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Biomedical subjects

R Laven

Publications and source records attributed to R Laven.

At least 19 recordsLinked to original sources
PubMed2006

A meta-analysis of the effects of Vitamin E supplementation on the incidence of retained foetal membranes in dairy cows.

A meta-analysis was performed to consolidate the results of studies which have evaluated the effects of Vitamin E supplementation during the dry period on the risk of retained foetal membranes (RFM) in the dairy cow. Twenty studies demonstrated a beneficial response to Vitamin E whilst 21 found no benefit and 3 reported an increase in the incidence of RFM in treated cows. The odds ratios (OR) of the available studies exhibited significant heterogeneity, so multivariable logistic regression analysis was performed to enable the identification of factors associated with the response to Vitamin E supplementation. Our multivariable analysis included parity and Vitamin E supplementation (control/treated) in the model, because all other factors were co-linear. Results indicated that Vitamin E supplementation led to a reduction in the incidence of RFM. A second multivariable analysis was undertaken on a subset of the data including only supplemented cows to determine the influence of supplementation factors on the risk of RFM. All factors were co-linear with each other, therefore, only type of Vitamin E supplementation was included in this analysis. The regression model demonstrated that administration of the synthetic Vitamin E alpha-tocopheryl acetate was associated with a lower risk of RFM than treatment with natural Vitamin E (alpha-tocopherol) (P=0.047, OR=0.49), whereas the difference between the synthetic Vitamin E alpha-tocopherol acetate and natural Vitamin E just failed to attain statistical significance (P=0.059, OR=0.53). Overall the analyses indicate that Vitamin E supplementation during the dry period is associated with a reduced risk of RFM, and that the synthetic forms of Vitamin E are more effective than the natural compound.

Animals↗
PubMed1991

Treatment and control of an outbreak of fat cow syndrome in a large dairy herd.

An outbreak of fat cow syndrome occurred in a herd of 300 Friesian and Friesian/Holstein dairy cows calving predominantly between January and May. The herd came in off grass in good condition despite a long and hot summer. The dry cows received a diet of grass silage, brewing waste and minerals until the end of December, but the grass silage was butyric and was partially replaced by maize silage. By January 23, 16 of 70 calving cows (23 per cent) had appeared to suffer milk fever. Subsequent blood tests revealed that the cows may have been ketotic, and clinical and post mortem examination showed that they were probably suffering from fat cow syndrome. The freshly calved sick cows were treated with glucose, and corticosteroids were injected every second day into those which remained ill. The cattle had received a high energy diet, but the cows still to calve were placed on a diet of low metabolisable energy (77 MJ/cow) but adequate levels of undegradable protein. The problem was associated with a possible clostridial infection in two cows and with reduced fertility.

Adrenal Cortex Hormones↗
PubMed1991

Long-acting antibiotic formulations in the treatment of calf pneumonia: a comparative study of tilmicosin and oxytetracycline.

The treatment of an outbreak of acute pneumonia in 50 four- to eight-month-old Friesian and Friesian cross calves is described. At the first visit (day 0) 16 calves received 20 mg/kg bodyweight of oxytetracycline dihydrate intramuscularly and 15 received 10 mg/kg of the macrolide tilmicosin subcutaneously. The remaining 19 in-contact animals were not considered ill enough to be included in the trial and received 20 mg/kg of oxytetracycline dihydrate. The rectal temperature, demeanour, respiratory rate and respiratory effort of each calf was assessed on days 1, 2, 3, 9, 14, 21 and 28, and calves which had not responded were given repeat injections of the same antibiotic. All the calves recovered from the outbreak and of the 19 calves treated strategically, three required a second injection. Among the calves with clinical pneumonia, fewer treatments (P less than 0.01) were required by those treated with tilmicosin. The rectal temperatures of both groups decreased (P less than 0.05) after the first injection, but on day 3 the decrease was greater (P less than 0.05) in the group treated with tilmicosin. Respiratory rates varied widely but respiratory effort was less (P less than 0.05) on day 2 in the calves treated with tilmicosin. When long-acting antibiotic injections are used to treat enzootic pneumonia it is suggested that a second visit should be made on day 3 to assess the animals' response to treatment.

Acute Disease↗
PubMed1982

[Elevation of the threshold in the rabbit dental pulp test with coumarin: unspecified (local) effect rather than analgesic activity?].

The antinociceptive efficacy of Coumarin was tested in mice, rats, and rabbits. No increase in threshold for the antinociceptive reaction was observed in the hot plate test and tail flick response in mice and rats. Using the tooth pulp test in rabbits, the threshold for the licking reaction was increased. This effect was dose dependent and could, at least partially, be antagonized by Naloxone. Because there is no direct opiate-like activity of Coumarin, these results suggest that the effect may be mediated by the release of endogeneous opiate-like peptides. It remains totally unclear why this effect could only be demonstrated in one particular test in one species.

Analgesics↗
PubMed1981

[Release of norfenefrine from sustained-release formulations by an in vitro dissolution model. Simulation of "drug levels" by calculation using pharmacokinetical constants and comparison with in vivo course of action (author's transl)].

Drug release and dissolution behaviour of 1-(3'-hydroxyphenyl)-2-amino-ethan-1-ol hydrochloride (norfenefrine-HCl) from a sustained-release norfenefrine preparation (Esbuphon) were tested by an in vitro dissolution model in comparison with other norfenefrine formulations. By using pharmacokinetical constants, relative "drug levels" were calculated and compared with the activity curves from animal experiments. Conformities in time course were shown. Variations are discussed. The application of the model is justified if determination of serum concentration of norfenefrine cannot be done.

2-Hydroxyphenethylamine↗
PubMed1978

Adrenergic and nonadrenergic activation of isolated human renal veins of normotensive and hypertensive patients.

In human renal venous strips from normotensive and hypertensive patients, adrenergic- and nonadrenergic-induced contractions were elicited. The maximal amplitude of contractions remained unchanged whatever the mode of activation. However, in the hypertensive group the forces generated reached only about 20% of those in the normotensive group. Furthermore, preparations from hypertensive patients showed a reduced sensitivity for noradrenaline: the ED50 was shifted from 0.13 +/- 0.03 to 0.66 +/- 0.19 microgram/ml (p less than 0.01). This reduced sensitivity is discussed in connection with the pathogenesis of hypertension.

Adolescent↗
PubMed1978

Modulation of the prostaglandin-induced intestinal motility in humans through the transmitters of the vegetative nervous system.

Research was done on the reciprocity between adrenergic and cholinergic stimulating or inhibiting pharmaceuticals and the prostaglandin-induced intestinal motility. By cholinergic activation, the amplitudes of the prostaglandin-dependent rhythmical contractions of human taenia coli were intensified. There was very little influence on the frequency of contractions, however. Simultaneous stimulation of adrenergic beta-receptors by increasing doses of adrenaline or noradrenaline caused the contraction amplitude and frequency to decrease continually until the contractions were completely eliminated. The cholinergic effect could be suppressed with atropine, the adrenergic-stimulated reaction was reversed by the blockage of beta-receptors. It was completely abolished by simultaneous addition of alpha- and beta-receptor-blocking drugs.

Acetylcholine↗
PubMed1978

[Colon dynamics in ileus].

All forms of ileus have one thing in common, namely a disorder of the intestinal motility, which, with increasing distension of the intestinal wall, finally leads to paralysis of the intestine. With the increase in distension mechanical and functional colon changes take place which are discussed in this study. During peristalsis the strain on the wall is directed against the intra-luminal course of pressure. In spite of the increase of the internal pressure from 5 cm H2O to 100 cm H2O, the tension of the wall remains low or even decreases (roughly 500 dyn/mm2). In ileus patients, however, the strain on the intestinal wall increases enormously (about 100000 dyn/mm2). The maximum contraction capacity of the large intestine's muscle system (50,000 dyn/mm2) is high and similar to that of the skeletal muscles.

Colon↗
PubMed1978

[Impairment of adrenergic innervation in achalasia (author's transl)].

Length tension diagrams and diagrams of isometrically developed active tension were set up for normal and aganglionic cardia-circular muscles. The effects of acetylcholin, adrenergic stimulating and inhibiting drugs were examined. The physiological parameters in healthy cardia and the cardia muscle system in achalasia did not vary significantly from one another. The acetylcholin threshold was higher in aganglionic cardia, while the maximum effective dose in healthy and aganglionic cardia remained the same. In achalasia no sensitisation to acetylcholine was detectable. There was a marked impairment in the balance between adrenergic alpha- and beta-receptors, with the contraction-inducing alpha-receptors obviously predominating.

Acetylcholine↗
PubMed1978

The role of prostaglandines in peristalsis of the human colon.

Prostaglandines (PG) of the E and F series cause peristaltic activity in isolated longitudinal muscle strips of the human colon. As this phasic motor reaction can be varied by acetyl choline and adrenaline it was supposed, that prostaglandines contribute to peristalsis. The role of PG E and F in the human colon was studied by inhibiting the prostaglandine synthesis and by antagonizing the prostaglandine-effects. Indomethacin proved to be a suitable inhibitor. HR 546 was found a powerful antagonist. The effect of Pentagastrin and Cholecystokinin (CCK) on peristaltic activity were suppressed by Indomethacin and HR 546. The inhibition of peristalsis by Indomethacin and HR 546 was removed by high doses of PG E and F. On the basis of these results the role of PG for the motility of the gut is discussed.

Cholecystokinin↗
PubMed1977

[Adrenergic receptors in the pathogenesis of congenital megacolon (author's transl)].

Contractions of fresh specimens of taenial musculature from human colon were investigated under the influence of depolarization (bathing in solutions high in potassium), of acetylcholine, and of adrenaline; definite changes of contractile tension could be induced by these agents. The investigations were carried out using normal musculature as well as specimens from patients with congenital megacolon taken from the narrow segment. Contractions after depolarization and after cholinergic stimulation were equal in all specimens investigated, pre-extension of these specimens not differing significantly. Relaxation of colon musculature mediated by adrenergic receptors was very pronounced in normal musculature, but was lacking in specimens taken from the narrow segments of congenital megacolon. Sympathetic stimulation of normal taenial musculature does abolish completely cholinergically induced contractions. On the other hand, a preparation relaxed by adrenaline contracts very little after additional application of acetylcholine. These findings do suggest a severe disturbance of adrenergic receptors in the colon, or of adrenergic neuromuscular transmission in congenital megacolon.

Humans↗
PubMed1977

[Computer assisted heart and circulation analysis in experimental septic shock (author's transl)].

Developping a model of shock applying to the clinical manifestation is necessary to investigate the pathogenesis of septic shock and to identify the letality causing organ. Perhaps the hyperkinetic syndrome may play an important role. The extensive experimental data is processed by a digital computer. Explanations are given for the experimental apparatus and the structure of the Fortran-program.

Animals↗
PubMed1977

[Functional studies of the cardia muscles in achalasia].

1. The mechanical properties - extension behaviour and ability to contract per muscle cross-section - were the same for healthy and aganglionic cardiac sphincter. 2. The acetyl choline threshold is higher in aganglionic muscle strips. The maximum effective acetyl choline dose (2 microgram/ml) remained the same. 3. Achalasia is characterized by a considerable reduction of adrenergic beta-receptor activity and alpha-receptor predominance.

Acetylcholine↗