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Biomedical subjects

A Kohn

Publications and source records attributed to A Kohn.

At least 37 records · Page 2Linked to original sources
PubMed1999

Chalcinotrema thatcheri n. sp. (Digenea: Haploporidae) from Brazilian freshwater fishes, a redescription of C. ruedasueltensis Thatcher, 1978 and comments on the validity of the genus.

Chalcinotrema thatcheri n. sp. from the intestine of Schizodon knerii is described. It is most closely related in general morphology to C. salobrensis Freitas, 1947 and C. ruedasueltensis Thatcher, 1978, from which it differs, respectively, in: testis-size, the distribution of the vitelline follicles and the distance between the gonads; and body-size, egg-size, the extent of the caeca and the shape of the seminal vesicle. The holotype of C. ruedasueltensis is redescribed with original figures. Chalcinotrema Freitas, 1947, is considered a good genus distinct from Carassotrema Park, 1938, on the basis of the presence of uterine loops between the ovary and testis and its totally different geographical distribution. Carassotrema tilapiae Nasir & Gomez, 1976 is transferred to the former genus as Chalcinotrema tilapiae (Nasir & Gomez, 1976) n. comb.

Animals↗
PubMed1999

New data on Oncophora melanocephala (Nematoda: Camallanidae), a little-known parasite of scombrid fishes.

The camallanid nematode Oncophora melanocephala (Rudolphi, 1819) is redescribed from specimens collected in tunas, Thunnus thynnus (L.), T. albacares (Bonnaterre), T. atlanticus (Lesson) and Auxis thazard (Lacépède) from the Atlantic littoral of Rio de Janeiro, Brazil. In addition to a specific structure of the buccal capsule, the species is characterized by the presence of seven pairs of preanal and five pairs of postanal subventral papillae in the male and by an unusual shape of body in the adult female; deirids are described for the first time in O. melanocephala. The structure of the buccal capsule of O. melanocephala, particularly the presence of a large posterior portion of capsule and a colourless connecting ring between buccal capsule and oesophagus, shows close affinities of Oncophora Diesing, 1851 with Paracamallanus Yorke et Maplestone, 1928. The findings of O. melanocephala in T. atlanticus and A thazard represent new host records.

Animals↗
PubMed1999

Prospective evaluation of transabdominal bowel sonography in the diagnosis of intestinal obstruction in Crohn's disease: comparison with plain abdominal film and small bowel enteroclysis.

Transabdominal ultrasonography is a noninvasive, radiation-free method that is well tolerated by patients with acute abdominal symptoms. The aim of this study was to investigate the validity of transabdominal ultrasonography, compared with plain abdominal film and small bowel enteroclysis in the diagnosis of small bowel obstruction in patients with Crohn's disease (CD). Forty-four patients with CD ileitis or ileocolitis and acute obstructive symptoms who received ultrasonography and plain abdominal film at hospital admission were evaluated by small bowel enema before dismissal or surgery and were considered for statistical analysis. Small bowel obstruction was diagnosed by ultrasonography in 23 of 44 patients (52%), by plain abdominal film in 26 of 44 patients (59%), and by small bowel enema in 28 of 44 patients (64%); the diagnostic accuracy of plain abdominal film and ultrasonography compared with small bowel enema was 73% and 89%, respectively. Ultrasonography proved to be highly specific (100%) with no false positive results. Surgery performed in 25 of 44 patients for symptoms refractory to medical treatment confirmed the high diagnostic value of ultrasonography. The result of this study indicates that transabdominal ultrasonography is accurate and highly specific in the diagnosis of small bowel obstruction and can be considered a valuable first choice examination in CD patients with obstructive symptoms.

Adolescent↗
PubMed1999

Spermatogenesis and spermiogenesis in Microcotyle sp. (Microcotylidae, Monogenea).

Ultrastructural observations of spermatogenesis and spermiogenesis in Microcotyle sp. a microcotylid monogenean parasite from the gills of Hypostomus sp., are described. The spermatogonia were irregularly shaped, forming a peripheral layer of cells; spermatocytes were larger than spermatogonia and a nuclear synaptonemal complex was observed; young spermatids were joined by a central cytophore forming rosettes. Spermiogenesis was characterized by the outgrowth of a cytoplasmic protuberance, the zone of differentiation, containing the basal bodies, separated by an intercentriolar body, from which flagella grow out and fuse posteriorly with the median process. Cross sections of the anterior and the middle regions of spermatozoa revealed nuclei, mitochondria, peripheral microtubules, and paired axonemes each with a 9+1 pattern.

Animals↗
PubMed1998

South American Monogenea--list of species, hosts and geographical distribution.

Five-hundred and twenty-three species of monogeneans have been recorded in South America: 43 from Argentina, one from Bolivia, 252 from Brazil, 29 from Chile, 15 from Colombia, eight from Ecuador, 26 from Falkland and Patagonian regions, four from French Guyana, 11 from Galapagos, two from Guiana, four from Paraguay, 92 from Peru, 16 from Uruguay and 20 from Venezuela. A list of these species with hosts and geographical distribution is presented.

Animals↗
PubMed1997

Optical imaging in vitro provides evidence for the minicolumnar nature of cortical response.

The response of rat neocortical slices to electrical stimulation at the layer VI/white matter border was recorded using intrinsic signal optical imaging. The optical response of the slice is column-shaped, extends from layer VI to the pial surface, and is strongly correlated with the amplitude of simultaneously recorded evoked potentials. Spectral analysis revealed radially oriented spatial variations in the intensity of the optical signal with a period of 30-60 microm/cycle. Nissl-stained sections of slices also exhibited a radially oriented periodicity in optical density with the same period. We conclude that the periodic variations in the intrinsic optical signal correspond to stimulus-activated minicolumns.

Animals↗
PubMed1997

High-level expression of the prohormones proenkephalin, pro-neuropeptide Y, proopiomelanocortin, and beta-protachykinin for in vitro prohormone processing.

Prohormone substrates are required for investigation of the proteolytic processing of prohormones and proproteins into active peptide hormones and neurotransmitters. However, the lack of prohormone proteins has been a limiting factor in elucidating proteolytic mechanisms for conversion of prohormones into active peptides. Therefore, in this study, cloned cDNAs encoding the prohormones proenkephalin (PE), pro-neuropeptide Y (pro-NPY), pro-opiomelanocortin (POMC), and beta-protachykinin (beta-PT) were utilized to express recombinant prohormones in Escherichia coli. High-level expression of milligrams of prohormones was achieved with the pET3c expression vector utilizing the T7 promoter for production of PE, pro-NPY, and POMC, as demonstrated by SDS-PAGE gel electrophoresis, Western blots, and 35S-methionine labeling. In addition, beta-PT was expressed at high levels as fusion proteins with the maltose-binding protein and glutathione S-transferase by the pMAL-c and pGEX-2T expression vectors, respectively. Relative rates of processing by the established processing proteases "prohormone thiol protease" (PTP), 70-kDa aspartyl protease, and PC1/ 3 and PC2 (PC, prohormone convertase) were examined with purified PE, pro-NPY, and POMC. Distinct preferences of processing enzymes for different prohormones was demonstrated. PTP preferred PE and pro-NPY substrates, whereas little processing of POMC was detected. In contrast, the 70-kDa aspartyl protease cleaved POMC more readily than pro-NPY or PE. However, PC1/3 and PC2 prefer POMC as substrate. Demonstration of selectivity of processing enzymes for prohormone substrates illustrates the importance of expressing recombinant prohormones for in vitro processing studies.

Animals↗
PubMed1997

New observations on seuratoid nematodes parasitic in fishes of the Paraná River, Brasil.

The present paper comprises a systematic survey of nematodes of the superfamily Seuratoidea collected from fishes of the Paraná River, southern Brazil, in 1992-1995. The following species were recorded: Neoparaseuratum travassosi Moravec, Kohn et Fernandes, 1992, Spectatus sp., Seuratoidea gen. sp. larvae, Cucullanus brevispiculus Moravec, Kohn et Fernandes, 1993, C. pinnai pinnai Travassos, Artigas et Pereira, 1928, C. pinnai pterodorasi subsp. n., C. rhamphichthydis sp. n., C. zungaro Vaz et Pereira, 1934, and Dichelyne pimelodi sp. n. C. pinnai pterodorasi (type host Pterodoras granulosus) differs from C. p. pinnai in the shape of the oesophagus and in the position of the nerve ring. C. rhamphichthydis (only females) (type host Rhamphichthys rostratus) is characterized mainly by the postoesophageal position of the excretory pore and deirids, complex structure of the cuticular lining of oesophastome and by markedly narrow body, whereas D. pimelodi (one male) (type host Pimelodus sp.) by the length of spicules (1.46 mm), postoesophageal position of the excretory pore and deirids and by the arrangement of genital papillae. Most species are briefly described (females of C. brevispiculus and Seuratoidea gen. sp. larvae for the first time) and illustrated and some problems concerning their taxonomy, hosts and geographical distribution are discussed.

Animals↗
PubMed1996

An antibiotic regimen for the treatment of active Crohn's disease: a randomized, controlled clinical trial of metronidazole plus ciprofloxacin.

OBJECTIVES: Bacteria in the gut lumen may play a role in the etiology and/or the symptoms of Crohn's disease (CD). Although various antibacterial drugs have been employed in clinical practice, few controlled trials have been conducted, and those had conflicting results. The aim of this study was to investigate the efficacy and the safety of a combination of metronidazole and ciprofloxacin, compared with methylprednisolone, in treating 41 consecutive patients with active CD. METHODS: Eligible patients, 13 men and 28 women, mean age 38 yr, were randomly allocated to receive, for 12 wk, ciprofloxacin 500 mg twice daily plus metronidazole 250 mg four times daily or methylprednisolone 0.7-l mg/kg/day, with variable tapering to 40 mg, followed by tapering of 4 mg weekly. RESULTS: Ten of the 22 antibiotic patients (45.5%) and 12 of the 19 steroid patients (63%) obtained clinical remission (Crohn's Disease Activity Index < or = 150) at the end of the 12-wk study (p = NS). Five patients on antibiotics (22.7%) and five patients on steroids (26.3%) were considered treatment failures because of deterioration or persistent symptoms. Six patients receiving antibiotics (27.3%) and two on steroids (10.6%) were withdrawn from the trial because of side effects. One patient on antibiotics was not compliant. CONCLUSIONS: metronidazole and ciprofloxacin could be an alternative to steroids in treating the acute phase of CD.

Adolescent↗
PubMed1994

[Data torturing].

Explore the source record for details and available documents.

Confidence Intervals↗
PubMed1994

Structure of the cephalic end of two little-known oxyuroid genera, Travnema Pereira, 1938 and Cosmoxynemoides Travassos, 1949, parasites of fishes, as revealed by SEM.

The cephalic end of the type species of pharyngodonid genera Travnema and Cosmoxynemoides, T. travnema Pereira, 1938 and C. aguirrei Travassos, 1949, parasites of Brazilian freshwater fishes, was studied by scanning electron microscopy. The mouth aperture of Travnema was found to be circular, surrounded by four cephalic papillae and two lateral amphids and the cuticle of the cephalic end had a conspicuous dense sculpture. On the other hand, the mouth aperture of Cosmoxynemoides was triangular, surrounded by three lip-like elevations covering the whole surface of the relatively flat cephalic extremity, each with two inner lobes separated one from another by a short groove; the lip-like elevations bore four medium-sized, kidney-shaped cephalic papillae and two minute amphids (two papillae on the dorsal elevation and one papilla and one amphid on each of two ventrolateral elevations); the cuticle of the cephalic end was smooth. Both species were noted for the absence of oral lamellae and the presence of lateral alae. Both genera are listed in the family Pharyngodonidae but Travnema (and also Hakynema), due to its morphological peculiarities, is considered to represent a distinct subfamily Travnematinae within the Pharyngodonidae. The finding of both T. travnema and C. aguirrei in the characid fish Astyanax bimaculatus lacustris represents new host records.

Animals↗
PubMed1994

Two new species of the genus Goezia, G. brasiliensis sp. n. and G. brevicaeca sp. n. (Nematoda: Anisakidae), from freshwater fishes in Brazil.

Examination of freshwater fishes from the Paraná River in southern Brazil during March 1992, revealed the presence of two new, previously undescribed species of the genus Goezia: G. brasiliensis sp. n. is described from the stomach of Brycon hilarii (family Characidae) (type host) and the intestine of Pseudoplatystoma coruscans (Pimelodidae) and it is characterized mainly by the length (0.802 mm) of spicules, number and arrangement of male caudal papillae (10 pairs of preanals and 4 pairs of postanals) and body measurements (male 11 mm, female 10-16 mm); the main characteristics of G. brevicaeca sp. n., described from the stomach of Brycon hilarii, are a short anterior intestinal caecum reaching anteriorly only to the posterior end of oesophagus, comparatively short spicules (0.367 mm), number of male caudal papillae (20 pairs of preanals and 4 pairs of post-anals) and an elongate, rather long body (male 17 mm, female 23 mm).

Animals↗