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Biomedical subjects

D S Taylor

Publications and source records attributed to D S Taylor.

At least 55 records · Page 3Linked to original sources
PubMed1994

Stringhalt secondary to trauma to the dorsoproximal region of the metatarsus in horses: 10 cases (1986-1991).

A review of medical records was used to identify 10 horses in which stringhalt developed subsequent to trauma to the dorsal metatarsus. Six horses developed stringhalt within 3 months after injury, 3 horses developed stringhalt > 3 months after injury, and time from injury to stringhalt was unknown for 1 horse. Horses were treated with exercise, including daily hand-walking with pasture turnout, followed by lunging; or surgically, using lateral digital extensor myotenectomy. Of the horses treated with exercise, 1 had resolution of stringhalt, 2 improved but had residual stringhalt, and 1 had no change. Two of the horses having lateral digital extensor myotenectomy had resolution of stringhalt. Two of the remaining 3 horses treated surgically had varying degrees of improvement, and in 1 horse there was no change. Stringhalt is a potential complication following trauma to the dorsal metatarsal region. Potential causes include tendon adhesions enhancing tarsocrural joint flexion or abnormalities in the myotatic reflex caused by tendon injury that result in abnormal flexion of the tarsocrural joint.

Animals↗
PubMed1994

Identification of a critical regulatory site in the human interleukin-3 promoter by in vivo footprinting.

Interleukin-3 (IL-3) is involved in proliferation and differentiation of hematopoietic progenitor cells. Its expression is subject to precise, tissue-specific regulation, and has been studied extensively in the gibbon T-cell line MLA 144 by a combination of functional assays and DNA binding experiments. To extend these studies, the gibbon IL-3 promoter was cloned and in vivo footprinting of the gibbon and human IL-3 proximal promoters was performed. The gibbon IL-3 promoter was found to be highly homologous to its human counterpart and both promoters yielded identical in vivo footprints after induction of IL-3 synthesis. In particular, we observed specific protection of three guanines over a core sequence TGTGGTTT (IF-1IL3) that had not been recognized in previous studies. IF-1IL3 is not found in other cytokine promoters, but it is conserved in the IL-3 promoter of several species and is similar to a recurring motif in viral and T-cell-specific cellular enhancers. IF-1IL3 binds a specific complex in MLA 144 and Jurkat nuclear extracts in vitro, which shares the same specificity as the complex bound by the polyoma virus and T-cell receptor delta enhancers. Mutation of the three guanines in IF-1IL3 core sequence disrupts binding in vitro and abrogates the ability of the IL-3 promoter to mediate inducible expression in T cells. Although IF-1IL3 is necessary for IL-3 expression, it is not sufficient: a truncated IL-3 promoter with an intact IF-1IL3 site but no other activator sites is transcriptionally silent. These studies describe a new regulatory element within the IL-3 promoter that is essential for expression and conserved between species.

Amino Acid Sequence↗
PubMed1994

Angiotensin II induces delayed mitogenesis and cellular proliferation in rat aortic smooth muscle cells. Correlation with the expression of specific endogenous growth factors and reversal by suramin.

By means of a rat aortic smooth muscle (RASM) cell culture model, the effects of angiotensin II (AII) on early proto-oncogene gene expression, DNA synthesis, and cell proliferation were measured and compared to known mitogens. In 24-h [3H]-thymidine incorporation assays, AII was found to be a weak mitogen when compared to potent mitogens such as fetal bovine serum and platelet-derived growth factor (PDGF). In contrast, when assays were carried out for 48 h, AII induced a significant dose-dependent stimulation of DNA synthesis, which more than doubled at 3 nM AII, and was maximal (five- to eightfold above control) at 100 nM AII. Treatment of cells with the AII type 1 receptor antagonist losartan inhibited the mitogenic effects of AII. AII also stimulated smooth muscle cell proliferation, as indicated by an absolute increase in cell number after AII stimulation of RASM cells for 5 d. AII stimulation of RASM cell growth correlated with the increased expression of specific endogenous growth factors, including transforming growth factor beta 1 (TGF-beta 1) and PDGF A-chain. However, addition of either PDGF- or TGF-beta 1-neutralizing antibodies failed to significantly reduce the delayed mitogenic effects induced by AII. In contrast, we found that AII-stimulated mitogenesis could be inhibited in a dose-dependent manner by the growth factor inhibitor drug suramin. Taken together, our results indicate that enhanced endogenous growth factor expression may represent the direct mechanism by which AII promotes smooth muscle cell growth in some vascular hyperproliferative diseases.

3T3 Cells↗
PubMed1994

Endothelin-1 and angiotensin-II stimulate delayed mitogenesis in cultured rat aortic smooth muscle cells: evidence for common signaling mechanisms.

The vasoactive peptides endothelin-1 (ET-1) and angiotensin-II (AII) have been implicated in chronic hypertension and may play important roles in related vascular diseases such as restenosis and atherosclerosis. Using a rat aortic smooth muscle (RASM) cell model, both ET-1 and AII induced concentration-dependent delayed increases in DNA synthesis relative to that in the serum-deprived controls. Stimulation of DNA synthesis was maximal at 100 nM for each peptide. All treatment of RASM cells resulted in a greater mitogenic effect (4- to 7-fold) than that observed for ET-1 (3-fold). When added in the presence of AII, ET-1 had a supplemental effect on DNA synthesis (5- to 10-fold above control). Although RASM cells expressed both ETA and AT1 receptors, radioligand binding experiments indicated that approximately 10-fold as many AT1 receptors as ETA receptors were present. In signal transduction studies, ET-1 and AII each elicited concentration-dependent increases in the intracellular Ca2+ concentration. ET-1 and AII also stimulated phosphoinositide metabolism and phosphorylation of a specific substrate for protein kinase-C. The release of total inositol phosphates in response to ET-1 and AII was concentration dependent and inhibited by the ETA receptor-selective antagonist BQ-123 and the AT1 receptor-selective antagonist losartan, respectively. In addition, tyrosine phosphorylation of 120- and 75-kilodalton proteins as well as the mitogen-activated protein kinases p44mapk and p42mapk was observed within 5 min of the addition of either ET-1 or AII. Taken together, these data indicate that ET-1 and AII may promote smooth muscle cell growth through common intracellular signaling mechanisms.

Angiotensin II↗
PubMed1993

Effects of thrombin receptor activating peptide on phosphoinositide hydrolysis and protein kinase C activation in cultured rat aortic smooth muscle cells: evidence for "tethered-ligand" activation of smooth muscle cell thrombin receptors.

Phosphoinositide hydrolysis and protein kinase C (PKC) activation were examined in response to treatment of rat aortic smooth muscle cells with alpha-thrombin and a seven amino acid thrombin receptor activating peptide (TRAP-7; SFLLRNP). alpha-Thrombin and TRAP-7 stimulated total inositol phosphate (IP) accumulation and phosphorylation of a specific endogenous substrate for activated PKC. Acetylated TRAP-7 and "reverse" TRAP (FSLLRNPNDKYEPF) were ineffective in stimulating signal transduction. The active site inhibitor, MD805 (argatroban), and the anion-binding exosite inhibitor, BMS 180,742, reduced the IP response to alpha-thrombin in a concentration-dependent manner. In contrast, the TRAP-7-induced IP response was not affected by either inhibitor. These data are consistent with the tethered-ligand hypothesis for thrombin receptor activation in rat aortic smooth muscle cells.

Animals↗
PubMed1993

Angiotensin II stimulation of rapid protein tyrosine phosphorylation and protein kinase activation in rat aortic smooth muscle cells.

In cultured rat aortic smooth muscle cells, angiotensin II (AII) treatment led to increased tyrosine phosphorylation of cellular proteins with apparent molecular masses of 42, 44, 75, and 120 kDa, respectively, as assessed by antiphosphotyrosine immunoblotting. Increased protein tyrosine phosphorylation was observed within 1 min of AII addition and was maximal by 30 min. The overall pattern of AII-stimulated protein tyrosine phosphorylation was distinct from that observed following treatment of rat aortic smooth muscle cells with platelet-derived growth factor-BB. Specific antibodies were used to identify the AII-stimulated 42- and 44-kDa tyrosine-phosphorylated proteins as the "mitogen-activated protein kinases," p42mapk and p44mapk, respectively. Raf-1, a 70-74-kDa serine/threonine protein kinase, was not tyrosine-phosphorylated in response to AII but was found to be hyperphosphorylated as evidenced by retarded protein mobility in SDS gel analysis. Taken together, these data indicate that AII binding to vascular smooth muscle cells leads to rapid activation of a complex cascade of protein kinases, including protein kinase C, Raf-1, MAP kinases, and an undefined intracellular protein tyrosine kinase(s) that may be coordinately involved in signal transduction leading to cell proliferation.

Angiotensin II↗
PubMed1993

Eye movements in children with opsoclonus-polymyoclonus.

The anatomical localisation of the abnormality underlying opsoclonus-polymyoclonus-the "Dancing Eye Syndrome"-is uncertain and both the brainstem and cerebellum have been implicated. We used electrooculographic recordings to assess the eye movements in five children with this syndrome. Overshoot dysmetria was the consistent feature for the saccades of all five cases. One patient was also assessed after the main symptoms of ataxia and opsoclonus (saccadic oscillations, without an intersaccadic interval) had resolved and the saccades were found to remain hypermetric. Smooth pursuit and optokinetic nystagmus were normal, although the opsoclonus occurred throughout the recording session and were superimposed upon the normal eye movement waveforms. The vestibulo-ocular reflex was normal in four patients, but in one case, the time-constant was significantly prolonged: this has only been reported in experimental lesions of the nodulus in monkeys. The presence of saccadic overshoot dysmetria is highly suggestive of a cerebellar origin for the abnormal eye movements in these children. However, the preservation of normal smooth pursuit and the absence of gaze-paretic, rebound and downbeat nystagmus, implies the sparing of the flocculus and paraflocculus. We propose that the origin of these oculomotor deficits could be the cerebellar fastigial nuclei.

Adrenocorticotropic Hormone↗
PubMed1993

Distribution and ecology of Haemagogus aeritinctus in Belize, Central America.

Immatures of Haemagogus aeritinctus are reported from a black mangrove (Avicennia germinans) tree hole on an offshore key in the Belize barrier reef. This is the first report of this species from other than coastal mainland sites in Central America. The high salinity (10,000 ppm) recorded in the tree hole water suggests that this species has a tolerance, or possibly a requirement, for soluble salts that may explain its affiliation solely with mangrove habitats.

Animals↗
PubMed1992

Extreme clonal diversity and divergence in populations of a selfing hermaphroditic fish.

Recombination is unknown in natural populations of Rivulus marmoratus, a selfing hermaphrodite, and genetic variation is likely due to mutation alone. DNA fingerprinting with an array of microsatellite [e.g., (CT)9] and minisatellite (e.g., the 33.15 core sequence) probes reveals very high clonal diversity within samples of seven Floridian populations, of which five contain about as many clones as there are individuals. There are 42 clones among 58 individuals surveyed (mean, 1.4 individuals per clone), a level of genetic diversity unprecedented among clonal animals. Moreover, all of the probes recognize the same clones even though, at high hybridization stringencies, there is little overlap in the fingerprint patterns they generate. This suggests that most sympatric clones differ by multiple and independent mutational steps. In one population studied in detail, the average number of mutational steps separating two clones is estimated at 9 or 10 and may be substantially higher. The mutational discontinuities among sympatric clones make it unlikely that they evolved by accumulation of neutral mutations in populations that are otherwise genetically uniform. The data argue that the mixing of unrelated individuals from different local populations occurs to an extent previously unappreciated and/or that divergence of clones is mediated by natural selection. If confirmed, the latter would be a serious challenge to current ideas on the predominant role of recombination in promoting the evolution of biological novelty.

Animals↗
PubMed1992

Mucolipidosis type IV. Presentation of a mild variant.

The authors report a 16-year-old girl with mucolipidosis type IV. She was referred because of deteriorating vision over the past three years. Corneal clouding with the appearance of cornea verticillata and retinal dystrophy were the main ophthalmological findings. Except for clumsiness no psychomotor retardation was present. Ultrastructural analysis of a conjunctival biopsy and cultured fibroblasts suggested a diagnosis of mucolipidosis type IV which was confirmed by biochemical studies. This patient represents the mildest described presentation of mucolipidosis type IV.

Adolescent↗
PubMed1992

The killifish Rivulus marmoratus: a potential biocontrol agent for Aedes taeniorhynchus and brackish water Culex.

In the laboratory, newly hatched fry of Rivulus marmoratus were effective predators on 1st-instar Aedes taeniorhynchus. Adult fish consumed 4th-instar Ae. taeniorhynchus and egg rafts of Culex quinquefasciatus at a rate increasing with standard length of the fish. Predation of Rivulus marmoratus on Ae. taeniorhynchus larvae in the field was documented by observing the passage of larval/pupal remains through the gut. Laboratory reared fish released at known Ae. taeniorhynchus breeding sites survived over 1.5 years, but did not reproduce.

Aedes↗
PubMed1991

Salmonella typhimurium abscess as a postoperative complication in a horse with colic.

An 11-year-old, 430-kg fox-trotter stallion was referred for evaluation of colic. A right-sided inguinal hernia was diagnosed. At exploratory laparotomy, the ileum was found to be herniated through the right inguinal canal. Compromised small intestine was resected, jejunocecal anastomosis was performed, and the horse was castrated. Three days after surgery, the stallion would not bear weight on the left hind limb. The musculature of the left thigh region became swollen. Aspiration of the left thigh region yielded serosanguineous fluid from which Salmonella typhimurium was isolated. Ultrasonography of the left thigh revealed multiple hypoechoic areas suggestive of abscess. The left medial thigh region was surgically incised, and a large abscess was drained. Bacteriologic culture of feces yielded S typhimurium. The owner elected to have the horse euthanatized.

Abscess↗
PubMed1991

Heterogeneity in dominant anterior segment malformations.

Peters' anomaly is usually a sporadic or autosomal recessive condition. We present three families whose members had dominantly inherited anterior segment anomalies with variable expression, including typical Peters' anomaly in at least one family member. Slit-lamp examination of parents and family members of children with Peters' anomaly is therefore important to exclude dominant inheritance.

Abnormalities, Multiple↗
PubMed1991

[Optic neuritis in children].

Study of 40 children who presented a first episode of idiopathic optic neuritis. A mean follow-up of more than 8 years revealed only 15% of multiple sclerosis. This frequency is much lower than in adults. The visual outcome is also better. Significant factors are: absence of papilloedema, unilaterality, recurrence, HLA B7 and DR2, oligoclonal cerebrospinal fluid, anomalies of the VEPs.

Adolescent↗
PubMed1990

Acute oxalate poisoning attributable to ingestion of curly dock (Rumex crispus) in sheep.

Ten of 100 mature ewes were afflicted with acute oxalate toxicosis within 40 hours after being temporarily penned in a lot that contained considerable growing Rumex crispus (curly dock). Clinical signs of toxicosis included excess salivation, tremors, ataxia, and recumbency. Affected ewes were markedly hypocalcemic and azotemic. Oxalate crystals were not observed in urine. Gross postmortem lesions were minimal and nondiagnostic in 2 ewes that died peracutely, but perirenal edema and renal tubular degeneration were clearly observable in ewes euthanatized on the third day of toxicosis. Diagnosis of oxalate toxicosis was confirmed by histopathologic findings. Samples of Rumex spp contained 6.6 to 11.1% oxalic acid on a dry-weight basis, a concentration comparable with that in other oxalate-containing plants that have caused acute oxalate toxicosis.

Acute Kidney Injury↗
PubMed1990

Albinism in childhood: a flash VEP and ERG study.

Flash visual evoked potentials (F. VEPs) and electroretinograms (ERGs) were recorded in a total of 20 young children with albinism (age range 5 months to 11 years, mean 4 years). All recordings were made without sedation. There were 13 oculocutaneous cases (one with Hermansky-Pudlak syndrome) and seven ocular albinos. Monocular flash stimulation commonly elicited an asymmetrical occipital VEP distribution with a well lateralised component at around 80 ms which was of opposite polarity in a comparison of VEPs from each eye. None of the normally pigmented matched controls or obligate female carriers showed this anomalous distribution. The albino electroretinogram, compared with controls, recorded under fully darkened conditions had a significantly larger a wave and significantly shorter latencies for both a and b waves. The accentuated ERG and asymmetrical VEP recorded in infants and young children with albinism permits distinction of these patients from those with congenital cone dysfunction and idiopathic nystagmus, with whom they may be confused by a clinical examination only.

Albinism↗
PubMed1990

The eye in the CHARGE association.

CHARGE association includes patients with at least four features prefixed by the letters of the mnemonic: Coloboma, Heart defects, Atresia of the choanae, Retarded growth and development, Genital hypoplasia, Ear anomalies and/or hearing loss. Many also have facial palsy. We report a series identified by collaboration within one centre of all specialties concerned in the management of the CHARGE association. Ocular abnormalities were found in 44 out of 50 patients with the CHARGE association. Of these, 41 had 'typical' colobomata. The majority had retinochoroidal colobomata with optic nerve involvement, but only 13 patients had an iris defect. Two patients had atypical iris colobomata with normal fundi. Additional features were microphthalmos in 21 patients, optic nerve hypoplasia in four, nystagmus in 12, and a vertical disorder of eye movement in four of the 22 cases with facial palsy. We report an incidence of coloboma in the CHARGE association of 86% (43/50) compared with a previous cumulative reported incidence of 66% (112/170). We believe that there may have been previous underdiagnosis of colobomata in children with multiple congenital abnormalities.

Abnormalities, Multiple↗