Search PubMed⌕ Search

Biomedical subjects

R G Williams

Publications and source records attributed to R G Williams.

At least 37 records · Page 2Linked to original sources

In vitro response of Escherichia coli to antibiotics and ultrasound at various insonation intensities.

Microbial infections on implanted medical devices are difficult to treat. Application of 70 kHz ultrasonic irradiation to gentamicin treatment greatly enhanced the action of the antibiotic in terms of reduced viable bacterial concentrations. Ultrasonic irradiation was carried out at various insonation intensities that were noninhibitory in the absence of antibiotic. Synergistic killing was observed to be a function of ultrasonic intensity. Greatest killing (approximately 5 log reduction in viable population) was realized at full intensity (4.5 W/cm2), and decreased with reductions in power density. At lowest intensity (10 mW/cm2), no significant acoustic enhanced killing was noted.

Energy Transfer↗

The effect of medical education on students' patient-satisfaction ratings.

PURPOSE: To determine whether medical students' interpersonal and communication skills, as measured by satisfaction ratings given by standardized patients (SPs), improves or deteriorates with additional training and experience. METHOD: A longitudinal study was made of a single cohort of 133 medical students scheduled to graduate in 1994 from the University of Illinois College of Medicine at Chicago. Clinical performance examinations employing clinical encounters with SPs were given at the end of the students' second year at the end of the first quarter of their fourth year. The second-year examination consisted of four student-SP encounters for each student; the fourth-year examination consisted of 16 such encounters. For each examination, SP perceptions of interpersonal and communication skills were measured using six items from the American Board of Internal Medicine Patient Satisfaction Questionnaire; the items employed five ordinal-scale descriptors (from 1 = poor to 5 = excellent). The unit of analysis was the student-SP encounter. For each year, ratings on each item were averaged across encounters to produce a mean rating for each item; in addition, ratings across all the encounters and items were averaged to produce a mean total patient satisfaction rating. The percentage of fail or poor ratings given for each item was calculated, as was the average of these percentages across the items. All rating calculations were done between years and between genders. Two-tailed, paired t-tests and F-ratios were used for comparisons between years and between genders, respectively. Finally, ratings for a comparison group of first-, second-, and third-year internal medicine residents were gathered under similar testing conditions. RESULTS: Mean total patient satisfaction with the students' clinical performances improved from the first examination (3.51, SD, .84) to the second (3.60, SD, .86). The percentage of student encounters receiving fair or poor ratings decreased from 14.5% in the second year to 12% in the fourth year; resident encounters received a fair or poor rating 7.8% of the time. The female students received fewer fair or poor ratings than did the male students both in their second year (11.7% vs 16%) and in their fourth year (9.3% vs 12.8%). Of the six patient-satisfaction items, both the students and the residents consistently were ranked lowest in encouraging patients to ask questions and answering patient questions. CONCLUSION: Contrary to the stated beliefs of some physician-educators that students' skills deteriorate during the course of training, these medical students' interpersonal and communication skills improved with additional training and experience.

Communication↗

Usefulness of banding of the pulmonary trunk with single ventricle physiology at risk for subaortic obstruction.

This study addresses the effects of early banding of the pulmonary trunk and subsequent management of subaortic obstruction on the attainment of acceptable pre-Fontan hemodynamics in patients with a single left ventricle and aorta arising from an outflow chamber. We report our experience with 26 patients seen at our institution between January 1984 and December 1994 with a diagnosis of double-inlet left ventricle or tricuspid atresia and transposed great arteries, who were initially managed with pulmonary artery banding in the first 6 months of life. Pulmonary artery band placement was performed at an age of 2.1 +/- 1.8 months (mean +/- SD). Associated aortic arch abnormalities were present in 8 patients (31%). There were 19 patients (73%) who underwent treatment with a Damus-Kaye-Stansel procedure or ventricular septal defect (VSD) enlargement for a significant subaortic gradient or morphologically small VSD, alone or in conjunction with a Glenn or Fontan procedure. Eighteen of 26 patients (69%) underwent cardiac catheterization to assess their candidacy for the Fontan operation. Of this group, 16 were classified as low to moderate risk and 2 as high-risk Fontan candidates, based on hemodynamic criteria. The cumulative mortality for the entire cohort was 19%. Our results suggest that this high-risk group of patients can undergo effective pulmonary artery banding as an initial palliative step, with subsequent intervention for subaortic ob- struction when it is documented or highly suspected, and that acceptable pre-Fontan hemodynamic parameters can be achieved.

Cardiac Catheterization↗

Does the presence of heparin and dexamethasone in the vitrectomy infusate reduce reproliferation in proliferative vitreoretinopathy?

BACKGROUND: Reproliferation following vitrectomy for proliferative vitreoretinopathy (PVR) causes redetachment in up to 55% of cases. Heparin and corticosteroids have each been shown to inhibit the development of proliferative vitreoretinopathy (PVR) in experimental models. However, little information is available on the use of these agents in humans. METHODS: In this pilot study, 62 eyes of 62 patients with severe PVR requiring vitrectomy were prospectively randomized to receive either BSS Plus (control) or BSS Plus with heparin and dexamethasone (HD) in the infusate. RESULTS: After one operation, the retina was reattached in 42 (71%) of 59 eyes: 22 (65%) of 34 eyes in the control group and 20 (80%) of 25 eyes in the HD group (P = 0.16). Reproliferation developed in 26.5% of the control group (9 of 34 eyes) and 16% of the HD group (4 of 25 eyes; P = 0.26). Postoperative hemorrhage was significantly more frequent in the HD group (P = 0.02) but did not influence final visual or anatomic outcome. Hypotony was less frequent in the HD group but the difference was not significant (P = 0.063). CONCLUSION: The trend from this randomized pilot study suggests that HD supplementation of the vitrectomy infusate may reduce the reproliferation rate in PVR and possibly reduce the rate of hypotony. Postoperative hemorrhage was more frequent with HD but did not cause redetachment or alter visual outcome. A multicenter trial involving more patients would be required to better evaluate the efficacy of HD as a pharmacologic adjunct to PVR surgery.

Adolescent↗

The antiepileptic agent gabapentin (Neurontin) possesses anxiolytic-like and antinociceptive actions that are reversed by D-serine.

This report describes the activity of the antiepileptic agent gabapentin (Neurontin) in animal models predictive of anxiolysis and analgesia. Gabapentin displayed anxiolytic-like action in the rat conflict test, the mouse light/dark box and the rat elevated X-maze with respective minimum effective doses (MEDs) of 3, 10 and 30 mg/kg. Furthermore, gabapentin also induced behavioural changes suggestive of anxiolysis in the marmoset human threat test with a MED of 30 mg/kg. In the rat formalin test of tonic nociception, gabapentin dose-dependently (30-300 mg/kg) and selectively blocked the late phase with a MED of 100 mg/kg. However, it failed to block carrageenan-induced paw oedema. The intracerebroventricular (ICV) administration of the glycine/NMDA receptor agonist D-Serine, dose-dependently (10-100 micrograms/animal) reversed the antinociceptive action of gabapentin (200 mg/kg, SC). D-Serine (30 micrograms/animal, ICV) also reversed the anxiolytic-like effects (in the light/dark box and the rat elevated X-maze) of gabapentin (30 mg/kg). In contrast, L-Serine (100 micrograms, ICV) failed to block the antinociceptive action of gabapentin. The antinociceptive action of (+)-HA-966 (25 mg/kg, SC), a partial agonist at the glycine/NMDA receptor, was reversed by D-Serine (100 micrograms/animal, ICV). However, D-Serine (100 micrograms/animal, ICV) failed to affect the antinociceptive action of a competitive NMDA receptor antagonist CGS 19755 (3 mg/kg, SC). Gabapentin has negligible affinity for the strychnine insensitive [3H]glycine binding site. This indicates that the interaction between gabapentin and D-Serine may not involve the NMDA receptor complex. Gabapentin may represent a novel type of anxiolytic and analgesic agent.

Acetates↗

NADPH diaphorase activity in peptidergic neurones of the parasitic nematode, Ascaris suum.

The histochemical marker for nitric oxide synthase, NADPH diaphorase, is known to co-localize in mammalian neurones with various classical neurotransmitters and neuropeptides. The nervous system of the parasitic nematode Ascaris suum has previously been shown to contain both NADPH diaphorase activity and neuropeptide immunoreactivity. This study examined the possibility that NADPH diaphorase and neuropeptide immunoreactivity may co-exist in the same neurones. Two antisera were used, one raised to KYSALMFamide, a C-terminal synthetic analogue of SALMFamide 1 (GFNSALMFamide), and another that recognizes calcitonin-gene-related peptide (CGRP). We provide evidence that in a distinct subset of neurones in the ventral, dorsal and lateral ganglia NADPH diaphorase staining and SALMFamide-like immunoreactivity are co-localized, suggesting a possible role for nitric oxide in modulating neuropeptide activity in these regions. CGRP-like immunoreactivity was less widely distributed, and was not consistently co-localized with NADPH diaphorase.

Animals↗

Pathophysiology and treatment of cocaine toxicity: implications for the heart and cardiovascular system.

OBJECTIVE: To review the data on pharmacology, pathophysiology and treatment of cocaine toxicity, with particular relevance to the heart and cardiovascular system. DATA SOURCE AND STUDY SELECTION: Published epidemiology, laboratory and clinical studies on the pharmacology, electrophysiology and pathophysiology of cocaine toxicity and its treatment. MAIN RESULTS: Cocaine toxicity-related morbidity and mortality are frequent due to the potent pharmacological effects of the drug as an indirect-acting sympathomimetic agent and its class I antiarrhythmic property paradoxically inducing pro-arrhythmia. The cardiac and cardiovascular toxic effects of cocaine include various degrees of myocardial ischemia, cardiac arrhythmias, cardiotoxicity, hypertensive effects, cerebrovascular effects and a hypercoagulable state. Treatment of cocaine toxicity must be based on the multiple factors leading to the toxicity. Sodium bicarbonate appears to have an important role in the acute setting with conduction abnormalities, seizures or acidosis. Unopposed alpha-stimulation provided by beta-blockade should be avoided. Central nervous system hyperexcitability should be treated with diazepam. The use of calcium antagonists appears logical. CONCLUSION: Cocaine is an alkaloid with widespread illicit use. The rationale for treating acute cocaine intoxication has become clearer and more logical with increased knowledge of its mechanisms of action.

Arrhythmias, Cardiac↗

Anomalous origin of the left main pulmonary artery from the ascending aorta associated with DiGeorge syndrome.

We place on record 2 infants with the DiGeorge syndrome and anomalous origin of the left pulmonary artery from the ascending aorta. We postulate that: (1) embryogenesis of anomalous origin of the left pulmonary artery from the ascending aorta might be due to the persistent fifth aortic arch connecting both arterial systems; (2) an anomalous pulmonary artery arising from the ascending aorta is part of the aortic arch abnormality accompanied by normal conotruncal septation; and (3) in the DiGeorge syndrome, cardiac anomalies that originate from the conotruncus or aortic arch, or both, may have the same embryologic mechanisms.

Aorta↗

Factors influencing survival in patients undergoing the bidirectional Glenn anastomosis.

The bidirectional Glenn anastomosis (BGA) has long been used as a surgical intervention for patients with single ventricle physiology. Initially, this procedure was the final stage in palliation and was performed in older children. Eventually, as the Fontan procedure came to be used as a method to separate circulations, the Glenn procedure was performed as an intermediate step. Over time, the BGA was performed as an alternative for patients who were considered to be at high risk with the Fontan procedure. Between January 1, 1988, and January 1, 1994, 129 patients underwent BGA at the University of California-Los Angeles. These patients were reviewed retrospectively, including clinic visits, catheterization, and echocardiographic information. The overall survival rate was 87% (112 of 129 patients). The average length of follow-up was 27 months. This information was then analyzed by univariate and multivariate analysis. Several factors were related to failure in patients who underwent BGA including pulmonary artery pressure, systemic right ventricle, and presence of anomolous pulmonary venous drainage and heterotaxy syndrome.

Adolescent↗

Mycobacterium marches back.

The resurgence of tuberculosis world-wide and its association with HIV infection means a greater likelihood of otolaryngologists encountering the disease in one form or another. In this review the features of primary and secondary tuberculosis in various head and neck sites are described, and recent advances in diagnosis are discussed. For the otolaryngologists other important aspects such as infections with atypical mycobacteria, the differential diagnosis of cervical lymphadenopathy in HIV-infected patients, recently recognized problems in drug treatment, and the role of surgery in head and neck tuberculosis are also discussed.

HIV Infections↗

The effect of the nematode peptides SDPNFLRFamide (PF1) and SADPNFLRFamide (PF2) on synaptic transmission in the parasitic nematode Ascaris suum.

The action of two peptides isolated from the nematode Panagrellus redivivus, PF1 (SDPNFLRFamide) and PF2 (SADPNFLRFamide) have been studied on synaptic transmission in the motornervous system of the parasitic nematode Ascaris suum. Intracellular recordings were made from Ascaris somatic muscle cells and excitatory junction potentials (EJPs) elicited by stimulation of the ventral nerve cord. The EJPs were cholinergic as they were blocked by the Ascaris nicotinic receptor antagonist, benzoquinonium. PF1 caused a slow hyperpolarization, similar to the action of this peptide first reported by Bowman, Geary & Thompson (1990) and further characterized by Franks et al. (1994). The hyperpolarization was accompanied by a marked decrease in the amplitude of the EJPs with an EC50 of 311 +/- 30 nM (n = 5). This inhibition is unlikely to be due to a post-synaptic site of action of the peptide as the muscle cell input conductance was not significantly altered by PF1 and furthermore the response to bath-applied acetylcholine was not inhibited by PF1 at concentrations up to 10 microM (n = 6). PF2 also inhibited the EJPs in a similar manner to PF1. These studies indicate that both of the peptides isolated from the free-living nematode Panagrellus redivivus have biological activity in the parasitic nematode Ascaris suum. PF1 and PF2 have inhibitory actions in contrast to the predominantly excitatory actions of the Ascaris endogenous peptides AF1 (KNEFIRFamide) and AF2 (KHEYLRFamide). The potent actions of the Panagrellus neuropeptides PF1 and PF2 in Ascaris suggest that peptides with a similar or identical sequence may also occur in Ascaris and have an inhibitory role in the motornervous system.

Acetylcholine↗

Histochemical mapping of NADPH diaphorase in the nervous system of the parasitic nematode Ascaris suum.

NADPH diaphorase has recently been discovered to be responsible for neuronal nitric oxide (NO) synthase activity in mammals. It thus serves as a histochemical marker for the localization of NO synthase in the nervous system. The histochemical technique was used to map out potential NO-producing neurones in the nervous system of the parasitic nematode, Ascaris suum. Positive staining for NADPH diaphorase was present in various parts of the central nervous system, in particular within selective cell bodies and fibres in the ventral ganglion, the retrovesicular ganglion, ventral and dorsal cords and sublateral lines. Intense staining was also present in the motorneurone commissures, indicating a potential role for NO as a neurotransmitter at the neuromuscular junction. NADPH disphorase-positive neurones were not confined to the central nervous system. Selective staining was also present in the enteric nervous system, in particular the pharynx and in the peripheral nervous system innervating the sensory organs.

Animals↗

The FMRFamide-like neuropeptide AF2 is present in the parasitic nematode Haemonchus contortus.

Peptides belonging to the FMRFamide family are widely distributed amongst invertebrates. We report here on the isolation of the FMRFamide neuropeptide AF2 (Lys-His-Glu-Tyr-Leu-Arg-Phe-NH2) from the parasitic nematode Haemonchus contortus. Immunocytochemical techniques showed that FMRFamide-like material was distributed in several regions of these organisms including nerve cords and cell bodies of the central nervous system. AF2 was isolated using a method that employed 6 steps of reverse-phase HPLC. The concentration of AF2 in this organism was approximately 30 pmol/g of nematode.

Amino Acid Sequence↗