Boomslang (Dispholidus typus) envenomation in a patient on warfarin therapy.

The venom of the boomslang (Dispholidus typus) has potent effects on the coagulation system. It is known to produce a venom-induced consumptive coagulopathy (VICC) through the proposed activation of clotting factor II (prothrombin), factor X, and possibly factor IX. Warfarin, an anticoagulant medication, decreases the circulating vitamin K-dependent clotting factors II, VII, IX and X. We report a unique case of a boomslang bite in a patient on warfarin therapy. During the patient's hospital stay he developed abnormal clotting profiles indicating an underlying VICC, but without major bleeding. He received monovalent antivenom and recovered with no complications. We discuss two possible outcomes of a boomslang bite in a patient on warfarin therapy, exploring the underlying pathophysiology that could lead to the presentation of a reduced risk of overall bleeding or, alternatively, that the bleeding could be compounded and exacerbated. It is possible that in our case the anticoagulant effect of warfarin was wholly obscured by the VICC of the boomslang venom. The composition of the snake venom may have been a contributory factor in the reduced clinical bleeding observed.

Berg adder (Bitis atropos): An unusual case of acute poisoning.

A 5-year-old boy presented to hospital with mild local cytotoxic and severe neurotoxic symptoms. The neurotoxic symptoms included ptosis, fixed dilated pupils and flaccid paralysis with respiratory failure. Mild hyponatraemia was also a clinical feature. After various unsuccessful treatment options were followed, the Tygerberg Poison Information Centre was contacted and a diagnosis of berg adder bite was made. Berg adder bites are uncommon and therefore not usually considered in the differential diagnosis of a patient presenting with an unexplained clinical picture. A timeous poison information helpline consultation is recommended in this situation.

Purification and partial characterization of a 'short' insectotoxin-like peptide from the venom of the scorpion Parabuthus schlechteri.

A disulfide-rich, low-molecular-mass toxin-like peptide has been isolated from Parabuthus schlechteri venom using gel filtration, ion exchange, and reversed phase chromatography. Partial characterization of this peptide reveals a relationship with four-disulfide bridge proteins belonging to the family of 'short' insectotoxins (44% residue identity). In recognition hereof, the peptide was named PBITx1 (sITx10). Our work also reports on the deduced sequences of two other 'short' insectotoxins from Buthus eupeus, I3 and I4, and it provides a consensus sequence and nomenclature for all known 'short' insectotoxins. Finally, sequence similarities with K+ channel blockers (charybdotoxin, kappa-conotoxin), and a Cl- channel blocker (chlorotoxin) are highlighted.

Comparison and characterization of the venoms of three Parabuthus scorpion species occurring in southern Africa.

Parabuthus transvaalicus, P. granulatus, and P. villosus are three medically important scorpion species occurring in southern Africa which can cause severe envenoming among people. In contrast to many other genera, no data is available on the venom composition of scorpions belonging to the genus Parabuthus. Here we have investigated the components which may contribute to the venomous potential. The constancy of venom composition within each of the three species and between the three species was investigated by means of gel filtration chromatography. The venoms of the three species each were characterized by a constant and typical elution pattern, resulting in a 'gel filtration fingerprint' which allows distinction between each species. It appears that certain components in the venoms are common to either all three species, or to two of the three species. This points to a clear interspecies relationship within the genus. We also describe the isolation and characterization of some of the polypeptide toxins present in the venoms of P. villosus, P. transvaalicus and P. granulatus by means of reversed phase chromatography and screening of the toxic components on voltage-activated potassium and sodium channels. Our results confirm that toxins which inhibit potassium channels and alter sodium channel gating are present in the venoms studied.

Photosynthetic gas exchange of the mangrove, Rhizophora stylosa Griff., in its natural environment.

Photosynthetic gas exchange properties of leaves of the mangrove, Rhizophora stylosa Griff., were investigated in order to assess its productivity and gain some insight into the constraints set upon it by the saline habitat. Mature trees of this dominant species were studied in their natural, tidal-forest environment at Hinchinbrook Is., North Queensland for two periods during the dry season. Individual leaves were enclosed in a chamber wherein environmental conditions were varied. CO2 assimilation, transpiration and environmental parameters were monitored during daylight hours by instrumentation housed in a mobile laboratory mounted on a barge. Analysis of the daily course of leaf gas exchange revealed a CO2 assimilation capacity comparable with that of many glycophytic trees. Photosynthesis was strongly influenced by leaf temperature as well as photon flux density. There was a strong and steadily increasing inhibition of gas exchange as leaf temperatures and, consequently, the leaf to air VPD increased. CO2 assimilation rates and leaf conductances to water vapour diffusion were strongly correlated, resulting in nearly constant internal CO2 concentrations in the leaves under the full range of conditions. The effect of leaf orientation in minimizing the leaf-to-air temperature difference was striking. The close coordination between stomatal conductance and CO2 assimilation rate in this mangrove results in high water use efficiency. This sparing use of water may be an important factor underlying the high salinity tolerance of mangroves.

Flexible waveguides for Er-YAG laser radiation delivery.

Flexible plastic waveguides (FPW) were devised for the delivery of Er-YAG laser radiation. The FPW characteristics were studied under various conditions. In vitro studies were carried out to explore the drilling procedure on extracted teeth and the FPW-tissue mutual effects. The results which were obtained proved that the FPW as a delivery device might be a substitute hand applicator for the pneumatic turbine for drilling in teeth.

[Contact cyclophotocoagulation with the continuous wave Nd:YAG laser with quartz fiber. Optimizing coagulation parameters]. / Kontaktzyklophotokoagulation mit dem Dauerstrich-Nd:YAG-Laser über Quarzfaser. Optimierung der Koagulationsparameter.

Transscleral cyclo-photocoagulation with a cw-Nd:YAG-laser was studied in enucleated porcine eyes with application times of between 10 ms and 1.5 s. Contact coagulation via a quartz fiber (core 600 microns) required about 32% less power to create visible ciliary body coagulation compared to non-contact coagulation via a focusing handpiece. Application of focusing fiber tips led to a further reduction in the coagulation threshold by a factor of 0.6. The energy per laser application required for ciliary body coagulation increased with application time. During contact coagulation using plane fiber tips a pronounced temperature rise was sometimes observed at the fiber tip due to deposits of carbonized tissue with the subsequent risk of scleral damage. In a pilot study five eyes with secondary glaucoma were treated under coagulation conditions found to be optimal (8 W at 0.2 s).

Transmission of 308 nm excimer laser radiation for ophthalmic microsurgery--medical, technical and safety aspects.

A surgical system using 308 nm excimer laser radiation transmitted by quartz fibers is described. In-vitro surgery has been performed on the cornea, in the anterior chamber angle, on the lens and in the vitreous with a special application tip for each procedure. Possible damage of ocular structures by 308 nm radiation is discussed. In-vitro experiments showed that UV exposure of intraocular structures sensitive to 308 nm radiation can be reduced by appropriate design of the application tips and by the application of UV absorbing drugs.

Toxicovigilance. I: A survey of acute poisonings in South Africa based on Tygerberg Poison Information Centre data.

BACKGROUND: The incidence and spectrum of acute poisonings in South Africa are unknown. Poisoning data can be derived from sources such as hospital admission records and poison information centre (PIC) records. OBJECTIVES: This study was conducted to examine the extent of the problem and to identify trends and toxicovigilance issues using PIC data. METHODS: A survey was conducted based on Tygerberg Poison Information Centre (TPIC) consultations over 1 year. TPIC consultation forms were analysed for patient demographics and causes of poisoning. RESULTS: The TPIC dealt with 4 771 consultations related to human exposures to poisonous substances. The study showed that accidental exposure was more common than intentional poisoning (65.2% v. 34.8%); that 55.8% of cases were adults, of which 57.6% were females; and that 61.4% of adult cases were intentional exposures, and of these 64.3% were females. There was a predominance of accidental exposures (98.8%) and a male predominance (59.7%) in children. Categories of poisoning exposures across all age groups were non-drug chemicals (52.7%), medicines (35.2%) and biological toxins (12.6%). Pesticides (34.8%), irritant/corrosive substances (27.7%) and volatile hydrocarbons (8.3%) were the most common classes of non-drug chemical exposures. Cholinesterase inhibitors (8.8%), anticoagulant rodenticides (7.1%) and pyrethroids (5.0%) were the most commonly ingested non-drug chemicals. Aldicarb and amitraz poisoning were identified as toxicovigilance targets. Analgesics (26.1%) were the most common class of medicine-related exposure, and paracetamol (15.8%), benzodiazepines (9.2%) and antihistamines (5.2%) were the most common medicine-related exposures. CONCLUSION: The study provided information on evolving trends and identified toxicovigilance targets and the need for continuing toxicology education programmes.

Toxicovigilance. II: A survey of the spectrum of acute poisoning and current practices in the initial management of poisoning cases admitted to South African hospitals.

BACKGROUND: Initial management of acute poisoning in South African (SA) hospitals such as gastric decontamination and use of antidotes has not been evaluated relevant to current international guidelines. OBJECTIVES: The objective of this study was to conduct a toxicovigilance survey of SA hospital admissions to assess the spectrum of acute poisonings, current practices in gastric decontamination, and use of antidotes in the management of acute poisoning. METHODS: A survey was undertaken based on acute poisoning admissions to Tygerberg Academic Hospital (TAH) as well as hospital-based poisoning consultations with the Tygerberg Poison Information Centre (TPIC) over 1 year to investigate trends in admissions and the initial management of hospital admissions for acute poisoning. TAH admission details and TPIC consultation forms for hospital-based cases were analysed for patient demographics, causes of poisoning, gastric decontamination measures and use of antidotes. RESULTS: There were 662 admissions to TAH and 2 459 hospital-based TPIC consultations. Paracetamol and cholinesterase inhibitors were the most common exposures in both studies. Gastric decontamination measures were employed at TAH in 47.7% of cases and in 5.3% of hospital cases reported to the TPIC. Of these, 67.4% in the TAH study and 26.1% in the TPIC study did not comply with international guidelines. N-acetylcysteine was administered inappropriately in 22.1% of the paracetamol poisoning cases at TAH and in 1.6% in the TPIC study. Atropine was administered unnecessarily in 12 of 30 TPIC cases. CONCLUSION: This study has identified the need for directed training on gastric decontamination measures and use of antidotes and, combined with the previous study, has identified national trends in poisoning.

Black and brown widow spider bites in South Africa. A series of 45 cases.

Cases of black widow (Latrodectus indistinctus) and brown widow (L. geometricus) spider bites referred to the Tygerberg Pharmacology and Toxicology Consultation Centre from the summer of 1987/88 to the summer of 1991/92 were entered into this series. Of a total of 45 patients, 30 had been bitten by black and 15 by brown widow spiders. It was evident that black widow spider bites caused a more severe form of envenomation than brown widow bites, characterised by generalised muscle pain and cramps, abdominal muscle rigidity, profuse sweating, raised blood pressure and tachycardia. The symptoms and signs of brown widow bites were mild and tended to be restricted to the bite site and surrounding tissues. Conditions which should be considered in the differential diagnosis include cytotoxic spider bite, scorpion sting, snakebite, acute abdominal conditions, myocardial infarction, alcohol withdrawal and organophosphate poisoning. To prevent the development of complications, the administration of black widow spider antivenom is recommended in severe cases because untreated latrodectism could become protracted, without improvement, for several days.

Scorpionism in South Africa. A report of 42 serious scorpion envenomations.

Forty-two cases of serious scorpion envenomation, of which 4 had a fatal outcome, are presented. The clinical profile, differential diagnosis and management of scorpionism are discussed. Most envenomations occurred in the summer months, peaking in January and February. An immediate local burning pain was the most prominent symptom. Systemic symptoms and signs developed within 4 hours of the sting in most instances, characterised by general paraesthesia, hyperaesthesia, muscle pain and cramps. Other striking features included dysphagia, dysarthria and sialorrhoea with varying degrees of loss of pharyngeal reflexes. The blood pressure and the temperature were often raised and the tendon reflexes increased, while motor power was often impaired. In a considerable number of patients the course was complicated by varying degrees of respiratory dysfunction, which tended to be more serious in children. The oustanding feature in children was an extreme form of restlessness characterised by excessive neuromuscular activity. Victims of scorpion sting, particularly in high-risk localities, should be closely observed for 12-24 hours. Children and other high-risk patients should be hospitalised. All patients with symptoms and signs of systemic envenomation should receive antivenom. Parabuthus granulatus (Hemprich & Ehrenberg, 1828) has been identified as the most important venomous species in the western Cape. The antivenom is produced from the venom of the medically less important P. transvaalicus Purcell, 1899. A strong case can therefore be made for the inclusion of P. granulatus venom in the production of a polyvalent antivenom.

Drug and poison information--the Tygerberg experience.

This report is based on an analysis of 6,411 consultations processed by the Tygerberg Pharmacology and Toxicology Consultation Centre. Seventy-five per cent of the consultations were of a toxicological nature: 47% related to non-drug chemicals, 37% to drugs and 16% to plants and animals. Pesticides utilised in the home environment featured most prominently in the non-drug chemical group, while queries about paracetamol overdose topped the list in the drug group. The most frequent queries in the biological category concerned potentially poisonous plants. Twenty-five per cent of the consultations related to pharmacotherapeutics. Most potentially toxic exposures to non-drug chemicals occurred in the household setting. Contrary to popular belief, few acute pesticide poisonings were encountered as a result of exposures during farming activities. Another important finding was that there is a frustrating lack of reliable and readily available information in respect of potentially toxic ingredients contained in household and industrial preparations. The large number of household exposures high-lights the need for education in the safe storage and usage of non-drug chemicals. Legislation on the inclusion of basic toxicological information and warnings on labels of household and industrial non-drug chemical products should be considered. In addition, the Government should take responsibility for centralizing information on all potentially toxic non-drug chemicals and make this information available to poison centres at all times. It is also imperative that more attention be given to the training of health care professionals in applied pharmacokinetics and toxicology.