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Biomedical subjects

C Cervantes

Publications and source records attributed to C Cervantes.

At least 37 records · Page 2Linked to original sources
PubMed1991

Bacterial interactions with chromate.

Hexavalent chromium compounds (chromates and dichromates) are highly toxic and are considered as mutagens and carcinogens. These compounds are discharged frequently to the environment as a result of diverse industrial processes. Some microorganisms are able to reduce hexavalent chromium to the less toxic trivalent form. Chromate pollution has promoted the selection of bacterial strains possessing chromate resistance determinants, usually carried by plasmids. Strains combining both abilities, i.e. resistance to and reduction of chromate, are potentially useful for detoxifying chromate polluted waste waters.

Bacteria↗
PubMed1991

Nutritional dwarfing: a growth abnormality associated with reduced erythrocyte Na+,K(+)-ATPase activity.

To assess whether nonorganic nutritional dwarfing (ND) is accompanied by a biochemical adaptation to reduced nutrient intake, Na+,K(+)-ATPase activity of erythrocytes was examined. The study included 27 children with ND who demonstrated deteriorating linear growth and poor weight gain (caused by self-imposed dietary restrictions), 20 patients who initially exhibited ND growth patterns and subsequently experienced catch-up weight gain and growth after nutritional rehabilitation (NDR), and 32 normally growing children who had familial short stature and/or constitutional growth delay (F/CSS). Na+,K(+)-ATPase activity in erythrocytes was significantly lower in ND patients than in the NDR and F/CSS groups. Furthermore, Na+,K(+)-ATPase activity was positively correlated with incremental body weight gain. Na+,K(+)-ATPase concentrations did not differ significantly with regard to sex, chronological age, bone age, or pubertal status. These data suggest that the growth retardation of ND patients is associated with decreased erythrocyte Na+,K(+)-ATPase activity without other biochemical evidence of malnutrition.

Adolescent↗
PubMed1990

Chromate-resistance in a chromate-reducing strain of Enterobacter cloacae.

Resistance to toxic hexavalent chromium (chromate: CrO4(2)) in Enterobacter cloacae strain HO1, isolated from an activated sludge sample, was investigated under aerobic and anaerobic conditions. Decreased uptake of 51CrO4(2-) in E. cloacae strain HO1 was observed under aerobic conditions, when compared with a standard laboratory E. cloacae strain (IAM 1624). Under anaerobic conditions E. cloacae strain HO1 was able to reduce hexavalent chromium to the less toxic trivalent form. When E. clocacae strain HO1 was grown with nitrate anaerobically, the cells were observed to lose simultaneously their chromate-reducing ability and chromate-resistance under anaerobic conditions.

Anaerobiosis↗
PubMed1990

Chromium reduction in Pseudomonas putida.

Reduction of hexavalent chromium (chromate) to less-toxic trivalent chromium was studied by using cell suspensions and cell-free supernatant fluids from Pseudomonas putida PRS2000. Chromate reductase activity was associated with soluble protein and not with the membrane fraction. The crude enzyme activity was heat labile and showed a Km of 40 microM CrO4(2-). Neither sulfate nor nitrate affected chromate reduction either in vitro or with intact cells.

Chromates↗
PubMed1990

Cloning, nucleotide sequence, and expression of the chromate resistance determinant of Pseudomonas aeruginosa plasmid pUM505.

The chromate resistance determinant of Pseudomonas aeruginosa plasmid pUM505 was cloned into broad-host-range vector pSUP104. The hybrid plasmid containing an 11.1-kilobase insert conferred chromate resistance and reduced uptake of chromate in P. aeruginosa PAO1. Resistance to chromate was not expressed in Escherichia coli. Contiguous 1.6- and 6.3-kilobase HindIII fragments from this plasmid hybridized to pUM505 but not to P. aeruginosa chromosomal DNA and only weakly to chromate resistance plasmids pLHB1 and pMG6. Further subcloning produced a plasmid with an insert of 2,145 base pairs, which was sequenced. Analysis of deletions revealed that a single open reading frame was sufficient to determine chromate resistance. This open reading frame encodes a highly hydrophobic polypeptide, ChrA, of 416 amino acid residues that appeared to be expressed in E. coli under control of the T7 promoter. No significant homology was found between ChrA and proteins in the amino acid sequence libraries, but 29% amino acid identity was found with the ChrA amino acid sequence for another chromate resistance determinant sequenced in this laboratory from an Alcaligenes eutrophus plasmid (A. Nies, D. Nies, and S. Silver, submitted for publication).

Amino Acid Sequence↗
PubMed1990

Ferritin determination in elderly people by enzyme immunoassay.

Iron is associated with important biological processes: Cellular and molecular oxidation, muscle contraction and infection resistance. Iron stores can be estimated by Ferritin (FTN) determination. FTN quantitation can be used in the early diagnosis of ferropenic anemia (precedes 3-6 months the clinical appearance of anemia) in pregnant women, children and elderly people. FTN serum levels are associated with high incidence diseases as malignant tumors and hepatopathies. Serum FTN concentration is in the range of ng/ml. So, high sensitivity techniques with radioactive, enzymatic, fluorescent or luminescent tracers are needed for FTN quantitation. An affinity antibody enzyme labelled procedure with a 2.5-500 ng/ml range, compatible with various plastic solid supports was developed to study Ferritinemia in elderly persons. Ferritinemia was found to be less than 20 ng/ml in 12% institutionalized elderly persons.

Aged↗
PubMed1989

Comparison of peptidergic mechanisms in different parts of the guinea pig superior mesenteric artery: immunocytochemistry at the light and ultrastructural levels and responses in vitro of large and small arteries.

The presence and distribution of peptide-containing nerve fibres and axon terminals have been studied in the proximal part of the superior mesenteric artery (SMA) (i.e. conductance vessel) and in the finer ramifications of the SMA close to the intestine (outer diameter 200 microns, i.e. resistance vessel). Light microscopic immunocytochemistry revealed that the proximal part of the SMA possessed a rich supply of neuropeptide Y (NPY)- and tyrosine hydroxylase (TH)-immunoreactive nerve fibres, forming a loose perivascular network which increased in density distally. The vasoactive intestinal peptide (VIP) immunoreactivity was moderate in the proximal artery and only a few VIP fibres could be identified in the distal portion of the SMA. Calcitonin gene-related peptide (CGRP)-, neurokinin (NK)- and substance P (SP)-immunoreactive fibres had an intermediate density in both arterial regions, but their distribution pattern varied. Electron microscopic immunocytochemistry showed that NPY-immunoreactive nerve terminals were close to the smooth muscle cells of the medial layer in both parts of the SMA, indicative of a vasomotor role. Although the VIP-immunoreactive terminals had a similar localization they were seen less frequently. CGRP-, NK- and SP-immunoreactive axons had an identical distribution in the two vascular regions. Interestingly, they were usually seen more distant from the medial layer, localized in the adventitia. Examination of vasomotor responses to perivascular peptides revealed significant regional differences: NPY produced only weak contractions (13 +/- 3%) of proximal vessel segment of the conductance type, while strong concentration-dependent contractions were seen in distal parts of the SMA (resistance vessel). In neither region was any interaction with noradrenaline demonstrated. Proximal segments of the SMA revealed a stronger and more potent response to VIP and peptide histidine isoleucine than did distal segments, while on the other hand acetylcholine was more potent and elicited stronger effects in distal segments. CGRP, NKA and SP relaxed precontracted arteries by 50-75% and there was no significant difference in responsiveness to these peptides in the two regions of the SMA.

Animals↗
PubMed1989

Enzyme immunoassay for occult faecal blood.

The specificity and sensitivity of immuno-assays can be usefully exploited for early detection of digestive bleeding disorders. We have developed an enzyme immuno-assay (EIA) specific of human haemoglobin (Hb-Hu) by which occult faecal blood can be detected without any need for dietary restrictions or for repetitive sampling, as would be required with other procedures. This EIA can detect Hb-Hu by a sensitivity of 2.5 ng/ml of faecal extract as well as dissociated alpha and beta chains and peptic or tryptic proteolytic Hb-Hu fragments. The EIA, when applied to occult faecal bleeding in patients with malignant tumours in the digestive system, was positive on some 80 percent of all samples.

Colorectal Neoplasms↗
PubMed1988

Presence of calcitonin gene-related peptide (CGRP) and substance P (SP) immunoreactivity in intraepidermal free nerve endings of cat skin.

Immunocytochemistry against neuropeptides contained within primary afferent neurons was used to study the morphology and distribution of intraepidermal free nerve endings in cat facial skin. Calcitonin gene-related peptide (CGRP) and substance P (SP) immunoreactivity was found in similar intraepidermal nerve endings of cat glabrous and hairy skin epithelia. The greatest density of immunoreactive intraepidermal nerve endings was located in the nose epidermis. Small limited areas with immunoreactive intraepidermal nerve endings were also found in facial hairy skin.

Afferent Pathways↗
PubMed1988

Immunocytochemical analysis of calcitonin gene-related peptide and vasoactive intestinal polypeptide in Merkel cells and cutaneous free nerve endings of cats.

Calcitonin gene-related peptide (CGRP)- and vasoactive intestinal polypeptide (VIP)-immunoreactivity were observed to coexist in Merkel cells of cats. No differences in peptide content were found between Merkel cells located in epithelia of the hard palate, in hairy and glabrous skin of the upper lip, and in vibrissae follicles. CGRP- and VIP-immunoreactive nerve fibres were also found near CGRP/VIP-immunoreactive Merkel cells. In the vibrissae follicles some CGRP- and VIP-immunoreactive nerve terminals end abutting on the glassy membrane. Other CGRP-immunoreactive nerve fibres penetrate the epithelium of the skin and end within it. Electron microscopy of vibrissae follicles revealed that Merkel cell neurites are not immunostained and that immunostained nerve fibres form unmyelinated bundles before ending freely. Thus, CGRP- and VIP-immunoreactive nerve fibres in cat skin do not end as Merkel cell neurites but as different kinds of free nerve endings.

Animals↗
PubMed1987

Pituitary function assessment in short stature by a combined hormonal-stimulation test.

We utilized a combined, hormonal-stimulation test (CHST) using sequentially-administered insulin, thyrotropin-releasing hormone, gonadotropin-releasing hormone, and levodopa to assess 51 children with short stature and/or pathologic growth. Growth hormone, thyrotropin, gonadotropins, cortisol, and prolactin levels were sampled over two hours. All patients with appropriate predicted adult heights, delayed bone ages, and normal growth velocities of 4.0 cm/y or greater demonstrated normal pituitary responses. Two of 12 patients with predicted heights 2.5 SDs lower than target height and normal growth velocity demonstrated isolated growth hormone deficiency. Nine of 11 patients had a pathologic growth hormone deficiency or panhypopituitarism. Evaluation of pituitary function by combined sequential hormonal stimulation is fruitful in children with pathologic growth patterns but not in children with normal growth velocities and normal predicted adult height.

Adolescent↗
PubMed1987

Decreased chromate uptake in Pseudomonas fluorescens carrying a chromate resistance plasmid.

CrO4(2-) resistance in Pseudomonas fluorescens LB300(pLHB1) was related to reduced uptake of CrO4(2-) relative to the plasmidless strain LB303. 51CrO4(2-) was transported mainly via the SO4(2-) active transport system; thus, cells grown with 0.15 mM cysteine, a repressor of the SO4(2-) transport system, were much more resistant to CrO4(2-) than those grown with 0.15 mM djenkolic acid, which derepressed the 35SrO4(2-) uptake system. Kinetics of 51CrO4(2-) uptake by P. fluorescens with and without the plasmid showed that the Vmax for 51CrO4(2-) uptake with the resistant strain was 2.2 times less than the Vmax for the sensitive strain, whereas the Km remained constant.

Biological Transport, Active↗
PubMed1985

Calcitonin gene-related peptide (CGRP)-immunoreactive sensory and motor nerves of the mammalian palate.

The distribution of calcitonin gene-related peptide (CGRP)-immunoreactive nerve fibres in the palate of rat, cat and monkey was studied using immunocytochemistry and radioimmunoassay. CGRP-containing nerve fibres were found, in all species studied, to form a rich plexus in the subepithelial and submucous layers, around excretory ducts and blood vessels. A small number of CGRP-containing nerve fibres penetrated the epithelium of the hard and soft palate, and terminated as free endings. Some CGRP-containing nerve fibres were found in the vicinity of the mucous glands. CGRP-immunoreactive motor end plates were seen in the striated muscle (tensor veli palatini) of the soft palate. Following capsaicin treatment a small depletion in CGRP-immunoreactive nerve fibres in the rat palate epithelium was noted. In contrast, CGRP immunoreactive fibres forming rich plexuses in other layers of the palate, including motor end plates, were not affected. The extractable CGRP showed no significant depletion (normal animals [n = 10] 21.7 +/- 2.4 pmol/g compared with capsaicin-treated animals [n = 10] 17.5 +/- 1.8 pmol CGRP/g wet weight). The reduction in the number of visible immunoreactive nerves following capsaicin application tends to confirm the sensory character of the CGRP-containing nerve fibres terminating in the epithelium of the hard and soft palate. The capsaicin insensitive CGRP-immunoreactive nerve fibres may thus have a predominantly motor function.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Paramethasone acetate (PA): corticosteroid potency vs hypothalamic pituitary-gonadal axis.

Because paramethasone acetate (PA) suppresses basal and midcycle LH surge and blocks estrogen synthesis in the female, its possible effect upon testicular physiology was evaluated in 13 healthy men by measuring the circulating levels of FSH, LH, prolactin (PRL), testosterone (T), dihydrotestosterone (DHT), androstenedione (A), estradiol (E2) and cortisol (C) every 4 h throughout the day, before (control) and after PA (6 mg/d/7 d). The total concentrations of each hormone, as well as the PA-induced suppressibility (measured as percent decrease in the mean 24 h plasma level) were analyzed. PA suppressed neither the basal nor circadian rhythm of T and had no effect on LH, FSH or PRL output. DHT, A, E2 were significantly reduced and the basal concentrations and circadian variations of C were abolished. PA showed a dual control on the pituitary gonadal axis and while causing a maximal suppressed adrenocortical activity it had no interference in testosterone synthesis.

Adult↗