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Biomedical subjects

R Peters

Publications and source records attributed to R Peters.

At least 289 records · Page 16Linked to original sources
PubMed1979

Quantitation of the third component of human complement attached to the surface of opsonized bacteria: opsonin-deficient sera and phagocytosis-resistant strains.

The role of the third component of human complement (C3) in the opsonization of bacteria in nonimmune human sera was evaluated. The amount of C3 that becomes attached to the surface of bacteria upon incubation in serum was measured in a quantitative fluorescent immunoassay using fluorescein-conjugated monospecific antiserum to human C3. The intensity of the fluorescence from opsonized bacteria was found to be directly proportional to the absolute amount of C3 fixed, and this enabled the detection of as few as 300 molecules of bound C3 per bacterium. In normal serum the rate of C3 fixation was closely correlated with an increase in opsonization of the bacteria for human PMNs. Both C3 fixation and opsonization were maximal after 15 min of incubation. C3 fixation was also observed, albeit at a significantly slower rate, in human serum with a nonfunctional classical pathway but an intact alternative complement pathway and in serum deficient in immunoglobulins. Again, the kinetics of C3 fixation correlated with bacterial opsonization. Using a total of 21 strains of several bacterial species, including Staphylococcus aureus and Escherichia coli, encapsulation of bacteria was found to interfere with the process of C3 fixation in normal human serum, rendering these organisms resistant to subsequent phagocytosis by human polymorphonuclear leukocytes.

Bacteria↗
PubMed1979

Staphylococcus aureus opsonization mediated via the classical and alternative complement pathways. A kinetic study using MgEGTA chelated serum and human sera deficient in IgG and complement factors C1s and C2.

Staphylococcus aureus opsonization was studied kinetically by: (1) determination of the uptake of [3H]-thymidine labelled bacteria by human PMN's; (2) fluorescent anti-C3 and anti-IgG staining of opsonized bacteria; and (3) measuring bacterial complement consumption. Maximum opsonization in normal serum occurred within 5 min of incubation. About 80% of staphylococci were then taken up by PMN's, and IgG and C3b could be detected on the bacterial surface. In the absence of a functional classical complement pathway, as in sera deficient in C1s and C2 and in MgEGTA chelated serum, maximal opsonization was only achieved after 30--60 min incubation. Opsonization in IgG deficient serum occurred at a rate similar to that found in C2 deficient or MgEGTA chelated serum. Opsonization was greatly enhanced when sera were reconstituted. It was concluded that in IgG deficient serum Staphylococcus aureus opsonization is mediated via the alternative complement pathway. Dilution of normal serum primarily affected the classical complement pathway, resulting in a decreased rate of opsonization. In normal serum IgG did not appear to be a rate-limiting factor. S. Aureus opsonization was best studied by the phagocytosis assay and the fluorescent-antibody technique. Measuring haemolytic complement consumption was found to be an insensitive indicator of bacterial complement activation and opsonization.

Complement Activation↗
PubMed1979

The role of Staphylococcus aureus cell-wall peptidoglycan, teichoic acid and protein A in the processes of complement activation and opsonization.

The role of cell-wall peptidoglycan, teichoic acid and protein A in the processes of Staphylococcus aureus complement activation and opsonization was investigated. CH50 consumption studies reveal that, although all cell-surface fractions were capable of activating the classical C pathway, only peptidoglycan consumed C via the alternative pathway. Using a quantitative immunofluorescence assay, peptidoglycan was shown to bind C3 molecules via the classical as well as via the alternative C pathway and in the absence of IgG and IgA class antibodies. C activation via the classical and the alternative pathway could be distinguished by kinetic analysis. By comparing the rates of staphylococcal C consumption, C3 fixation and opsonization it was found that the CH50 consumption assay is a relatively insensitive method and may yield results that do not necessarily reflect the process of bacterial opsonization.

Complement Activation↗
PubMed1979

Regional concentrations of serotonin, tryptophan, 5-hydroxyindoleacetic acid, dopamine, and norepinephrine in the ovine brain.

Regional concentrations of tryptophan, serotonin (5HT), 5-hydroxyindoleacetic acid (5HIAA), norepinephrine, and dopamine were determined in the ovine brain. Tryptophan concentrations varied between 18.6 nmoles/g of tissue (hypothalamus, midbrain) and 26.9 nmoles/g (cerebellum). The 5HT concentrations varied 0.34 nmoles/g (cerebellum) and 3.75 nmoles/g (midbrain). The concentration of 5HIAA varied between 1.78 nmoles/g (cerebellum) and 5.02 nmoles/g (hypothalamus). Large concentrations of norepinephrine were found in the hypothalamus (4.37 nmoles/g) and midbrain (2.08 nmoles/g), while the frontal cortex, thalamaus, hippocampus, and cerebellum were all relatively low in norepinephrine (0.65 to 0.95 nmoles/g). The concentration of dopamine was between 0.32 nmoles/g (hippocampus) and 39.8 nmoles/g (caudate nucleus). Generally, the distribution of these compounds in the ovine brain is similar to their regional distribution in other mammalian species. It was observed, however, that the ratio of 5HT/5HIAA appears to be relatively lower in sheep than in other species, suggesting that interspecies differences in the metabolism of 5HT or elimination of 5HIAA (or both) may exist.

Animals↗
PubMed1978

Phagocytosis and killing of staphylococci by human polymorphonuclear and mononuclear leucocytes.

The phagocytosis and killing of 3H-thymidine-labelled Staphylococcus aureus by polymorphonuclear leucocytes (PMNs) and monocytes (MNs) obtained from 50 health donors were evaluated. In addition, extracellular factors that might influence phagocytosis and killing were studied. The method described gave highly reproducible results. No significant difference was observed in the phagocytic and killing functions of a single donor's PMNs and MNs when studied several times in one day and longitudinally over a period of 1-12 weeks for six donors tested. Likewise, no signigicant difference in uptake and killing was observed when bacteria were opsonised with sera from 11 different normal donors. When Staph. aureus opsonised with normal serum was added to the leucocytes in a ratio of 10 bacteria: 1 leucocyte, the uptake by PMNs and MNs from 50 donors after 20 minutes' incubation was 85% +/- 7 standard deviation (SD) (range 75-98%) and 69% +/- 11 SD (range 54-90%), respectively. The rate of uptake by MNs in the first three minutes of the assay period was only 60% of that by PMNs.

Blood Bactericidal Activity↗
PubMed1978

Clinical and electrophysiologic findings in patients with paroxysmal slowing of the sinus rate and apparent Mobitz type II atrioventricular block.

Over five years, 13 patients with episodic apparent type II atrioventricular (AV) block associated with sinus slowing were seen. This phenomenon occurred only transiently during an acute illness in eight patients (group I) but recurred chronically in five (groupII). For the group as a whole, the mean spontaneous cycle length was 42% longer during the period of AV block compared with periods of 1:1 AV conduction (800 +/- 116 msec to 1138 +/- 489 msec) (P less than 0.05). Electrophysiologic studies in four group I patients showed no abnormalities, whereas abnormalities in AV nodal conduction and refractoriness or provocation of intranodal Mobitz type II AV block (during carotid massage) were observed in three patients in group II and were totally abolished by atropine. In group I patients, apparent type II AV block was self-limited. In the chronic group, recurrent symptoms required insertion of permanent pacemakers in two patients. Simultaneous type II block and sinus slowing appeared to be related to the effects of increased vagal tone on both nodal structures. Intracardiac pacing is not indicated for patients with transient episodes associated with an acute illness, but may be required for symptomatic patients with recurrent episodes.

Adult↗
PubMed1977

[Epidemiology of hypodontia in the permanent dentition].

The incidence of hypodontia of the permanent dentition was studied in a total of 3986 students, 11 to 21 years old, in secondary schools in Fürth in Bavaria. In 5.1% of all subjects hypodontia was observed. Most frequently involved were the lower second premalars (37.8%), the upper lateral incisors (29.0%), and the upper second premolars (22.4%).

Adolescent↗
PubMed1976

Influence of cultural conditions and mutations on the composition of the outer membrane proteins of Escherichia coli.

Various Escherichia coli strains differ in the composition of their major outer membrane proteins. However, all E. coli K12 strains tested possess the same major outer membrane proteins a, b, c and d, although quantitative differences were detected. The influence of growth conditions on the composition of the major outer membrane proteins of E. coli was analyzed. It was found that neither the growth phase at which the cells are harvested, nor the fatty acid composition of the phospholipids has a considerable influence on the composition of these proteins. However, the composition of the growth medium, and, to a less extent, the growth temperature, have a pronounced influence. Certain mutants, changed in the composition of their lipopolysaccharide, are deficient in protein b. Also mutants deficient in protein c and d respectively, are described. Proteins b and c of E. coli K12 were found to be associated with peptidoglycan. Protein bands, corresponding with flagellin and pilin respectively, were identified.

Bacterial Proteins↗
PubMed1976

Distribution of lipids in cytoplasmic and outer membranes of Escherichia coli K12.

The lipid composition of cytoplasmic and outer membranes of Escherichia coli K12 was studied. Compared with the cytoplasmic membrane, the outer membrane is enriched in both saturated fatty acids and phosphatidylethanolamine. This is also the case when the fatty acid composition of the phospholipids is changed, either by varying the growth temperature or by using mutants with alterations in their fatty acid metabolism. Phosphatidylethanolamine of the outer membrane contains relatively more saturated fatty acids than phosphatidylethanolamine of the cytoplasmic membrane.

Cell Membrane↗
PubMed1975

Tuberculous enteritis. Review of a protean disease.

Prior to the advent of antituberculosis drugs, at least 70% of patients with far advanced pulmonary tuberculosis had tuberculous enteritis. Despite the effectiveness of drug therapy, overt cases of tuberculous enteritis occur in the United States and particularly among immigrants from endemic areas. Clinicians often forget to consider this entity. The patient may have no or minimal abdominal complaints. Vague abdominal distress, anorexia and weight loss can be overlooked because of the extensive pulmonary exudative or cavitary disease. Even after an enteric lesion is identified, often it is mistaken for other entities, particularly neoplasm or Crohn's disease. Obviously, the diagnosis is difficult but certain radiological criteria can be indicative of the disease. This report demonstrates the protean manifestations of this entity, the complications which occur despite drug therapy and the need for continued awareness of its existence.

Adult↗