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Biomedical subjects

J Hogg

Publications and source records attributed to J Hogg.

At least 55 records · Page 3Linked to original sources
PubMed1991

Growth factor control of pancreatic B cell hyperplasia.

Pancreatic B cell hyperplasia is an essential feature of normal fetal and childhood development in order to maintain insulin availability to the growing organism. While glucose, amino acids and pituitary growth hormone have all been shown to increase B cell DNA synthesis in cultures of isolated islets of Langerhans, there is also evidence for a local regulation of growth by trophic factors. IGF-I and IGF-II are expressed and released by pancreatic B cells and have the capacity to act as B cell mitogens. Specific IGFBPs are also released by islets which may modulate the bioactivity of IGFs. While IGF release is not under acute nutrient control, at least in vitro, the mitogenic actions of growth hormone on islets are mediated in part by an increase in the local release of IGF-I. Other peptide growth factors reported to influence B cell DNA synthesis include PDGF, EGF, TGF-beta and TRH. The contribution of peptide growth factors to pathological abnormalities of pancreatic islet growth is unknown.

Animals↗
PubMed1991

Chondromyxoid fibromas of the neurocranium.

We report a case of a chondromyxoid fibroma involving the upper clivus in a 73-year-old man. Chondromyxoid fibromas are uncommon benign bone tumors that rarely involve the skull. Chondromyxoid fibromas arising in the membranous neurocranium resemble their extracranial counterparts, appearing as radiolucent lesions with sclerotic margins and presenting most often as a painless focal swelling. Chondromyxoid fibromas arising in the chondrocranium differ from their extracranial counterparts and from those arising in the membranous neurocranium. They appear as locally destructive, often calcified, and exophytic lesions without sclerotic margins and present with cranial nerve dysfunction and symptoms caused by central nervous system compression.

Journal Article↗
PubMed1989

Growth factors and the regulation of pre- and postnatal growth.

Peptide growth factors represent a largely paracrine level of intercellular communication that is basic to the process of life. Growth factors are present in the ovum and are amongst the first products expressed by the embryonic genome. They function as both signals and progression factors for embryonic tissue growth, induction, differentiation, maturation and function. While a widespread tissue expression is demonstrable during fetal development, and in certain postnatal tissues such as the epiphyseal growth plate, growth factor presence in the adult is restricted to tissues sharing rapid cellular turnover such as ovary. However, a transient re-expression of peptide growth factors occurs during adult tissue repair. In addition to mitogenic peptides such as IGFs or EGF, the family of growth factors also includes physiological growth inhibitors such as TGF beta and certain neuropeptides. Insulin is mitogenic in the early embryo and evidence is presented to support a continuation of this role, under defined nutritional conditions, in late gestation. The importance of insulin to pre- and postnatal growth has prompted an expanding literature dealing with the interactions of nutrients, hormones and growth factors during the growth and functional maturation of the islets of Langerhans. While the expression of growth factors in the early embryo is apparently autonomous, some, such as IGFs, become increasingly dependent on nutrient, insulin and GH availability during fetal development and in childhood growth. This has resulted in circulating IGF I and II determinations becoming useful diagnostic markers of endocrine-based growth disorder and nitrogen balance.

Embryonic and Fetal Development↗
PubMed1987

Biochemical characterization of individual normal, floppy and rheumatic human mitral valves.

Human mitral valves (32 floppy and 17 rheumatic) obtained at surgery were analysed and compared with 35 normal (autopsy) valves. Total amounts of collagen, proteoglycan and elastin were increased approx. 3-fold in floppy and rheumatic valves. The water content of rheumatic cusps was lower than normal. The most significant changes in floppy valves were the 59% increase in mean value of the proteoglycan content, a large increase in the ease of extractability of proteoglycans from 26.7 to 57.2% of the total and a 62% increase in mean value of the elastin content in the anterior cusps. Normal human mitral valve cusps contained a mean proportion of 29.3 (and chordae 26.6) type III collagen (as % of total types III + I collagen), the values increasing significantly to 33.2 and 36.3% respectively in chronic rheumatic disease. The ratio observed in floppy valves depended on the extent of secondary surface fibrosis, which could be demonstrated histologically; in valve cusps with considerable secondary fibrosis, the percentage of type III increased significantly (to 34.4%), whereas it decreased significantly (to 25.2%) when fibrosis was negligible. It is concluded that the ratio of collagen types in floppy valves reflects the extent of secondary fibrosis rather than the pathogenesis of the disrupted collagen in the central core of the valve.

Amino Acids↗
PubMed1986

The effects of mechanical stability on the macromolecules of the connective tissue matrices produced during fracture healing. I. The collagens.

The distribution of types I, II, III, V and IX collagens in healing fractures of the rabbit tibia has been demonstrated by immunofluorescent techniques. It has also been shown that the mechanical stability of the healing fracture affects both the distribution and types of the collagens present. The initial fibrous matrix contains types III and V collagens; type I collagen was only located in this matrix if unfixed tissue was used. In mechanically stable fractures, cancellous bone forms over the entire periosteal surface by 5-7 days; type I collagen is laid down within the previous fibrous matrix. The trabeculae are heterogeneous in their collagen content. The cavities contain a matrix of types III and V collagens. Small nodules of cartilage may be present between 7 and 14 days; these contain types II and IX collagens. In mechanically unstable fractures, cancellous bone is initially formed away from the fracture gap. The fibrous tissue over the gap is replaced by cartilage; types II and IX collagens are laid down on the pre-existing fibrous matrix. The cartilage is replaced by endochondral ossification. At the ossification front, type I collagen is found around the chondrocyte lacunae of the spicules of cartilage. The new trabeculae contain a core of cartilage which is surrounded by a bone matrix of types I and V collagens. The fracture gaps are invaded by fibrous tissue, which contain types III and V collagens. this is later replaced by cancellous bone.

Animals↗
PubMed1986

Two unusual pathological reactions to nitrofurantoin: case reports.

Idiosyncratic pulmonary reactions to nitrofurantoin are not unusual, often presenting as eosinophilic pneumonia. We report two cases of uncommon pathological reactions, one resembling a hypersensitivity pneumonitis and the other mimicking a giant cell interstitial pneumonia.

Aged↗
PubMed1986

A strategy for the prevention of the transmission of Chagas' disease during blood transfusion.

Our strategy for preventing the transmission of Chagas' disease during blood transfusion is discussed. In addition, the possibility that the Peru, Sonya, Tulahuen and Y strains of Trypanosoma cruzi show varying sensitivities to a series of amphiphilic cationic drugs in vitro at 4 degrees C was investigated using a microscope lysis test. All 21 drugs tested at a concentration of 10(-3) M lysed Sonya bloodstream trypomastigotes, but Peru, Tulahuen and Y strains were affected by 17, 17 and 11 drugs, respectively. All four strains were most sensitive to the acridines; acranil, aminacrine and mepacrine. Although some variation was seen in their responses to certain drugs, no one strain was particularly insensitive to the series as a whole. The effects of gentian violet, maprotiline and mepacrine on the infectivity of Sonya trypomastigotes following incubation at 4 degrees C for 24 h were evaluated. Mepacrine, at a concentration of 2.5 X 10(-4) M greatly decreased the viability of trypomastigotes, while 10(-3) M concentrations of both maprotiline, mepacrine, and gentian violet (at low parasite densities only) apparently abolished all infectivity. Although the compounds we tested did not show a significant improvement over gentian violet, the compound currently used in some blood banks, other existing amphiphilic cationic drugs could be of use in preventing the transmission of Chagas' disease during blood transfusion.

Chagas Disease↗
PubMed1985

Trypanosoma cruzi: possible control of parasite transmission by blood transfusion using amphiphilic cationic drugs.

About 200 clinically used amphiphilic cationic drugs have been shown to be active in vitro against Trypanosoma cruzi at concentrations of less than or equal to 1 mM. Activity against epimastigote and trypomastigote forms was similar, and in both cases the most potent drugs were litracene, maprotiline, thioproperazine, and the acridines: acranil, aminacrine, and mepacrine. Fluorescence microscopy demonstrated that epimastigotes rapidly accumulate acridines initially in discrete subcellular organelles. The amount of drug incorporated during 15 min of incubation was sufficient to produce subsequent lysis of both trypomastigotes and epimastigotes within 24 hr at 4 C. Trypanocidal activity was dependent on the extracellular pH (optimum greater than or equal to 8) and drug exposure time, but was independent of red blood cell density, serum dilution, and temperature (4 to 37 C). Despite their trypanocidal activity, amphiphilic cationic drugs appear to have no significant effect on the energy state of red blood cells at a concentration of 1 mM. These drugs have a possible role in the prevention of Chagas' disease by blood transfusion.

Aminoacridines↗
PubMed1984

A classroom rating scale for use with mentally retarded children.

A behaviour rating scale intended primarily for use with mentally retarded children is described that is based on the behavioural descriptions of such children given by Pevsner (1963). A factor analysis showed that these descriptions could be viewed as being representable by two independent factors. The first of these factors, the AD factor may be seen to relate to attention/distractibility aspects of behaviour and shows a reliable correlation with verbal age and verbal quotient as assessed by the English Picture Vocabulary Test (EPVT), such that low EPVT scores predict greater distractibility. The second factor, the inhibition/excitation (IE) factor, did not correlate significantly with verbal age or verbal quotient but has, in other studies, shown relationships with style of social interaction and may be interpreted as relating to aspects of temperament. It is concluded that individual differences in the classroom behaviour of mentally retarded children may not be qualitatively different from those in non-retarded children and that the scale described is a useful instrument for measuring these individual differences.

Adolescent↗
PubMed1983

Sensory and social reinforcement of head-turning in a profoundly retarded multiply handicapped child.

Head-turning by a nine-year-old multiply handicapped profoundly retarded child (highest item passed on the Mental Scale of the Bayley Infant development test: 2.6 months; highest item passed on Motor Scale of Infant development test: 0.1 month) was reinforced by a variety of potential reinforcers: auditory; vibratory; social; visual. In addition various elicitation and shaping procedures were employed. Relative to base-line performance only visual reinforcement produced a substantial increase in head-turning. This finding is discussed in terms of the compatibility of operant and reinforcer and is related to the recent literature on constraints and predispositions in learning. The extent to which visual reinforcement also had eliciting effects is considered and further experimental controls and operations described.

Acoustic Stimulation↗
PubMed1983

The development and integration of fine motor sequences in 12- to 18-month-old children: a test of the modular theory of motor skill acquisition.

According to the modular model, skill development proceeds through the development of stable units of action called subroutines. The development of these programmed units frees the child to attend to those parts of the action not yet mastered. Once consolidated they can be applied to many different contexts. Thus, complex skill sequences can be produced. The theory generates several predictions, most fundamental being an association between increasing proficiency and increasing consistency. Experiment 1 was a longitudinal study in which six 12-month-old children were observed over a period of eight months. Various manipulative tasks were used, notably the placement of rods in corresponding holes. Experiment 2 was a cross-sectional study of performance consistency in rod placement (N = 30). Results showed that consistency decreases as proficiency increases. It is concluded therefore that the programmed components of complex actions are not characterized by the invariance predicted by modular theory.

Child Development↗
PubMed1982

A method for making reproducible experimental fractures of the rabbit tibia.

A method for making reproducible fractures of the tibia of the rabbit is described. The fractures may be stabilized by plating with either metallic compression, or plastic plates. If a stainless steel dynamic compression plate is used, the rigid immobilization of the fragments leads to direct Haversian remodelling across the fracture, i.e. primary healing, whereas when a plastic plate is used, the fixation is unstable and this leads to secondary healing with the development of a cartilaginous callus. Thus the method of healing may be determined predictably.

Animals↗