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Biomedical subjects

E Hewitt

Publications and source records attributed to E Hewitt.

14 recordsLinked to original sources
PubMed2006

Effects of oxygen tension on the establishment and lactate dehydrogenase activity of murine embryonic stem cells.

The lack of a standardized culture environment for establishment of embryonic stem cell lines has hindered the orchestrated differentiation of cells and the application of this technology. Oxygen concentration has a profound effect on proliferation and differentiation of many cell types. This study tested the hypothesis that establishment dynamics, lactate dehydrogenase (LDH) isoforms, and mRNA expression patterns would be affected by the oxygen tension in the culture environment. Recovered (day 4) murine blastocysts were cultured in a gas environment of 6% CO(2) and either 20% or 5% O(2) (balance supplemented with N(2)). More (p < 0.05) blastocysts produced outgrowths in the low (79.3 +/- 0.1%) compared to the high (57.1 +/- 0.1%) O(2) groups, and more (p < 0.05) colonies in the low O(2) group (14/15; 93.3 +/- 0.1%) stained positive for alkaline phosphatase relative to the high O(2) group (9/15; 60.6 +/- 0.1%). Oxygen treatment had no effect on the activity of the oxioreductase lactate dehydrogenase. Interestingly, the stem cell lines in both treatments displayed multiple isoforms (III, IV, and V) of LDH, whereas the outgrowths displayed isoforms I and V. In contrast, two-cell embryos and blastocysts displayed only isoform I, and fibroblasts displayed isoforms IV and V. There were no treatment differences in mRNA expression of LDHalpha in the outgrowths, or established stem cells. LDH transition from the heart (I) to the muscle (V) isoform indicated an increase in glycolytic activity, consistent with the peri-hatching/implantation time period. Reduced O(2) environment had significant positive effects on the establishment and maintenance of murine stem cells, supporting the hypothesis, whereas the LDH isozyme transition was consistent among treatments.

Animals↗
PubMed2001

Human oesophagostomiasis: a histomorphometric study of 13 new cases in northern Ghana.

Oesophagostomiasis is an infrequently described and recognised parasitic infection in humans, caused by Oesophagostomum bifurcum. Although the disease is most often found in the northern part of Togo and the neighbouring part of Ghana, sporadic cases have been described in other parts of Africa and in Asia and South America: Uganda, Ivory Coast, Sudan, Kenya, Ethiopia, Indonesia, Malaysia and Brazil. Infection probably occurs by way of the ingestion of L3 larvae. These larvae penetrate the intestinal wall, especially that of the colon. Some of these larvae develop into young adult worms and return to the bowel lumen. Other larvae, however, develop into immature worms, which fail to settle in the lumen, forming abscesses in the bowel wall and causing pathology. In the literature 105 human cases have been described, many originating in the northern regions of Ghana and Togo. The present study was performed to evaluate 13 new cases originating in the northern part of Ghana (7 female and 6 male patients, aged between 2 and 60 years). Histopathologically, the patients could be divided into two groups: the first group showed multinodular disease, while patients in the second group presented with a single, nodular mass. In the first group, abscesses were seen throughout the colonic wall. The mean size of the cavities was 4.3+/-0.7 mm. There was no relation between the size and the localisation in the colonic wall. Abscesses were significantly larger in male patients than in female patients. There was no correlation with age. In the second group, histopathological examination showed a cyst of variable wall thickness with very limited inflammation. These cysts represented older lesions, often encapsulated in the mesentery. In conclusion, in this study we present 13 new cases of human oesophagostomiasis. The abscess formation was found to be organ specific, independent of age, and gender-related, producing a more intense tissue reaction in male patients.

Abscess↗
PubMed2000

The structures of the H(C) fragment of tetanus toxin with carbohydrate subunit complexes provide insight into ganglioside binding.

The entry of tetanus neurotoxin into neuronal cells proceeds through the initial binding of the toxin to gangliosides on the cell surface. The carboxyl-terminal fragment of the heavy chain of tetanus neurotoxin contains the ganglioside-binding site, which has not yet been fully characterized. The crystal structures of native H(C) and of H(C) soaked with carbohydrates reveal a number of binding sites and provide insight into the possible mode of ganglioside binding.

Acetylgalactosamine↗
PubMed1998

Deletion analysis of yeast Sec65p reveals a central domain that is sufficient for function in vivo.

The Saccharomyces cerevisiae SEC65 gene encodes a 32 kDa subunit of yeast signal recognition particle that is homologous to human SRP19. Sequence comparisons suggest that the yeast protein comprises three distinct domains. The central domain (residues 98-171) exhibits substantial sequence similarity to the 144 residue SRP19. In contrast, the N-terminal and C-terminal domains (residues 1-97 and 172-273 respectively) share no similarity to SRP19, with the exception of a cluster of positively charged residues at the extreme C-terminus of both proteins. Here, we report the cloning of a Sec65p homologue from the yeast Candida albicans that shares the same extended domain structure as its S. cerevisiae counterpart. This conservation of sequence is reflected at the functional level, as the C. albicans gene can complement the conditional lethal sec65-1 mutation in S. cerevisiae. In order to examine the role of the N- and C- terminal domains in Sec65p function, we have engineered truncation mutants of S. cerevisiae SEC65 and tested these for complementing activity in vivo and for SRP integrity in vitro. These studies indicate that a minimal Sec65p comprising residues 76-209, which includes the entire central SRP19-like domain, is sufficient for SRP function in yeast.

Amino Acid Sequence↗
PubMed1997

Cloning, isolation, and characterization of mammalian legumain, an asparaginyl endopeptidase.

Legumain is a cysteine endopeptidase that shows strict specificity for hydrolysis of asparaginyl bonds. The enzyme belongs to peptidase family C13, and is thus unrelated to the better known cysteine peptidases of the papain family, C1 (Rawlings, N. D., and Barrett, A. J. (1994) Methods Enzymol. 244, 461-486). To date, legumain has been described only from plants and a blood fluke, Schistosoma mansoni. We now show that legumain is present in mammals. We have cloned and sequenced human legumain and part of pig legumain. We have also purified legumain to homogeneity (2200-fold, 8% yield) from pig kidney. The mammalian sequences are clearly homologous with legumains from non-mammalian species. Pig legumain is a glycoprotein of about 34 kDa, decreasing to 31 kDa on deglycosylation. It is an asparaginyl endopeptidase, hydrolyzing Z-Ala-Ala-Asn-7-(4-methyl)coumarylamide and benzoyl-Asn-p-nitroanilide. Maximal activity is seen at pH 5.8 under normal assay conditions, and the enzyme is irreversibly denatured at pH 7 and above. Mammalian legumain is a cysteine endopeptidase, inhibited by iodoacetamide and maleimides, but unaffected by compound E64 (trans-epoxysuccinyl-L-leucylamido-(4-guanidino)butane). It is inhibited by ovocystatin (cystatin from chicken egg white) and human cystatin C with Ki values < 5 nM. We discuss the significance of the discovery of a cysteine endopeptidase of a new family and distinctive specificity in man and other mammals.

Amino Acid Sequence↗
PubMed1997

Surgical interruption of a midline dorsal column visceral pain pathway. Case report and review of the literature.

A punctate midline myelotomy performed in a patient effectively eliminated residual, intractable pelvic pain, which remained after resolution of uterine cervical cancer. The authors describe the case history of the patient, in whom pain assessments were made, and a surgical procedure performed. Despite large doses of opiate analgesic medications, the patient experienced constant pressure pain in the right lower pelvis, with excruciating pain on bowel movement. Severe weight loss necessitated better pain control. A minimally invasive surgical procedure, a 5-mm deep puncture using a 16-gauge needle on either side of the median septum in the dorsal column of the spinal cord (T-8), resulted in no new neurological deficits. Narcotic medication was tapered, no pain was reported, and the patient resumed daily household activity. Midline myelotomy has typically been performed with the intention of eliminating the crossing fibers of the spinothalamic tract in the anterior white matter commissure. The punctate midline myelotomy described here was performed with the specific intention of interrupting a newly described visceral pain pathway that ascends to higher brain centers through the midline of the dorsal column. The effectiveness of the pain relief seen in this patient suggests that visceral pain of the pelvis in humans may be transmitted in the midline of the dorsal column, as has been recently reported in studies using rats. The effectiveness of the punctate midline myelotomy performed in this one case of pelvic visceral pain suggests that the surgery may eventually be effective in greatly reducing or replacing opiate narcotic medication for visceral pain management.

Activities of Daily Living↗
PubMed1996

Nerve growth factor (NGF) content in adult rat brain tissues is several-fold higher than generally reported and is largely associated with sedimentable fractions.

Initial studies had revealed that the bioactivity of nerve growth factor (NGF) in sonicates of adult rat hippocampal formation (HF) is several-fold greater in their pellet than their supernatant fractions. Such observations have prompted an analysis of NGF antigen (NGF-Ag) contents in pellets and supernatants from a variety of adult rat CNS tissues, both in the absence and the presence of exogenous beta-NGF. With HF tissues, NGF-Ag in the supernatants was comparable to most literature values, but pellet NGF-Ag was 3 to 5 times that amount. All other CNS tissue sonicates also revealed 3-6 fold higher NGF-Ag in their pellets than their supernatants, hence overall NGF-Ag contents were greatly in excess of reported ones. Presentation of mouse beta-NGF to a tissue, its sonicate, or its standard pellet resulted in a transfer to the final pellet of 30-50% of the added soluble NGF-Ag (and 30% of the added bioactivity). This percentage is much lower than that present in native pellets (80%), suggesting that the association of endogenous NGF with particulate matter may involve at least two compartments. Treatments of pellets with salt, alkaline pH, and/or the detergent Triton X-100 have revealed a third subset, namely additional pellet NGF-Ag that was not initially recognized by the antibody in our ELISA assay. The treatments also caused substantial release of NGF from pellet to supernatant. Further studies should clarify the nature of the association between NGF and the three subsets of pellet NGF and allow the investigation of the pellet molecules responsible for it.

Animals↗
PubMed1978

Some new singular Fourier-Stieltjes series.

Singular continuous probability measures on the circle group are constructed whose Fourier-Stieltjes transforms converge to zero very rapidly and also have positive partial sums. Partial results for the line and for arbitary compact infinite Abelian groups are also obtained.

Journal Article↗
PubMed1971

Lacunarity for compact groups.

Let G be a compact Abelian group with character group X. A subset Delta of X is called a [unk](q) set (1 < q < infinity) if for all trigonometric polynomials f = [unk](k=1) (n) alpha(k)chi(k) (chi(1),...,chi(n) [unk] Delta) an inequality parallelf parallel(q) [unk] [unk] parallelf parallel(1) obtains, where [unk] is a positive constant depending only on Delta. The subset Delta is called a Sidon set if every bounded function on Delta can be matched by a Fourier-Stieltjes transform. It is known that every Sidon set is a [unk](q) set for all q. For G = T, X = Z, Rudin (J. Math. Mech., 9, 203 (1960)) has found a set that is [unk](q) for all q but not Sidon. We extend this result to all infinite compact Abelian groups G: the character group X contains a subset Delta that is [unk](q) for all q, 1 < q < infinity, but Delta is not a Sidon set.

Journal Article↗
PubMedDate not supplied

Clinical epidemiology and classification of human oesophagostomiasis.

The intestinal helminth Oesophagostomum bifurcum is highly and focally endemic in northern Ghana and Togo, and its juveniles produce a nodular inflammatory response as they develop in the intestinal wall. This pathology can produce clinical symptoms. We report on 156 cases of oesophagostomiasis presenting in 1996-98 to Nalerigu hospital in northern Ghana. The disease accounted for 0.2% of the out-patient department new presentations (about 1 patient per week), and 1% (16) of the major acute surgical cases. Children aged 5-9 years were most commonly affected. Multinodular disease (13% of the cases) results from hundreds of pea-sized nodules within the colon wall and other intra-abdominal structures, and presents with general abdominal pain, persistent diarrhoea and weight loss. Dapaong tumour (87%) presents as an abdominal inflammatory mass often associated with fever. The 3-6-cm tumour is painful, well-delineated, smooth, spherical, 'wooden', periumbilical, and adhered to the abdominal wall. Cases most commonly presented during the late rains and early dry season. Diagnosis by ultrasound has reduced the need for exploratory surgery, and the ability to sonographically evaluate conservative treatment with albendazole has curtailed management by colectomy or incision and drainage.

Abdominal Pain↗