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Biomedical subjects

M A Rubin

Publications and source records attributed to M A Rubin.

At least 91 records · Page 5Linked to original sources
PubMed1997

Effect of guanine nucleotides on [3H]glutamate binding and on adenylate cyclase activity in rat brain membranes.

GMP-PNP, a non-hydrolyzable analog of GTP binds tightly to G-protein in the presence of Mg2+, so that the binding is stable even after exhaustive washings. This property was exploited to prepare membrane samples of rat brain where G-protein GTP-binding sites were saturated with GMP-PNP. Experiments carried out with these membranes showed that GTP, GMP-PNP, GDP-S and GMP (1 mM) inhibit the sodium-independent [3H]glutamate binding by 30-40% [F(4,40) = 5.9; p < .001], whereas only GMP-PNP activates adenylate cyclase activity [F(6,42) = 3.56; p < .01]. The inhibition of sodium-independent [3H]glutamate binding occurred in the absence of Mg2+. These findings suggest that guanine nucleotides may inhibit glutamate binding and activate adenylate cyclase through distinct mechanisms by acting on different sites.

Adenylyl Cyclases↗
PubMed1997

Effects of methylmalonate and propionate on [3H]glutamate binding, adenylate cyclase activity and lipid synthesis in rat cerebral cortex.

The effects of methylmalonic (MMA) and propionic acid (PPA), metabolites that accumulate in methylmalonic and propionic acidemia respectively, on [3H]glutamate binding, adenylate cyclase activity and [U-14C]acetate incorporation into lipids were investigated in rat cerebral cortex. Neither acid effected [3H]glutamate binding, regardless of the presence of sodium in the incubation medium. Also, the acids had no effect on basal or GMP-PNP-stimulated adenylate cyclase activity. These results suggest that MMA and PPA do not interact with glutamate binding sites and have no effect on basal or guanine nucleotide-stimulated adenylate cyclase activity. In contrast, [U-14C]acetate incorporation into brain lipids was significantly blocked by both acids, the effects being more pronounced with PPA, indicating an inhibition of brain lipid biosynthesis caused by MMA and PPA. These results may explain at least in part the hypomyelinization and/or demyelinization characteristic of patients affected by methylmalonic acidemia and propionic acidemia.

Acetates↗
PubMed1997

Intravascular large cell lymphoma coexisting within hemangiomas of the skin.

Intravascular lymphomatosis is a rare and peculiar subtype of large cell lymphoma. The authors present the pathologic, clinical, and radiologic findings of a patient with intravascular large cell lymphoma coexisting within hemangiomas of the skin. Initially the lymphoma was clinically confined to the hemangiomas and the patient was closely observed for disease progression. Within 10 months the patient developed disseminated lymphoma involving both adrenals. A clinical remission was achieved, but the patient soon relapsed, and despite further chemotherapy he died with disseminated disease 23 months after the initial diagnosis. This report presents the only known case of an intravascular large cell lymphoma coexisting within a vascular lesion and highlights the potential aggressive nature of intravascular lymphomas.

Adrenal Gland Neoplasms↗
PubMed1996

GMP reverses the facilitatory effect of glutamate on inhibitory avoidance task in rats.

Previous studies have demonstrated that post-training intrahippocampal glutamate administration improves inhibitory avoidance task performance in rats. Antagonism of the agonist actions of glutamate by guanine nucleotides has been shown at the molecular and behavioural level. In the present investigation we demonstrate that intrahippocampal co-administration of GMP (guanosine 5'-monophosphate) reverses the facilitatory effect of glutamate on the inhibitory avoidance learning paradigm and inhibits [3H]glutamate binding in hippocampal synaptic plasma membranes. These results suggest that guanine nucleotides may modulate glutamate actions.

Analysis of Variance↗
PubMed1996

Intrastriatal methylmalonic acid administration induces rotational behavior and convulsions through glutamatergic mechanisms.

The effect of intrastriatal administration of methylmalonic acid (MMA), a metabolite that accumulates in methylmalonic aciduria, on behavior of adult male Wistar rats was investigated. After cannula placing, rats received unilateral intrastriatal injections of MMA (buffered to pH 7.4 with NaOH) or NaCl. MMA induced rotational behavior toward the contralateral side of injection and clonic convulsions in a dose-dependent manner. Rotational behavior and convulsions were prevented by intrastriatal preadministration of MK-801 and attenuated by preadministration of succinate. This study provides evidence for a participation of NMDA receptors in the MMA-induced behavioral alterations, where succinate dehydrogenase inhibition seems to have a pivotal role.

Animals↗
PubMed1996

Therapeutic effectiveness of the immunity elicited by P815 tumor cells engineered to express the B7-2 costimulatory molecule.

It is well accepted that inoculation of B7-1-transfected tumor cells into normal mice leads to tumor rejection and subsequent resistance to challenge. However, the effectiveness of B7-2-transfected tumor cells in eliciting protective antitumor immunity is less clear. Here we show that B7-2-transfected P815 tumor cells (B7-2+) are as effective as B7-1-transfected P815 tumor cells (B7-1+) in eliciting protective immunity in normal DBA/2 mice. In addition, B7-2+ cells were found to be at least as effective as B7-1+ cells retarding tumor progression when admixed with parental P815 tumor cells prior to inoculation into normal mice. Moreover, the B7-2+ cells and the B7-1+ cells were equivalent in their ability to retard tumor growth when administered peritumorally into mice bearing established (approx. 3 mm in diameter) parental P815 tumors. Finally, P815 tumor cells infected with a recombinant replication-defective adenovirus encoding the murine B7-2 gene were effective in retarding the growth of established parental P815 tumors. Thus, B7-1 and B7-2 are comparable in terms of their ability to stimulate the generation of tumor-eradicating immunity in normal mice as well as in mice bearing established parental tumors. Moreover, adenovirus vectors can be used to generate B7-2-expressing tumor cells effective in the immunotherapy of established parental tumors.

Adenoviridae↗
PubMed1996

Giant malignant fibrous histiocytoma of the testis/spermatic cord: psychologic and possible etiologic complications of unethical Nazi medical experimentation.

This case of malignant fibrous histiocytoma of the testis/spermatic cord was found in a Holocaust survivor who was injected with an unknown substance in the left testicle while in Auschwitz concentration camp in 1943. Because malignant fibrous histiocytoma is a neoplasm rarely found in this location, with only 26 previously reported cases, a review of this entity was performed. A review of Nazi medical practices in the literature and through the Holocaust Museum research department was undertaken in an attempt to ascertain identification of the unknown substance injected into this patient; however, exact identification of the Auschwitz experiment or experimenter could not be determined. A left radical orchiectomy was performed, and subsequent histolopathologic review revealed a well-encapsulated 27 x 22 x 17-cm malignant fibrous histiocytoma. The left testis was not clearly identified due to necrosis of the tumor. This is the largest malignant fibrous histiocytoma of the spermatic cord/testis recorded in the literature to date. Based on the unusual location and size, the intratesticular injection probably contributed to the tumor development and certainly caused the patient's delay in seeking medical treatment.

Aged↗
PubMed1996

The role of the reverse-transcriptase polymerase chain reaction assay for prostate-specific antigen in the selection of patients for radical prostatectomy.

Prostate cells present in the peripheral circulation can be detected using an enhanced reverse-transcriptase polymerase chain reaction (RT-PCR) for prostate-specific antigen (PSA) assay. In one study, preoperative enhanced RT-PCR for PSA status was a significant predictor of surgical pathology and postoperative biomechanical recurrence. The use of RT-PCR may enhance the urologist's ability to stage potential candidates for radical prostatectomy, as the assay is a more sensitive and specific predictor of microscopic extracapsular extension than conventional staging modalities. This highly adaptable assay also may have roles in screening for recurrence and in staging other solid tumors.

Adenocarcinoma↗
PubMed1996

Corpus callosum morphology in children with Tourette syndrome and attention deficit hyperactivity disorder.

The aim of this study was to investigate the morphology of the corpus callosum (CC) in Tourette syndrome (TS) and attention deficit hyperactivity disorder (ADHD) to determine whether these conditions affect distinct regional differences. Seventy-seven children and adolescents, aged 6 to 16 years, comprised the four research groups--16 patients with TS, 21 patients with TS plus ADHD, 13 patients with ADHD, and 27 unaffected control subjects. A semiautomated, computer-assisted procedure was used to measure the total area, five subregions, centerline length, perimeter, and bending angle of the CC. MRI data were analyzed using several statistical methods, primarily two-tailed analysis of variance to test the effects of TS and ADHD status, while controlling for the influence of age, gender, and total intracranial area (an estimate of brain size). TS was associated with significant increases in the area of four of five subdivisions, the total area, and the perimeter of the CC. ADHD was associated with a significant decrease in the area of the rostral body. There were no interactions between TS and ADHD factors. These findings suggest that the area of the CC is larger in children with TS, and that this difference is independent of age, handedness, intracranial area, and the diagnosis of ADHD. Our findings support hypotheses that the neurobiologic mechanisms in TS and ADHD involve frontal/subcortical circuits.

Adolescent↗
PubMed1996

Oral condyloma acuminatum associated with human papillomavirus and p53 overexpression mimicking cyclosporine effect in a transplant patient.

A case of human papillomavirus-associated condyloma acuminatum in the oral cavity, presumed to be fulminant cyclosporine-induced gingival hyperplasia, is reported in a 55-year-old cardiac transplant patient. Approximately 47 months following the transplant, the patient developed severe hyperplasia of the uvula and oral mucosa, resulting in difficulty swallowing. The histopathologic features of the lesion were typical of those of condyloma acuminatum. In situ hybridization of the paraffin-embedded material revealed infection with human papillomavirus types 6/11. This case lends further support to the putative role of long-term cellular immunosuppression in the development of human papillomavirus-associated squamous lesions. In addition, positive staining for p53 protein raises the possibility of concomitant p53 involvement in the pathogenesis of this oral lesion.

Condylomata Acuminata↗
PubMed1995

Neurochemical effects of L-pyroglutamic acid.

The effect of L-pyroglutamic acid, a metabolite that accumulates in pyroglutamic aciduria, on different neurochemical parameters was investigated in adult male Wistar rats. Glutamate binding, adenylate cyclase activity and G protein coupling to adenylate cyclase were assayed in the presence of the acid. L-pyroglutamic acid decreased Na(+)-dependent and Na(+)-independent glutamate binding. Basal and GMP-PNP stimulated adenylate cyclase activity were not affected by the acid. Furthermore, rats received unilateral intrastriatal injections of 10-300 nmol of buffered L-pyroglutamic acid. Vehicle (0.25 M Tris-Cl, pH 7.35-7.4) was injected into the contralateral striatum. Neurotoxic damage was assessed seven days after the injection by histological examination and by weighing both cerebral hemispheres. No difference in histology or weight could be identified between hemispheres. These results suggest that, although capable of interfering with glutamate binding, pyroglutamate did not cause a major lesion in the present model of neurotoxicity.

Adenylyl Cyclases↗
PubMed1995

Cardiac papillary fibroelastoma: an immunohistochemical investigation and unusual clinical manifestations.

Cardiac papillary fibroelastoma (CPF) is a morphologically distinctive, but rare, cardiac lesion that is usually found incidentally at autopsy or during open heart surgery. Because of improved diagnostic imaging techniques, the premortem or preoperative diagnosis of CPF is becoming more frequent. The histogenesis of CPF, however, remains controversial. Herein we report an immunohistochemical investigation of 11 cases of CPF; two cases showed unusual embolization phenomena, including one with histologically documented pulmonary arterial embolism. For comparison, nine cardiac myxomas (CMs) and eight examples of organizing thrombi were also studied. Immunohistochemical markers included keratin, vimentin, collagen type IV, muscle-specific actin, desmin, factor VIII-related antigen, CD34, and S-100 protein. The cells covering the surface of both CPFs and CMs were positive for vimentin, factor VIII-related antigen, and CD34, in keeping with their presumed vascular endothelial origin. Interestingly, the surface lining cells were also positive for S-100 protein in all CPF and in eight of nine CMs. In CPF, collagen type IV showed multilayered linear staining beneath the surface that was virtually identical to the staining pattern for elastic tissue. The major immunophenotypic difference between CPF and CM is the frequent presence of muscle-specific actin in the stellate cells of the stroma in CM but not in CPF. Although this study did not clarify whether CPF is a hamartomatous, neoplastic, or reparative process, it demonstrated active participation of the surface endothelial lining cells with excessive formation of basal membrane material in the formation of CPF.

Adult↗
PubMed1994

Effects of strength training on total and regional body composition in older men.

The effects of a 16-wk strength-training program on total and regional body composition were assessed by dual-energy X-ray absorptiometry (DEXA), magnetic resonance imaging (MRI), and hydrodensitometry in 13 untrained healthy men [60 +/- 4 (SD) yr]. Nine additional men (62 +/- 6 yr) served as inactive controls. The strength-training program resulted in substantial increases in both upper (39 +/- 8%; P < 0.001) and lower (42 +/- 14%; P < 0.001) body strength. Total fat-free mass (FFM) increased by 2 kg (62.0 +/- 7.1 to 64.0 +/- 7.2 kg; P < 0.001), and total fat mass decreased by the same amount (23.8 +/- 6.7 to 21.8 +/- 6.0 kg; P < 0.001) when measured by DEXA. When measured by hydrodensitometry, similar increases in FFM (61.3 +/- 7.8 to 63.0 +/- 7.6 kg; P < 0.01) and decreases in fat mass (23.8 +/- 7.9 to 22.1 +/- 7.7 kg; P < 0.001) were observed. When measured by DEXA, FFM was increased in the arms (6.045 +/- 0.860 to 6.418 +/- 0.803 kg; P < 0.01), legs (19.416 +/- 2.228 to 20.131 +/- 2.303 kg; P < 0.001), and trunk (29.229 +/- 4.108 to 30.134 +/- 4.184 kg; P < 0.01), whereas fat mass was reduced in the arms (2.383 +/- 0.830 to 2.128 +/- 0.714 kg; P < 0.01), legs (7.583 +/- 1.675 to 6.945 +/- 1.551 kg; P < 0.001), and trunk (12.216 +/- 4.143 to 11.281 +/- 3.653 kg; P < 0.01) as a result of training.(ABSTRACT TRUNCATED AT 250 WORDS)

Absorptiometry, Photon↗
PubMed1994

Effects of strength training on bone mineral density: hormonal and bone turnover relationships.

The effects of a 16-wk strength-training program on bone mineral density (BMD) was assessed by dual-energy X-ray absorptiometry in 21 men [age 61 +/- 1 (SE) yr]. Sixteen men (age 59 +/- 2 yr) served as control subjects. To investigate the possible hormonal relationships underlying the effects on BMD, serum concentrations of growth hormone, insulin-like growth factor I, and testosterone were determined before and after training. In addition, osteocalcin and skeletal alkaline phosphatase (markers of bone formation) and tartrate-resistant acid phosphatase (a marker of bone resorption) were measured before and after training to assess bone turnover. The training program resulted in a 2.8 +/- 0.6% increase in femoral neck BMD (1.004 +/- 0.037 vs. 1.031 +/- 0.037 g/cm2; P < 0.001). However, there were no significant changes in total body, anterioposterior spine, lateral spine, Ward's triangle, or greater trochanter BMD. Moreover, there were no significant changes in growth hormone, insulin-like growth factor I, testosterone, osteocalcin, or skeletal alkaline phosphatase. There were no changes in the control group. Thus, strength training can increase femoral neck BMD, and this effect does not appear to be accompanied by changes in anabolic hormones or markers of bone formation and resorption.

Absorptiometry, Photon↗
PubMed1993

Lead exposure and latent learning ability of adult female rats.

The present report investigates the effects of lead exposure during the pre- and postnatal period on the latent learning ability in a maze. Rats were submitted to lead acetate intoxication by giving their dams 0.5, 1.0, or 4.0 mM lead acetate or deionized water. Rats were weaned at 21 days, and the treatment was continued by giving the same solution of lead acetate in the drinking water until behavioral testing. Under a nonappetitive condition, rats were exposed either to an open field or to a maze apparatus. They were thereafter deprived of food and tested in the maze apparatus. Lead treatment induced an increase in locomotor activity in the open field during training sessions, and animals failed to habituate to the environment. Nevertheless, both lead-treated and control rats that had been previously exposed to the maze performed better than those exposed to the open field. These results suggest that rats intoxicated with lead are able to learn about the environment when no immediate reinforcement is involved.

Animals↗
PubMed1992

Diminished concentration of the NF-H subunit of neurofilaments in cerebral cortex of rats chronically treated with proline, methylmalonate and phenylalanine plus alpha-methylphenylalanine.

Wistar rats from the same litter were randomly divided into four groups and received subcutaneously from the 6th to 28th day post partum one of the following drugs: L-proline, methylmalonate, L-phenylalanine plus alpha-methylphenylalanine, or equivalent volumes of 0.9% (w/v) saline (controls). On day 30, the animals were killed, the brain was removed and the cerebral cortex and cerebellum was immediately dissected. Total intermediate filament fraction (IF) was obtained from cerebral cortex and cerebellum by using a high-salt phosphate-buffered solution supplemented by 1% Triton X-100. The pellet contained the bulk of the IF proteins. Following SDS-polyacrylamide gel electrophoresis, these proteins were identified as the 200, 150 and 68 kD subunits of neurofilaments (NF-H, NF-M and NF-L, respectively), the 66 kDa associated protein, the 57 kDa intermediate filament-like protein and the 52 kDa glial fibrillary acidic protein (GFAP). They were further scanned through densitometry from enriched fractions of controls and of animals treated with the various drugs in order to determine the effects of the treatments on their concentration. Our results showed that the concentration of IF protein in cerebellum was not affected by the treatments, whereas chronic administration of all drugs significantly decreased NF-H subunit concentration in rat cerebral cortex.

Animals↗
PubMed1992

Malnutrition increases insoluble-to-soluble tubulin ratio and in vitro incorporation of 32ATP in rat cerebral cortex.

Wistar rats were fed a normal protein (25% casein) or an isoenergetic low protein (8% casein) diet from the day of birth to weaning on day 21. Litters were killed at weaning and cerebral cortex was removed. Tubulin was prepared by centrifugation at 100,000 g, 4 degrees C, as described by Shelansky et al. [Proc. Natn. Acad. Sci. U.S.A. 70, 765-768 (1973)]. Cold-insoluble tubulin was recovered in the pellet (P1) fraction and cold-soluble tubulin in the supernatant (S1) fraction. Alpha and beta tubulin were quantified by electrophoretic and immunological methods in both fractions. Our results indicated that malnutrition enhanced the ratio of cold-insoluble-tubulin-to-cold-soluble-tubulin. Furthermore malnutrition induced an increased in vitro incorporation of 32P into both soluble and insoluble tubulins. Although tubulin phosphorylation has been related to tubulin stability properties, we cannot unequivocally ascribe the increased insoluble/soluble tubulin ratio with malnutrition to increased in vitro incorporation of 32P.

Adenosine Triphosphate↗