Biomedical subjects
Publications and source records attributed to J Benitez.
Mutations in the yeast fructose 1,6 biphosphatase structural gene severely reduced expression of a fructose 1,6 biphosphatase-endoglucanase A hybrid protein introduced into yeast on multicopy or centromeric vectors. Upon glucose limitation the mutant yeasts were incapable of de-repressing endoglucanase A synthesis.
The recently developed strategy for the detection of monoclonal B-cell populations, based on the selective amplification of predominant immunoglobulin heavy chain gene (IgH) rearrangement, is seen to be a suitable alternative to Southern blot analysis. The new technique uses a pair of consensus primers for variable (VH) and joining (JH) regions. We first tested the accuracy of this new approach on a broad series of 67 samples that had been well characterized by both Southern blot and immunohistochemical techniques before being subjected to blind testing. Our results show that this technique gave 100% specificity (absence of false-positive results) and approximately 70% sensitivity (30% false-negative results). The only exception was the presence of an IgH polymerase chain reaction ambiguous result in a case of Sezary's syndrome. The polymerase chain reaction technique was then applied to a panel of 27 frozen gastric endoscopy biopsy specimens following previous clinical suspicion of lymphoma. Monoclonality was detected in nine of 13 samples previously diagnosed as lymphomas and in one of two carcinomas. Further examination of the gastrectomy specimen in the latter case disclosed a B-cell lymphoma associated with the carcinoma. In spite of its limited sensitivity, the high specificity attained by this technique in the detection of monoclonality makes it a useful adjunct to routine morphologic criteria, as it is sometimes capable of detecting true positive cases that conventional morphology studies show to be negative.
Retinitis pigmentosa is a group of clinically and genetically heterogeneous retinopathies and a significant cause of worldwide visual handicap. We have typed DNA from members of a Spanish family segregating an autosomal dominant form of retinitis pigmentosa (adRP) using a large series of simple sequence polymorphic markers. Positive two-point lod scores have been obtained with fifteen markers including D7S480 (theta max = 0.00, Zmax = 7.22). Multipoint analyses using a subset of these markers gave a lod score of 7.51 maximizing at D7S480. These data provide definitive evidence for the localisation of an adRP gene on chromosome 7q, and highlight the extensive genetic heterogeneity that exists in the autosomal dominant form of this disease.
D1 dopamine receptors are present on terminals of striatal neurons to the pars reticulata of the substantia nigra in the rat. Here we have studied the effect of the activation of these receptors on the synthesis of gamma-aminobutyric acid (GABA) in slices of the pars reticulata of the substantia nigra isolated from 6-hydroxydopamine-lesioned rats. The synthesis was judged by the accumulation of GABA after inhibiting GABA transaminase with aminooxyacetic acid. Both dopamine and SCH 23390, a D1 agonist, stimulated the synthesis. The effect of both compounds was blocked by SCH 23390, a D1 antagonist, but not by sulpiride, a D2 antagonist. In the absence of receptor activation, the synthesis was very slow. The results suggest a trophic influence of dopamine upon the synthesis of GABA via D1 receptors.
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Four of the five open reading frames (ORFs) present in Myobacterium fortuitum pAL5000 plasmid (ORF1, ORF3, ORF4, and ORF5) are dispensable for replication in M. fortuitum. However, two additional ORFs (ORF1 and ORF5) were necessary for replication in a Myobacterium smegmatis heterologous host containing an efficient plasmid transformation mutation.
A comparison between cytogenetic and molecular results of t(14;18) has been performed in 12 patients with follicular lymphomas: five nodular and seven diffuse. Ten cases showed cytogenetic alterations with different markers, including a 14q+ in eight: in four it was the result of a t(14;18). Molecular analysis by Southern blotting with bcl2 probes from major and minor cluster regions, and PCR with primers from major and minor regions showed differences versus the cytogenetic results. The correlation found between cytogenetic and molecular results suggests other factors, such as geographical differences or different pathogenetic mechanisms, more than methodologic aspects, to explain the different frequencies of this marker among countries.
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The debrisoquine oxidation phenotype was assessed in 137 healthy Italian volunteers and in 41 drug-free schizophrenic patients. A bimodal distribution of the urinary debrisoquine/4-hydroxydebrisoquine metabolic ratio was observed in healthy volunteers. Ten subjects were identified as poor metabolizers, yielding a frequency of 7.3% which is similar to that reported in other European countries. The prevalence of the poor metabolizer phenotype was 9.8% among schizophrenic patients. This indicates that there is no association between polymorphic drug oxidation and schizophrenic disorder. Treatment with chlorpromazine (100 or 150 mg daily) significantly increased the debrisoquine metabolic ratio in nine patients (P less than 0.01). These results confirm that neuroleptics of the phenothiazine class inhibit the oxidative metabolism of debrisoquine.
Retinitis Pigmentosa (RP) is a group of inherited retinopathies which affect approximately 1 in 4,000 individuals. The disorder can be classified on the basis of inheritance; dominant, recessive and X-linked forms have been well documented. The existence of genetic heterogeneity within autosomal dominant RP (adRP) had been previously demonstrated. As a result of extensive linkage studies in 2 large Irish families and 1 American pedigree three adRP genes have been mapped. adRP genes have been localised to chromosome 3q close to the rod photoreceptor gene, rhodopsin; to chromosome 6p close to another transmembrane photoreceptor gene, peripherin/RDS and to the pericentric region of chromosome 8, although the causative gene in this region has not yet been identified. Here we report the results of a linkage study in a Spanish family, who exhibit an early-onset form of adRP. The adRP gene segregating in this family has been excluded from the three known adRP loci on chromosomes 3q, 6p and 8 using a series of both intragenic microsatellite markers from the rhodopsin and peripherin/RDS genes and markers flanking the three known loci. These results provide definitive evidence for the existence of a fourth adRP locus, further emphasising the genetic heterogeneity that exists within adRP.
A morphological, immunophenotypic and ultrastructural study, cell cycle estimation, DNA and cytogenetic analysis were performed in ten cases of B-MALT lymphomas. Five had low grade lymphoma and five had high grade. Low and high grade cases showed the same cells but in different percentages: These included centrocyte-like cells with occasional monocytoid cytoplasmic changes, and centroblast-like cells. However, in high grade cases more dysplastic and large cells were present. All cellular types showed an important development of rough endoplasmic reticulum. In all cases a large panel of monoclonal antibodies was employed to study the B-cell immunophenotype. Ki-67 positivity ranged from 5% to 30% in low-grade cases and from 50% to 70% in high-grade cases. Gene rearrangement analysis showed rearrangement with Jh probe and half of the cases were also rearranged with the Kde probe (Kappa constant chain gene). A rearrangement banding pattern with TCR genes was not present in any of the cases. Cytogenetic study showed complex alterations in high grade cases and a normal karyotype in low grade lymphomas. Only one case had rearrangement for the bcl-2 probe.
Experimental evidence indicates that angiotensin II can modulate sodium channel and gap junction function. This raises the possibility that variations in angiotensin II could alter the effect of drugs that act on these mechanisms. In this study, the influence of changing salt status and angiotensin II activity has been investigated by evaluating the QRS prolonging effects of the sodium channel blocking drug, desmethylimipramine. In control rats with a normal salt intake, intravenous infusion of desmethylimipramine (0.8 mg/kg/min) over 60 min increased QRS duration over time to 150% of control by 60 min; mean arterial blood pressure and pulse rate were decreased. In salt-deplete rats, the response to desmethylimipramine was similar to controls for 30 min. Thereafter, QRS duration increased more rapidly than controls. In rats on a high salt diet, the same desmethylimipramine infusion produced no change in QRS duration for 30 min, despite equivalent reductions in mean arterial blood pressure. Thereafter, QRS duration increased, reaching values similar to control by 60 min. In rats on a normal salt diet pretreated with captopril, there was a similar blunting of the QRS response to desmethylimipramine to that observed in salt-loaded rats. The QRS response to desmethylimipramine and salt-loaded rats on normal salt diets receiving captopril returned to the control pattern after a subpressor infusion of angiotensin II (3 ng/min), while a higher rate of angiotensin II (10 ng/min) further enhanced the QRS prolonging effect of desmethylimipramine. These data demonstrate that endogenous angiotensin II contributes to the regulation of the cardiac electro-physiological response to DMI.
UNLABELLED: One hundred patients with occult gastrointestinal bleeding (OGIB) (i.e., guaiac-positive stools and/or iron deficiency anemia) were prospectively evaluated with bidirectional endoscopy [upper endoscopy (EGD) and colonoscopy] to determine the origin of occult bleeding. Predetermined criteria were used to prospectively define gastrointestinal bleeding sources. Among the 58 males and 42 females, the median age was 65 yr. Thirty-one percent of the group had gastrointestinal symptoms. Sixty-six percent of the study group were inpatients. Bidirectional endoscopy detected the source of OGIB in 53% of patients, with a positive finding on EGD of 36%, and with colonoscopy, of 26%. In only 9% of patients was a source of OGIB detected on both EGD and colonoscopy. Acid peptic disease accounted for the source of OGIB in 27%, colonic adenomas 14%, angiodysplasia 13%, colorectal carcinoma 6%, and gastric cancer in 1% of patients. The diagnostic yield was significantly higher with EGD than with colonoscopy in patients with anemia and guaiac-positive stools (45% vs. 26%, p less than 0.01). Upper endoscopy directed a change in patient management in 29 patients. IN CONCLUSION: for the patient population described in this study, bidirectional endoscopy determined the source of OGIB in 50%. As expected, colonoscopy resulted in a higher cancer detection rate than EGD--yet EGD detected the origin of OGIB in 68% (36/53) of patients found to have an occult bleeding source, and resulted in a therapeutic initiation or a change in therapy for 30% of all patients.
We have constructed a set of replicating and integrating vectors that allow expression and secretion of Clostridium thermocellum endoglucanase A in Saccharomyces cerevisiae using the alpha-factor or the invertase promoters and secretion signals. The enzyme expressed in yeast was enzymatically active regardless of its degree of glycosylation and was released into the culture medium. One advantage of using this experimental system is that secretion of the reporter enzyme can be detected in individual colonies facilitating the isolation of mutants. A second advantage is that transit through the secretory pathway, as judged from the extent of glycosylation, can be easily monitored by staining for enzyme activity in agar replicas of polyacrylamide gels.
The debrisoquine oxidation phenotype was determined in 91 schizophrenic patients on monotherapy with different neuroleptics and in 67 untreated healthy volunteers. The prevalence of poor metabolizers of debrisoquine was significantly higher in the patients (46.2%) than in the healthy subjects (7.5%). Treatment with phenothiazine antipsychotics (chlorpromazine, levomepromazine and thioridazine) was associated with a higher debrisoquine metabolic ratio than treatment with haloperidol. On the other hand, treatment with clothiapine appeared not to interfere with debrisoquine oxidation. Oral administration of 50 mg thioridazine daily to 8 healthy subjects resulted in a marked increase in the debrisoquine metabolic ratio and 4 of them were transformed into phenotypically poor metabolizers. The results confirm the fact that phenothiazines, and to a lesser extent haloperidol, inhibit the oxidative metabolism of debrisoquine. They show also that clothiapine administration does not disturb the debrisoquine metabolic ratio.
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