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Biomedical subjects

H Rico

Publications and source records attributed to H Rico.

At least 181 records · Page 10Linked to original sources
PubMed1983

Synthesis and assembly of wall polymers on regenerating yeast protoplasts.

Accumulation of chitin and glucan on S. cerevisiae and C. albicans protoplasts begins shortly after resuspension in the regeneration medium, and mannoprotein molecules also appear retained by the regenerating wall after 30-60 minutes in S. cerevisiae or after a longer lag period in C. albicans. Nevertheless, a considerable fraction of the synthesized mannoproteins, which in SDS-acrylamide gels exhibit a different pattern from that of wall manno-proteins of cells, are still released to the growth medium during at least eight hours. De novo synthesis of chitin synthase, but not of glucan synthase, is observed in S. cerevisiae from about 30 minutes after initiation of the regeneration process. The interaction between microfibrils of nascent chitin formed by C. albicans protoplasts is altered by strains as Calcofluor White or Congo Red. In the presence of the former one, no microcrystalline lattice of the polymer is formed and protoplasts do not regenerate correctly.

Candida albicans↗
PubMed1983

Cell wall composition and protoplast regeneration in Candida albicans.

The transition of blastospores to the mycelial phase in Candida albicans was induced after the blastospores were kept at 4 degrees C for several hours and then transferred to a fresh medium prewarmed at 37 degrees C. Glucan was the most abundant polymer in the wall in the two morphogenetic forms but the amount of chitin was higher in the mycelial form than in blastospores. Efficient protoplasting required reducing agents and proteases together with beta-glucanases (zymolyase). Protein synthesis in regenerating protoplasts was initiated after about 30 min. Chitin synthetase, initially very low, was incorporated in important amounts into cell membranes mainly in a zymogenic state. After a few hours chitin was the most abundant polymer found in the aberrant wall of the regenerating protoplast.

Candida albicans↗
PubMed1983

Calcofluor white alters the assembly of chitin fibrils in Saccharomyces cerevisiae and Candida albicans cells.

In the presence of calcofluor white, budding scars and dividing cross-walls of Saccharomyces cerevisiae exhibited fluorescence, indicating that the brightener was a specific marker of fungal chitin. In addition, incubation of cells in the presence of the brightener did not stop protein and wall-polymer formation, but abnormal deposition of chitin occurred. Chitin synthesis was normal in regenerating protoplasts of Candida albicans in the presence of calcofluor, but formation of the crystalline lattice was blocked. These results suggest that crystallization of nascent subunits may occur by a self-assembly mechanism that was blocked by the stain.

Benzenesulfonates↗
PubMed1979

The role of growth hormone in the pathogenesis of postmenopausal osteoporosis.

The secretory response of somatotropic hormone (STH) to arginine hydrochloride stimulation (0.5 g/kg) was studied in 13 postmenopausal women. Eight showed evidence of osteoporosis, based on clinical and morphoradiological data and on metacarpal cortical thickness measurement, and five had normal bone mass. In addition, the response to levodopa (500 mg) was determined in four of the osteoporotic patients. Baseline STH concentrations in the osteoporotic subjects did not differ from those in the nonosteoporotic group, but the latter showed a significant increase over the former at 45, 60, 90, and 120 minutes after stimulation. Similar findings were obtained with levodopa stimulation. Without necessarily implying a cause-effect relationship, our data appear to support the hypothesis that the poor secretory response of STH may be to some degree responsible for the osteopenia observed during the climateric.

Adult↗
PubMed1978

Metacarpal cortical thickness in uremic patients on regular hemodialysis.

Metacarpal cortical thickness was measured in 83 patients with chronic renal failure undergoing periodic hemodialysis. Patients were dialyzed twice weekly, 8--9h per session, with a calcium concentration in dialysate of 6.5 mg/dl. Supplements of calcium, vitamin D (5,000 I.U. a day), steroid anabolic hormones, and aluminium hydroxyde were administered to all patients. They were on a normal protein intake and unrestricted physical activity. The results show that the young males have a reduction in cortical thickness as compared to age-matched controls, and that there is a progressive loss in cortical width as the length of dialysis increases. This bone loss is statistically significant in males during their first 18 months of dialysis.

Adolescent↗
PubMedDate not supplied

Electrophoretic mobility of external invertase from free and gel-immobilized yeast cells.

Electrophoretic mobility of secreted invertase (E.C. 3.2.1.26) from gelatin-immobilized yeast cells was analysed and compared with that of secreted invertase from freely suspended batch-grown cells. Invertase from immobilized cells showed a lower mobility after 24 h of incubation, in medium containing either glucose or raffinose as carbon source. Changes in invertase mobility were also followed in a time course both for immobilized and for freely suspended batch-grown cells. Mobility of invertase from free cells increased after approximately 15 h of incubation, independently of the carbon source, whilst that of invertase from immobilized cells remained constant. The differences observed were attributed to a different level of glycosylation of the protein moiety in free and immobilized cells. The amount of mannoproteins in the cell walls of immobilized cells was also investigated by ConA-ferritin labelling and quantification of ferritin particle density in ultrathin sections; the results of this experiment showed a higher content of mannoproteins in the walls of immobilized cells when compared with free cells. As a whole, these results are indicative of physiological changes that can be ascribed to the peculiar microenvironment of gel-immobilized cells.

Blotting, Western↗
PubMedDate not supplied

Bone mineral content and body composition in postpubertal cyclist boys.

The effect of sports activity on bone mass was assessed by dual-energy X-ray absorptiometry in a group of 22 young cyclists aged 16.2 +/- 0.7 years. These athletes trained for 10 hours a week for over two years. Bone mass values were compared with those of 27 sedentary youngsters aged 16.9 +/- 0.3 years. There were no differences in total body bone mineral (TBBM) between groups. The leg bone mineral content (LBMC), body weight, and percentage fat were lower in the cyclists than in controls (p < 0.02, p < 0.01, and p < 0.001 respectively). No changes were observed when TBBM was normalized for weight. The changes observed earlier in LBMC disappeared when normalized for body weight. These results suggest that cycling does not stimulate bone mass in youngsters, and that the type, quality, and length of sports activity need to be defined.

Absorptiometry, Photon↗
PubMedDate not supplied

Metacarpal cortical thickness by computed radiography in osteoporosis.

Computed radiography was used to make radiogrammetric measurements of the second metacarpal in 240 women, 180 considered normal and 60 osteoporotic. These measurements had a coefficient of variation for the external diameter of 0.74% in normal women and 0.75% in osteoporotic women, and for the internal diameter of 2.4% and 2.03%, respectively. The group of women with osteoporosis was divided according to external diameter and internal diameter into a group with osteoporosis due to increased bone resorption (61.1%, normal external diameter and increased internal diameter), and osteoporosis due to deficient bone formation (26.1%, decreased external diameter and normal internal diameter). In the remaining subjects (12.8%), osteoporosis was attributed to both mechanisms. There was a significant linear regression between internal diameter and tartrate-resistant acid phosphatase concentration (p < 0.0001) in the group of increased bone resorption, which was absent (p = ns) in the group with deficient bone mass formation. No changes were observed in the size of the two groups. The low coefficient of variation of radiogrammetric measurements with computed radiography validate it as an accurate technique for bone mass studies. Moreover, it has the additional advantage of permitting determination of the proportion of women with osteoporosis due to increased bone resorption and/or deficient bone mass formation.

Acid Phosphatase↗
PubMedDate not supplied

Initial steps of wall protoplast regeneration in Candida albicans.

Cell wall regeneration of individual Candida albicans yeast and mycelial protoplasts was studied with confocal and electron microscopy using polyclonal antibodies and lectins. Quantitative measurements of the fluorescence emitted by individual protoplasts during the process of regeneration indicate that chitin is the first polymer to be laid down, whereas beta (1,3)- and beta (1,6)glucan are incorporated at a later stage. Mannoproteins were found on the surface of fresh protoplasts and those newly synthesized were then deposited with time. During the first steps of wall regeneration, the proteins that interacted covalently with chitin or glucan were different, but the same species were found linked to each polymer in yeast and mycelial regenerating forms. The aggregates formed by regenerating protoplasts were shown to be due to the chitin and mannoprotein network initially laid.

Blotting, Western↗
PubMedDate not supplied

The effect of supplemental copper on osteopenia induced by ovariectomy in rats.

OBJECTIVE: The effect of a copper supplement on preventing bone mass loss induced by ovariectomy in rats was investigated. DESIGN: Three groups of fifteen 100-day-old female Wistar rats, each with a mean initial weight of approximately 260 g per animal, were selected for a 30-day experiment. One group of 15 ovariectomized rats was fed a diet supplemented with 15 mg of copper per kilogram of feed. The other two groups: 15 ovariectomized and 15 Sham- ovariectomized rats did not receive the supplement. Morphometric (weight and length) and densitometric studies with dual-energy x-ray absorptiometry were performed on the whole femur and the fifth lumbar vertebra of each animal at the end of the 30-day period. RESULTS: The ovariectomized rat group fed a diet supplemented with copper did not show the bone mass loss at the axial (fifth lumbar vertebra) or peripheral (femur) level that was evidenced in the ovariectomized group. CONCLUSIONS: The results of the measurement of axial and peripheral bones show that a supplement of copper may have a potential therapeutic application in the treatment and prevention of involutional osteoporosis.

Absorptiometry, Photon↗
PubMedDate not supplied

Effect of adjuvant-induced arthritis on bone mass in rats and its prevention by non-steroid anti-inflammatory drugs (NSAIDs).

The effect of two propionic acid derived drugs, ketoprofene and butibufene, on the prevention of osteopenia due to adjuvant-induced anti-inflammatory arthritis, was studied in groups composed of 10 rats each. Another group of 10 rats was treated with a placebo and 20 non-treated rats served as controls. Once arthritis was evoked, propionic acid derived drugs were administered at equivalent doses, in the form of a local cream applied on the foot where arthritis was induced. The placebo group was treated with the cream without propionic acid derivatives. Rats were sacrificed at the end of the study and the femurs where arthritis was induced were dissected. Bone densitometry studies were conducted with double energy X-ray on these bones to calculate the bone mass. Bone mass was higher in the group treated with ketoprofene (p < 0.025) than in the butibufene and placebo-treated groups, and these 3 groups showed lower values than the control (p < 0.001). These results suggest that propionic acid derivatives can prevent the osteopenia induced by inflammation and the subsequent lack of limb use, an effect which may be related to its analgesic and/or anti-inflammatory effects. In addition, this may serve as a good model for the indirect measurement of the effectiveness of analgesic and/or non-steroid anti-inflammatory drugs in experimental animals.

Absorptiometry, Photon↗
PubMedDate not supplied

Etidronate versus clodronate in the prevention of postovariectomy bone loss. An experimental study in rats.

OBJECTIVE: We compared the diphosphonates etidronate and clodronate to find out which was more effective in inhibiting the loss of bone mass after ovariectomy in rats. METHODS: Five lots of female Sprague Dawley rats, each containing 15 rats (14 wks old; mean weight 290 g), were kept under identical living conditions (12 hrs of light and 12 hrs of darkness), habitat, and diet following the current norms of the European Economic Community. One lot was kept as a control; one lot underwent sham ovariectomy (Sham-OVX); and the remaining 3 lots were anesthesized and underwent double ovariectomy (OVX). One lot of ovariectomized rats was given etidronate by esophageal tube, 5 mg/kg/day (OVX-E); one lot was treated with intraperitoneal clodronate, 5 mg/kg/3 days (OVX-Cl). The remaining lot was not manipulated (OVX). The animals' right femurs were then dissected for measurements of the bone mineral content. RESULTS AND CONCLUSION: Bone densitometry revealed that loss of bone mass 2 months after ovariectomy in the OVX-Cl group was 2.3%, not differing from that of the control group; bone loss in the OVX-E group was 11.7%, significantly different from the control group and from the OVX-Cl group (p < 0.001). These results show that clodronate is superior to etidronate in inhibiting osteopenia after ovariectomy in rats.

Animals↗
PubMedDate not supplied

Serum osteocalcin and calcitropic hormones in a homogeneous group of patients with rheumatoid arthritis: its implication in the osteopenia of the disease.

Different mechanisms may play a role in the pathogenesis of the generalized osteopenia found in rheumatoid arthritis (RA). We measured the calcium, osteocalcin (BGP), parathyroid hormone (PTH), calcitonin (CT) and 25(OH)D3 levels as well as urine 24 hr calcium, Ca/Cr and OHP/Cr in a homogeneous group of 30 non-disabled patients (10 men, 8 premenopausal women and 12 postmenopausal women) recently diagnosed as having RA (disease duration 4 to 6 months). They had normal serum levels of vitamin K, were not on previous or present treatments known to interfere with calcium metabolism, and were not pregnant if females of fertile age. The group was compared with an age-matched control group of 32 healthy subjects (10 men, 8 premenopausal women and 14 postmenopausal women). We observed significantly decreased levels of 25(OH)D3 (29.9 +/- 9.9 vs 48.7 +/- 12.1 ng/mL; p < 0.005) and significantly increased levels of urine OHP/Cr (2.24 +/- 0.71 vs 1.56 +/- 0.82 mg/mg; p < 0.001) in the RA group. No differences in these two parameters were found between the three subgroups of RA patients. Male RA patients showed decreased levels of serum BGP (7.3 +/- 1.0 vs 8.2 +/- 1.7 ng/mL; p < 0.01). The remaining parameters did not differ significantly between RA patients and controls. These data suggest that the generalised osteopenia found in RA may be a consequence of increased bone resorption without a concomitant increase in bone formation, perhaps related to mechanisms inherent to the disease.

Adult↗