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Biomedical subjects

M Paoli

Publications and source records attributed to M Paoli.

16 recordsLinked to original sources
PubMed1996

Crystal structure of T state haemoglobin with oxygen bound at all four haems.

The cooperative binding of oxygen by haemoglobin results from restraints on ligand binding in the T state. The unfavourable interactions made by the ligands at the haems destabilise the T state and favour the high affinity R state. The T <==> R equilibrium leads, in the presence of a ligand, to a rapid increase in the R state population and therefore generates cooperative binding. There is now considerable understanding of this phenomenon, but the interactions that reduce ligand affinity in the T state have not yet been fully explored, owing to the difficulties in preparing T state haemoglobin crystals in which all the subunits are oxygenated. A protocol has been developed to oxygenate deoxy T state adult human haemoglobin (HbA) crystals in air at 4 C at all four haems without significant loss of crystalline order. The X-ray crystal structure, determined to 2.1 A spacing, shows significant changes in the alpha and beta haem pockets as well as changes at the alpha(1)beta(2) interface in the direction of the R quaternary structure. Most of the shifts and deviations from deoxy T state HbA are similar to, but larger than, those previously observed in the T state met and other partially liganded T state forms. They provide clear evidence of haem-haem interaction in the T state.

Adult↗
PubMed1995

Resonance Raman studies of the heme active site of the homodimeric myoglobin from Nassa mutabilis: a peculiar case.

A spectroscopic investigation by resonance Raman has been carried out at pH 7.0 in 0.1 M phosphate buffer on the cooperative homodimeric myoglobin from Nassa mutabilis. The study has been performed on the unligated ferrous form, as well as on the ligated species MbO2 and MbC, and on the ferric form met-Mb. Two v(C = C) vinyl stretching modes have been observed in all the investigated forms, reflecting different degrees of vinyl conjugation with the porphyrin ring, as a consequence of a strongly asymmetric environment for the two side groups of the heme. Furthermore, the ferric form displays a hexacoordinate low-spin heme, which suggests the presence of an endogenous ligand bound to the Fe atom. The frequency of the v(Fe-Im) stretching mode of Mb from Nassa mutabilis shifts down by 4 cm-1 as compared with that of horse heart myoglobin, reflecting a protein-induced proximal strain as a result of heme-heme interaction due to the close proximity of the two hemes in the dimer. The lower frequency of the v(Fe-Im) stretching mode agrees well with the lower affinity for oxygen binding found for Nassa mutabilis Mb and with the slight heme core expansion with respect to horse heart Mb, suggesting a critical role for the Fe-His bond on the heme's function and structure.

Animals↗
PubMed1995

Bone mineral density of prepubertal age girls with Turner's syndrome while on growth hormone therapy.

Bone mineral densities and growth velocities of young girls with Turner's syndrome treated with recombinant human growth hormone at an age before the decreased levels of estrogens secondary to their ovarian failure could contribute to osteopenia were studied. Twelve patients with a mean chronological age of 8.9 +/- 0.9 years and a mean bone age of 6.9 +/- 0.8 years received growth hormone therapy for over 2 years (0.5 IU/kg/week s.c.) Mean growth velocities increased significantly from a baseline level of 3.5 +/- 0.4 cm/year to 6.4 +/- 0.3 and 5.7 +/- 0.4 cm/year at 12 and 24 months of therapy, while height SDS improved from -3.1 +/- 0.4 at baseline to -2.7 +/- 0.3 and -2.4 +/- 0.3 at 12 and 24 months, respectively. Total bone calcium as well as cortical bone mineral density of our density of our patients while on recombinant human growth hormone were similar to that of a control group of prepubertal healthy growth children paired for bone age and height; bone density of trabecular bone was however increased in our patients when compared to healthy controls (0.791 +/- 0.04 vs. 0.669 +/- 0.02 g/cm2; p < 0.025). We conclude from our study that the bone mineral status of young girls with Turner's syndrome on growth hormone therapy seems to be normal.

Age Determination by Skeleton↗
PubMed1994

Characterization of recombinant horseradish peroxidase C and three site-directed mutants, F41V, F41W, and R38K, by resonance Raman spectroscopy.

Resonance Raman spectra are reported for recombinant horseradish peroxidase C (HRP-C*) and three protein variants prepared by in vitro refolding after Escherichia coli expression. The spectra of their FeII and FeIII forms and of their complexes with benzohydroxamic acid (BHA) were recorded at neutral pH. The residues mutated were on the distal [Phe41-->Trp or Val (F41W, F41V) and Arg38-->Lys (R38K)] side of the heme. The spectra give information on the spin and ligation states via the frequencies of the core size marker bands. No detectable modification in the enzyme structure or in the heme group has been observed in the wild-type recombinant HRP-C*. The FeIII forms of both the recombinant and the plant proteins show the coexistence of a 5-(5-cHS) and a 6-coordinate high-spin (6-cHS) heme, characterized by the anomalous frequencies of certain bands, namely, v3 and v10, which we attribute to a different degree of distortion of the heme planarity with respect to other heme proteins and model compounds, resulting from external forces such as steric contacts within the protein. This effect is partially relieved upon complexation with BHA or as a result of mutation. F41W and F41V are characterized by an increase in a 6-cHS form at the expense of the 5-cHS species, and the R38K by an increase in both the 6-c high-(HS) and low-spin (LS) hemes. The 6-cHS and -LS species are characterized by normal core size marker band frequencies. The FeII-His RR band is at 243 cm-1 in HRP-C*, the high frequency value being due to hydrogen-bonding interactions between the proximal His170 N delta and the carboxylate acceptor group on Asp247. Mutation at position 38 causes a downshift of 3 cm-1 in the v(Fe-Im) stretching mode, suggesting a weakening of the Fe-Im bond strength. By comparing the results obtained with HRP-C* mutants with those previously reported for the corresponding cytochrome c peroxidase (CCP) mutants, it appears that the distal heme pocket architecture is significantly different in the two peroxidases, although the hydrogen-bonding network coupling the distal and the proximal sides of the heme appears to be conserved. Mutations on the distal side dramatically affect the capability of the protein to bind BHA. F41W and R38K mutants do not bind the substrate, whereas the F41V variant shows a 2-fold increase in affinity.(ABSTRACT TRUNCATED AT 400 WORDS)

Base Sequence↗
PubMed1994

Spin state and axial ligand bonding in the hydroxide complexes of metmyoglobin, methemoglobin, and horseradish peroxidase at room and low temperatures.

Absorption and resonance Raman spectra using Soret excitation of alkaline metmyoglobin (metMb), methemoglobin (metHb), and horseradish peroxidase (HRP) were obtained at room and low temperature. At 298 K both metMb and metHb exhibit two isotope-sensitive bands assigned to high- and low-spin nu(Fe-OH) stretching modes, respectively, which are correlated with the spin-state population. The low-spin stretch occurs 60 cm-1 to higher energy than the corresponding high-spin vibration. When the temperature is lowered, only the low-spin species is observed. HRP exhibits at both 298 and 20 K only the low-spin nu(Fe-OH) stretching mode, which occurs 50 cm-1 to lower energy than the corresponding modes observed in the globins. This is explained in the context of a strong hydrogen bond between the hydroxyl ligand and the distal His42 and/or Arg38. Lowering temperature causes in all of the examined proteins a strengthening of the Fe-OH bond and a contraction of the core of about 0.01 A, as determined by the upshifting of the low-spin nu(Fe-OH) stretching mode and the core size marker bands. Both effects are ascribed to an increase of the packing forces.

Animals↗
PubMed1984

The ethological approach to the assessment of depressive disorders.

The ward behavior of 29 inpatients with a diagnosis of major depressive disorder and that of six mixed psychiatric patients was studied by means of an observational method derived from ethological techniques. By these means the occurrence of a wide variety of behaviors was monitored. Depressives before treatment differed from the same group after 4 week of treatment on several items: eye contact, exploration of the environment, verbal communication, and all social behaviors increased, whereas crying, nonsocial behaviors, and pathological behaviors decreased. The same behavioral categories distinguished depressed patients in baseline conditions from controls. When depressives were divided into responders and nonresponders on the basis of their Hamilton scores, behavior differences were notable only in the responders. Some behavioral patterns, such as the rate of social behaviors, were related to personality traits, which were assessed by means of the Maudsley Personality Inventory. Finally, some behavioral categories bore some weak, though significant, relationships to the Hamilton Rating Scale. The above results seem to indicate that a behavior pattern specific to depressive psychopathology does exist and closely resembles the one identified by the classical clinical description of depression. Ethological assessment may therefore be a useful tool in psychiatry, as it can evaluate the clinical picture in a different frame of reference from psychiatric interviews.

Adult↗
PubMed1979

[Anti-edema activity of injectable Venoruton in abdominal surgery].

The anti-oedema activity of an injectable drug (HR; active principle: 0-(beta-hydroxyethyl)-rutoside) was assessed in 60 gastric extrahepatic bile duct, and large intestine surgery patients (30 being used as controls). Gastroscopy (with biopsy), gastroduodenoscopy, colonoscopy (with biopsy) and radiological examination were usually performed on the 5th and 10th post-operative days. The drug showed significant therapeutic effects: rapid resolution of oedema, especially at the sutures, leading to early cicatrisation, canalisation and the prevention of dehiscence. Finally, duration of hospitalisation was less than in the untreated cases. The gastroscopic, radiographic and biopsy findings are considered to have shown clear evidence of the drug's action against oedema formation.

Adult↗
PubMed1977

[Post-amputation dehiscence. A problem resolved].

70 peripheral amputations of the lower extremities in arteriosclerotic and diabetic vasculopathics have been examined. In a number of cases, the postoperative period was complicated by dehiscence of the suture on the stump, with lengthening of hospitalization time, risk of infection in the underlying bone and thus further amputation. To solve this problem, dehiscence was treated with dermo-epidermal autografts to cover the missing tissue area. The dehiscence was cleaned with compresses of 2% amuchina associated with topical instillations of Lincomycin hydrochloride. The cure percentage after grafting was about 80%.

Aged↗