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Biomedical subjects

H Karg

Publications and source records attributed to H Karg.

At least 19 recordsLinked to original sources
PubMed1998

Bone morphogenetic protein-7 (osteogenic protein-1, OP-1) and tooth development.

Bone morphogenetic proteins (BMPs) form a family of growth factors originally isolated from extracellular bone matrix that are capable of inducing bone formation ectopically. We studied the expression, tissue localization, and function of BMP-7 (OP-1) during tooth development in rodents. Patterns of BMP-7 gene expression and peptide distribution indicated that BMP-7 was present in dental epithelium during the dental lamina, bud, and cap stages. During the bell stage, BMP-7 mRNA expression and protein distribution shifted from dental epithelium toward the dental mesenchyme. With advancing differentiation of odontoblasts, BMP-7 protein staining in the dental papilla became restricted to the layer of fully functional odontoblasts in the process of depositing (pre)dentin. Secretory-stage ameloblasts exhibited weak immunostaining for BMP-7. A restricted pattern of staining in ameloblasts became apparent in post-secretory stages of amelogenesis. Also, cells of the forming periodontal ligament were immunopositive. Histological analysis of tooth development in neonatal BMP-7-deficient mice did not reveal obvious changes compared with wild-type mice. We conclude that, in developing dental tissues, BMP-7 has distribution and expression patterns similar to those of other BMP members but is not an essential growth factor for tooth development, possibly because of functional redundancy with other BMP members or related growth factors.

Ameloblasts↗
PubMed1997

Spatiotemporal expression of the homeobox gene S8 during mouse tooth development.

The murine S8 gene encodes a nuclear homeodomain containing transcription factor that is expressed at sites of epithelial-mesenchymal interactions, including those in cranofacial tissues. The spatiotemporal expression of S8 mRNA was examined in tooth primordia by in situ hybridization. S8 transcripts were found in all stages of tooth development in 13- to 16.5-day-old mouse embryos (E13-E16.5), covering the early bud stage up to the late bell stage. S8 mRNA was found exclusively in the ectomesenchyme and its derivatives that originate from the neural crest: future pulp cells, odontoblast precursors and dental follicle cells. Expression was highest at the late cap and early bud stages and declined at the mid-bell stage, in both first molar and incisor primordia. In E13 jaw explants grown in organ culture for 48 h, S8 mRNA was still present in first and second molar primordia after culture. At E15.5, S8 mRNA was also transiently present in the surrounding osteogenic tissue. It is concluded that the distribution pattern of S8 mRNA during tooth development indicates a role for the gene in defining the identity of dental papilla and follicle cells. It is speculated that the time-restricted expression of S8 in tooth primordia involves establishing the definitive form of the tooth organ.

Animals↗
PubMed1995

Accumulation of the beta-agonist clenbuterol by pigmented tissues in rat eye and hair of veal calves.

Two independent experiments were carried out to determine whether Clenbuterol is accumulated by pigmented tissues. In the first experiment, unpigmented and pigmented rats were injected two times with 5 micrograms of Clenbuterol subcutaneously and the eyes were analyzed after 63 h of withdrawal by enzyme immunoassay. Only pigmented rat eyes showed a clear accumulation of Clenbuterol (68.1 to 81.5 ng/g), whereas the eyes of unpigmented treated rats demonstrated levels similar to the negative controls (< .27 ng/g). In the second experiment, two Holstein-Friesian calves were fed with .8 microgram of Clenbuterol/kg BW two times a day (therapeutic dose) in milk replacer and black and white hair was collected separately before, during, and after the treatment. The hair was analyzed with an enzyme immunoassay that provided blanks less than 1.0 ng/g and a mean recovery of 67%. This experiment showed an accumulation of Clenbuterol in both sets of hair, but a definitely higher accumulation of Clenbuterol in black (pigmented) hair than in white hair. The black/white quotient amounted to approximately 50 at 1 wk after treatment. Results of these experiments favor the use of the eye as well as the hair for residue analysis but in case of hair, variation of pigmentation in different animals must be considered.

Adrenergic beta-Agonists↗
PubMed1994

Bovine seminal plasma aSFP: localization of disulfide bridges and detection of three different isoelectric forms.

Acidic seminal fluid protein (aSFP) is a major 13 kDa protein isolated from bull seminal plasma and characterized as a new growth factor which stimulates in vitro cell division and progesterone secretion by ovarian cells. Here, we establish that the four cysteines of oxidized aSFP form two disulfide bridges between nearest-neighbour residues. This pattern is conserved in boar spermadhesins, with which aSFP shares up to 50% amino acid sequence identity, and other proteins of the recently identified CUB domain family. Using isoelectric focusing in combination with sulfhydryl group-specific blotting, the three forms of aSFP were identified as completely oxidized (pI 4.7), partly reduced (pI 4.8) and fully reduced at pI 5.1. These results indicate that native aSFP possesses two pairs of cysteine residues of different reactivity. The observation that aSFP can protect sperm from oxidative damage might be explained by its reduction/oxidation behaviour.

Amino Acid Sequence↗
PubMed1992

Evidence for the presence of endogenous 19-nortestosterone in the cow peripartum and in the neonatal calf.

Urine samples were collected from five Brown Swiss cows during the 18 days prior to and 11 days after parturition and were analysed for 19-nortestosterone using an enzyme immunoassay. Nortestosterone concentrations ranged from 70 to 130 nmol/l in all samples taken before parturition. The levels declined within two days, and 11 days post partum no nortestosterone was detectable. In urine from newborn calves, maximal nortestosterone concentrations were determined during the first day of life (10.9-120 nmol/l), declining below 7.3 nmol/l until day 3 in most animals and remaining below the detection limit (less than 3.6 nmol/l) after day 8 in all animals. There was no obvious difference between cows carrying a male or a female calf nor between newborn male or female calves. Using the combined methods high performance liquid chromatography/enzyme immunoassay and high performance liquid chromatography/gas chromatography-mass spectrometry, the immunoreactivity in urine was identified to be 19-nortestosterone-17 alpha. Although there is unequivocal evidence for the endogenous production of nortestosterone in pregnant cows, its function for placenta physiology, pregnancy anabolism and parturition remains unclear. However, new threshold levels for residue control of nortestosterone need to be fixed in accordance with the endocrine status of the animals.

Animals↗
PubMed1990

[Control of the use of bovine somatotropin (bST) by the determination of bST and insulin-like growth factor I (IGF-I) in blood and milk of cows].

bST, a milk production-enhancing compound not yet registered in the EG and the USA, has been evaluated as safe for the consumer. Nevertheless, actual discussions include a possible ban of applications; therefore, effective measures of control are demanded. The evaluation of bST plus IGF-I in blood only allows a monitoring of bST treatment. Under the condition of two blood samplings from each cow with a 7-day interval and the favorable experimental design (1. sampling rigorous on days 4 or 6 after injection of a bST depot preparation), an efficiency of 96% correct evaluations could be obtained; under field conditions, despite analytical efforts, about 20% false estimations must be taken into account. There is no means of monitoring milk and other products of cows treated with bST, hence analytical measures for the control of imports seems to be useless.

Animals↗
PubMed1990

[Concentration of IGF-I and estradiol-17beta in the blood plasma of pregnant cattle].

Blood samples were collected from pregnant cows, heifers and also from non pregnant cows serving as controls. The determination of insulin-like-growth-factor-I (IGF-I) and estradiol-17 beta (E2) were performed immunologically. In the non pregnant cows E2 remained unchanged. IGF-I decreased around parturition and increased again commencing the 6th week of lactation. Compared to nonpregnant animals E2 but not IGF-I was slightly elevated during the first 10 weeks of pregnancy. During the 10th up to 20th week of pregnancy the mean values of IGF-I were increased as well as the ones of E2. During the late pregnancy the values of IGF-I in heifers are obviously more elevated as in lactating pregnant or non-pregnant cows; analogous high values were determined in pregnant cows only during the dry period. Before parturition even a negative correlation exists between IGF-I and E2. It is concluded that IGF-I is predominantly regulated by other factors.

Animals↗
PubMed1990

[The current status and risk evaluation of the use of hormone preparations in food producing animals].

Three groups of hormonal agents are currently in discussion for meat and milk production: sexual hormone active anabolics and beta-agonists, the latter acting as lipidmodulators to produce lean meat (for example, Clenbuterol, Salbutamol). Biologically active residues can result from illegal treatment only under exceptional circumstances. The analytical control measures, particularly for babyfood production, are of a very high standard in thr FRG and guarantee the safety of the products. The growth hormone that enhances milk yield has no importance as it is orally inactive.

Animal Feed↗
PubMed1987

[Manipulation of growth].

Explore the source record for details and available documents.

Animal Nutritional Physiological Phenomena↗
PubMed1986

Hormones in milk.

Protein hormones (especially prolactin) and steroid hormones (gestagens, estrogens, corticoids, and androgens) can be detected by bioassay and radioimmunoassay in milk in a variety of species. In addition, milk contains vitamin D and beta-casomorphins (opiate-like peptides). It has been assumed that most of the hormones are transferred into milk by diffusion. However, evidence is available for active mechanisms like those for progesterone in goats and prolactin in cows. Most of the hormone profiles in milk are similar to the ones in blood plasma. Hormone concentrations in milk seem to be a good estimate of the average hormone content in plasma, especially for the measurement of longer-lasting secretory activities like progesterone and estrogen release during the estrous cycle or seasonal changes of prolactin in ruminants. Determination of progesterone and estrone sulfate in milk serves as a diagnostic tool in fertility control, especially in cows. Enzyme immunoassay kits are available for this monitoring purpose. Exogenously administered hormones are also transferred into milk. Residue studies have shown that the dilution is so great that it may be assumed that there is no potential risk for the consumer.

Androgens↗
PubMed1982

Hormonal responses following treatment with different prostaglandin analogues for estrous cycle regulation in cattle.

The effect of four different prostaglandin F(2)alpha analogues on secretion of the pituitary hormones prolactin, LH, FSH and oxytocin was evaluated in heifers. In addition, the luteolytic activity was measured by means of progesterone concentrations. For the sake of comparison, the corpus luteum of two heifers was enucleated and the effect on the above hormones determined. There seemed to be no differences among the various analogues concerning their luteolytic action on the corpus luteum. No effect on FSH secretion was observed. Basal concentrations of LH increased about 4 - 5 h after injection of the analogues, concurrently with the decrease of progesterone. Enucleation of the corpus luteum was followed by a similar pattern of hormone secretion. Therefore, the increase in LH concentrations did not appear to be a specific effect of the analogues, but was probably a result of the decrease in progesterone concentration. Within twenty minutes after administration of the analogues a clear increase in plasma prolactin (2-4 h) and oxytocin concentrations (1-2 h) could be demonstrated.

Journal Article↗
PubMed1981

Endocrine patterns associated with puberty in male and female cattle.

In four studies secretion patterns of LH, FSH, prolactin, testosterone and progesterone were measured in male and female cattle to determine endocrine changes associated with sexual maturation. Two periods of increasing gonadotrophin secretion were observed, the second one coinciding with puberty. A short luteal phase of 8-12 days precedes the first oestrus at 10-11 or 14 months of age. The testosterone values of the bulls increased with age from 5-6 months. Prolactin levels in the bulls increased at the time of the first testosterone rise. A frequency of about 1-2 LH and FSH pulses/8 h occurred at 1, 2, 5 and 10 months of age. The pituitary response to GnRH (1 microgram/kg i.v.) was tested in 2 male and 2 female calves at monthly intervals. LH and FSH were released at all ages but a reduced FSH response occurred in both sexes after the 5th month. A small testosterone release was observed as early as 1 month after birth in males similar to those observed after endogenous LH pulses. We conclude that the initiation of puberty in both sexes is controlled by the same neuroendocrine mechanisms. The pituitary gland, ovaries and testes are already able to respond to specific stimuli long before puberty, and they may also be involved indirectly due to changes in the feedback system modulating gonadotrophin secretion.

Aging↗
PubMed1980

LH, FSH and progesterone concentrations in peripheral plasma of the female roe deer (Capreolus capreolus) during the rutting season.

Progesterone LH and FSH were measured in the plasma of 4 female roe deer (2 kept with the buck, 2 separated from the buck to prevent mating) from July until the end of September or October, i.e. including the rutting season from the middle of July to the middle of August. At least two distinct peaks of LH and FSH were observed before the first small progesterone increase lasting for about 5 days in late July. The next clear LH peak and, slight individual variations, FSH peak occurred exactly when progesterone values and fallen and before they rose again in a major elevation, i.e. after ovulation. LH and, with some variations, FSH values were generally basal while progesterone was high during the rest of the study. There were no obvious differences in hormone pattern in pregnant and non-pregnant animals.

Animals↗