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Biomedical subjects

R de Groot

Publications and source records attributed to R de Groot.

At least 145 records · Page 8Linked to original sources
PubMed1989

Use of a radon mould technique for skin cancer: results from the Peter MacCallum Cancer Institute (1975-1984).

During the period from 1975 to 1984, 642 patients had non-melanoma skin cancers (NMSC) treated by a radon mould technique following the principles of the Manchester system. The results of 77 out of 642 (12%) with histologically verified lesions are presented. The sites of the lesions were as follows: head and neck 25 (32%), upper limbs 38 (49%), lower limbs 13 (17%) and trunk one case only. The histological diagnosis was squamous cell carcinoma 48 (62%), basal cell carcinoma in 22 (29%) and other in seven (9%). There were nine out of 77 (12%) failures, four with persistent disease, which did not clear after initial treatment (and for whom the radon mould was an inappropriate choice of technique), and five (6%) recurrences after clearance of the initial lesion. There was a sharp rise in failures after 1979 when there was a change of radon supplier, but no calibration error was substantiated. It is clearly beneficial for institutions to cross-check the manufacturer's brachytherapy source data. There have been no further recurrences or any symptomatic late morbidity. This is a safe, effective and practical radiotherapeutic technique for superficial lesions (not exceeding a depth of 4 mm) in areas of poor radiation tolerance, and may obviate the need for a prolonged fractionated course of external-beam radiation in selected patients. Alternatives to radon are discussed.

Adult↗
PubMed1988

Congenital self-healing non-Langerhans cell histiocytosis.

Clinical, morphological, ultrastructural and immunological studies were performed in a case of congenital self-healing non-Langerhans cell histiocytosis. The patient showed several aspects that have not been published before: a large nodule in the vulvar region, vesiculobullous elements and pneumonia (asymptomatic). The relationship of the vesicles and pneumonia to the histiocytic disorder is not clear. Ultrastructurally, worm-like (comma-shaped) particles, dense bodies and Birbeck granules were not found. Histiocytes were Leu-6 negative, and S100 (partly), Leu M3 and HLA-DR positive. Positive reactions were also obtained with anti-lysozyme and non-specific esterase. Several aspects of this case and of others described previously are discussed.

Female↗
PubMed1988

Molecular cloning and mechanism of trimethoprim resistance in Haemophilus influenzae.

We studied 10 trimethoprim-resistant (Tmpr) Haemophilus influenzae isolates for which agar dilution MICs were 10 to greater than 200 micrograms/ml. Trimethoprim resistance was transferred from two Tmpr H. influenzae isolates to a Tmps strain by conjugation or transformation. Wild-type Tmpr strains and Tmpr transcipients did not contain detectable plasmid DNA. The trimethoprim resistance gene was cloned into a cosmid vector, and recombinant plasmids were transduced into Escherichia coli. A 0.50-kilobase intragenic probe derived from a 12.9-kilobase fragment which encoded trimethoprim resistance hybridized with whole-cell DNA from Tmps and Tmpr strains. Southern blot analysis of restricted DNA from isogenic Tmps and Tmpr H. influenzae indicated that acquisition of trimethoprim resistance involved a rearrangement or change in nucleotide sequence. Hybridization was not seen with DNA derived from Tmpr E. coli containing dihydrofolate reductase I, II, and III genes or with Tmpr Neisseria meningitidis, Neisseria gonorrhoeae, and Pseudomonas cepacia. Southern hybridization with 12 multiply resistant encapsulated H. influenzae strains confirmed that the trimethoprim resistance gene was chromosomally mediated. Dihydrofolate reductase activity was significantly greater in cell sonicate supernatants of Tmpr strains in comparison with isogenic Tmps recipients. Differences were not found in the trimethoprim inhibition profile of dihydrofolate reductase activity in Tmps and Tmpr strains. We conclude that the mechanism of trimethoprim resistance in H. influenzae is overproduction of chromosomally located dihydrofolate reductase.

Bacterial Outer Membrane Proteins↗
PubMed1987

The nucleotide sequence of the peplomer gene of porcine transmissible gastroenteritis virus (TGEV): comparison with the sequence of the peplomer protein of feline infectious peritonitis virus (FIPV).

The amino acid sequence of the peplomer protein of transmissible gastroenteritis virus (TGEV) has been derived from the cloned cDNA sequence. The gene encodes a protein of 1447 amino acids with a molecular weight of 159 574. Comparison with the primary structure of the peplomer protein of feline infectious peritonitis virus (FIPV) (de Groot et al., 1987b) revealed one domain, from amino acids 1 to 274, in which the nucleotide homology was 39%, whereas in the second domain (from residues 275 to 1447) the homology was 93%.

Amino Acid Sequence↗
PubMed1987

Antibiotic pharmacokinetics in cystic fibrosis. Differences and clinical significance.

Antibiotics are administered to cystic fibrosis patients for chronic endobronchial infection complicated by frequent exacerbations. Agents active against Staphylococcus aureus, Pseudomonas aeruginosa or both are administered. Serum antibiotic concentrations were measured in cystic fibrosis patients in an effort to optimise antibiotic dose and frequency. This led to the observation that cystic fibrosis subjects had (in general) a larger Vd and increased total body clearance of beta-lactams and aminoglycosides than non-cystic fibrosis subjects. The larger Vd is mainly due to the increased amount of lean body mass per kg bodyweight, although increased tissue binding may also account for part of this. The increased total body clearance of beta-lactams appears to be due to increased renal elimination, particularly tubular secretion. Decreased tubular reabsorption and increased non-renal clearance contribute to the increased total body clearance of metabolised beta-lactams and aminoglycosides. However, the lack of concomitant controls in many studies make these generalisations tentative. The result of the apparent cystic fibrosis-specific differences is lower peak serum antibiotic concentrations, a smaller AUC, and a shorter elimination half-life than non-cystic fibrosis subjects. Since sputum (and bronchial mucosal) concentration is dependent on the peak serum concentration (and AUC), cystic fibrosis subjects require larger doses of most antibiotics more frequently. Newer quinolones may be an exception. Studies comparing the efficacy and safety of larger and more frequent antibiotic doses to conventional therapy are not available. Although it appears logical to mimic serum antibiotic concentrations found in non-cystic fibrosis subjects, the lack of information on the ideal sputum concentration versus time curve should temper our enthusiasm for cystic fibrosis-specific dosage regimens.

Anti-Bacterial Agents↗
PubMed1985

Cohesive and adhesive fracture patterns of the composite-enamel bond.

A method was developed to adhere composite to a small (1 mm2) surface of human enamel. The geometrical configuration resulted in a complex stress distribution in the vicinity of the composite-enamel bond during fracture in a tension test. The fracture surfaces were examined by scanning electron microscopy. The observed fracture areas at the enamel showed cohesive (composite-composite) as well as adhesive (composite-enamel) parts. The adhesive part of the fracture surface was surrounded by a composite wall. The typical fracture pattern can be explained by the complex stress situation and the deviant structure of the composite near the edge.

Adhesiveness↗
PubMed1984

Primary restrictive foramen ovale.

A newborn infant with primary restrictive foramen ovale, tubular hypoplasia of the aortic arch, and some other developmental defects is described. This combination resulted in fetal hydrops, as was shown by ultrasonography. The child died 24 h after birth due to low output syndrome and extensive bronchopneumonia. The pathogenesis of this clinical entity is discussed.

Aorta, Thoracic↗
PubMedDate not supplied

Bronchial carcinoid tumor in a 12-year-old child.

Symptoms (hemoptysis, recurrent pulmonary infections), diagnostic work-up (roentgenology, bronchoscopy with biopsy), and treatment (surgical resection of a bronchial carcinoid tumor in a 12 year old girl) are discussed. Special attention was paid to the tumor histochemistry, showing serotonin containing granules. Levels of circulating hormones and vasoactive agents, including serotonin, were within normal limits.

Bronchial Neoplasms↗
PubMedDate not supplied

Childhood meningitis caused by enterococci and viridans streptococci.

Selected clinical and laboratory parameters were studied respectively in patients with meningitis caused by enterococci and viridans streptococci in an academic children's hospital. During a nine-year period (1981-1989), enterococci or viridans streptococci were isolated from the cerobrospinal fluid (CSF) of 48 patients. In nine of these 48 patients, enterococci or viridans streptococci were the causative agents of meningitis. These nine children constituted 2.0% of 450 patients with bacterial meningitis in this period. All nine children suffered from underlying diseases; neurosurgical procedures were performed in six of these patients, of whom four had ventricular drains. A head trauma preceded the development of meningitis in another patient. Drainage of the lacrimal duct was associated with the development of meningitis in another patients. One child concurrently suffered from severe gastroenteritis. CSF leukocyte count and CSF protein levels were moderately elevated, whereas CSF glucose levels were either slightly decreased or within the normal range. Meningitis due to enterococci or viridans streptococci is seen predominantly in children under the age of one year. Predisposing factors, including neurosurgical procedures, head trauma and severe gastroenteritis, are usually present in these patients. The prognosis for recovery is generally good.

Blood↗
PubMedDate not supplied

Bone and joint infections caused by Kingella kingae: six cases and review of the literature.

Six cases of Kingella kingae arthritis, osteomyelitis, and diskitis were studied, and data were reviewed from an additional 23 cases in the English-language literature. K. kingae is a slow-growing, fastidious, gram-negative microorganism that colonizes mucous membranes of the upper respiratory tract. Infections were predominantly seen in infants and young children (86% of cases) and were preceded by an upper respiratory tract infection in 31% of patients. Low-grade fever (38 degrees C-39 degrees C) and pain or swelling involving the affected limb developed insidiously. However, 76% of the infections were diagnosed within 1 week after the onset of symptoms. The knee was involved in 47% and the hip in 33% of cases of arthritis. Osteomyelitis mainly involved the femur (36%); four cases of osteomyelitis (29%) were diagnosed as diskitis. The erythrocyte sedimentation rate was greater than 20 mm/h in all patients. Gram stains of aspiration fluid were positive in 19% of cases, whereas blood cultures yielded growth in only 5%. Radiographic signs indicating the presence of osteomyelitis were observed in 93% of patients. All patients recovered completely. K. kingae is an important causative agent in indolent bone, joint, and intervertebral disk infections.

Arthritis, Infectious↗