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Biomedical subjects

M Knight

Publications and source records attributed to M Knight.

At least 55 records · Page 3Linked to original sources
PubMed1985

gamma-Aminobutyric acid in CSF of children with febrile seizures.

Previous studies have suggested that levels of cerebrospinal fluid (CSF) gamma-aminobutyric acid (GABA) may be decreased in children with febrile seizures. We used gas chromatography and mass spectrometry to measure CSF GABA levels in 14 children with febrile seizures. The results were compared with the GABA levels in six children with first-time afebrile seizures, three with recurrent febrile seizures, and 13 controls (febrile children undergoing lumbar puncture to rule out meningitis). Children with central nervous system infections or known neurologic disease were excluded. The CSF GABA levels in children with febrile seizures were not significantly different from those in controls and children with afebrile or recurrent febrile seizures. In the control group, CSF GABA levels correlated with increasing age. There was no correlation with severity of febrile response in any group. The results indicated that the CSF GABA level may not be abnormal in patients with first-time febrile convulsions.

Child↗
PubMed1985

Schistosoma mansoni: antigen preparations which induce antibodies to schistosomula surface antigens.

To determine the easiest method of raising antibodies to antigens exposed on the surface of schistosomula of Schistosoma mansoni, several crude preparations of the parasite were used to immunize mice. Schistosomula released products, whole worm homogenate, and parasite eggs all raised antibodies which bound to the surface of live schistosomula, although the anti-egg antiserum did so less strongly. Anti-schistosomula released products antiserum recognized three schistosomula surface antigens of Mr 15,000, 20,000, and 32,000, anti-whole worm homogenate recognized 20,000, 32,000, and 38,000 Mr surface antigens, and anti-egg recognized a less than 200,000 Mr surface antigen. None of these antigens was recognized when the labeled preparation was immunoprecipitated with its homologous antiserum. When these antisera were used to immunoprecipitate cell free translation products of adult worm RNA, the antischistosomula released products and anti-whole worm homogenate recognized an 11,000 Mr doublet while the anti-egg precipitated 14,000 and 44,000 Mr antigens. Other crude preparations were used to immunize rabbits; Formalin-fixed schistosomula, denuded adult worms, and purified worm tegument all induced antibodies which recognized the 20,000, 32,000, and 38,000 Mr schistosomula surface antigens.

Animals↗
PubMed1985

Isolation and characterisation of nucleic acids from the hydatid organisms, Echinococcus spp. (Cestoda).

DNA and RNA in combination have been prepared and characterised from the hydatid disease organisms, Echinococcus granulosus and Echinococcus multilocularis. The DNA obtained is of high molecular weight, pure and can be cleaved by restriction enzymes, thereby facilitating future production of genomic DNA probes for studies of Echinococcus gene expression. Moreover, cloned DNA segments from Schistosoma mansoni hybridise strongly to Echinococcus DNA following restriction and Southern blot analysis. The extracted RNA is functional and has been translated in vitro. The major translated polypeptides and antigens have been identified, and the technique can now be used to analyse differential gene expression during development and differentiation of the hydatid organisms and to identify specific polypeptide antigens which may have potential as immunodiagnostic reagents.

Animals↗
PubMed1985

The schistosomulum surface antigens of Schistosoma haematobium.

Surface antigens of Schistosoma haematobium were identified by 125I-surface labelling of schistosomula followed by immunoprecipitation of the solubilized, labelled surfaces. The major antigens, after electrophoresis, formed a continuous smear corresponding to a molecular weight in the range 35-24 000; in addition, a 17 000 antigen was also identified. These surface antigens, in contrast to somatic antigens, were species-specific, as judged by immunoprecipitation with human anti-S. mansoni serum and serum from mice vaccinated with highly irradiated S. mansoni cercariae. S. haematobium surface antigens, however, were recognized to some extent by serum from mice chronically infected with S. mansoni. It is suggested that this cross-reactivity may reflect the heterologous immunity demonstrated experimentally between these two species, whilst the species-specificity of vaccine sera to surface antigens may mirror the highly specific immunity induced by vaccination.

Animals↗
PubMed1985

CCK26-33 degrading activity in brain and nonneural tissue: a metalloendopeptidase.

Cholecystokinin octapeptide (CCK26-33) is metabolized by neural membranes with an initial cleavage to CCK29-33 and subsequent breakdown to CCK31-33 and CCK32-33; this pattern of proteolysis occurs on incubation with either P2 or purified lysed synaptosomal membranes. To determine whether the pattern of CCK26-33 proteolysis is unique to the brain and whether regional brain differences in its pathway or rate exist, we analyzed the proteolysis of CCK by synaptic membranes of various brain areas and cellular membranes of peripheral tissue. The pattern of degradation in brain did not differ among the regions studied. The overall proteolysis rate, as measured by the formation of tryptophan, was higher in the striatum than in the cortex, although CCK29-33 was formed at the same rate in both areas. In nonneural tissue, the rate of degradation was highest in liver membranes and lowest in pancreatic acinar cell preparations. Thus, it appears that degradative peptidases are not necessarily colocalized with CCK receptors. The pattern of product formation is the same in peripheral compared with CNS membranes; thus, the degradative pathway does not appear to be unique to brain tissue. The enzyme present in synaptic membranes that is responsible for CCK29-33 formation requires a metal ion and sulfydryl groups for the catalysis and thus is a metalloendopeptidase. Furthermore, its activity is inhibited by Ac-Gly-Phe-Nle-al, a peptide aldehyde whose sequence bears some homology to the amino acid sequence in the region of CCK26-33 that is cleaved by this enzyme.

Animals↗
PubMed1985

N-terminal fragments of CCK-(26-33) as cholecystokinin receptor antagonists in guinea pig pancreatic acini.

In the present study we synthesized different N-terminal fragments and analogues of the C-terminal octapeptide of cholecystokinin [CCK-(26-33)] and examined their actions on dispersed acini prepared from guinea pig pancreas. None of the N-terminal fragments or analogues altered basal amylase release. Analogues of CCK-(26-32), CCK-(26-31), and CCK-(26-30) inhibited CCK-(26-33)-stimulated amylase, and there was a close correlation between the ability of an analogue to inhibit stimulated amylase and the analogue's ability to inhibit binding of 125I-cholecystokinin. N-acetyl-CCK-(26-29)-amide at concentrations as high as 100 microM did not inhibit CCK-(26-33)-stimulated amylase release or binding of 125I-CCK. For those analogues that antagonized CCK-(26-33)-stimulated amylase release the antagonism was of the competitive type and was specific for those secretagogues that interact with the cholecystokinin receptor. Removing the C-terminal amide from N-acetyl-CCK-(26-31)-amide caused a 10-fold decrease in the inhibitory potency, whereas removing the C-terminal amide from N-acetyl-CCK-(26-30)-amide did not alter the inhibitory potency of the peptide. Removing the sulfate ester from the tyrosine residue in position 27 of N-acetyl-CCK-(26-31) did not alter the inhibitory potency of the peptide, whereas removing the sulfate ester from the tyrosine residue in position 27 of N-acetyl-(26-30) caused a three- to fivefold decrease in the inhibitory potency of the peptide.(ABSTRACT TRUNCATED AT 250 WORDS)

Amylases↗
PubMed1979

Enkephalin generating activity of rat brain endopeptidases.

An amphiphilic substrate was used as the basis of a specific assay for peptidases which generate the opioid peptide methionine enkephalin. The substrate [Homoarg-14C]Tyr-Gly-Gly-Phe-Met-Thr-Ser-Glu-Homoarg is prepared by guanidination of the lysine analogue (which is beta-lipotropin 61-69) with O-methyl-[14C]isourea and is quantitatively adsorbed to dextrancoated charcoal. The COOH-terminal tetrapeptide is not adsorbed and, since it carries the radioactive label, is easily assayed in the charcoal-free supernatant fluid. Two enzyme activities have been identified in rat brain which specifically convert the amphiphilic substrate to enkephalin and the resulting tetrapeptide tail. These activities are soluble and particulate, respectively, and differ in regional distribution within the brain, in their inhibition by other peptides and in Km. Based upon these characteristics, it seems likely that the soluble activity is not primarily involved in the biosynthesis of enkephalin. It does seem possible, however, that the particulate activity which we describe may play a role in opioid peptide synthesis from larger precursors.

Animals↗
PubMed1978

Metabolic regulation in Pseudomonas oxalaticus OX1. Enzyme and coenzyme concentration changes during substrate transition experiments.

Metabolic control associated with diauxic growth of Pseudomonas oxalaticus in batch cultures on mixtures of formate and oxalate was investigated by measuring intracellular enzyme and coenzyme concentrations and QO2 values during transition experiments from oxalate to formate and vice versa. In transition from oxalate to formate oxalyl-CoA reductase concentration declined after the exhaustion of oxalate and ribulose-1,5-diphosphate carboxylase and 14CO2 fixation appeared upon addition of formate. In the reciprocal transition, ribulose-1,5-diphosphate carboxylase and 14CO2 fixation rate declined sharply after formate exhaustion, and oxalyl-CoA reductase appeared only after addition of oxalate. The intracellular NAD and NADP concentrations measured in the same experiments are reported. At substrate exhaustion the proportion of NAD in the reduced form fell from 15-20% to 2%. On addition of formate to an oxalate-starved culture there was an immediate increase in the proportion of NADH to 50%; such an increase was not observed in the reverse experiment.

Aldehyde Oxidoreductases↗
PubMed1978

Combination chemotherapy and radiation therapy of undifferentiated small cell bronchogenic carcinoma.

We reviewed 76 cases of small cell bronchogenic carcinoma seen at the University of South Florida Medical Center. One third of the 55 patients who have subsequently died did so within one month of diagnosis. Thirty-five patients were treated with cyclophosphamide, adriamycin, vincristine, and radiation therapy including prophylactic cranial irradiation. Of these 35 patients, 40% demonstrated a complete remission for a total objective response rate of 63%. The projected median survival of patients referred for study is 14 months. Improved survival was found in patients less than 60 years of age, with limited disease, who responded to treatment and in whom there were no violations of protocol. Patients treated with combination therapy appear to survive longer than untreated patients and those treated with radiation therapy alone. Toxicity was tolerable and there were no deaths related to treatment. Small cell bronchogenic carcinoma is a rapidly progressive systemic disease responsive to multimodality therapy with long-term survival in some patients.

Adult↗
PubMed1977

Volvulus of the sigmoid colon.

The clinical presentation and treatment of 31 consecutive patients with sigmoid volvulus are reviewed. Nearly half of these patients had a history of mental illness and one-third of all patients were chronically constipated. The main clinical features of abdominal pain and gross abdominal distension had been present for an average of 8 days before presentation of the patient to hospital. The clinical diagnosis of sigmoid volvulus was not difficult but the presence of non-viable bowel was more difficult to establish. A silent abdomen was the most valuable indication of the presence of gangrenous bowel. Conservative measures, including sigmoidoscopy and therapeutic barium enema, successfully reduced the volvulus in half of the cases so treated. In those patients undergoing surgery the procedure associated with the lowest mortality was sigmoid resection with end-to-end anastomosis. The overall mortality was 35%.

Adult↗