Biomedical subjects

Peter Wohlsein

Publications and source records attributed to Peter Wohlsein.

13 recordsLinked to original sources

PubMed2006

Interventional atrial septal defect closure using a totally bioresorbable occluder matrix: development and preclinical evaluation of the BioSTAR device.

OBJECTIVES: We sought to test the hypothesis that interventional atrial septal defect (ASD) closure can be performed safely and effectively using a bioresorbable occluder matrix. BACKGROUND: The ideal septal occluder scaffold should promote the healthiest and most complete healing response while eventually facilitating the full resorption of the material and leaving "native" tissue behind, thus minimizing the potential for future complications from chronic foreign body and maintaining the possibility for later unobstructed transseptal access to the left atrium. METHODS: The STARFlex occluders (NMT Medical Inc., Boston, Massachusetts) were modified by substituting the conventional polyester fabric for a bioengineered, acellular type-I collagen matrix derived from porcine submucosa with a heparin-coated surface (BioSTAR occluder, NMT Medical Inc.). Comparative transcatheter closure of ASDs was performed in young sheep (n = 36). Gross pathology and histopathology were obtained after follow-up periods ranging from 7 days to 2 years. RESULTS: The STARFlex (control) devices were encapsulated time-dependently by ingrown fibrous tissue. Histology showed a mild but chronically persisting foreign body reaction. By contrast, BioSTAR devices exhibited a mild-to-moderate transient cellular immune response. Heparin coating of the BioSTAR surface improved the biocompatibility of the device by reducing surface thrombogencity. A remodeling process of the collagen scaffold, starting after 30 days in vivo, resulted in the full replacement of the matrix by host tissue after 2 years of follow-up. CONCLUSIONS: The BioSTAR device is the first septal occluder with a totally bioresorbable matrix that is fully replaced by host tissue during the healing process. The promising results of this study support testing of the BioSTAR device in clinical trials.

Absorbable Implants↗

PubMed2006

Severe Streptococcus infection in spotted hyenas in the Ngorongoro Crater, Tanzania.

In a population of spotted hyenas (Crocuta crocuta) monitored between 1996 and 2005 in the Ngorongoro Crater, Tanzania, 16 individuals from five of eight social groups displayed clinical signs of an infection, including severe unilateral swelling of the head followed by abscess formation at the mandibular angle, respiratory distress, mild ataxia, and lethargy. Two (12.5%) of these 16 individuals died within days of developing signs. Clinical signs in hyenas were first noted in 2001, and most cases occurred between September 2002 and February 2003, suggesting an outbreak of infection during this period. Histopathological examination of internal organs from one hyena that died with signs revealed morphological changes consistent with severe bacterial infection. Phenotypic examination and phylogenetic analysis of the 16S rRNA gene of the causative agent of infection revealed a Lancefield group C Streptococcus with a high level of homology to S. equi subsp. ruminatorum, a subspecies of S. equi recently described in domestic sheep (Ovis aries) and goats (Capra hircus) with mastitis in Spain. Strains similar to this bacterium were also isolated from two hyenas without obvious clinical signs, suggesting that hyenas may be 'carriers' of this bacterium, and from a sympatric Burchell's zebra (Equus burchelli), a herbivore species often consumed by hyenas. To our knowledge this is the first report of a Streptococcus infection in these two wildlife species. The high genetic similarity between the hyena and zebra isolates indicates that inter-specific transmission may occur, possibly when hyenas consume infected zebra carcasses.

Animals↗

PubMed2004

Congenital neuropathy and dilution of feather melanin in nestlings of urban-breeding northern goshawks (Accipiter gentilis).

A pair of northern goshawks (Accipiter gentilis) breeding in a public park in the city center of Hamburg, Germany, raised 12 healthy and five aberrant offspring between 1996 and 2000. Aberrant nestlings (three males and two females) had pale silver-blue plumage and displayed severe locomotor disorders. Histopathologically, the defects were characterized by adendritic feather melanocytes and mild degeneration of the cerebellar white matter. Epidemiologic results were suggestive of a hereditary autosomal recessive defect, which may have originated from close inbreeding during the foundation of Hamburg's urban population of northern goshawks.

Animals↗

PubMed2004

Phocine distemper in German seals, 2002.

Approximately 21,700 seals died during a morbillivirus epidemic in northwestern Europe in 2002. Phocine distemper virus 1 was isolated from seals in German waters. The sequence of the P gene showed 97% identity with the Dutch virus isolated in 1988. There was 100% identity with the Dutch isolate from 2002 and a single nucleotide mismatch with the Danish isolate.

Animals↗

PubMed2003

Degradation of tungsten coils implanted into the subclavian artery of New Zealand white rabbits is not associated with local or systemic toxicity.

OBJECTIVE: To assess whether corrosion of tungsten coils is related to residual shunting and to evaluate whether elevated tungsten serum levels are associated with local or systemic toxicity. METHODS: Tungsten coils (SPI, Balt, France) were implanted into the subclavian artery of New Zealand white rabbits leading to a residual high-flow shunt in 5/10 rabbits. Serial serum tungsten levels, complete blood count and clinical chemistry were analysed prior to the implantation as well as 15 min, 2 and 4 months thereafter. After 4 months the rabbits underwent repeat angiography before they were sacrificed and the internal organs were evaluated histopathologically. RESULTS: Mean tungsten levels rose from 0.48 microg/l prior to the implantation to 12.4 microg/l 4 months post-implantation. The rise in serum tungsten levels was neither associated with residual shunting present at the time of implantation nor with residual shunting at the time of explantation. One animal had to be sacrificed because of non-resolving palsy of the upper extremity. The remaining animals had an uneventful clinical course with no signs of toxicity of the elevated tungsten levels. Histological examination revealed no evidence of local or systemic toxicity of the tungsten coils. CONCLUSION: Tungsten coils corrode and lead to a steady increase in serum tungsten levels starting as early as 15 min after implantation. Residual shunting does not seem to influence the kinetics of corrosion of tungsten coils. Despite markedly elevated serum tungsten levels 4 months after implantation degradation of tungsten coils is not associated with local or systemic toxicity.

Animals↗

PubMed2003

Histopathological follow-up after bailout stenting for early postoperative stenosis of a central aorto-pulmonary shunt.

We treated a neonate with pulmonary atresia and a ventricular septal defect complicated by straddling of the atrioventricular valves by constructing a central aorto-pulmonary shunt. The postoperative course was complicated by obstruction of the shunt, which was treated by implantation of a coronary stent. Six months after the stenting, a Glenn anastomosis was created and the stented shunt removed. Analysis showed that the shunt was completely covered by a vascularized neointima. The stent had not produced injury to the shunt, with struts of the stent covered nicely by neoendothelium, with sparse inflammation surrounding the artificial implants.

Aortic Valve Stenosis↗

PubMed2003

A new biological matrix for septal occlusion.

The ideal septal occluder scaffold should promote the healthiest and most complete healing response possible while eventually facilitating the full resorption of the material, leaving "native" tissue behind. An excellent biocompatibility of the scaffold tissue is a prerequisite for quick, complete, and firm ingrowth of the device, optimizing outcomes and minimizing the potential for complications. Intestinal collagen layer (ICL) is a highly purified (acellular) bioengineered type-1 collagen derived from porcine submucosa. It is gradually resorbed by the host organism and subsequently replaced by the host tissue. CardioSEAL occluders were modified by substituting the conventional polyester fabric for an intestinal collagen layer (ICL). Percutaneous transcatheter closure of interventionally created atrial septal defects was performed in lambs using these modified occluders. A complete pathomorphological investigation including histology was carried out after 2, 4, and 12 weeks follow-up. Standard CardioSEAL implants served as a control group. After 2 weeks in vivo the devices were already covered completely by neo-endothelium. Compared with the conventional synthetic scaffold, ICL devices showed a quicker endothelialization, decreased thrombogenicity, and superior biocompatibility with no significant cellular infiltration observed in the histology of explants with ICL fabrics. After 3 months in vivo the collagen layer remained mechanically intact, but began to show the first histological signs of mild disintegration, gradual resorption, and remodeling. In conclusion, short-term results from preliminary in vivo experiments using a bioengineered collagen matrix as the occluder tissue scaffold showed excellent biocompatibility. This resulted in superior overall results: quicker endothelialization, a decreased thrombogenicity, and decreased immunological host response.

Absorbable Implants↗

PubMed2002

Experimental ASD closure using autologous cell-seeded interventional closure devices.

OBJECTIVE: Atrial septal defect (ASD) occluders are permanent implants in paediatric cardiology which serve as mechanical shields until complete overgrowth and incorporation of the occluding device by autologous tissue has occurred. Thereafter, the foreign body material making up the device is dispensable and bears potential long-term adverse effects. Rapid, firm and complete incorporation into the atrial septal wall should be a prerequisite for biodegradable devices. In this study, the feasibility of using autologous cell-seeded devices was investigated by (a) testing the influence of a collagen coating on cellular stress resistance in vitro and (b) comparing the short-term effects between cell-seeded, collagen-coated and acellular ASD occluders in vivo. METHODS: Native and collagen-coated Dacon fabrics and Starflex-devices were pre-seeded with autologous fibroblasts (skin biopsy) and evaluated using various mechanical stress tests. In a sheep model interventionally created ASDs were closed using either autologous pre-seeded or conventional (acellular) Starflex-devices. RESULTS: ASD closure devices were successfully pre-seeded with autologous cells. The incubation period needed, the cellular density achieved and the mechanical stability of the cytolayer after mechanical stressing (implantation) were improved by applying a collagen matrix on the fabric. Compared to the thin layer of ingrown tissue seen on conventional occluders after 30 days in vivo, a thicker layer of organising, newly formed granulation tissue on pre-seeded collagen-coated devices embedded not only the Dacron fabric, but also completely covered the spring arms of the device underneath a layer of neo-endothelium. CONCLUSION: Autologous cell pre-seeding of interventional closure devices is feasible since the cells survive the mechanical stress encountered during implantation. Rapid, firm and complete ingrowth of occluder devices into a thicker layer of young fibrous granulation tissue can be achieved, but an increased thrombogenicity currently limits the in vivo application.

Absorbable Implants↗

PubMed2002

Atherosclerosis with multifocal myocardial infarction in a Pacific walrus (Odobenus rosmarus divergens Illiger).

A 25-yr-old male captive walrus (Odobenus rosmarus divergens Illiger) died after suffering from periods of inactivity, anorexia, and weight loss for 8 wk. Necropsy revealed prominent, generalized atherosclerosis of cardiac arteries with widespread chronic myocardial infarction. Severe disseminated myocardial fibrosis most likely resulted in insidious cardiac failure that was ultimately the cause of death. Bouts of abdominal pain and disseminated cutaneous ulcers that had been observed 3 and 4 days before death, respectively, were attributed to circulatory failure and thrombosis. The cause of the vascular lesions remains unknown. When compared with humans, atherosclerosis is rare in animals and has not been described in a walrus.

Aging↗

PubMed2002

Persistent right aortic arch in a yearling captive wood bison (Bison bison athabascae).

An undersized, 16-mo-old, captive wood bison (Bison bison athabascae) was observed with dysphagia and postprandial regurgitation. The animal died shortly after anesthesia was initiated for diagnostic purposes. At necropsy, a persistent right aortic arch and aberrant left subclavian artery were diagnosed. The vascular ring structure around the esophagus and the trachea caused a megaesophagus with complete esophageal obstipation and ulcerative esophagitis. The aberrant left subclavian artery did not significantly compromise the esophagus. Persistence of the right aortic arch is relatively rare in ruminants and has not previously been reported in a bison.

Animals↗

PubMedDate not supplied

Transendoscopic electrosurgery of an equine pulmonary granular cell tumor.

OBJECTIVE: Description of transendoscopic electrosurgical treatment of a pulmonary granular cell tumor in a horse. STUDY DESIGN: Case report. ANIMALS: A 12-year-old Standardbred mare. METHODS: After endoscopic examination and transendoscopic biopsy, a granular cell tumor nodule was removed transendoscopically from the right principal bronchus of the sedated horse (0.02 mg/kg detomide intravenous) with a monopolar electrosurgical wire snare. Two days later, the surgical area was irradiated transendoscopically using a Nd-YAG laser. RESULTS: After surgery, the horse had no further signs of respiratory disease. Clinical and endoscopic examination and radiography performed 4 times during the following 2 years showed no evidence of recurrence. CONCLUSIONS: Transendoscopic electrosurgical removal of nodular masses located intraluminally in the principal bronchi is possible on the sedated standing horse. CLINICAL RELEVANCE: Granular tumors are rare lung neoplasms that lead to unspecific signs of a low airway disease. Diagnosis requires endoscopic examination of the large bronchi. Early intraluminal stages can be treated transendoscopically.

Animals↗

PubMedDate not supplied

Hereditary ataxia in the Jack Russell Terrier--clinical and genetic investigations.

Hereditary ataxia in the Jack Russell Terrier (JRT) is characterized by a gait disturbance with symmetric generalized ataxia and hypermetric and spastic movements. Histopathology shows a disease of the entire central nervous system, predominantly an axonopathy. In the present study, 35 clinically affected dogs were examined. Gait abnormalities began at 2-9 months of age. Generalized seizures occurred in 13 dogs in addition to the ataxia, and 7 dogs developed respiratory distress. Brain stem auditory-evoked potentials (BAEPs) were abnormal in 4 of 8 examined dogs, in which only waves I and II were detected. Abnormal BAEPs suggest the possibility of hereditary ataxia in the JRT. Investigations regarding the mode of inheritance were performed by complex segregation analyses on 3 pedigrees with a total of 115 JRTs (27 clinically affected dogs and 88 unaffected littermates and ancestors). Different modes of inheritance were tested, including monogenic, mixed, and polygenic models, as well as a model with environmental effects only. Models with genetic effects explained the data significantly better than the environmental model. The monogenic model had to be rejected in this study because of an insufficient match of data when compared to that of the most general model. The polygenic and mixed major gene models explained the pedigree data best and therefore have to be regarded as possible hypotheses for the mode of inheritance of hereditary ataxia in the JRT. The polygenic model proved best suited to explain the segregation pattern in the JRT, because it had the fewest number of parameters.

Animals↗

PubMedDate not supplied

[Computertomographic characteristics of primary brain tumors in dogs and cats].

Since computed tomography (CT) was introduced to veterinary medicine in the beginnings of the 80s, the CT of the skull has mainly been used for the diagnosis of brain tumors. The present study includes 18 dogs and five cats, all patients of the Clinic of Small Animals of the School of Veterinary Medicine Hannover. After a CT of their skull was made, a primary intracranial neoplasm was confirmed by a pathomorphological and -histogical examination post mortem. Four of the five cats had a meningioma, one cat an astrocytoma. With five cases the meningioma also predominated in the dogs, followed by primary lymphoma with four cases. An astrocytoma, an oligodendroglioma and a choroid plexus papilloma were diagnosed respectively in two dogs. A pituitary gland tumor, a germ cell tumor and a medulloblastoma represented individual cases. Based on the pathomorphologically and -histologically confirmed diagnosis, characteristics of these primary brain neoplasms can be found in their CT image. However, changes are not pathognomonic for a certain type of tumor; a definitive diagnosis cannot be made from the CT image.

Animals↗