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Biomedical subjects

L E Freeman

Publications and source records attributed to L E Freeman.

11 recordsLinked to original sources
PubMed2001

Drugs used in the treatment of attention-deficit/hyperactivity disorder affect postsynaptic firing rate and oscillation without preferential dopamine autoreceptor action.

BACKGROUND: Current theories propose that low doses of catecholaminergic stimulants reduce symptoms in patients with attention-deficit/hyperactivity disorder by acting on autoreceptors to reduce catecholaminergic transmission; few data are available that directly address this hypothesis. METHODS: We investigated the autoreceptor and postsynaptic receptor actions of systemically administered stimulants on dopaminergic systems in rats with single-unit recording in the substantia nigra pars compacta and globus pallidus, respectively. RESULTS: Dose-response curves for rate indicated that the potencies of the indirect-acting agonists methylphenidate and D-amphetamine at dopaminergic autoreceptors were not greater than at postsynaptic receptors; in fact, D-amphetamine was more potent postsynaptically. In addition to effects on firing rate, spectral/wavelet analyses indicated that these drugs had prominent effects on postsynaptic multisecond oscillations. These oscillations were shifted by stimulants from baseline periods of approximately 30 sec to periods of 5-10 sec. Effects on pattern were found at doses as low as 1.0 mg/kg (methylphenidate) and 0.2 mg/kg (D-amphetamine). At this latter dose, D-amphetamine had little effect presynaptically. CONCLUSIONS: These and prior results demonstrate that there is no autoreceptor-preferring dose range of catecholaminergic stimulants; these drugs at low doses are unlikely to reduce motor activity by this mechanism. Nonetheless, they might affect attentive and cognitive processes by modulating multisecond temporal patterns of central activity.

Animals↗
PubMed2001

Cocaine or selective block of dopamine transporters influences multisecond oscillations in firing rate in the globus pallidus.

Previous studies have shown that direct-acting dopamine agonists modulate the multisecond oscillations which are present in globus pallidus spike trains in vivo in awake rats. To investigate possible modulation by endogenous dopamine and by other monoamines, and by drugs with abuse potential, cocaine or selective monoamine uptake blockers were injected systemically during extracellular recording of single globus pallidus neurons and the results analyzed with spectral and wavelet methods. Both cocaine and the selective dopamine uptake blocker GBR-12909 significantly shortened the period of multisecond oscillations, as well as increasing overall firing rate. Cocaine effects were blocked by dopamine antagonist pretreatment, as well as by N-methyl-D-aspartate receptor antagonist (MK-801) pretreatment. Desipramine and fluoxetine (blockers of norepinephrine and serotonin uptake, respectively) had no significant effects on multisecond oscillations. The results suggest that dopamine has a primary role among monoamines in modulating multisecond oscillations in globus pallidus activity, and that tonic dopaminergic and glutamatergic transmission is necessary for normal slow oscillatory function.

Action Potentials↗
PubMed1996

Alterations in equine guttural pouch morphology with head position: observations using a new technique for producing accurate casts.

BACKGROUND: An improved technique for preparing casts of the equine guttural pouch is described. The new technique is simplified and inexpensive in comparison to previous techniques and produces highly accurate anatomic models which are both durable and flexible. METHODS: Silicone rubber bathtub caulk was injected into the guttural pouches of horse cadavers. The silicone was allowed to cure overnight, and casts were removed by dissection. The new technique was then used to evaluate changes in the shape of the guttural pouch with changes in head position. RESULTS: With flexion of the atlanto-occipital joint, the lateral compartment of the guttural pouch in particular was found to change considerably in size in shape. The angle of inclination of the ventral border of this pouch increased with flexion, as did the depth of the impression made by the rostral portion of the stylohyoid bone. In addition, the lateral compartment diminished in thickness rostrally in casts from flexed animals. CONCLUSIONS: The viscous silicone caulk resulted in superior casts of the equine guttural pouch. Observations of changed pouch shape with head position agree well with previous reports of increased difficulty in draining the lateral compartment of the horse's guttural pouch when the head is held in the flexed position.

Animals↗
PubMed1991

Axial pattern flap based on the caudal auricular artery in dogs.

An axial pattern flap that was based on the sternocleidomastoideus branches of the caudal auricular artery and vein was developed. Control flaps, which included ligation and division of the caudal auricular artery and vein, were similarly developed on the contralateral aspect of the neck. Mean survival of caudal auricular artery axial pattern flaps (85.2%), compared with control flaps (63.9%), was significantly different (P less than 0.05). On the basis of results of this study, an axial pattern flap based on the sternocleidomastoideus branches of the caudal auricular artery and vein may be a source of skin for reconstructive procedures of the head and neck.

Animals↗
PubMed1986

Observations about the normal and abnormal embryogenesis of the canine lip and palate.

Twenty-three puppies with cranofacial and limb abnormalities from a family of Australian shepherd dogs were studied anatomically. Limb abnormalities included lumbar scoliosis, short malformed tibias and fibulas, and polydactyly. Craniofacial abnormalities consisted of retronathia, cleft palate, and cleft lip. The clefts can be separated into three categories: group I, cleft of the secondary palate associated with a midline cleft lip; group II, unilateral cleft of the lip and primary and secondary palate; and group III, complete bilateral cleft of the lip and primary and secondary palate. Comparing human clefts with the canine clefts suggests that the development of the secondary palate is similar whereas the development of the upper lip is different. In the dog, the maxillary processes fuse in the midline to produce the majority of the upper lip, whereas in the human the upper lip is composed of fused maxillary and medial nasal processes.

Animals↗
PubMed1985

Lymph drainage of the conjunctiva: topographic anatomic study in calves.

The topographic pattern of lymph drainage from the conjuctiva was ascertained in 1- to 2-week-old calves. Multiple, small lymph vessels within and on the surface of the orbicularis oculi muscle converged to form fewer vessels which followed the course of the superficial temporal artery and vein or crossed the zygomatic arch in a more rostral position to reach the primary site of lymph collection, the parotid lymph node. Marker dye, injected into the subconjunctiva, was collected in the midrostral and rostroventral parts of the node. Drainage from the parotid node passed via multiple lymph vessels into the lateral retropharyngeal node, where marker dye concentrated in the rostrodorsal aspect of the node. Single or multiple lymph vessels carried drainage from the lateral retropharyngeal node indirectly by way of the cranial deep cervical lymph node or directly into the tracheal lymph trunk.

Animals↗
PubMed1984

Ectopia cordis thoracoabdominalis in a piglet.

A congenital anomaly characterised by displacement of the heart through a ventral body wall fissure involving the thoracic and cranial abdominal regions was recorded in a female Yorkshire-cross piglet. Dissection to assess the morphology of the developmental defect and a summary review of the literature on ectopia cordis were made. This case appears to be one of only three of ectopia cordis thoracoabdominalis reported in swine.

Abdominal Muscles↗
PubMed1976

Structure of plant cell walls. Purification and characterization of a beta-1,4-galactanase which degrades a structural component of the primary cell walls of dicots.

Wild type Bacillus subtilis, when grown on a soybean arabinan-galactan, secretes a beta-1,4-galactanase which has been purified more than 200-fold from the culture fluid. Affinity chromatography was the most effective step in a purification procedure which resulted in a preparation that contained only a single 40,000 molecular weight protein band upon sodium dodecyl sulfate-disc gel electrophoresis. The purified galactanase digests a beta-1,4-galactan purified from citrus pectin and digests partially the isolated cell walls of suspension-cultured sycamore cells. The predominant product of the enzymic degradation of the substrates tested is a 4-linked tetragalactose. Evidence is presented to support the hypothesis that the galactanase attacks its substrates in both an exo- and endo-manner. The products obtained upon galactanase digestion of the soybean arabianin-galactan demonstrate that the earlier proposal concerning the structure of this polysaccharide must be incorrect.

Bacillus subtilis↗