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H Gerhards

Publications and source records attributed to H Gerhards.

At least 19 recordsLinked to original sources
PubMed2006

[Depiction of the structure of the vitreous body in horses without ocular diseases and in horses with equine recurrent uveitis (ERU) using transmission electron microscopy].

Neither the ultrastructure of the vitreous body from horses without ocular diseases, nor the pathomorphological changes in the vitreous body associated with equine recurrent uveitis (ERU) have been described. However, the vitreous body plays an important role in the pathogenesis of ERU. Ten vitreous body samples obtained from 5 horses without ocular disease, and 38 vitreous body samples from horses with ERU (collected during vitrectomy) were examined by transmission electron microscopy. The vitreous body samples of horses without ocular diseases were characterized by a loose network of unbranched fibrils 10-12 nm in width. In the vitreous body samples of horses with ERU numerous dense bundles of fibrils, mononuclear inflammatory cells and necrotic cells represent the destruction of the vitreous fibrillar network. In this study, equine vitreous body ultrastructure was described for the first time. Thus, demonstrating ultramorphologically, the clinically apparent changes of the vitreous body associated with ERU.

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PubMed2006

[Detection of leptospira in the vitreous body of horses without ocular diseases and of horses with equine recurrent uveitis (ERU) using transmission-electron microscopy].

Equine recurrent uveitis (ERU) is caused by persistent intraocular leptospira, which appear to use the vitreous body as a refuge. The detection of leptospira in the vitreous body of horses with spontaneous ERU by histological methods has not yet been described. Thirty eight vitreous body samples from 36 horses with ERU (collected during vitrectomy), and 10 vitreous body samples obtained from 5 horses without ocular disease (control group) were examined by transmission electron microscopy. Prior to sample collection, 2 ml of a leptospira culture suspension were injected into the vitreous body of 2 eyes enucleated from horses of the control group. The detection of leptospira in samples, experimentally inoculated with these bacteria was uncomplicated; in vitreous body samples from horses with spontaneous ERU the detection was successful in only a few cases (3/38). The morphologically varying envelope of leptospira in vitreous body samples of horses which developed ERU spontaneously suggests the existence of a bacterial masquerade in vivo.

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PubMed2003

[Phylogeny, form and function of canine teeth in the horse].

The canine teeth of the horse developed phylogenically from the simple, pointed, short-rooted tooth form of the leaf eating, in pairs living, Eocene horse Hyracotherium and served up to the Oligocene as a means of defense (self preservation). In the Miocene the living conditions of the Merychippus changed and they took to eating grass and adopted as a new behavior the life in a herd. The canine teeth possibly played an important role in fights for social ranking; they changed from a crown form to knife-like shape. In the Pliohippus the canine tooth usually remained in male horses and since the Pliocene, it contributed to the fights between stallions, to ensure that the offspring only came from the strongest animals (preservation of the species). Form and construction of the canine tooth are described and discussed in detail under the above mentioned phylogenic and ethologic aspects.

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PubMed2001

Serum and vitreous humor antibody titers in and isolation of Leptospira interrogans from horses with recurrent uveitis.

OBJECTIVE: To measure antibody titers against Leptospira interrogans in serum and vitreous humor and determine the prevalence of L interrogans in vitreous humor of horses with recurrent uveitis. DESIGN: Cross-sectional study. ANIMALS: 242 horses (270 eyes) with recurrent uveitis undergoing vitrectomy and 39 control horses (54 eyes) without any history or clinical signs of recurrent uveitis undergoing euthanasia or enucleation for unrelated reasons. PROCEDURE: Serum and vitreous humor were tested for antibodies against 13 serovars of L interrogans. Vitreous humor was submitted for leptospiral culture; isolates were typed to the serogroup level. RESULTS: Leptospira interrogans was isolated from vitreous humor from 120/229 (52%) horses (126/252 [50%] eyes) with recurrent uveitis but was not isolated from vitreous humor from 36 eyes of 21 control horses. Duration of recurrent uveitis was > or = 1 year for 45 of the 120 (38%) horses from which the organism was isolated. Geometric mean antibody titers against L interrogans in the vitreous humor and serum of horses with recurrent uveitis were 1:1,332 and 1:186, respectively. Only 91 of 120 (76%) horses from which the organism was isolated had a 4-fold or greater difference between serum and vitreous humor antibody titers. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that persistent ocular infection with L interrogans is common in horses with recurrent uveitis. A 4-fold increase in vitreous humor versus serum antibody titers may not be a sensitive test for the diagnosis of L interrogans-induced recurrent uveitis. We hypothesize that the immune component of recurrent uveitis can be directly induced and maintained by persistent infection of the eye with L interrogans.

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PubMed2001

Immune responses to retinal autoantigens and peptides in equine recurrent uveitis.

PURPOSE: To test the hypothesis that autoimmune mechanisms are involved in horses in which equine recurrent uveitis (ERU) develops spontaneously. METHODS: Material obtained from horses treated for spontaneous disease by therapeutic routine vitrectomy was analyzed for total IgG content and IgG specific for S-Antigen (S-Ag) and interphotoreceptor retinoid-binding protein (IRBP). The cellular infiltrate of the vitreous was analyzed by differential counts of cytospin preparations and flow cytometry using equine lymphocyte-specific antibodies. Antigen-specific proliferation assays were performed comparing peripheral blood lymphocytes (PBLs) with vitreal lymphocytes by stimulation with S-Ag and several S-Ag- and IRBP-derived peptides. RESULTS: The total IgG content of specimens from horses with ERU was very high with great variability among the investigated samples (11.5 +/- 8.0 mg). Autoantibodies to S-Ag or IRBP or both were found in 72% of vitreous specimens from horses with uveitis. The leukocyte infiltrates (up to 2 x 10(8) cells per sample) were dominated by lymphocytes (>90%) in most cases (22/32). Flow cytometry showed that more than 50% of these cells were CD4(+) T cells. In vitro stimulation of vitreal lymphocytes, but not of PBL, showed a strong proliferative response to peptides derived from S-Ag or IRBP in 9 of 12 patients. CONCLUSIONS: In the eyes of horses with ERU, IgG antibodies and autoreactive T cells specific for retinal antigens were detected. These results strongly support the hypothesis that ERU is an autoimmune-mediated disease and is highly similar to recurrent uveitis in humans in both clinical and immunologic parameters.

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PubMed1999

[Radiologic examination of the spine in "back problems" of the standing horse].

The radiological examination of the thoracolumbar spine of a horse with a potential back problem is most important in order to come to a diagnosis and the imaging method of choice. The use of parallel grid-cassettes, appropriate films, rare earth screens and aluminium filters requires radiographic equipment with an output of 60-120 kV and 25-90 mAs. By use of this technique in the standing horse it is possible to obtain radiographs of the summits of the dorsal spinal processes of the thoracolumbar spine from the first thoracic (T1) to approximately the third of fourth lumbar vertebrae (L3/4). Since the thickness of soft tissue is increasing from distal to proximal it is necessary to increase the output to image the processus articulares craniales et caudales. Therefore additional radiographs have to be taken.

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PubMed1998

[Intraocular and serum antibody titers to Leptospira in 150 horses with equine recurrent uveitis (ERU) subjected to vitrectomy].

Between February 1993 and July 1997, 150 horses suffering from recurrent uveitis were subjected to parsplana vitrectomy. In these horses, antibody titers to Leptospira serovars were determined in serum samples and in samples from diluted vitreous collected during vitrectomy. Although the vitreous samples were diluted with 250 ml of balanced salt solution, in 86 of the 150 vitreous samples (= 57%) the antibody titers were higher than in the serum samples. Additionally, serum samples from 77 horses suffering from ERU, but which were not subjected to vitrectomy, and serum samples from 97 horses with clinically normal eyes were analyzed for antibodies to Leptospira serovars. Among the 227 horses with ERU (150 treated surgically, 77 treated conservatively) 50 horses (50 of 227 = 22%) had serum antibody titers to Leptospira serovars of > or = 1:800. Among the 97 horses with clinically normal eyes, 24 horses (24 of 97 = 25%) had serum antibody titers to Leptospira serovars of > or = 1:800. In undiluted vitreous samples from 20 horses with clinically normal eyes, no antibody titers to Leptospira serovars could be detected. Among the 150 horses with ERU, 90 animals (90 of 150 = 60%) had antibody titers of > or = 1:100 in the diluted vitreous samples, the difference being highly significant (p < 0.001). The findings are discussed in relation to the etiology of recurrent uveitis in horses.

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PubMed1998

[Radiologic description of the growth plates of the atlas and axis in foals].

Fractures of the first two cervical vertebrae, atlas and axis, may occur in foals for different reasons, e.g. in cases of a fall, going head over heels or when being hit by a hoof. The tentative clinical diagnosis can be confirmed by x-raying the standing animal, with aid of computed tomography in the anaesthetized foal respectively. The growth plates however, and their time of closure have to be considered when interpreting radiographs. In the atlas there are two ventrolateral plates and one dorsomedian cartilagineous plate. Only the dorsal plate, however, can be found in the dorsoventral projection up to an age of about 12 months. The ventrolateral growth plates which have closed at about six months of age cannot be seen in either ther dorsoventral or laterolateral projection. In transversely oriented CT-scans all of the three centres of ossification can easily be made visible in the atlas. In the axis the cartilagineous gaps between the dens axis and the cranial epiphysis as well as the cranial and caudal epiphyseal growth plate can be shown in normal x-radiographs in both planes of projection. Besides this there are growth plates between the corpus vertebrae and the arcus vertebrae in the axis which cannot be seen in either radiographic projection. They become clearly visible in transversal CT-scans and are ossified at the age of three to four months. At the end of the first year the growth plates between the dens axis and the cranial epiphysis have closed. The cranial and caudal epiphyseal plate are gone at an age of about four to five years.

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PubMed1997

[Application possibilities of laser surgery in veterinary medicine. 3: Literature review and some case reports].

The transmission of the laser beam trough flexible fibers enables an endoscopic application. Since this technique is minimal invasive and often does not require general anaesthesia there is an increasing interest in the use of laser techniques-for example in equine upper respiratory tract surgery. This paper gives a review about reported laser application in the different fields of veterinary surgery with emphasis on laser practice in dermatology, ophthalmology and endoscopic laser application.

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PubMed1996

Retinal detachment in horses.

Ten horses with partial or total retinal detachment were investigated using light and electron microscopy (TEM, SEM). Several lesions were observed and compared with normal retinal morphology. Three weeks after the initial retinal detachment, hypertrophy of the pigment epithelium with transformation of the apical microvilli could be observed. The lesions were accompanied by progressive degeneration and atrophy of the sensory retina, starting at the photoreceptor outer segments. Hypertrophy of Müller cells was a concomitant finding. Retinal detachment represents a sequel either to inflammatory processes or trauma.

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PubMed1996

[Antibody titers against Borrelia in horses in serum and in eyes and occurrence of equine recurrent uveitis].

In Germany very little is known about antibody titers against Borrelia burgdorferi in the horse. In the USA there exist some studies on the titer levels and symptoms due to borrelia infections. Beside lameness, fever, polyarthritis, pneumonia and dullness there is a study showing a connection between panuveitis and Borrelia infection in the horse. In human medicine the infection with Borrelia burgdorferi becomes more and more important. Uveitis and other eye diseases due to Borrelia burgdorferi are proved and documented. The goal of this study was to find a connection between antibodies to Borrelia burgdorferi and cases of equine recurrent uveitis (ERU). The antibody titer against Borrelia burgdorferi was determined by IFT in 153 horses with no sign of disease of the eye and in 79 horses with equine recurrent uveitis (ERU). 48% of all horses were found to be positive (titer 1:64 or higher). In addition 22 sera were tested in western-blot for antibody titers. There was no significant correlation between signs of ERU and increased antibody titers against Borrelia burgdorferi (p > 0.05). No clinical signs were seen in horses with elevated titers. No correlation between the age of the horses and the antibody level could be found. There was a connection between the antibody titer and the month of examination (p < 0.05). Highest titer levels were seen in May and November. This is both one month later than the activity of the transmitting ticks (I. ricinus).

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PubMed1996

[Possibilities for the us of laser surgery in veterinary medicine. Part 2: Effects of laser beams on tissue].

The effect of a certain laser beam on tissue is dependent on the different properties of the tissue. The various kinds of laser radiation are absorbed from different components of an organ. Only where absorption takes place there will be a transformation of the energy of radiation to other forms of energy and changes in tissue will occur. The arising thermal energy not only heats the area exposed to the laser beam but the surrounding tissue. The extent of the heating effect on tissue is due to properties of the tissue, e.g. the degree of blood supply and with it the draining of heat, and the parameters of the laser system, e.g. time of exposition and power of radiation. By increasing power of radiation the effect will be an unspecific heat stimulation, coagulation of tissue up to vaporization of tissue. By using different ways of transmission the effects produced by laser will change and can be adapted to various medical and anatomical requirements.

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PubMed1995

[Application of laser surgery in veterinary medicine. 1. Fundamentals].

This article will outline the key words of laser physics. Albert Einstein set the basics of laser physics by characterizing the principles of stimulated emission of radiation in 1914. An excited atom can change from these excited energy level to a lower level by emitting energy in form of photons. If this photon strikes another excited atom, it will stimulate emission of another photon. By these action two identical photons will emerge. An optical resonator is used to amplify the stimulated light emission coming from a laser medium. Laser differs from other light sources in three important properties: coherence, collimation, and monochromasia.

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PubMed1993

[Bilateral blindness after injury in a riding horse].

Bilateral blindness was diagnosed in a 5-year-old Hanoverian gelding presented for evaluation of a corneal opacity in one eye. About 12 months prior to the examination, the gelding had fallen head over, hitting his head and the cornea. Clinical and electroretinographic findings as well as pathohistologic and ultrastructural lesions of both eyes including the optic nerves are presented. Ophthalmoscopically visible pigment disruption of the non-tapetal fundus adjacent to the optic discs correlated morphologically with foci of degeneration and atrophy of the retina, whereas ophthalmoscopically visible accumulation of pigment was morphologically characterized by hypertrophy of the pigment epithelium, increased intracellular pigment accumulation and by migration of pigment cells into the inner lamina of the retina. Severe atrophy of the retinal neuronal layer was linked to traumatic optic nerve degeneration.

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PubMed1993

[Infection with Bacillus piliformis (Tyzzer's disease) in foals].

Tyzzer's disease, caused by Bacillus piliformis and characterized by a multifocal, necrotizing hepatitis was diagnosed in a 25 days old, male, German warmblood foal. The animal was submitted to the clinic of horses because of colic symptoms and a severe depression. Upon arrival it was comatose, recumbent and showed opisthotonos. Due to a severe, metabolic acidosis and a rapid progression of the disease, the foal was euthanatized. In immediately formalin-fixed tissue samples Bacillus piliformis was detected in the cytoplasma of hepatocytes by different histological techniques (Giemsa stain, silver impregnation technique by Warthin-Starry, immunohistology). This case is discussed within a literature review.

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