, 2-[2-(dimethylamino)ethyl]-2,3-dihydro-4-methylpyrido-[3,2-f]-1,4- oxazepine-5(4H)-thione (E)-2-butenedioate)] is a rapid-acting, potent, nonsedating antihistamine. In guinea pigs challenged with a lethal dose of histamine, rocastine is as effective [based on 1 hr. oral, protective dose (PD50S)] as brompheniramine, chlorpheniramine, pyrilamine, and promethazine and superior to astemizole, diphenhydramine, terfenadine, and oxatomide. Rocastine has a faster onset of action than does terfenadine; rocastine being as effective with a 15 min pretreatment time (PD50 = 0.13 mg/kg) as it is with a 1 hr pretreatment time (PD50 = 0.12 mg/kg), while the 15 min PD50 of terfenadine (PD50 = 44.0 mg/kg) is 22 times greater than the 1 hr PD50 (PD50 = 1.93 mg/kg). Against aerosolized histamine, rocastine was 7.12 x, 2.63 x, and equipotent to pyrilamine in preventing histamine-induced prostration at pretreatment times of 1,3, and 6 hr, respectively. Rocastine protected guinea pigs from collapse induced by aerosolized antigen; rocastine was approximately 36 x more potent (based on 1 hr PD50) than diphenhydramine and as potent as oxatomide and terfenadine. Rocastine did not alter the EEG of cats at doses in vast excess (150x) of its antihistaminic dose nor did it potentiate yohimbine toxicity in mice. Further, rocastine possesses no anticholinergic, antiadrenergic, or antiserotonergic properties in vitro. Rocastine is a selective, nonsedating, H1-antagonist with a rapid onset of action.

Anaphylaxis↗
PubMed1989

Benzo- and pyrido-1,4-oxazepin-5-ones and -thiones: synthesis and structure-activity relationships of a new series of H1 antihistamines.

A series of novel benzo- and pyrido-1,4-oxazepinones and -thiones which represents a new structural class of compounds possessing H1 antihistaminic activity was synthesized, and the SARs were evaluated. The antihistaminic activity was determined by blockade of histamine-induced lethality in guinea pigs. The sedative potential was determined by comparison of the EEG profiles of the compounds with those of known sedating and nonsedating antihistamines. Several of the compounds were shown to possess potent H1 antihistaminic activity and to be free of the cortical slowing with synchronized waves and spindling activity found in the EEG of sedative antihistamines. One compound, 2-[2-(dimethylamino)ethyl]-3,4-dihydro-4-methylpyrido[3,2-f]-1,4- oxazepine-5(2H)-thione (rocastine) is currently undergoing clinical evaluation as a nonsedating H1 antihistamine.

Animals↗
PubMed1986

Antagonism of cisplatin-induced emesis by metoclopramide and dazopride through enhancement of gastric motility.

The antiemetic activity, gastric motor activity, and dopamine receptor effects of metoclopramide, dazopride, and sulpiride were assessed to establish if enhancement of gastric motility or antagonism of central dopamine receptors is the predominant action for drug-induced suppression of cisplatin-induced emesis. Emesis produced in dogs by cisplatin is antagonized by metoclopramide and dazopride. The antiemetic actions of metoclopramide and dazopride are associated with their ability to enhance gastric motor activity. Dazopride, unlike metoclopramide, has minimal dopamine receptor antagonist properties. Sulpiride is a potent dopamine receptor antagonist; however, it had no effect on the stomach and was ineffective in suppressing cisplatin-induced emesis.

Animals↗
PubMed1979

AHR-6646: a new, long-acting neuroleptic.

1. AHR-6646 blocked d-amphetamine lethality in mice under aggregated conditions when the pretreatment interval was between one hour and seven days. 2. Conditioned avoidance responding in mice and cats was suppressed by AHR-6646 in doses that did not impair escape behavior. The duration of this effect was markedly prolonged. 3. AHR-6646 produced catalepsy in rats. The onset of this effect was delayed and the duration was prolonged when compared with that of chlorpromazine. 4. Apomorphine-induced pivoting in mice with unilateral lesions of the caudate nucleus was suppressed by AHR-6646. 5. AHR-6646 was a potent antiemetic agent in dogs, with a delayed onset and prolonged duration of action.

Animals↗