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Biomedical subjects

A D Smith

Publications and source records attributed to A D Smith.

At least 271 records · Page 15Linked to original sources
PubMed1991

Endourology of lower urinary tract.

Two methods for obtaining percutaneous access to the bladder are described. Depending on whether or not urethral access is available an endoscopic or fluoroscopic technique may be applied. We have successfully performed suprapubic percutaneous cystolitholapaxy, antegrade fulguration of posterior urethral valves, antegrade cystourethroscopy as an adjunct for urethroplasty, and internal drainage of a bulbar urethral abscess. Endourologic techniques may be readily applied to the lower urinary tract and may be specifically indicated in certain situations.

Abscess↗
PubMed1991

Individual differences in locomotor activity and sensitization.

Male rats were screened for locomotor activity in a novel environment and divided into high (HR) and low (LR) responders based on whether their locomotor activity score for the first hour was above or below the median locomotor activity for the subject sample. Subsequently, the locomotor response to repeated administration of either amphetamine (AMPH; 0.5 mg/kg), cocaine (10 mg/kg), scopolamine (0.5 mg/kg) or saline was monitored in separate groups of HR and LR rats. HR rats had significantly higher overall activity scores than LR rats for all 3 drugs. Both HR and LR rats developed tolerance at the same rate to repeated scopolamine administration. In contrast, only HR rats showed pronounced sensitization to the locomotor stimulating properties of AMPH and a direct correlation was evident between the locomotor response to novelty and the magnitude of sensitization. These results suggest that an individual's response to a novel environment can, to a certain extent, predict drug-induced locomotor activity and that individual differences in the response to novelty and sensitization to AMPH may result from individual variations in a common neural mechanism.

Amphetamine↗
PubMed1991

The in vivo microdialysis recovery of dopamine is altered independently of basal level by 6-hydroxydopamine lesions to the nucleus accumbens.

The present study was designed to test the hypothesis that the active neurotransmitter processes of release and uptake affect the in vivo microdialysis recovery of dopamine (DA) in the nucleus accumbens (N ACC) of the rat. The in vivo recovery for DA was established for rats which had received either unilateral infusions of the neurotoxin 6-hydroxydopamine (6-OHDA, 8 micrograms) or vehicle (0.2 micrograms ascorbate). In the quantitative dialysis method used (point of no net flux method), DA is added to the perfusate at concentrations above and below the expected extracellular concentration (0, 5, 10 and 20 nM) and DA is measured in the dialysate from the brain to generate a series of points. A linear fit is performed, the slope of which is the in vivo recovery of the dialysis probe. The in vivo recovery of the 6-OHDA group was 30 +/- 3% which was significantly lower (P less than 0.002) than the in vivo recovery of the control group which was 60 +/- 3% (mean +/- SEM; n = 6/group). The zero intercept of this regression is the point of no net flux, which is the extracellular concentration of DA independent of the probe sampling characteristics. The extracellular DA concentration for the 6-OHDA group was 7.8 +/- 1.1 nM, which was not significantly different than the control group which was 6.9 +/- 0.7 nM.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Importance of basic and applied research from the viewpoints of investigators in the psychology of aging.

In this series of presentations, the importance and practical implications of many different research programs in the psychology of aging is presented from the viewpoints of the investigators themselves. These scientists discuss the implications and significance of their work for society as it affects other scientists, policy-makers, the media, and the public. The discussions make clear that the many of the problems associated with aging are essentially behavioral problems which can be prevented through behavioral change in the early as well as later years of the lifespan.

Aged↗
PubMed1991

Endopyelotomy.

Explore the source record for details and available documents.

Humans↗
PubMed1991

The partial dissection trabeculectomy.

We retrospectively reviewed the results of the first 20 procedures of a modification of the penetrating trabeculectomy ab externo procedure in which an attempt is made to limit subconjunctival fibrosis at the filtering site. With a follow-up ranging from 2 to 29 months, the average intraocular pressure was reduced from 33 to 12 mm Hg.

Adolescent↗
PubMed1990

Purification and characterization of bovine brain type I phosphatidylinositol kinase.

Investigation into the phosphatidylinositol kinase activities in bovine brain has revealed the presence of a type I PtdIns kinase activity. This classification is based upon potent inhibition by neutral detergent and the production of a phosphatidylinositol phosphate that can be distinguished from phosphatidyl-inositol-4-phosphate [PtdIns(4)P] by thin-layer chromatography. The enzyme has been substantially purified and the activity is associated with an 85-kDa polypeptide on SDS/polyacrylamide gel electrophoresis. Analysis of the product confirms the identification of the enzyme as a type I PtdIns kinase. The purified kinase has been characterized with respect to substrate dependence (Mg2+, ATP, PtdIns), substrate presentation (pure lipid versus mixed micelle) and specificity [PtdIns versus PtdIns(4)P and phosphatidylinositol 4,5-bisphosphate].

1-Phosphatidylinositol 4-Kinase↗
PubMed1990

Verapamil inhibits phosphatidic acid formation and modifies phosphoinositide metabolism in stimulated platelets.

Rabbit platelet-rich plasma was incubated with [32P]orthophosphate, after which the platelets were washed, further incubated in the absence or presence of verapamil and subsequently stimulated with PAF-acether or thrombin. In the absence of verapamil, a rapid increase in radioactivity in phosphatidic acid was observed in platelets stimulated with PAF-acether or thrombin. This was inhibited by verapamil over the concentration range 10(-7) to 10(-4) M, at which concentration the rise in phosphatidic acid was completely abolished. In unstimulated platelets, 10(-4) M verapamil induced an increase in radioactivity in polyphosphoinositides but not significantly in phosphatidylinositol. When these verapamil-treated platelets were stimulated with PAF-acether or thrombin, there was a rapid, sustained loss of the additional radioactivity induced in the polyphosphoinositides by verapamil. Polyphosphoinositide radioactivity remained unchanged in platelets stimulated in the absence of verapamil. Verapamil may stimulate formation of a separate pool of polyphosphoinositide which is susceptible to agonist-induced phospholipase C, and failure to re-synthesize this polyphosphoinositide could result from inhibition of phosphatidic acid synthesis.

Animals↗
PubMed1990

Electron microscopic evidence of a monosynaptic pathway between cells in the caudal raphé nuclei and sympathetic preganglionic neurons in the rat spinal cord.

Electrophysiological and anatomical studies have suggested the existence of a pathway between the caudal raphé nuclei and regions of the spinal cord containing the sympathetic preganglionic neurons. However synaptic connections between cells in the raphé nuclei and identified sympathetic preganglionic neurons have not yet been shown. We have used a combination of anterograde tracing using Phaseolus vulgaris leucoagglutinin (PHA-L), retrograde tracing using a conjugate of cholera B chain and HRP and electron microscopy to look for such a pathway in rats. When PHA-L had been injected into the regions mainly restricted to the raphé pallidus and raphé magnus, synaptic contacts were found between PHA-L containing terminals and preganglionic neurons retrogradely labelled from the adrenal medulla. Out of the 43 synaptic contacts analysed, 26 were onto somata and 14 onto dendrites. 75% of the total appeared to have symmetric membrane specialisations, 20% asymmetric and the remainder could not be classified. Synaptic contacts were not seen in an animal in which the PHA-L injection site involved cells in the ventral raphé obscurus and surrounding gigantocellular reticular formation. These findings provide evidence of the existence of a direct monosynaptic pathway between cells in the raphé pallidus and/or caudal raphé magnus, and identified sympathetic preganglionic neurons and give further support for a role for the caudal raphé nuclei in sympathetic autonomic regulation.

Adrenergic Fibers↗
PubMed1990

Colocalicostomy. A solution to an obliterated renal pelvis.

A thirty-nine-year-old paraplegic with an ileal conduit urinary diversion and long ureteral strictures bilaterally required urinary tract reconstruction to establish effective internal drainage. Reported techniques proved infeasible. Therefore, the right kidney with its small intrarenal pelvis was opened by anatrophic nephrotomy and anastomosed to a segment of transverse colon in two layers. The left kidney could not be anastomosed directly to the colon segment, so it was anastomosed end-to-side to an isolated jejunal segment. Colocalicostomy should be considered in the repair of an obliterated renal pelvis or an isolated, obstructed lower-pole calix.

Adult↗
PubMed1990

The neural network of the basal ganglia as revealed by the study of synaptic connections of identified neurones.

The study of synaptic connections in the electron microscope has established an 'elementary' circuit for the neostriatum which consists of a pathway from cortical areas (neocortex, hippocampus, amygdala) to medium spiny neurones of the striatum that also receive converging synaptic input from midbrain dopamine neurones. The striatal medium spiny neurones are projection neurones and they form synaptic contacts with output neurones in the globus pallidus and substantia nigra reticulata. In this way, dopaminergic afferents can directly modulate the flow of information from cortical areas through the striatum to the 'premotor' areas of the brainstem and to the thalamus. It is proposed that certain parts of the striatum can themselves control the activity of midbrain dopamine neurones and so one part of the striatum can 'gate' the flow of information through another part.

Animals↗
PubMed1990

Absence of persisting parenchymal damage after extracorporeal shock wave lithotripsy as judged by excretion of renal tubular enzymes.

Four renal tubular enzymes, N-acetyl-beta-glucosaminidase, beta-galactosidase, angiotensin-converting enzyme and gamma-glutamyltransferase, were measured in the urine before, and 24 hours and 1 week after extracorporeal shock wave lithotripsy in 20 consecutive patients. Extracorporeal shock wave lithotripsy was performed on the Sonolith 2000 device with the patient under intravenous narcotic sedation with fentanyl. Enzymatic activity per gram of urinary creatinine was consistently but not significantly higher before extracorporeal shock wave lithotripsy than in control subjects. All 4 enzymes were elevated 24 hours after extracorporeal shock wave lithotripsy, with the increases in beta-galactosidase and angiotensin-converting enzyme being statistically significant. However, by 7 days after the procedure the enzymes had decreased to pre-procedure concentrations or below. These data suggest that any renal tubular damage induced by extracorporeal shock wave lithotripsy is of limited magnitude and brief duration.

Acetylglucosaminidase↗
PubMed1990

Absence of effect of allopurinol on oxalate excretion by stone patients on random and controlled diets.

After 1 year of allopurinol treatment in 36 patients with a history of uric acid and/or calcium oxalate lithiasis and hyperuricosuria, we observed that in addition to the desired decreases in uric acid there were apparently significant decreases in urinary oxalate levels: 37 +/- 3 mg. per day (mean +/- standard error) before therapy and 31 +/- 4 mg. per day after a mean decrease of 16% (p less than 0.05) with an equivalent decrease in the supersaturation (calcium oxalate) of the urine. However, the decrease in oxalate could have been related to changes in dietary habits rather than to any specific effects of allopurinol on oxalate metabolism. Therefore, we recruited 26 of the patients for a study in which dietary factors were controlled. Each participant was assigned to 1 of 3 diet groups: low or high protein, or a customary diet. Each patient collected a urine specimen while on allopurinol and again after the medication was discontinued. With analytical procedures that we ascertained to be free of any significant methodological bias, we observed no significant changes in urinary oxalate excretion that could be attributed to allopurinol. There were significant differences in oxalate excretion on versus off allopurinol between the low and high protein groups, with higher oxalate levels found for the latter group. Our results indicate that allopurinol does not have a specific effect on oxalate metabolism or oxaluria.

Adult↗
PubMed1990

Biochemical evaluation of calcium stone patients: how soon can it be done after stone surgery/passage?

Biochemical evaluations were done two times for 29 outpatients with calcium stone disease, the first time within one month after surgical extraction or passage of stones and the second time two months or more later. Classification of the etiologic basis for the stone disease was the same after both tests in 27 patients. In the other 2 patients the diagnosis was changed from renal to absorptive hypercalciuria. Both of these patients had creatinine clearance rates less than 60 percent of normal during the first test. One also had multiple residual stones during both evaluations, and the second had a urinary tract infection during the first test that resolved with a normal creatinine clearance by the second test period. When nephrogenous cyclic adenosine monophosphate (cAMPn) assays were done on fasting specimens in these patients, the results were consistent with absorptive hypercalciuria. Almost all patients can be evaluated and placed in management programs within a few weeks after surgery. If cAMPn assays are not done, patients with decreased renal function secondary to residual stones or infection can be tested at a later time.

Adolescent↗
PubMed1990

Effects of distinctive context on memory for objects and their locations in young and elderly adults.

Sharps and Gollin (1987, 1988) reported that older adults' memory for both objects and their spatial location is more facilitated than that of young adults when items are studied in a distinctive visual context. They also reported that age differences in spatial memory and item memory can be ameliorated if the items are studied in a distinctive context. The goal of this study was to verify and extend these findings by examining memory for everyday objects when the objects were studied on a (a) plain surface, (b) black-and-white schematic map, or (c) colored model. In Experiment 1, item memory was examined, and in Experiment 2, spatial memory was studied. The results indicated that spatial memory improved with the addition of distinctive context but item memory did not. Moreover, there was no evidence that elderly adults were more facilitated by the distinctive context than were the young.

Age Factors↗