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Biomedical subjects

R C Hamilton

Publications and source records attributed to R C Hamilton.

At least 55 records · Page 3Linked to original sources
PubMed1992

Brain-stem anesthesia as a complication of regional anesthesia for ophthalmic surgery.

Brain-stem anesthesia is a serious complication of orbital regional anesthesia that may occur when the injected local anesthetic agent gains access to the central nervous system by direct spread from the apex of the orbit via submeningeal pathways. In most studies the reported incidence rate during retrobulbar block is one case per 350 to 500 patients. Failure to recognize the condition or to treat it adequately may be life threatening. Treatment includes reassurance, intravenous administration of fluids, pharmacologic circulatory support or suppression of convulsions, and cardiopulmonary resuscitation. With proper treatment complete recovery is the rule. In all situations in which orbital block is to be done, basic cardiopulmonary resuscitation equipment and personnel familiar with its use are essential. Monitoring of the blood pressure, electrocardiography and pulse oximetry should be routine. Having the globe in primary gaze renders the optic nerve less vulnerable, and avoidance of deep penetration of the orbit is of great importance.

Anesthesia↗
PubMed1988

The effect of prophylactic acetaminophen administration on reactions to DTP vaccination.

To determine the effect of prophylactic acetaminophen on reactions after diphtheria and tetanus toxoids and pertussis vaccination, 282 children received either acetaminophen or placebo in a double-blind, randomized fashion before and 3, 7, 12, and 18 hours after vaccination. Fever and local and systemic reactions were monitored. Switching to known acetaminophen was permitted if the patient's temperature was 38.9 degrees C or higher or for moderate pain. Overall, the reaction score of acetaminophen recipients was significantly less than that of placebo recipients. The rates of occurrence of fever and fussiness and the degree of pain at the injection site were significantly reduced by acetaminophen administration. Children who received acetaminophen were less likely to be switched to "open" acetaminophen than placebo recipients. It is concluded that prophylactic acetaminophen as given in this study had a moderating effect on fever, pain, and fussiness after diphtheria and tetanus toxoids and pertussis immunization.

Acetaminophen↗
PubMed1988

Regional anaesthesia for 12,000 cataract extraction and intraocular lens implantation procedures.

Twelve thousand regional anaesthetics for cataract extraction and intraocular lens implantation surgery were administered by one anaesthetist over a period of 52 months in a free-standing outpatient surgical facility. The ophthalmologist, who did all the operations, assessed the quality of the blocks using an objective scoring system which is described. The first 3,595 patients had retrobulbar and seventh nerve blocks. The following 1,640 patients had higher volume retrobulbar blocking alone. The next 3,478 had peribulbar blocks, followed by 2,226 who had a modified form of peribulbar blocking. A final group of 1,061 had a combination of peribulbar and periorbital blocks with added retrobulbar injection if indicated. As the method of blocking evolved, the more closely was the goal of safe, painless and effective regional anaesthesia approached. The requirements for effective anaesthesia of this type are presented, the complications described and the importance of familiarity with the anatomy of the orbit and its contents stressed.

Aged↗
PubMed1987

The effect of corneal contact lenses on the oxygen tension in the anterior chamber of the rabbit eye.

The oxygen tension in the aqueous humor in the anterior chamber of rabbit eyes was measured continuously with a polarographic electrode. The normal oxygen tension in the anterior chamber was 23 +/- 2 mm Hg (mean +/- SD, n = 4). A contact lens was then placed on the cornea for at least 10 min and the drop in oxygen tension recorded. A hard polymethylmethacrylate lens reduced the oxygen tension by 16 +/- 4 mm Hg, and a larger hydroxyethylmethacrylate soft lens (Soflens) decreased oxygen tension by 17 +/- 4 mm Hg (mean +/- SD, n = 4). Comparable statistically significant decreases were seen with the Permalens, Polycon II, and Silcon lenses. Only the elastofilcon A lens (Silsoft) did not decrease the oxygen tension in the anterior chamber significantly.

Animals↗
PubMed1986

The infectivity of Encephalitozoon cuniculi in vivo and in vitro.

The infectivity of Encephalitozoon cuniculi grown in cell cultures was determined in cultured cells and in wild and domestic rabbits. The ratio of the total to tissue culture viable count was 1,300 (median of seven determinations). The mean ratio of intact spore count to total count, as determined by electron microscopy was 0.12. Although variation between infectivity experiments was large, the median animal infective dose contained 51 FFU (cell culture focus-forming units) for wild rabbits (Oryctolagus cuniculus) and 40 FFU for domestic rabbits. These two infectivities were not statistically different.

Animals↗
PubMed1985

Restoring balance.

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Defensive Medicine↗
PubMed1981

The ultrastructure of Encephalitozoon cuniculi growing in renal tubules of rabbits.

A wild type rabbit infected orally with cell culture-grown Encephalitozoon cuniculi. Twelve weeks after infection the rabbit was killed and blocks of kidney tissue were fixed for histology and electron microscopy. E. cuniculi were observed within kidney collecting tubule cells. The ultrastructure and development of E. cuniculi in these cells was similar to that described in cultured cells and peritoneal macrophages.

Animals↗
PubMed1981

Temporary keratoprosthesis for use during pars plana vitrectomy.

We have developed a series of temporary keratoprostheses that permit closed pars plana vitrectomy in eyes with abnormal corneas. These devices are placed into a trephined opening in the cornea, and provide a clear, stable view of the intraocular contents. Immediately after vitrectomy, the keratoprosthesis is replaced with a corneal graft. We have used this technique successfully in four eyes with opaque or severely traumatized corneas.

Adult↗
PubMed1980

An immunofluorescence study of influenza virus filament formation.

A study is described in which filamentous forms of influenza virus were observed budding from host cell surfaces. Cell cultures infected with influenza virus were stained by indirect immunofluorescence using an antiserum to purified haemagglutinin. Filaments greater than 100 micrometers in length, with several branch points along their length were observed; the number and length of filaments varied according to the virus strain and the time after infection. Examination of infected cells by electron microscopy confirmed the presence of branched structures with an ultrastructure typical of filamentous forms of influenza virus. The immunofluorescence technique was quicker than thin section electron microscopy and was a more sensitive procedure for the detection of filamentous forms of influenza virus than electron microscopy using negative stain. It also enabled the antigenic composition of the filaments to be observed.

Animals↗
PubMed1980

Comparison of flunitrazepam and thiopentone for induction of general anaesthesia.

Forty female out-patients undergoing therapeutic abortion participated in a double-blind study comparing flunitrazepam 0.05 mg . kg-1 with thiopentone 6.0 mg . kg-1 as induction agents for general anaesthesia. Induction time, as measured by the time to loss of lid reflex and voluntary speech, was not only significantly longer in patients receiving flunitrazepam, but also much more variable and imprecise than with thiopentone. The Steward recovery room scores and psychomotor drawing test results revealed that recovery was significantly slower in the flunitrazepam group. Anterograde amnesia was observed in all patients who had received flunitrazepam and in one patient who had received thiopentone. No retrograde amnesia was found in either group. Flunitrazepam produced postoperative drowsiness, sedation, ataxia and nausea while with thiopentone discomfort from surgery and discomfort at the intravenous injection site were the main complaints. Because of the slowness of induction with flunitrazepam and marked individual variation, we do not feel that this drug can be considered a suitable agent for routine induction of general anaesthesia.

Abortion, Therapeutic↗
PubMed1980

Effects of Australian Eastern brown snake (Pseudonaja textilis) venom on the ultrastructure of nerve terminals on the rat diaphragm.

Isolated rat phrenic nerve diaphragm preparations were exposed to the venom of the Eastern brown snake (Pseudonaja textilis). The venom increased the number of 'coated omega figures' in the axolemma of the nerve terminals. The number of synaptic vesicles appeared to be decreased. The increase in coated omega figures in the axolemma is either caused by neurotoxins in the venom slowing down synaptic vesicle recycling or, after binding to axolemmal receptor, being internalized by receptor-mediated endocytosis. Synaptic vesicle recycling and receptor-mediated endocytosis may be related processes in motor nerve terminals.

Animals↗
PubMed1980

Ultrastructural effects of the venom of the small-scaled snake (Parademansia microlepidotus) on the nerve terminals of the rat diaphragm.

Venom of the small-scaled snake (Parademansia microlepidotus) causes a large increase in the number of coated omega figures inserted in the axolemma of nerve terminals. It also causes both a loss of synaptic vesicles and an increase in the number of neurofilaments in the nerve terminals. The actions of the venom are very similar to taipoxin, a pre-synaptic neurotoxin from the venom of the taipan (Oxyuranus scutellatus). The morphological changes in the nerve terminals caused by the small-scaled snake venom are not unusual and do not explain the extreme lethality of the venom.

Animals↗
PubMed1979

A marsupial oncovirus?

A virus-like particle was observed in two continuous cell lines derived from the marsupial Sminthopsis crassicaudata (Fat-tailed Dunnart). The development of the particle was similar to the development of D-type oncoviruses. Initially, a crescentof nucleoid material was observed near the nucleus in the region of the Golgi apparatus. This crescent developed into a doughnut-shaped-A-type particle which migrated through the cytoplasm towards the cell membrane where it budded either into a smooth membrane cytoplasmic vacuole or from the cell membrane. Only enveloped A-type particles were observed; no mature B-type, C-type or D-type particles were detected.

Animals↗
PubMed1979

An investigation of the route and progression of Encephalitozoon cuniculi infection in adult rabbits.

Rabbits infected either orally or intratracheally with cell culture-grown Encephalitozoon cuniculi were monitored regularly for serum antibody levels and E. cuniculi in the urine. Their responses were compared with intravenously inoculated and uninoculated control rabbits. All rabbits receiving E. cuniculi developed serum antibodies, generally within 3 weeks, and excreted E. cuniculi by 6 weeks. In the acute stage of infection, the organs most affected were lung, kidney and liver; the brain and gut were unaffected. However, during chronic infection, the brain, kidney, and heart were the only organs found to be involved. Antibody levels were very high at this stage. Thus both the oral and tracheal routes may be normal routes of infection with E. cuniculi in adult rabbits.

Animals↗