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G Almeida

Publications and source records attributed to G Almeida.

10 recordsLinked to original sources

Crystallization and preliminary X-ray analysis of a membrane-bound nitrite reductase from Desulfovibrio desulfuricans ATCC 27774.

Nitrite reductase from the sulfate-reducing bacterium Desulfovibrio desulfuricans ATCC 27774 is a multihaem (type c) membrane-bound enzyme that catalyzes the dissimilatory conversion of nitrite to ammonia. Crystals of the oxidized form of this enzyme were obtained using PEG and CaCl(2) as precipitants in the presence of 3--(decylmethylammonium)propane-1-sulfonate and belong to the space group P2(1)2(1)2(1), with unit-cell parameters a = 78.94, b = 104.59, c = 143.18 A. A complete data set to 2.30 A resolution was collected using synchrotron radiation at the ESRF. However, the crystals may diffract to beyond 1.7 A and high-resolution data will be collected in the near future.

Bacterial Proteins↗

[Primary hyperaldosteronism--12 clinical cases].

STUDY OBJECTIVES: To show clinical, biochemical, and morphological data of 12 patients with primary hyperaldosteronism: eight with an aldosterone-producing adenoma and four with adrenal hyperplasia. To compare clinical and biochemical parameters of the patients with adenoma and hyperplasia. For those with adenoma, to verify clinical and biochemical modifications after adrenalectomy. PATIENTS AND METHODS: In the 12 patients with hyperaldosteronism, retrospective analysis of clinical (age, sex, blood pressure), biochemical (plasmatic and urinary potassium, plasmatic aldosterone, plasma renin activity, and plasmatic aldosterone/renin activity ratio), and morphological (computed tomography, magnetic resonance, and norcholesterol scintigraphy) data was performed. RESULTS: 1--In the 12 patients with hyperaldosteronism (seven female), the age was 51.0 +/- 10.2 years (mean +/- standard deviation), the systolic pressure 200.9 +/- 34.5 mm Hg and the diastolic pressure 120.0 +/- 12.3 mm Hg. Hypertension was diagnosed 12.0 +/- 10.1 years before. As biochemical evidence, we found kalaemia of 3.06 +/- 0.28 and urinary potassium of 63.4 +/- 16.5 mEq/l, renin activity 0.98 +/- 1.02 ng/ml/h, plasmatic aldosterone of 49.4 +/- 36.0 ng/dl, aldosterone/renin activity > 30 in 83% of the cases. As morphological evidence, computed tomography allowed diagnosis in nine patients, suggested it in two, being doubtful in one. Performed on four patients, resonance confirmed the tomography in three and was not contributive in one. The scintigraphy performed in four patients visualized two adenomas, was negative in one adenoma and in one hyperplasia. 2--In the eight patients with adenoma (six female), the youngest age and the highest diastolic pressure compared with patients with hyperplasia were statistically significant (p < 0.01 and 0.05). In the adenomas, the biochemical changes were more pronounced, but not statistically significant. The plasmatic aldosterone/renin activity ratio was also higher in the adenoma cases. 3--After the adrenalectomy, blood pressure became normal in five patients and was more easily therapeutically controlled in three. The average systolic and diastolic pressures decreased and the biochemical parameters became normal in all patients. The pre/post surgical modification of these parameters had statistical significance (systolic pressure decrease, p < 0.01; diastolic pressure decrease, p < 0.01; kalaemia increase, p < 0.001; renin activity increase, p < 0.01; aldosterone decrease, p < 0.02). The plasmatic aldosterone/renine activity ratio normalized in all patients. CONCLUSIONS: In diagnosing primary hyperaldosteronism, biochemical (kalaemia, urinary potassium, plasmatic aldosterone, renin activity, aldosterone plasmatic/renin activity) and tomography studies were important. On comparing the patients with hyperplasia with those with adenoma, we found that the latter are younger and exhibit higher diastolic pressure, both findings with statistical significance. After adenoma surgery, blood pressure became normal in five patients and improved in three, these findings, and the improvement of the kalaemia, plasmatic aldosterone, and renin activity parameters were statistically significant.

Adenoma↗

The effect of short-chain fatty acids on the susceptibility of human umbilical vein endothelial cells to human cytomegalovirus infection.

We have compared the replication of three strains of human cytomegalovirus (HCMV), HCMV AD-169, HCMV Towne, or HCMV RC-256, an insertional mutant of Towne containing the LacZ gene of E. coli, in human umbilical vein endothelial cells (HUVEC) and human forskin fibroblasts (HFF). We also examine the effects of salts of short-chain fatty acids on the susceptibility of HUVEC to infection by HCMV. All three virus strains replicated in both cell types, but 10-to 100-fold less virus was produced in HUVEC cells than HFF. For all virus strains, expression of HCMV IE-1 antigen in HFF was > 70% 24 h after inoculation. In contrast, the number of HUVEC exhibiting IE-1 antigen at 24 h was < 15%. Treatment of HUVEC with sodium butyrate, sodium hexanoate, or sodium propionate prior to virus inoculation increased the IE-1 and late HCMV antigen expression in a dose- and time-dependent manner. Virus yield was also increased. This increased susceptibility was inhibited by cycloheximide and tunicamycin, indicating a requirement for new cellular protein synthesis. Treatment with both sodium hexanoate and propionate after virus inoculation increased HUVEC susceptibility to HCMV infection. Treatment of HUVEC with sodium butyrate after virus inoculation also increased HCMV IE-1 antigen expression, but only after removal of the drug. These studies demonstrate that the susceptibility of HUVEC to HCMV infection can be increased by the treatment of the host cell with salts of short-chain fatty acids, such as sodium butyrate, before or after virus inoculation.

Antigens, Viral↗

Abolition of seasonal testis changes in the Ile-de-France ram by short light cycles: relationship to luteinizing hormone and testosterone release.

The purpose of this study was to examine the relationships between testis weight and the luteinizing hormone (LH) and testosterone releases in rams subjected to 14 successive 2-mo artificial light cycles in which daylength increased from 8 to 16 h in one month and decreased from 16 to 8 h the following month. Testis weights were measured fortnightly. Serial bleedings were performed during 6 to 8 h the last three 2-mo light cycles, when daylengths were 8, 12 (increasing), 16 and 12 h (decreasing) and plasma LH and testosterone were measured by radioimmunoassay. The overall mean testis weight, continuously high and equal to 314 g per testis, was not correlated with daylength. Mean LH levels and LH pulse height varied significantly according to daylength (P<0.05 and P<0.01, respectively) and were maximal on short days (8 h). Both mean and maximal testosterone levels presented variations according to daylength (P=0.05). LH and testosterone pulsatility were quite high (equivalent to 7 to 10.3 pulses/day); however, mean plasma testosterone levels remained low. It is proposed that in rams under 2-mo light cycles, frequent but short stimulation of LH release by decreasing daylength phases allows maximal testis weight, while the interruption of LH stimulation by increasing daylengths prevents overstimulation of testosterone that can inhibit the LH release by negative feedback. Rams a under 2-mo light regimen presented a persistent high testis weight, indicating that seasonality had been broken down in the Ile-de-France male which is normally a marked seasonal breeder.

Journal Article↗

Photoperiodic and melatonin treatments for the control of seasonal reproduction in sheep and goats.

The control of seasonal reproductive activity in sheep and goats in open sheds, needs extra-light (E) during the photosensitive phase (equivalent to long days, LD), followed by treatment with melatonin (equivalent to short days, SD). In autumn-born Ile-de-France or Lacaune ram lambs, 2 months of E followed by decreasing daylength for 90 days, advanced onset of the first breeding season by allowing males to reach their maximum testis volume and sperm production earlier than for untreated ram lambs. Substitution of decreasing daylength with melatonin implants allowed a transient increase in testis volume. Adult Ile-de-France rams maintained under short light rhythms with 2 month-period, demonstrated, during at least 2 consecutive years, a testis volume equivalent to that observed during the normal breeding season. These light-treated rams produced, during non-breeding season, spermatozoa in the same quantity and quality as during the normal breeding season. In anovulatory out-of-season dairy goats, E treatment was demonstrated to be necessary before melatonin treatment and melatonin to be necessary after E treatment to stimulate oestrous and ovulatory activities. Stimulation of the anovulatory females by the introduction of treated males ("male effect"), appeared to be necessary to obtain maximum stimulation of the treated females. Two months of E, followed by melatonin treatment (daily injection or drenching or subcutaneous implants) allowed cycles with ovulation to be maintained for more than 2 months. Although effective for control of out-of-season reproductive activity, melatonin slightly decreased milk production when applied soon after kidding. So, total control of reproduction in sheep and goats by manipulation of photoperiod in open sheds and melatonin treatments appears feasible in both sexes.

Animals↗

Short light cycles induce persistent reproductive activity in Ile-de-France rams.

European breeds of rams appear to be responsive to photoperiodic changes even though there are large differences between breeds in the timing and amplitude of endocrine (LH and testosterone) and gametogenetic variations before the sexual season. Light regimens such as 6-month light cycles or alternations of constant short and long days every 12-16 weeks are able to entrain the parameters of sexual activity. In these regimens in which the period of the light cycle is shortened, LH release is markedly stimulated during decreasing daylength and evidence is presented, from the relationship of LH and testosterone patterns, that the dampening of LH stimulation could simply result from the effect of steroid feedback. However, there is a gap of several weeks between the maximum LH and testosterone concentrations during which testis growth occurs. Experiments were conducted with Ile-de-France rams, markedly seasonal breeders, in which the period of the light cycle was decreased, in different groups of animals, from 6 to 4, 3, 2 or 1 month. Rams submitted to the three light regimens with the longest periods presented testicular variations which paralleled those of the photoperiod, but those kept in the two regimens with the shortest periods had a progressive increase in testicular weight up to the maximum value (300-350 g) with no further major changes. Therefore, in rams kept in 2-month light cycles, testicular weight remained constant for twelve successive cycles (2 years). LH and testosterone plasma measurements indicated that LH was sufficiently stimulated to maintain testicular development during each decreasing daylength phase but that the stimulation was shifted before testosterone could reach levels at which feedback effects could be exerted. However, all the measures of sperm production were at values characteristic of the sexual season. Similar testicular weight maintenance was also obtained in rams submitted to a regimen in which short days (8L:16D) alternated every month with a split photoperiod interpreted as a long day (7L:8D:1L:8D). It is concluded that short light cycles are able to induce persistent reproductive activity in Ile-de-France rams, which may have practical applications in sheep production systems.

Animals↗

[Endocrine arterial hypertension. Pheochromocytoma].

The authors emphasize some embryologic features of the chromaffin tissue as a basis of understanding of both the physiopathologic and clinical aspects of Pheochromocytoma. The appropriate sequence of diagnostic procedures was established in order to obtain clinical, biochemical and anatomical evidence of the tumor. It was concluded that an early diagnosis is mandatory in order to plan a curative surgical therapeutic approach. The embryologic and biochemical understanding of the Pheochromocytoma, in the context of the neuroendocrine tumors, allows a better rationale both for the diagnosis and therapy of this condition.

Adrenal Gland Neoplasms↗