Known and suspected teratogenic hazards in range plants

Biochemistry of hemlock (Conium maculatum L.) alkaloids and their acute and chronic toxicity in livestock. A review

The literature on Conium maculatum biochemistry and toxicology, dispersed in a large number of scientific publications, has been put together in this review. C. maculatum is a weed known almost worldwide by its toxicity to many domestic animals and to human beings. It is an Umbelliferae, characterized by long, hollow stems, reaching up to 2 m height at maturity, producing a large amount of lush foliage during its vegetative growth. Its flowers are white, grouped in umbels formed by numerous umbellules. It produces a large number of seeds that allow the plant to form thick stands in modified soils, sometimes encroaching on cultivated fields, to the extent of impeding the growth of any other vegetation inside the C. maculatum area of growth. Eight piperidinic alkaloids have been identified in this species. Two of them, gamma-coniceine and coniine are generally the most abundant and they account for most of the plant acute and chronic toxicity. These alkaloids are synthesized by the plant from eight acetate units from the metabolic pool, forming a polyketoacid which cyclises through an aminotransferase and forms gamma-coniceine as the parent alkaloid via reduction by a NADPH-dependent reductase. The acute toxicity is observed when animals ingest C. maculatum vegetative and flowering plants and seeds. In a short time the alkaloids produce a neuromuscular blockage conducive to death when the respiratory muscles are affected. The chronic toxicity affects only pregnant animals. When they are poisoned by C. maculatum during the fetuses organ formation period, the offspring is born with malformations, mainly palatoschisis and multiple congenital contractures (MCC; frequently described as arthrogryposis). Acute toxicity, if not lethal, may resolve in the spontaneous recovery of the affected animals provided further exposure to C. maculatum is avoided. It has been observed that poisoned animals tend to return to feed on this plant. Chronic toxicity is irreversible and although MCC can be surgically corrected in some cases, most of the malformed animals are lost. Since no specific antidote is available, prevention is the only way to deal with the production loses caused by this weed. Control with herbicides and grazing with less susceptible animals (such as sheep) have been suggested. C. maculatum alkaloids can be transferred to milk and to fowl muscle tissue through which the former can reach the human food chain. The losses produced by C. maculatum chronic toxicity may be largely underestimated, at least in some regions, because of the difficulty in associate malformations in offspring with the much earlier maternal poisoning.

Histopathological study of experimental acute poisoning of cattle by autumn crocus (Colchicum autumnale L.)

Crude or dehydrated bulbs of autumn crocus (Colchicum autumnale L.) were fed to eleven calves. All the calves developed severe diarrhea and died or euthanized within 63 hr. At necropsy, the gastro-intestinal mucosa was edematous and hemorrhagic. Histologically, necrosis and degeneration with karyopyknosis and karyorrhexis were shown in the basal cell layer of the tongue, esophagus, forestomach, renal pelvis, urinary bladder, neck cell layer of the abomasal gastric glands, and intestinal cryps. These findings were also seen in Kupffer cells, renal tubular epithelial cells, and lymphocytes in the lymphoid and hemopoietic systems. The lesion of the present acute crocus poisoning of cattle closely resembled those reported in humans with colchicine intoxication. Refined acetone extract of organs of poisoned cattle proved to contain colchicine and demecolcine by high performance liquid chromatography.

Pharmacologic considerations in the management of peripartum conditions in the cow

As is true with the use of drugs in veterinary medicine in general, there are many controversial issues in the management of peripartum conditions in the cow. For example, the use of PG versus antibacterial drugs in the management of postpartum uterine infections has advocates for the use of either approach. Intrauterine versus systemic administration of antibacterial drugs for the prophylaxis or treatment of postpartum metritis is another area of debate. Clearly, more research is needed in this area. Equally clearly, however, the research results that are available are being disregarded on a daily basis. In considering this discussion of the use of drugs in the peripartum period, one is struck by the frequency that optimum drug therapy of a condition relies on the extralabel use of nonapproved preparations. What guidelines are available to the practitioner in this regard? One example is lack of availability of appropriate dosage regimens or withdrawal times for food derived from treated animals. Unfortunately, pharmacokinetic and residue studies that would aid in establishing guidelines generally are not available and, in most instances, are not forthcoming. Extrapolation of data from other species to the ruminant or extrapolation of information from one drug to a related compound (such as prediction of residue and withdrawal data from an approved aminoglycoside, dihydrostreptomycin, to another unapproved drug, gentamicin) is fraught with difficulties. The need for research in this area is obvious, and lack of such information is one of the major dilemmas in trying to establish rational drug therapy in the food-producing animal. Recent developments in drug therapy have led to innovative approaches for the management of peripartum and other diseases in cattle. The use of PG in the treatment of reproductive disorders, so commonplace and widely accepted in contemporary veterinary practice, is a relatively recent approach that continues to be refined with the development of new, more potent, more specific PG analogs. What will be the role of ceftiofur, a potent, third-generation cephalosporin that currently is approved only for the treatment of respiratory infections in cattle, in the management of reproductive tract infections? The fluoroquinolones, which represent a novel approach to the control of infectious diseases, are being increasingly used in veterinary and human medicine, and one may predict that these powerful antimicrobial drugs will find application in bovine practice, including for the treatment of peripartum infections. Pharmacologic manipulation of immune and defense mechanisms also is an approach with some promise.(ABSTRACT TRUNCATED AT 400 WORDS)

Hereditary peromelia in Mohair goats

The occurrence of a new congenital defect of the appendicular skeleton in Mohair goats is described. The malformation is peromelia and occurs in a familiar pattern. The defect seems to have an autosomal recessive mode of inheritance with variation in the expressivity of the genotype. The pathological abnormalities were described in 8 cases, all characterized by agenesia of the phalanges and parts of the metacarpus or metatarsus affecting one or more limbs. In some cases additional skeletal defects were found. Furthermore, 5 cases were reported by the owners with a description of the limb affected and 1 case was examined clinically. Predisposition for pelvic limbs to be affected was observed. The defect, which does not seem to have been described in goats previously, is phenotypically similar to and possibly also genetically homologous to a defect described in sheep.

The developmental toxicity of an isolate from the plant Solanum dimidiatum (potato-weed) in Syrian golden hamsters

The developmental toxicity of an ethanol extract from Solanum dimidiatum was investigated in date-bred Syrian golden hamsters. Neural tube defects were seen in three Syrian golden hamster fetuses, from one litter out of 12, at a maternal dose of 1.52 mg of plant isolate per g of body weight. Other malformations observed were syndactyly in a single fetus, from one litter out of ten, in the 0.45 mg/g dose group and gastroschisis in a single fetus, from one litter out of nine, in the 1.01 mg/g dose group. These findings suggest minimal developmental toxicity for this plant isolate.

Inhibition of limb chondrogenesis by a Veratrum alkaloid: temporal specificity in vivo and in vitro

It has been demonstrated that jervine, a steroidal alkaloid derived from plants of the genus Veratrum, exerts teratogenic effects in several animal species. Defects were restricted to structures which depend upon normal chondrogenesis for their development. Here we report studies of the temporal specificity of cellular sensitivity using limb bud mesenchyme cells obtained from Day 10 mouse embryos. These cells, when grown as high-density "spot" cultures, undergo chondrogenesis in vitro. Prior to differentiation, exposure of limb cell cultures to jervine suppressed subsequent accumulation of cartilage proteoglycans. Treatment after differentiation had no significant effect. Additionally, there was a genetic component to jervine sensitivity: C57BL/6J mice were sensitive, whereas NIH Swiss-Webster mice were insensitive. This strain-dependent difference was observed both in vivo and in vitro, supporting the validity of limb mesenchyme spot cultures as a model for jervine-induced teratogenicity. Our studies indicate that jervine acts specifically during an early phase of the differentiation of mesenchyme into cartilage. It is likely that a specific stem cell population is the target tissue of this compound.

Congenital defects in calves from maternal ingestion of Nicotiana glauca of high anabasine content

Administration of Nicotiana glauca to four cows from the 50th to the 75th days of gestation induced congenital deformities in their calves. All four calves had arthrogryposis of forelimbs and one also had spinal curvature and rib cage deformity. The plant material contained 0.113% of the piperidine alkaloid anabasine as authenticated by gas chromatography and by infrared spectroscopy. Because of the presence of anabasine at a high concentration and because of its structural relationship to known teratogens, anabasine may be responsible teratogen.

Veterinary toxicology: the epidemiology of poisonings in domestic animals

Animals are constantly exposed to a wide variety of foreign chemicals, many of which are potentially toxic and some of which result in the clinical poisonings. Pesticides are applied on or around animals for the control of insects and rodents. These chemicals may be placed in areas without regard for accessibility to household pets and domestic livestock. Insecticides, herbicides, and fungicides are routinely and haphazardly applied to animal and environmental surfaces alike with apparent disregard for differences in absorptive capability. Fortunately, newer herbicides and fungicides are relatively nonhazardous. Drugs are considered to have therapeutic effects, but the lay and professional person's disregard for species differences and variations in recommended dosages can result in poisonings. Adverse reactions may be misnomers for errors in judgment. Failure to provide satisfactory storage facilities for animal feeds and the improper preservation and handling of feedstuffs allow the growth and development of a variety of mycotoxins. Ignorance on the part of animal owners and livestockmen can result in a number of unusual and sometimes fatal clinical syndromes. The dependence of domestic animals and livestock upon their owners for the total environment makes these animals extremely susceptible to environmental pollutants. Exposure to noxious gases, irritating and hazardous industrial materials and wastes, water contaminants, and casually discarded compounds of our own use can and frequently do result in animal illnesses and death. Persons responsible for animals may be unaware of the potential hazard or lack good judgment in the use of these chemicals. Forceful and continuing education for the safe and sensible use of all foreign compounds on and around domestic animals and livestock is needed. Persons handling and applying these materials must recognize their responsibility, not only to themselves but also to their neighbors and the animals in their care.