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Biomedical subjects

A S Miller

Publications and source records attributed to A S Miller.

At least 19 recordsLinked to original sources
PubMed1995

Effects of a cannabinoid on spontaneous and evoked neuronal activity in the substantia nigra pars reticulata.

Single unit electrophysiology was used to explore the role of cannabinoid receptors in the substantia nigra pars reticulata. Intravenous and intraperitoneal injections of the potent and selective synthetic cannabinoid (R)-(+)-[2,3-dihydro-5-methyl-3-[(4-morpholinyl)methyl]pyrrolo[1,2,3- de]-1,4-benzoxazin-6-yl](1-naphthalenyl) methanone (WIN 55,212-2) produced modest but significant increases in the spontaneous firing rate of neurons in the substantia nigra pars reticulata. In a second set of experiments, WIN 55,212-2 (up to 1.0 mg/kg i.v.) antagonized the inhibition of firing produced in the substantia nigra pars reticulata by electrical stimulation of the striatum. The pharmacological specificity of this effect was demonstrated using the inactive enantiomer WIN 55,212-3. The possibility that WIN 55,212-2 exerts its effects by regulating gamma-aminobutyric acid (GABA) release from striatonigral fibers was suggested by the observation that bicuculline (up to 0.5 mg/kg i.v.) reversed the effect of striatal stimulation. It thus appears that cannabinoid receptors on striatonigral neuron terminals may regulate movement by disinhibiting the activity of substantia nigra pars reticulata neurons, perhaps by inhibiting the release of GABA into the substantia nigra pars reticulata.

Analgesics↗
PubMed1995

Identification of the ligand-binding domains of CD22, a member of the immunoglobulin superfamily that uniquely binds a sialic acid-dependent ligand.

CD22 is a B cell-restricted member of the immunoglobulin (Ig) superfamily that functions as an adhesion receptor for leukocytes and erythrocytes. CD22 is unique among members of the Ig superfamily in that it has been suggested to bind a series of sialic acid-dependent ligands, potentially through different functional domains expressed by different splice variants of CD22. In this study, the epitopes identified by a large panel of function-blocking and non-function-blocking CD22 monoclonal antibodies were localized to specific Ig-like domains, revealing that all function-blocking monoclonal antibodies bound to the first and/or second Ig-like domains. Consistent with a single ligand-binding region, the two amino-terminal domains were the functional unit that mediated CD22 adhesion with lymphocytes, neutrophils, monocytes, and erythrocytes. The predominant cell surface species of CD22 was a full length 140,000 relative molecular mass seven Ig-like domain glycoprotein and a minor 130,000 relative molecular mass form lacking the fourth domain. While the two amino-terminal Ig-like domains of CD22 are structurally similar to those found in other members of the Ig superfamily involved in cell adhesion and containing an amino acid sequence motif associated with integrin recognition, site-directed mutagenesis of critical residues surrounding this motif did not disrupt CD22-mediated adhesion. These results demonstrate that the unique ligand-binding properties of CD22 are distinct from those of other members of the Ig superfamily involved in integrin-mediated cell adhesion.

Amino Acid Sequence↗
PubMed1995

Factors that influence functional outcome after coloanal anastomosis for carcinoma of the rectum.

Thirty consecutive patients had laboratory assessment of anorectal function after rectal excision and stapled coloanal anastomosis for rectal carcinoma. Eleven patients experienced perfect continence but 19 had faecal leakage with or without urgency of defaecation. Median (interquartile range) function was related to the pressures generated in the anal sphincter at rest (good versus poor function: 80 (63-91) versus 51 (23-60) cmH2O, P < 0.01), during maximum squeeze (160 (126-203) versus 102 (58-112) cmH2O, P < 0.01) and during reflex inhibition (58 (23-63) versus 36 (18-54) cmH2O, P < 0.05). Poor function was significantly commoner in women than in men (P < 0.01). These findings suggest that occult damage may have occurred to the anal sphincter before low anterior resection. Careful preoperative evaluation with manometry and endoanal ultrasonography may detect such damage and allow selection of patients for colopouch reconstruction.

Adult↗
PubMed1995

Clinical and physiological evaluation of anorectal eversion during restorative proctocolectomy.

Fifty patients had a restorative proctocolectomy with stapled end-to-end ileoanal anastomosis by the eversion technique. Median (interquartile range) maximum resting anal pressure was 90 (73-116) cmH2O before restorative proctocolectomy and 71 (51-88) cmH2O 1 year after surgery (P < 0.001). Median maximum squeeze pressure was 141 (110-185) cmH2O before surgery and 146 (118-186) cmH2O 1 year after surgery (P not significant). Median thresholds for sensation in the lower third of the anal canal before and 1 year after surgery were 5.3 and 7.1 mA, respectively (P = 0.006). One year after restorative proctocolectomy, all patients were continent, although two experienced leakage of mucus requiring a pad. Forty-two patients (84 per cent) could discriminate between faeces and flatus. Eversion of the anorectum during restorative proctocolectomy impairs the motor and sensory functions of the anal sphincter. Most patients achieved satisfactory anal continence, however, despite these physiological changes.

Adolescent↗
PubMed1995

Recovery of physiologic and clinical function after low anterior resection of the rectum for carcinoma: myth or reality?

PURPOSE: The aim of this study was to examine the serial changes that take place in the first year after low anterior resection for rectal carcinoma, in terms both of anorectal physiology and clinical bowel function. Our hypothesis was that some patients never regain satisfactory anorectal function, because the operative procedure leads to permanent impairment of anorectal reflex and motor function. METHOD: Nineteen patients underwent serial tests of anorectal function, before and for one year after low anterior resection. The median level of the anastomosis above the anal high-pressure zone was 3 (range, 1-6) cm. RESULTS: Anal resting pressure (median (interquartile range)) was significantly decreased three months after operation (62 (46-72) cm H2O) and one year after operation was still significantly less (58 (48-73) cm H2O) than before operation (77 (58-93) cm H2O) (P < 0.01). Maximum tolerated volume in the neorectum decreased from 130 (88-193) ml before operation to 80 (51-89) ml three months after operation (P < 0.005) but returned to preoperative values by six months (125 (60-140) ml) (P = not significant) and remained at these values one year after operation. The volume in the "neorectal" balloon required to elicit a maximum rectoanal inhibitory reflex was significantly less three months after operation than before operation (50 (43-60) ml compared with 100 (73-100) ml; P < 0.005); one year after operation, the volume required was still significantly less than before operation (50 ml vs. 100 ml) (P < 0.015). Bowel frequency increased from 1 (1-2) in 24 hours before operation to 4 (2-5) times in 24 hours after operation and remained at 4 times in 24 hours throughout the first year after operation. Three months after operation, 53 percent of patients experienced some degree of fecal leakage and 24 percent experienced urgency of defecation. These aspects of bowel function improved with time, but even one year after operation, 29 percent of patients continued to experience fecal leakage and 18 percent wore a protective pad. CONCLUSIONS: Anal resting pressure decreased significantly after low anterior resection and did not recover in the course of the first year after operation. Moreover, the volume of an air-filled balloon in the neorectum that was required to elicit maximum inhibition of the anal sphincter was significantly less after anterior resection that before operation. These long-term and presumably permanent changes in physiologic behavior of the anoneorectum after low anterior resection provide an explanation for the failure of some patients to regain satisfactory bowel function following that procedure.

Aged↗
PubMed1995

Rhabdomyosarcoma of the oral cavity. Report of four cases.

Clinical and pathologic findings of four cases of rhabdomyosarcoma of the oral soft tissues are described that include findings from immunohistochemistry and electron microscopy. Three cases occurred in children under 16 years of age and one in a 22-year-old. Included is a brief discussion on reported gene abnormalities that may contribute to neoplastic development.

Adolescent↗
PubMed1995

Search for evidence of three viral agents in radicular (periapical) cysts with immunohistochemistry.

Sections from 20 paraffin-embedded radicular cysts and positive-control subjects were subjected to immunostaining procedures after treatment of the sections with polyclonal antibodies was performed to search for evidence of human papilloma virus and herpes viruses 1 and 2 in the lining epithelium. All 20 specimens examined were negative for the presence of all three viruses.

Herpesvirus 1, Human↗
PubMed1995

Preservation of complete anal sphincteric proprioception in restorative proctocolectomy: the inhibitory reflex and fine control of continence need not be impaired.

This study evaluates whether reflux function of the anal sphincter remains unchanged after restorative proctocolectomy, provided that the sphincter remaining is kept intact, without mucosal stripping or endo-anal anastomosis. Paired tests of anorectal function were performed before, and a median of 6 (range 2-12) months after restorative proctocolectomy with stapled, end to end pouch-anal anastomosis. Beforehand, distension of the rectum with 50 ml of air produced a median (interquartile range) increase in pressure within the rectum of 22 (15-29) cm H2O and reflex inhibition of the anal sphincter from a pressure of 76 (62-106) cm H2O to a pressure of 34 (15-52) cm H2O. After the procedure, distension of the ileal pouch with 50 ml of air produced an increase in pressure within the pouch of only 5 (4-8) cm H2O (p < 0.001 compared with beforehand) and reflex inhibition of the anal sphincter from a pressure of 62 (25-79) cm H2O to 37 (17-68) cm H2O. Maximal reflex inhibition of the upper third if the anal sphincter to a pressure of 26 (15-48) cm H2O was observed when pressure within the pouch increased by 16 (11-22) cm H2O. After restorative proctocolectomy, all patients were continent (two experienced minor nocturnal leakage of mucus) and 25 could discriminate between flatus and faeces. Thus, reflux function was preserved in response to changes in pressure, ensuring that the subtler aspects of anal continence were preserved.

Adolescent↗
PubMed1995

The perfect pelvic pouch--what makes the difference?

The aim of this study was to determine what factors are important for the achievement of perfect anal continence after restorative proctocolectomy. One hundred patients underwent paired studies of anorectal physiology before and one year after restorative proctocolectomy with pelvic ileal reservoir (11 S, 25 J, 64 W) with stapled ileoanal anastomosis, without mucosectomy. Fifty seven patients attained perfect anal continence and were able to discriminate flatus from faeces with such confidence that they were able to release flatus safely without fear of faecal soiling. The remaining 43 patients experienced minor problems in this regard. Four factors were found to correlate significantly with a perfect functional result (median, perfect v imperfect): maximum resting anal pressure (72 v 57 cm H2O, p < 0.02), the sensory threshold in the upper and mid-anal canal (7.3 v 8.6 and 5.3 v 7.0 mA, p < 0.05 and p < 0.02), compliance of the ileal reservoir (12.4 v 7.6 ml/cm H2O, p < 0.01), and the presence of a pouch-anal inhibitory reflex (56 of 57 patients v 29 of 43 patients, p < 0.01). The quality of anal continence depends on several factors: a complaint ileal reservoir, a strong sensitive anal sphincter, and normal reflex coordination of the activities of the reservoir and the sphincter. Excellent pouch-anal coordination is obtainable irrespective of the design of the reservoir, provided that these criteria are satisfied.

Adolescent↗
PubMed1994

Peripheral odontogenic keratocyst.

The gingival cyst of the adult exhibits an epithelial lining that is essentially the same as the lateral periodontal cyst. Although the gingival cyst of the adult exhibits some morphologic variability, its lining is generally considered to be nonkeratinized. Nonetheless, rare cases of gingival cyst of the adult that exhibit a keratinized epithelial lining have been reported in the literature. There is now a growing tendency to consider this variant as a separate entity. This article describes six cases of gingival cysts that exhibit the histologic features of the odontogenic keratocyst. Evidence from this series suggests that the biologic behavior of this subset of gingival cysts is different from that of the generic gingival cyst of the adult and that the term peripheral odontogenic keratocyst more accurately describes this entity.

Adult↗
PubMed1992

Review of neural network applications in medical imaging and signal processing.

The current applications of neural networks to in vivo medical imaging and signal processing are reviewed. As is evident from the literature neural networks have already been used for a wide variety of tasks within medicine. As this trend is expected to continue this review contains a description of recent studies to provide an appreciation of the problems associated with implementing neural networks for medical imaging and signal processing.

Diagnostic Imaging↗
PubMed1992

Survey of tissue diagnostic services in U.S. dental schools - 1990.

Tissue diagnostic services in U.S. dental schools were surveyed to determine activities during 1990. Results were compared with those of similar surveys conducted in 1953, 1958, 1969, 1975, 1980, and 1985. The information gathered from this survey reveals a progressive growth and development of tissue diagnostic services. This is seen not only in the increased numbers of biopsy accessions, which increased by 37% since the last survey, but is also reflected in the diversity of services now offered by oral pathologists.

Biopsy↗
PubMed1992

Neural networks for electrical impedance tomography image characterisation.

The Southampton electrical impedance tomography (EIT) system used a Sheffield data acquisition unit and a PC based 'Harlequin' transputer card to reconstruct and display images of the distribution of internal conductivity within the thorax. The system produces real-time images relating to both cardiac and pulmonary function. As a first step towards diagnosis using these images neural nets have been applied to the identification of regions of interest in the EIT images for which some activity with time, such as ventricular ejection, is sought. This paper addresses the use of a back-projection network to identify characteristic regions within the images. The network facilitates the production of automated real-time activity plots by defining their effective extent in the images of specific organs. The application is novel within the medical imaging field as the aim is to use neural networks for real-time image analysis.

Electric Conductivity↗
PubMed1991

Amyloidosis of the oral cavity: report of five cases.

Five cases of amyloidosis involving structures in the oral cavity are reported. Three cases appeared to be secondary systemic amyloidosis, one case was the systemic form associated with multiple myeloma, and one case appeared to represent nodular or localized amyloidosis. All cases appeared in persons over 63 years of age, and the most common area of involvement was the tongue. The nature of so-called amyloid deposits in certain odontogenic tumors is discussed in light of recent knowledge of amelogenins and enamelins.

Aged↗
PubMed1990

Effect of enamel microabrasion compound on human gingiva: report of a case.

A new material to be used in the procedure of enamel microabrasion has been recently introduced. Because the compound contains hydrochloric acid, the manufacturer recommends many safety precautions, especially use of the rubber dam. This case report documents the effect of the enamel microabrasion compound on the gingiva of one human subject and verifies the need for careful handling of the material.

Adult↗
PubMed1989

The relationship between gastrin cells and bombesin-like immunoreactive nerve fibres in the gastric antral mucosa of guinea-pig, rat, dog and man.

The relationship between bombesin-like immunoreactive (bombesin-LI) nerve fibres and gastrin-LI G-cells was examined in gastric antral mucosa from guinea-pig, rat, dog and man using a double-labelling fluorescence immunohistochemical technique. The greatest density of bombesin-LI nerve fibres was found within the basal mucosa in all species and the density of innervation decreased towards the luminal surface. Most G-cells were in a band occupying approximately the middle third of the mucosa. The proportion of G-cells found within a distance of 2 microns from bombesin-LI nerve fibres was low in all species (6% in the guinea-pig, 22% in the rat, 14% in the dog, and 9% in the human). It is proposed that the neuropeptide released from bombesin-LI antral mucosal nerve fibres traverses distances of greater than several microns to reach the target G-cells. This may be achieved by passage through the mucosal microcirculation.

Adult↗
PubMed1988

Survey of tissue-diagnostic services in United States dental schools--1985.

Tissue-diagnostic services in United States dental schools were surveyed to determine activities during 1985. Results were compared with those of similar surveys conducted in 1953, 1958, 1969, 1975, and 1980. A continuing increase in the number of specimens processed has occurred, and there has been a parallel increase in the number of malignant specimens noted. The percentage of malignant specimens in relation to total specimens processed has not changed significantly.

Biopsy↗