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Biomedical subjects

J Frens

Publications and source records attributed to J Frens.

At least 19 recordsLinked to original sources
PubMed1987

[Veterinary drugs, the veterinarian and the Veterinary Drug Act].

A number of features of the Veterinary Medicinal Products Act, which are of importance to veterinarians, are reviewed. These features result in a number of consequences connected with obtaining and handling veterinary drugs. These consequences are discussed.

Animals↗
PubMed1986

[Veterinary Drug Act].

The Dutch Veterinary Drug Act is reviewed and the consequences of a number of aspects of this act are discussed.

Animals↗
PubMed1985

[Why still using chloramphenicol?].

The use of chloramphenicol (CAP) is discussed in the light of the potential residues that may occur when CAP is not used correctly in veterinary therapy. A description of CAP and of the regulations in force is followed by suggestions of methods by which chloramphenicol residues may be prevented.

Animals↗
PubMed1984

[Records and the use of veterinary drugs].

The new Veterinary Drugs Act is in process of development. The final form which this law will take on will probably be clearer by the time of the 1983 annual congress. It can be expected that only registered drugs will then be permissible for use in treatment. A drug is registered when records are provided and found to be adequate, which show that the drug is effective and does not have any injurious side-effects or results in the appearance of residues after normal use. Drawing up a record of this type requires thorough investigation of the drug, in which experimental studies in animals play an important role. The problem of residues does not enter into the matter in the case of veterinary drugs used in companion animals, though beyond this the registration system will not differ markedly from that of other agents. This means that drugs used in human medicine as such are not permissible for use in companion animals. As several of the required data from the records of these drugs will then be available, composing a complete record will not cause any insurmountable problems. The situation is more complicated in the case of homeopathic and allied therapeutic agents.

Animals↗
PubMed1978

Comparison of the thermoregulatory responses to intracerebroventricularly injected dopamine, noradrenaline and 5-hydroxytryptamine in the goat.

The thermoregulatory responses to dopamine (DA), noradrenaline (NA) and 5-hydroxytryptamine (5-HT), injected into the third cerebral ventricle of goats at 20 degrees C ambient temperature (Ta) or during cold exposure, were compared before and after pretreatment with the DA receptor blocker haloperidol or the 5-HT receptor blocker methysergide. At 20 degrees C Ta, intracerebroventricular (i.c.v.) injection of DA (800 microgram), NA (200 microgram) or 5-HT (800 microgram) induced a decrease in body temperature (Tb) and dilatation of the ear vessels. After DA and 5-HT, but not after NA, panting was observed. During cold exposure both DA and NA caused a suppression of shivering and a fall in Tb. Pretreatment with haloperidol (400 microgram, i.c.v.) attenuated the thermoregulatory effects of i.c.v. DA other than the dilatation of the ear vessels at 20 degrees C Ta. Haloperidol did not influence the responses after i.c.v. NA or 5-HT. Methysergide (1.0 mg, i.c.v.) blocked panting and attenuated the decrease in Tb caused by i.c.v. DA and 5-HT at 20 degrees C Ta and blocked the peripheral vasodilatation caused by 5-HT but not the dilatation caused by DA. During cold exposure methysergide antagonized the thermoregulatory effects of DA, but not those of NA. Ic.v. injection of haloperidol (400 microgram) or methysergide (1.0 mg) during heat exposure induced in panting and a rise in body temperature, which suggests that both DA and 5-HT have a physiological role in the mediation of heat loss in the goat. We conclude that in the central thermoregulatory system of the goat are excitatory DA receptors in the pathway from heat sensors to heat effectors. Activation of these receptors by i.c.v. DA or by heat exposure results in a secondaary release of 5-HT. Since the vasodilating effect of DA was not influenced by haloperidol or methysergide, this effect could be mediated by haloperidol-insensitive (possibly inhibitory) DA receptors on the pathway controlling peripheral vasomotor tone. The thermoregulatory effects of i.c.v. NA are probably mediated by inhibitory NA receptors on the pathway from cold sensors to heat production effectors.

Animals↗
PubMed1978

Comparison of the thermoregulatory responses to intracerebroventricularly injected dopamine and noradrenaline in the sheep.

The thermoregulatory effects of dopamine (DA), given by intracerebroventricular (i.c.v.) injection to sheep, have been examined and compared with those of i.c.v. noradrenaline (NA). At ambient temperatures (Ta) of 20 degrees and 30 degrees C both DA (200 nmol . kg-1) and NA (100 nmol . kg-1) induced constriction of the ear vessels, a decrease in respiratory frequency and an increase in rectal temperature (Tr). At Ta of 10 degrees and 0 degrees C both substances caused a decrease in heat production and a fall in Tr. The DA receptor blocker spiroperone (30 nmol . kg-1, i.c.v.), which itself had a vasodilatatory effect at 20 degrees C Ta, blocked the peripheral vasoconstriction and slightly attenuated the rise in Tr normally caused by i.c.v. DA or NA at this Ta, but did not eliminate the suppression of respiratory frequency. During i.c.v. infusion, at 20 degrees C Ta, with the DA-beta-hydroxylase inhibitor FLA-63, the effect of i.c.v. DA on Tr was attenuated, while that of NA was enhanced. These results suggest that in sheep central thermoregulatory system there are DA receptors which stimulate the pathway that controls peripheral vasomotor tone. The inhibitory effect of NA and DA on heat production and evaporative heat loss is probably mediated by noradrenergic receptors, which can also be activated by DA both directly and after its conversion to NA.

Animals↗
PubMed1977

Thermoregulatory effects of intraventricularly injected dopamine in the goat.

Dopamine (DA) was injected in the third brain ventricle of goats and the thermoregulatory effects were studied under different ambient conditions. The effects depended on dose, ambient conditions and cannula used. In the cold, there was a drop in body temperature, sometimes accompanied by suppression of shivering and by vasodilatation. Both temperature decrease and suppression of shivering were dose-dependent but there was no relation between magnitude of temperature drop and occurrence of shivering suppression. In a thermoneutral environment, there was either a slight vasoconstriction or hypothermia, occasionally accompanied by induction of panting. In the heat, either hypothermia or hyperthermia was observed. Hypothermia was accompanied by an increase in panting. Hyperthermia only occurred when the animals became excited as a result of the injection of DA. It is concluded that DA acts by stimulating the thermoregulatory pathway from heat sensors to heat loss effectors at a locus similar to that for 5-hydroxytryptamine in the thermoregulation model of Bligh et al. (1971).

Animals↗