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Biomedical subjects

K Smith

Publications and source records attributed to K Smith.

At least 451 records · Page 25Linked to original sources
PubMed1987

Site specific glycosylation patterns of H-2K: effects of allelic polymorphism and mitogenic stimulation.

The site-specific glycosylation patterns of two H-2K alleles, k and b, were determined on splenic T cells metabolically labeled with [3H]mannose. Cells from B10, B10.A, (B10 X B10.A)F1, and C3H mice were examined, along with the effect of short- (8 hr) and long-term (36 hr) mitogenic stimulation. For both glycosylation sites (Asn86 and Asn176) of both antigens, 80% of the structures consisted of mono- and bisialylated biantennary N-linked complex oligosaccharides, with the remaining consisting of smaller (probably high mannose) structures. Asn176 of both H-2Kk and H-2Kb contained the same ratio (2.8 to 1) of bi- to monosialylated chains. However, Asn86 of H-2Kb contained a higher ratio (5 to 1), while Asn86 of H-2Kk a lower ratio (1.5 to 1). This difference was seen on antigens isolated from cells of the parental strains as well as from the F1 cross. The glycosylation of H-2Kk did not vary between B10.A and C3H mice. Mitogenic stimulation increased markedly both total [3H]mannose incorporation and the spectrum of N-linked oligosaccharides labeled. For H-2Kk, it had no effect on sialylation, but resulted in a slight under galactosylation of the monosialylated structures at both sites. A comparison of the patterns seen here, determined on nontransformed T cells, with those previously determined on H-2Kk from a B lymphoma line, revealed marked differences in sialylation and branching patterns at both sites. These data indicate that glycosylation differences may be found between highly homologous (91%) alleles of an H-2 gene, even when co-dominantly expressed by F1 cells; however, the patterns do change with mitogenic stimulation, and between normal and transformed cells.

Alleles↗
PubMed1987

A comparative analysis of grade 1 and grade 2 water in the Tygerberg Hospital in vitro fertilisation programme.

There are conflicting reports in the literature about the effect of the water source for growth and insemination media in an in vitro fertilisation (IVF) programme. A controlled trial was carried out in which two-cell mouse embryos were cultured in Ham F10 medium containing either grade 1 water (test group) or grade 2 water (control group). Of the two-cell embryos, 92.0% (69 of 75) in the test group and 91.8% (67 of 73) in the control group cleaved to the blastocyst stage (no statistically significant difference). On the basis of this experiment grade 2 water was used in the Tygerberg Hospital human IVF programme with good results. A continuing pregnancy rate of 23% per embryo transfer over a 1-year period is reported.

Animals↗
PubMed1987

Nucleolar organizer regions in small cell tumours of childhood.

A silver colloid technique for nucleolar organizer regions (AgNORs) was applied to paraffin sections of 50 small cell tumours of childhood. These comprised 20 neuroblastomas, 10 Ewing's sarcoma, and 20 rhabdomyosarcomas, including spindle cell, myxoid, and round cell variants. On the basis of the number of AgNORs, one could differentiate between the three groups. The differences observed were statistically significant (P = 0.01-0.001). The subtypes of rhabdomyosarcoma could not be distinguished from one another on the basis of AgNOR counts. We suggest that this simple histochemical technique may be a useful adjunct to the range of special techniques now available to assist the pathologist in the diagnosis of small round cell tumours.

Adrenal Gland Neoplasms↗
PubMed1987

The effect of serum supplementation on the cleavage of human embryos.

The effect of serum supplementation was evaluated on 108 oocytes obtained from 29 patients. The oocytes were all mature and randomly distributed in two groups. Each ovum was paired with another ovum within the same patient. The experimental group contained no serum in the insemination and growth medium, but in the control group 10% serum was added to the insemination and growth medium. In the experimental group the cleavage rate was 66.7%, compared to 83.3% in the control group. The embryos from each patient were individually evaluated. The sign test was used for statistical analysis. A significant difference between the two groups (P = 0.01) indicated that in this study the addition of serum to the medium gives better cleavage results. The effect of serum on embryos is discussed, as well as the practical implications of this finding.

Blood Proteins↗
PubMed1987

Defective lateralized attention for non-verbal sounds in developmental dyslexia.

The performance of dyslexic and control children--matched for age, sex, handedness and performance IQ--was compared on a dichotic listening task in which the stimuli were environmental sounds. Two findings emerged. First, the dyslexic group showed a normal, left ear perceptual advantage for these non-verbal materials. Second, the dyslexics were incapable of occluding dichotically presented sounds to the left ear when required to deploy attention only to sounds entering the right ear. This failure of unilateral selective attention was not found in the controls, nor in either group under a condition of left ear only attention. The data were interpreted as undermining the bihemispheric non-verbal processing hypothesis of developmental dyslexia. It was argued that the dyslexics' apparent inability to override voluntarily the reflexive lateral orienting mechanism was most consistent with explanatory models emphasizing defective functioning, or even malformation, of the left cerebral hemisphere alone.

Adolescent↗
PubMed1987

Proteolytic activities in the supragingival plaque of monkeys (Macaca fascicularis).

Thirteen peptidase substrates were hydrolysed by this plaque. After fasting the monkeys for 24 h, the rates of hydrolysis of N-leucyl-, N-alanyl-, N-isoleucyl- and N-tyrosyl-2-naphthylamines, glycyl-L-proline 4-nitroanilide, N alpha-benzoyl-DL-arginine-2-naphthylamine and L-leucyglycine were significantly increased. Changes in these peptidase activities may serve to enhance the mobilization of amino acids and peptides, and they may explain why the growth rates of dental-plaque bacteria in vivo are generally unaffected by the availability of the host's diet.

Animals↗
PubMed1987

[Therapy studies of the German Hodgkin's Study Group. Intermediate results of the study protocols HD1, HD2, and HD3].

Between July 1983 and September 1986 358 untreated patients with Hodgkin's lymphoma qualified for the protocols HD1 (stages I to IIIA with risk factors), HD2 (stage IIIA), and HD3 (stages IIIB and IVAB). Patients in HD1 received a combined chemo-radiotherapy (2 X COPP/ABVD + 40 Gy EF vs. 2 X COPP/ABVD + 20 Gy EF). Patients in HD2 were randomized into radiotherapy (TNI 40 Gy) vs. combined chemo-radiotherapy (2 X COPP/ABVD + 20 Gy IF). Patients in HD3 received induction chemotherapy (3 X COPP/ABVD) and were randomized into consolidation by radiotherapy (20 Gy IF) vs. chemotherapy (1 X COPP/ABVD). In HD1, 51 out of 65 evaluable patients (78%) achieved a complete remission. The survival of HD1 patients is as good as the survival of patients in stages I and II without risk factors. In HD3, 58 out of 93 patients (62%) achieved complete remission after induction chemotherapy with COPP/ABVD. This is significantly better than the 31% complete remission rate observed in a pilot study with COPP alone (p less than 0.01). Including salvage therapy (radiotherapy in case of persisting nodal disease; chemotherapy with 4 X CEVD in case of persisting disseminated disease), a total of 71% complete remissions in stages IIIB/IVAB were achieved. The progression-free survival of HD3 patients who received consolidation therapy is significantly longer than of patients who refused consolidation therapy.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1986

Storage of platelets for tests of platelet function: effects of temperature on platelet aggregation, platelet morphology and liberation of beta-thromboglobulin.

We have studied the effect of temperature on platelets during storage for tests of platelet function. Aliquots of PRP were stored at constant pH at 37 degrees C, room temperature and 4 degrees C. At intervals up to five hours, samples were taken for estimation of platelet shape, plasma levels of beta-thromboglobulin and 14C-serotonin, and assessment of platelet aggregation in response to a range of concentrations of ADP and collagen. When PRP was stored at 37 degrees C there was a gradual decrease in the aggregation response during the period of storage. At room temperature the decrease was slower but the response to ADP often increased dramatically before decreasing; at this temperature there was pronounced liberation of beta TG while there was none at 37 degrees C. Platelets stored at 37 degrees C were smooth and elliptical when examined by electron microscopy, but those stored at room temperature showed partial loss of discoid shape and formation of some pseudopodia. Storage at 4 degrees C was associated with total loss of discoid shape and formation of many large pseudopodia. Light transmission studies also showed loss of discoid shape at room temperature and 4 degrees C. We conclude that storage at 4 degrees C or at room temperature causes platelet activation. To avoid this PRP should be stored at 37 degrees C prior to tests of platelet function.

Blood Platelets↗
PubMed1986

Action of surfactants on porcine heart malate dehydrogenase isoenzymes and a simple method for the differential assay of these isoenzymes.

The cationic surfactant, cetyl (hexadecyl) trimethylammonium bromide (CTAB), completely inactivates porcine heart cytoplasmic malate dehydrogenase (L-malate:NAD+ oxidoreductase, EC 1.1.1.37) at concentrations (of surfactant) which do not affect the activity of the mitochondrial isoenzyme. These concentrations are close to, or higher than, the critical micelle concentration of CTAB. An increase in the ionic strength of the medium significantly retards the CTAB-induced inactivation of the cytoplasmic enzyme. The enzyme is also markedly protected against CTAB inactivation by NADH; L-malate on its own has no effect but a combination of NADH and L-malate affords greater protection than NADH alone. The CTAB inactivation is not reversed by dilution of the surfactant. The highly selective action of CTAB on the two malate dehydrogenases, which correlates well with their electrostatic charges, has been exploited for a simple and reliable differential assay of these isoenzymes. The anionic surfactant, sodium dodecyl sulphate (SDS), at concentrations well below the critical micelle concentration, inactivates both isoenzymes, but the mitochondrial enzyme is significantly more sensitive than its cytoplasmic counterpart. There is thus some correlation, though not as strong as with CTAB, between SDS inactivation and the charges of the two malate dehydrogenases. An increase in ionic strength has opposite effects on the two isoenzymes: the mitochondrial enzyme becomes more resistant and the cytoplasmic enzyme less so. Both isoenzymes are rendered more resistant to SDS by the inclusion of NADH. Inactivation of the enzymes caused by short exposure to SDS is largely reversed by dilution of the detergent, but longer exposure leads to progressive irreversible loss of activity. NADH very effectively protects the isoenzymes against irreversible inactivation. It is likely that a reversible phase of inactivation precedes an irreversible phase and that in the former phase SDS acts competitively with NADH. Both malate dehydrogenases possess considerable resistance to the nonionic detergent, Triton X-100.

Animals↗
PubMed1986

The development of one- and two-cell mouse embryos in the absence of human serum.

One- and two-cell embryos were obtained from F1 hybrid female mice stimulated with human menopausal gonadotrophin and randomly distributed into two groups--group 1 (no serum) and group 2 (10% patient's serum). Fifty of 53 (94.3%) one-cell embryos in group 1 had cleaved to the blastocyst stage and 44 of 49 (89.79%) in group 2 after 96 hours (no significant difference--chi-square test). In the two-cell embryos in group 1, 78 of 89 (87.6%) reached the blastocyst stage after 72 hours and 80 of 86 (93.02%) in group 2 (no significant difference--chi-square test). According to microscopic evaluation cleavage to the blastocyst stage without serum supplementation is possible. The value of serum is discussed.

Animals↗
PubMed1986

HLA-DQ beta-chain polymorphism linked to myasthenia gravis.

The HLA-DR3 haplotype is associated with increased risk of myasthenia gravis (MG) and a number of other autoimmune diseases, including insulin-dependent diabetes mellitus (IDDM), coeliac disease, and premature ovarian failure (POF). With a cDNA probe for a DQ beta gene, a 15 kb Hinc II restriction fragment has been demonstrated in genomic DNA from 7 of 16 HLA-DR3 patients with MG, 1 of 19 healthy DR3 controls, and none of 24 DR3 patients with IDDM, coeliac disease, or POF. The HLA-DQ polymorphism may be closely linked to a genetic locus regulating immune responsiveness to acetylcholine receptor and susceptibility to MG.

Celiac Disease↗
PubMed1986

The association between social withdrawal and internalizing problems of children.

Children identified as low-frequency interactors or socially withdrawn were compared to outgoing children to evaluate whether socially withdrawn children display concurrent internalizing problems. From a sample of 640 children in grades 2-5, 48 children were identified by teachers as low-frequency interactors and 72 children were selected as outgoing or sociable. When these two groups were compared on a battery of teacher, peer, and self-report measures that assessed internalizing difficulties, the low-frequency interactors were found to display concurrent problems in adjustment. Children who rarely interacted with peers were less well liked by their peers, displayed poorer self-concepts, and were more depressed and anxious than sociable children. In contrast to these findings regarding internalizing problems, the two groups did not differ on measures of externalizing problems. The results lend support to the concurrent validity of the low-interaction method of identifying socially withdrawn children.

Anxiety↗
PubMed1986

The growth of bacteria and the production of exoglycosidic enzymes in the dental plaque of macaque monkeys.

The rate of growth of the predominant bacterial strains of plaque from the developmental grooves of first deciduous molar teeth was determined. Median doubling times were 3.32, 3.45, 2.88 and 4.54 h for streptococci, lactobacilli, actinomyces and Neisseria mucosa respectively. Withdrawal of dietary food did not greatly influence the number of bacteria found in the grooves 18 h after they had been cleaned when compared to the number in fed monkeys; exceptions were significant increases in Streptococcus mitior and N. mucosa. Addition of 0.5 per cent (w/v) glucose to the drinking water of fasted monkeys also did not influence the size of this bacterial population 18 h after cleaning, so bacteria growing in cleaned grooves must gain a major part of their nutritional needs from their immediate environment, most likely salivary constituents. The ability of oral bacteria to use the oligosaccharide side-chains of salivary glycoproteins was then explored. Exoglycosidases for the preferred anomeric linkages of the principal monosaccharide units of salivary glycoproteins were produced both by oral bacteria in vitro and by dental plaque in vivo. Thus plaque flora has the potential to degrade glycoproteins and this may explain how bacteria in the grooves grow in the absence of dietary food.

Actinomyces↗