Age-related changes in the pressure diuresis and natriuresis response

The renal-excretory responses to changes in renal perfusion pressure (RPP) were studied in anesthetized young (3 mo old), adult (12 mo old), and senescent (24 mo old) rats to evaluate whether the pressure diuresis and natriuresis mechanism is altered as a function of age. Experiments were performed in anesthetized animals in which nervous and systemic hormonal influences to the kidney were fixed. Mean arterial pressure was similar in all three groups: 97.6 +/- 2.6, 102.1 +/- 3.7, and 95.2 +/- 5.2 mmHg in young, adult, and senescent rats, respectively. The relationships between RPP and diuresis/natriuresis or fractional excretions of water and sodium were similar in young and adult rats. However, in senescent rats the pressure-diuretic and pressure-natriuretic responses were slightly shifted to the right, so that diuresis and natriuresis were significantly lower at higher levels of RPP. Glomerular filtration rate was well autoregulated, and there were no differences between young and adult rats at each level of RPP. However, a significantly lower glomerular filtration rate was observed in senescent rats. These results indicate an age-related decline in the pressure-dependent sodium and water excretion that appears to be due to a decrease in glomerular filtration and an increase in tubular sodium reabsorption.

Proteasome subunits, low-molecular-mass polypeptides 2 and 7 are hyperexpressed by target cells in autoimmune thyroid disease but not in insulin-dependent diabetes mellitus: implications for autoimmunity

Autoimmune thyroid diseases (AITD) and insulin-dependent diabetes mellitus (IDDM) are two autoimmune syndromes of unknown etiology with common immune features. One is that the target cells, thyrocytes and pancreatic islet beta cells respectively, hyperexpress several proteins encoded in the HLA region: HLA class I, HLA class II and transporter associated with antigen processing (TAP-1): the clinical course and many aspects of the immunopathology are, however, quite different. Low-molecular-mass polypeptides 2 and 7 (LMP2 and LMP7) are proteasome subunits that increase the efficiency of endogenous antigen processing and are encoded in close vicinity to the TAP genes. We investigated whether LMP2 and LMP7 are hyperexpressed in thyrocytes and islet cells in AITD and IDDM. Thyroid tissue from Graves' disease patients (GD, n = 8) and Hashimoto thyroiditis (HT, n = 1) and pancreatic tissue from IDDM patients (n = 4) as well as control tissues were examined by the two-color indirect immunofluorescence technique. The results demonstrate that, in normal glands, thyrocytes and pancreatic islet cells express comparable moderate to low levels of LMP2 and LMP7. In AITD and IDDM, expression of LMP2/7 in the endocrine cells was disparate: while in AITD glands there was hyperexpression of LMP2 and 7 parallel to that of HLA class I and TAP-1, in the islet cells of recent onset diabetic pancreases (n = 2) the level of LMP2 and 7 expression was totally normal, including islets that were infiltrated by lymphocytes and hyperexpressed HLA class I and TAP-1. These observations suggest different mechanisms of endogenous peptides generation at the target cells in AITD from IDDM. Since this is a key step for the maintenance of peripheral tolerance, it may help to understand some of the different clinical features of the two autoimmune diseases.

Usefulness of cryohemolysis test in the diagnosis of hereditary spherocytosis

The clinical suspicion of hereditary spherocytosis (HS) must be confirmed at the clinical laboratory. The osmotic fragility test (OFT) and the autohemolysis test (AHT) are the worldwide accepted assays to establish a definite diagnosis of HS; however, they have some disadvantages. We describe herein our experience with the cryohemolysis test (CHT) as a tool to confirm the HS diagnosis. We included four groups of subjects, namely, patients with clinical HS, patients with mechanical heart valve prosthesis, malignant hematological diseases and healthy blood donors. CHT was carried out in all the groups, while OFT and AHT only in the HS patients and healthy individuals. OFT and AHT were performed according to previously described techniques. CHT was performed using red blood cells incubated in a hypertonic solution, preheated for 10 min and then transferred to an ice bath for an additional 10 min. The resulting cryohemolysis was determined measuring the free hemoglobin in the sample. There were no differences among the groups in terms of general characteristics. All HS suspicious patients had a positive OFT and AHT. CHT was positive in all patients from the HS group but in none of the subjects from the control groups (p < 0.001). We found that CHT is a faster and easier-to-perform assay compared with OFT and AHT. Moreover, using CHT, the zone between normal and abnormal results is wider than OFT or AHT. We propose 0.7 to 11% hemolysis as reference values for CHT.

Role of the renin-angiotensin system in the development of thyroxine-induced hypertension

OBJECTIVE

We evaluated the influence of chronic blockade of the renin-angiotensin system on hypertension induced by long-term thyroxin (T4) administration. To this end, we determined the effects of chronic treatment with captopril on blood pressure, cardiac hypertrophy and other renal and metabolic variables of hypertensive hyperthyroid rats.

METHODS

T4 was administered s.c. at 0.38 mumol/kg per day and captopril was given in the drinking water (1.38 mmol/l). Both treatments were maintained for 6 weeks. Control rats received tap water. After the treatment period, the rats were placed in metabolic cages. Later, blood pressure was measured in conscious rats by intra-arterial determination.

RESULTS

T4-treated rats showed an increased mean arterial pressure (MAP) whereas, in rats treated with T4 plus captopril, MAP was similar to that of the control group. Captopril did not affect the increased heart rate or ventricular weight/body weight ratio of hyperthyroid rats, but it improved the reduced creatinine clearance of these animals.

CONCLUSIONS

The elevation in blood pressure produced by long-term T4 administration was prevented by chronic blockade of the renin-angiotensin system. Captopril improved the renal function of hyperthyroid rats, but did not affect the relative cardiac hypertrophy of these animals.

Genetic variability and microdistribution of Triatoma infestans genotypes and Trypanosoma cruzi clones in Arequipa region (Peru)

The genetic variability of Triatoma infestans and Trypanosoma cruzi populations was studied by isoenzyme analysis in two distinct areas of Arequipa province (Peru); one, Santa Rita de Siguas, being an endemic area for Chagas' disease, the second, Arequipa, recently infected. Analysis of T. infestans genetic variability indicates, (i) temporal stability of genotypes found in Santa Rita de Siguas, (ii) high genetic differences between Arequipa and Santa Rita de Siguas populations suggesting minor contact between them, (iii) multiple origin of the T. infestans population in Arequipa, and (iv) poor dispersal capacity of T. infestans: the panmictic unit could be reduce to a house. Parasite isoenzyme analysis was performed in 29 Peruvian stocks of T. cruzi, mainly isolated from bugs taken in a single locality, Santa Rita de Siguas. The results show, (i) a high genetic polymorphism, (ii) nine different multilocus genotypes were detected and clustered in two different clades, (iii) most of the parasite isolates pertained to one of the clade and were genetically similar to those analyzed 12 years before. This sample allowed the study of the mating system of T. cruzi in strict sympathic conditions and gave more strength to the hypothesis of the clonal structure of T. cruzi populations.

Genetic disorders in normally androgenized infertile men and the use of intracytoplasmic sperm injection as a way of treatment

OBJECTIVE

To determine the incidence of chromosomal abnormalities in normally androgenized infertile men with no other recognized causes of infertility or who had ever been submitted to other unsuccessful methods of treatment.

DESIGN

Collaborative retrospective study of clinical experience collected by an endocrinologist and a geneticist over a 5-year period.

SETTING

Outpatients at an endocrinology clinic.

PATIENT(S)

Infertile male patients with azoospermia (n = 23), oligozoospermia (n = 66), and normozoospermia (n = 14) presenting normal (n = 85) or subnormal (n = 18) testicular volume.

INTERVENTION(S)

All patients were submitted to cytogenetic analysis.

MAIN OUTCOME MEASURE(S)

Two patients were referred to intracytoplasmic sperm injection (ICSI), and in one case, a successful gemellar pregnancy ended up uneventful. Children's genetic testing were not performed according to parents' request.

RESULT(S)

Abnormal karyotypes were found in 11 (10.6%) patients. Chromosomal abnormalities were found in 17.3% of the 23 azoospermic patients, in 10.6% of the 66 oligozoospermic patients, and in none of the 14 normozoospermic patients. These disorders were found only in patients with normal testicular volumes and no more than 10 x 10(6) spermatozoa per mL.

CONCLUSION(S)

A high incidence of chromosomal abnormalities was found in a selected group of normally androgenized infertile male patients. The elevated rate of fertilization achieved in one patient indicates that ICSI is, at the moment, the only choice for treatment of male infertility because of chromosomal abnormalities.

Endogenous inhibitor of Na-K-Cl cotransport system in inbred Dahl rats

Dahl salt-sensitive (DS) rats seem characterized by a ubiquitous increase in Na-K-Cl cotransport activity. Here, an endogenous inhibitor of the Na-K-Cl cotransport system (cotransport inhibitory factor, CIF) was investigated in inbred Dahl salt-sensitive (DS) and salt-resistant (DR) rats. The animals were orally loaded for 10 days with 2% NaCl. Plasma from salt-loaded DS rats inhibited cotransport with a 50% inhibition concentration value (IC50) of 6.4 +/- 0.6% (% plasma concentration, vol/vol) vs. 24.2 +/- 2.2% in DR rats (P < 0.0001). In urine, IC50 for cotransport inhibition was constantly lower in DS before and all during the whole salt-loading period (after 10 days of salt loading, IC50 was 2.59 +/- 0.11% and 6.00 +/- 0.24% in DS and DR rats, respectively; P < 0.0001). After 3 days of salt loading, higher salt appetite in DS rats magnified the differences in urinary CIF excretion. In erythrocytes from DS rats, increased cotransport activity was strongly correlated with urinary CIF excretion (r = 0.967). In conclusion, DS rats present increased plasmatic and urinary CIF levels. This can be a compensatory phenomenon to reduce cotransport hyperactivity and increased NaCl reabsorption at the thick ascending limb of Henle's loop.

Abnormal renal vascular reactivity to acetylcholine and nitroprusside in aging rats

1. The actions of acetylcholine (ACh), CaCl2 and nitroprusside (NP) were studied in aortic strips and in the perfused kidneys from adult (4-6 months old) and aging (23-24 months old) rats. 2. ACh and CaCl2 produced a dose-related relaxation in aortic strips from adult and old rats; maximal responses to both vasodilators were significantly reduced (ACh: adult = 66.4 +/- 6.1%, Old = 27.1 +/- 5.7%, P < 0.001; CaCl2: adult = 75.6 +/- 3.9%, Old = 54.1 +/- 4.1%, P < 0.01) in aortas from old rats. NP-evoked relaxation was not significantly different between the two groups. 3. In kidneys from adult rats, ACh produced dose-related decreases in renal perfusion pressure (RPP), whereas, in kidneys from old rats, ACh produced a dose-related decrease at low doses, and biphasic responses (vasodilatation followed by vasoconstriction) at medium to high doses, with a reduced vasodilator component. Vasodilator response to ACh to the highest dose; ACh; adult = 78.7 +/- 2.8%, Old = 40.6 +/- 2.6%, P < 0.001). In kidneys from adult rats, NP produced a dose-related decrease in RPP. However, in kidneys from old rats, NP produced vasoconstriction at low doses, biphasic responses at medium doses (vasoconstriction followed by vasodilation), and vasodilation at the highest dose. 4. The results of the present study demonstrated that: (a) The isolated perfused kidney from aging rats had a dual response (with an important vasoconstrictor component) to ACh and NP, which may be due to the release of a nonprostanoid vasoconstrictor or to abnormalities in the renal vascular smooth muscle. In contrast, in aortic-strips from old and adult rats, these agents only caused relaxation; (b) aging is accompanied by reduced endothelium-dependent relaxation both in large arteries and in resistance vessels; and (c) large arteries from aging rats require a higher concentration of extracellular calcium to stabilize the membrane of smooth muscle cells.

[Improvement of expected and final height in girls with central precocious puberty treated with gonadotropin releasing hormone analogues]

BACKGROUND

To evaluate the effect of GnRH-analogue triptoreline on the predicted adult height and final height in central precocious puberty (CPP).

PATIENTS AND METHODS

The study included 14 girls with CPP treated for 1-6 years with triptoreline depot (75 micrograms/kg/28 days/i.m.; group 1). The criteria for diagnosis included the following: compelling evidence of rapid progression of puberty, with a bone age (BA) greater than 2 SD above the mean value for chronological age (CA) associated with poor initial predicted final height and growth speed greater than 2 SD above the mean value for age. In addition we obtained data from 6 untreated girls with advanced puberty and good predicted adult height followed during the same period of time (group II). 7 of 14 girls of group I and 5 of 6 girls of group II attained final height.

RESULTS

A decrease in growth speed and an increase and in CA/BA ratio were observed after three years of treatment (+4.9 +/- 0.7 SD to -1.45 +/- 2.63 SD and 0.62 +/- 0.14 to 0.74 +/- 0.09 respectively; P = 0.034; n = 6). The predicted adult height increased significantly after two years of treatment (153.1 +/- 4.49 to 156.94 +/- 5 cm; p = 0.041; n = 10) and was more evident after three years of treatment (153.84 +/- 5.77 to 160.7 +/- 7.5 cm; p = 0.03; n = 6). The final height of 7 girls of group I who attained it was similar to target height (161 +/- 3.1 vs. 159 +/- 1.3 cm; NS) and greater than initial predicted adult height (161 +/- 3.1 vs. 154 +/- 2.1 cm; p = 0.044) and than final height of the 5 girls of group II (161 +/- 3.1 vs. 154.28 +/- 6.1 cm).

CONCLUSIONS

Triptorelin depot improves predicted adult height and final height of girls with early central puberty may be over their target height.

Effects of methimazole in the early and established phases of NG-nitro-L-arginine methyl ester hypertension

In the present study we evaluated the effects of methimazole, an antithyroid drug, on blood pressure and other variables in the early and established phases of hypertension induced by the inhibition of nitric oxide synthesis with the oral administration of NG-nitro-L-arginine methyl ester (L-NAME), 75 mg/100 ml in the drinking water. Moreover, we also evaluated the acute pressor effect of L-NAME on systemic blood pressure in control and rats treated chronically with methimazole, administered via drinking water (30 mg/100 ml). Oral administration of methimazole maintained the blood pressure of L-NAME-treated rats at normal levels 25 days after induction of hypertension. However, after 25 days of methimazole treatment in rats made hypertensive with L-NAME (for 25 days), high blood pressure was similar in methimazole-treated and non-treated L-NAME rats, despite the fact that a hypothyroid state had been achieved in the methimazole-treated rats. Acute intravenous injection of L-NAME caused a similar increase in mean arterial pressure in control and methimazole-treated rats at the lowest dose; however, smaller pressor responses were observed with increasing doses in hypothyroid rats. These results clearly demonstrate that hypothyroidism induced by methimazole prevents, but does not reverse, L-NAME hypertension and reduces the acute pressor responsiveness to L-NAME administration.

Trypanosoma cruzi: study of the distribution of two widespread clonal genotypes in Bolivian Triatoma infestans vectors shows a high frequency of mixed infections

The detection of two widespread Trypanosoma cruzi clonal genotypes (20 and 39) in feces of Bolivian specimens of the vector Triatoma infestans was performed by a combination of polymerase chain reaction and clone-specific DNA hybridization. The hybridization pattern of 186 PCR positive samples cf T. infestans feces collected in two Bolivian departments identified clone 20 in 74.2% and clone 39 in 63.4% of the triatomine bugs. For the first time, a high percentage (mean: 43.2 +/- 26%) of mixed infections (presence of both clones in a given fecal sample) in various localities was recorded. Results were in agreement with the two assumptions of independent transmission of clones 20 and 39 and of the absence of selection in the natural cycles under survey. Statistical analysis of the geographical distribution of clones 20 and 39 favored the hypotheses that the frequencies of T. cruzi natural clones are different among localities and that these differences are not proportional to the distances that separate the localities. The epidemiological significance of these results is discussed.

Photodegradation of bezafibrate in aqueous media. Studies of its in vitro phototoxicity

Aqueous solutions of the antihyperlipoproteinemic drug bezafibrate (CAS 41859-67-0) are photolabile towards UV-B light under aerobic conditions. Two compounds were isolated and identified spectroscopically as well as by alternative synthesis as the only photoproducts formed. Their formation involves primary cleavage of the aryloxy-carbon bond and decarboxylation followed by hydrogen abstraction or dimerization. Bezafibrate is phototoxic in vitro as indicated by the photohemolysis test. Furthermore bezafibrate photo-sensitizes peroxidation of linoleic acid as monitored by the UV detection of dienic hydroperoxides. Partial inhibition of these processes on addition of butylated hydroxyanisole (BHA), reduced glutathione (GSH), sodium azide (NaN3) or 1,4-diazabicyclo [2.2.2] octane (DABCO) suggests the involvement of type I as well as type II mechanisms.

Advantages of using a cell separator and metrizamide gradients for human islet purification

Human islet transplantation has a high rate of failure, often due to primary nonfunction, which suggests that islets are damaged during the processing of the pancreas. The preparation of human islets for transplantation is still a complex process that requires large teams of surgical and laboratory personnel. To overcome this problem, we have adopted the use of the IBM 2991 COBE cell separator and a metrizamide/Ficoll density medium that is easy to prepare. Twenty-seven pancreatic glands have been processed using the COBE cell separator, 23 of which were purified in metrizamide/Ficoll gradients and 4 in bovine serum albumin gradients. The results show an improvement of recovery and viability in these preparations when compared retrospectively with manual gradients. More importantly, the time required for purification was shortened to one fourth the usual time and total processing time is about half as long. Moreover, a team of two laboratory staff was regularly able to prepare islets for transplantation, reducing the separation time from 7 hr to 3.5 hr. We conclude that the automatic cell separator and metrizamide-based separation medium are useful modifications of current islet purification methods.

A radioimmunoassay for the tripeptide Gly-Trp-Met, a major metabolite of endogenous cholecystokinin in brain

We developed a specific and sensitive radioimmunoassay for the tripeptide Gly-Trp-Met (GWM) after its derivatization with p-benzoquinone. Measurable amounts of endogenous GWM-like immunoreactivity (GWM-ir), coeluting in HPLC with authentic GMW were detected in the medium of depolarized slices of rat cerebral cortex. The tripeptide GWM appears as the major inactive CCK-8 metabolite since a major fraction of CCK-8-ir released from the slices was apparently recovered in the medium as GWM. In addition, in the presence of the serine reagent diisopropylfluorophosphate, a strong decrease of GWM formation was observed to accompany the corresponding increase of CCK-8-ir recovery in medium. The present study confirms that (a) serine peptidase(s) is(are) responsible for inactivating endogenous CCK-8 in brain as previously proposed (Rose et al. Proc Natl Acad Sci USA 1988; 85:8326).

Expression of transporter associated with antigen processing-1 in the endocrine cells of human pancreatic islets: effect of cytokines and evidence of hyperexpression in IDDM

A possible role of transporter associated with antigen processing (TAP)-1 in the pathogenesis of IDDM has been investigated by examining the level of TAP-1 expression in the islets of IDDM pancreas and by studying in vitro the effect of interferon (IFN)-gamma, IFN-alpha, and tumor necrosis factor-alpha in TAP-1 expression by cultured islet cells. A remarkable hyperexpression of TAP-1 has been found in the endocrine cells (beta and non-beta) of IDDM islets, which constitutes first evidence of hyperexpression of this molecule in the target organ of an autoimmune disease. TAP-1 hyperexpression correlated clearly with HLA class I hyperexpression but only very partially with HLA class II ectopic expression. IFN-gamma and IFN-alpha, both cytokines putatively implicated in IDDM pathogenesis, were capable of inducing TAP-1 protein (as assessed by immunofluorescence flow cytometry) and message (by Northern blot analysis and reverse transcription polymerase chain reaction). These findings suggest that under the influence of cytokines (most probably IFN-alpha) beta-cells may express in their surface a high density of HLA class I-peptide complexes that may facilitate their recognition and lysis by low-affinity CD8+ T-cells.

The tumor association of a trisaccharide epitope: specificity of antiserum developed to galactose beta1->3 N-acetyl glucosamine beta1-->3 galactose

A pentasaccharide carbohydrate epitope described by Nozawa et at (1) is expressed by 35% of the neoplastic tissue samples from patients with endometrial cancer but not by normal endometrium. This epitope was detected using a human monoclonal antibody (HMST-1) produced by fusion of lymphocytes from an endometrial cancer patient. We chemically linked a synthetically produced nonreducing terminal trisaccharide portion of this pentasaccharide to bovine serum albumin to create an effective immunogen, Galbeta1->3GlcNAcbeta1->3Gal-BSA. A rabbit polyclonal antibody was produced and tested against panels of tumor and normal tissues. In contrast to the results obtained with HMST-1, 100% of the endometrial adenocarcinomas we studied stained with this polyclonal antiserum while normal endometrium was non-reactive. The reactivity with other tyes of adenocarcinomas was approximately 80%, whereas most normal tissues were not reactive with the antiserum. Immunological specificity analysis was performed with structurally related carbohydrates and this shows the fine specificity reaction of the antiserum. This antigen may be clinically useful for immunolocalization and for immunotargeting.

Characterization and inhibition of a cholecystokinin-inactivating serine peptidase

A cholecystokinin (CCK)-inactivating peptidase was purified and identified as a membrane-bound isoform of tripeptidyl peptidase II (EC 3.4.14.10), a cytosolic subtilisin-like peptidase of previously unknown functions. The peptidase was found in neurons responding to cholecystokinin, as well as in non-neuronal cells. Butabindide, a potent and specific inhibitor, was designed and shown to protect endogenous cholecystokinin from inactivation and to display pro-satiating effects mediated by the CCKA receptor.

Renal vascular reactivity to ATP in hyper- and hypothyroid rats

The effects of adenosine triphosphate (ATP) on the renal vasculature of isolated kidneys from control, hyper- and hypothyroid rats were characterized. ATP responsiveness was evaluated in basal tone and in raised tone (phenylephrine 10(-6) M) preparations. These responses were compared with those obtained with barium chloride or sodium nitroprusside (SNP), used respectively as nonreceptor agonist for vasoconstriction or vasodilation. In preparations at basal tone, ATP produced dose-related vasoconstriction, which was increased in hyperthyroid kidneys, and was severely attenuated in kidneys from hypothyroid rats. In raised tone preparations from control rats ATP produced a dual response: vasoconstriction at low doses, which declined with increasing doses to give way to vasodilator responses; biphasic responses were found in some kidneys. Hyperthyroid kidneys showed increased pressor responses and a vasodilator response similar to those seen in kidneys from control rats. However, in hypothyroid kidneys the vasodilator response was abolished. The responses to barium chloride and to SNP were significantly increased and decreased in hyper- and hypothyroid kidneys, respectively; vasoconstrictor responses to SNP were also found in hypothyroid kidneys. Hence the abnormal responses to ATP observed in both thyroid dysfunctions may be partially explained by unspecific alterations in the contractile machinery of the renal vasculature in these kidneys. However, ATP responsiveness (vasoconstriction at low tone and vasodilation at raised tone) was more severly affected in hypothyroid kidneys, suggesting that purinergic (P2X and P2Y) receptor activity may be decreased in these organs.