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Biomedical subjects

L A Rodriguez

Publications and source records attributed to L A Rodriguez.

At least 37 records · Page 2Linked to original sources
PubMed1991

An extracellular acetylcholinesterase produced by Aeromonas hydrophila is a major lethal toxin for fish.

A hitherto unrecognised lethal toxin from the extracellular products (ECP) of Aeromonas hydrophila is described. The pure toxin was 300 times more toxic than the crude ECP and is the most toxic substance so far described from this bacterium, with a minimum lethal dose of 0.05 micrograms g-1 fish. The toxin had high acetylcholinesterase activity and occurred in native ECP as a monomeric 15.5 kDa polypeptide. The purified toxin had five isoelectric focusing forms ranging from pl 4.45 to 4.70. The ECP of each of six strains of A. hydrophila isolated from fish possessed acetylcholinesterase activity suggesting that the toxin is common in this species. The toxin was not a cytolysin and produced no gross pathology in injected fish. Its enzymic nature, low lethal dose, lack of tissue pathology and its apparent narcotic effect suggest that this toxin may act upon the central nervous system of the fish.

Acetylcholinesterase↗
PubMed1991

Impulsivity, sensation seeking, and behavioral and emotional responses to alcohol.

Three hundred forty-two male and female subjects from the Colorado Alcohol Research on Twins and Adoptees returned a mailed questionnaire that included the Eysenck Impulsivity-Venturesomeness-Empathy scales. These subjects had previously been tested in a procedure in which they were given a 0.8 g/kg dose of ethanol to bring their peak blood alcohol concentration (BAC) to near 0.10 g/dl, given topping doses to maintain this BAC over a 3-hr period, and repeatedly tested on a battery of diverse physiological, psychomotor, perceptual speed, and mood measures. Impulsivity was significantly correlated with higher levels of self-reported alcohol use and the occurrence of alcohol use problems in males, while both impulsivity and venturesomeness (sensation seeking) were significantly correlated with lessened motor impairment following alcohol use in males. These personality measures, however, were not significantly correlated with mood measures following initial alcohol dosing. Impulsivity and venturesomeness were uncorrelated with alcohol use and responses to alcohol in females, but as with males, impulsivity was related to the occurrence of alcohol use problems in females.

Adult↗
PubMed1990

Bromodeoxyuridine labeling study of intracranial meningiomas: proliferative potential and recurrence.

Ninety-six patients with intracranial meningiomas and two with hemangiopericytic variants received a 30-min intravenous infusion of bromodeoxyuridine (BrdUrd), 200 mg/m2, before tumor removal. Excised tumor specimens were stained by the indirect immunoperoxidase method to determine the BrdUrd labeling index (LI), or percentage of cells in DNA synthesis. The BrdUrd LI was less than 1% in 63 (86.3%) of 73 nonmalignant meningiomas and less than 1% in 20 (87%) of 23 malignant meningiomas. Of 23 malignant meningiomas 11 were recurrent tumors; 8 patients had recurrence 3 to 33 months after the study. The recurrence rate was 100% (five of five) in patients whose tumors had a BrdUrd LI greater than 5%, 44% (11 of 25) in those with a BrdUrd LI 1% to 5%, and 6.1% (4 of 66) in those with an LI less than 1%. Thus, meningiomas with a BrdUrd LI greater than 1% may grow faster and recur more frequently. Among patients with malignant meningiomas, the mean time to recurrence after the study was 7.5 months in those with a BrdUrd LI greater than 5% and 20.2 months for those with an LI 1% to 5%. The mean time to recurrence was 97.8 months in patients with nonmalignant meningiomas. Both hemangiopericytic variants were recurrent and showed LIs of 0.5% and 4.1%; the former tumor recurred 8 years after complete resection, while the latter recurred three times in 3.5 years. Thus, the proliferative potential of intracranial meningiomas as reflected by the BrdUrd LI appears to be a prognostic variable that can help to elucidate the biological behavior of individual meningiomas.

Adolescent↗
PubMed1990

Management of hypothalamic gliomas in children: an analysis of 33 cases.

The cases of 33 children with hypothalamic-chiasmatic gliomas are reviewed. Radiation therapy produced clinical or radiographic improvement in 11 (46%) of 24 patients. Progression was documented in 18 patients (54%). Overall, the median time to tumor progression was 60 months; it was 70 months in patients who received radiation therapy and 30 months in those who did not (P less than 0.05). Chemotherapy, either given initially or at the time of progression, caused the tumor to respond or to stabilize in 10 patients. Partial resection of the tumor led to improvement in 3 of 12 patients, obviating the need for a shunt in 2 of them; there were no deaths and postoperative morbidity was transient and minimal (diabetes insipidus, intraventricular hemorrhage, and left hemiparesis in one patient each). The 5- and 10-year survival probabilities were 93 and 74%, respectively. Patients with neurofibromatosis had a better prognosis.

Adolescent↗
PubMed1989

Reevaluation of procarbazine for the treatment of recurrent malignant central nervous system tumors.

Ninety-nine patients with primary recurrent malignant tumors of the central nervous system were treated with procarbazine as a single agent. Procarbazine was not given as a specified protocol, but for patients who were ineligible or refused other protocols. All patients had been treated previously with radiotherapy and 96 patients had also received previous chemotherapy. Twenty-five patients were treated at the first progression of their tumor, 47 were treated at the second progression, and 27 were treated at the third progression of their tumor. For the aggregate, the response plus stabilization rate was 27% for glioblastoma multiforme with median time to tumor progression of 30 weeks, and 28% for other anaplastic gliomas with a median time to tumor progression of 49 weeks. With respect to the percent of patients who responded or stabilized to treatment, these results are inferior to those reported previously for patients treated with procarbazine at recurrence. With respect to duration of response and stabilization, the data are comparable.

Adolescent↗
PubMed1988

Treatment of recurrent brain stem gliomas and other central nervous system tumors with 5-fluorouracil, CCNU, hydroxyurea, and 6-mercaptopurine.

Twenty-one patients with recurrent malignant central nervous system gliomas were treated with a combination of 5-fluorouracil, CCNU, hydroxyurea, and 6-mercaptopurine. Thirteen patients had brain stem gliomas, 3 patients had spinal cord gliomas, 3 patients had thalamic gliomas, and 2 patients had cerebellar astrocytomas. All patients had received radiation therapy, and 4 brain stem patients had also been treated with chemotherapy. Sixteen patients (76%) responded to treatment with either stabilization of disease or improvement. Nine of the 13 patients with brain stem gliomas (71%) had response or stabilization of disease. The median time to tumor progression (TTP) for the brain stem patients who responded or had stabilization of disease was 25 weeks. The median survival from recurrence for the brain stem glioma patients was 27 weeks. Patients with cerebellar, thalamic, and spinal cord tumors did very well, with an 87% response or stabilization of disease and a median TTP of 122 weeks.

Adolescent↗
PubMed1988

Interactions of climatic factors affecting milk yield and composition.

Objectives were to evaluate effects of interactions of maximum temperature, minimum relative humidity, and solar radiation on milk yield and constituent traits. Effects of climate variables and their interactions were significant but small in most cases. Second order regression models were developed for several variables. Six were examined in detail: Holstein and Jersey milk yields, Holstein fat and Feulgen-DNA reflectance percent, and Jersey protein percent and yield. Maximum temperature had greatest influence on each response, followed by minimum relative humidity and solar radiation. Optimum conditions for milk production were at maximum temperatures below 19.4 degrees C, increasing solar radiation, and minimum relative humidity between 33.4 and 78.2% (cool sunny days, moderate humidity). Maximum Holstein fat percent of 3.5% was predicted for maximum temperatures below 30.8 degrees C, minimum relative humidity below 89%, and solar radiation below 109 Langleys; actual mean Holstein fat percent was 3.35%. Optimum climatic conditions for Jersey protein percent were at maximum temperature of 10.6 degrees C with solar radiation at 300 Langleys and relative humidity at 16% (cool sunny days, low humidity). Because noteworthy interactions existed between climate effects, response surface methodology was suitable for determining optimum climatic conditions for milk production.

Animals↗
PubMed1988

Treatment of medulloblastoma with procarbazine, hydroxyurea, and reduced radiation doses to whole brain and spine.

Forty-seven patients with medulloblastoma were treated postoperatively with procarbazine, followed by craniospinal radiation therapy in combination with hydroxyurea. The radiation dose to the posterior fossa was 55 Gy; the spinal cord received 25 Gy and the whole brain 25 to 35 Gy (mean 33 Gy). Seventeen tumors recurred. Only one initial recurrence was in the spinal subarachnoid space; 10 (59%) were in the posterior fossa, and four (24%) were supratentorial. The estimated 5-year disease-free survival probability was 55%; the 5-year overall survival rate was 66%. Myelotoxicity occurred in 38% of patients, but in only one case was it severe enough to warrant reducing the total dose of radiation. It was concluded that good-risk medulloblastoma patients may be treated with radiation dosages as low as 25 Gy to the spinal axis and to the whole brain without increasing the risk of recurrence outside the posterior fossa. Chemotherapy with procarbazine followed by radiation therapy and hydroxyurea during radiation therapy was well tolerated and may play a role in reducing radiation dosages outside the posterior fossa.

Adolescent↗
PubMed1988

Prognostic implications of the proliferative potential of low-grade astrocytomas.

The proliferative potential of low-grade astrocytomas was estimated in 47 patients. Each patient received an intravenous infusion of bromodeoxyuridine (BUdR), 150 to 200 mg/sq m, at the time of craniotomy to label cells in deoxyribonucleic acid (DNA) synthesis; the percentage of S-phase cells, or BUdR labeling index (LI), of each tumor was determined immunohistochemically. In 29 patients (60%), the tumors had BUdR LI's of less than 1%, indicating a slow growth rate; only three (10%) of these patients died of recurrent tumor during a follow-up period of up to 3 1/2 years. In contrast, of the 18 patients (40%) whose tumors had BUdR LI's of 1% or more, 12 (67%) had a recurrence and nine died during the same follow-up period. These results show that the proliferative potential, as reflected by the BUdR LI, is an important prognostic factor that separates low-grade astrocytomas into two groups and provides a more scientific rationale for selecting treatment for individual patients.

Astrocytoma↗
PubMed1987

Does chemotherapy benefit the patient with a central nervous system glioma?

The authors discuss the results of clinical trials assessing the value of chemotherapy for brain tumors in the adjuvant setting as well as at recurrence. Adjuvant chemotherapy does benefit some patients with malignant brain gliomas. Improved survival rates seem to be related to an increased number of long-term survivors. The most effective chemotherapy is BCNU or a combination of CCNU, procarbazine, and vincristine (PCV). Drugs that potentiate radiation therapy, such as hydroxyurea and BUdR, are also useful in some patients.

Antineoplastic Agents↗
PubMed1986

Perioral behaviors induced by cholinesterase inhibitors: a controversial animal model.

Perioral behaviors induced by neuroleptic drugs have been interpreted as an animal model of tardive dyskinesia. However, these behaviors have also been induced or enhanced by physostigmine, a cholinesterase inhibitor. The latter result is contradictory to the clinical effect of physostigmine in human tardive dyskinesia. In view of this contradiction and other considerations, perioral behaviors have also been interpreted as a model of acute dystonia. The present experiments replicated an earlier failure to observe spontaneous perioral behaviors after long-term neuroleptic treatment in rats as well as the paradoxical effect of physostigmine. The effect of physostigmine was also compared to phenylmethanesulfonyl fluoride and methanesulfonyl fluoride, irreversible CNS active cholinesterase inhibitors. There were significant differences between the effects of the various cholinesterase inhibitors and their interactions with perioral behaviors and neuroleptic treatment. It is concluded that the effects of cholinesterase inhibitors on perioral behaviors in rodents may not be accounted for entirely by cholinesterase inhibition. Further experiments using additional agonists and antagonists will be required to clarify the behavioral effects of these cholinesterase inhibitors.

Animals↗
PubMed1985

Comparative behavioral effects of CNS cholinesterase inhibitors.

Phenylmethanesulfonyl fluoride, methanesulfonyl fluoride, and physostigmine were compared on the efficacy with which each could suppress methylphenidate-induced stereotyped gnawing, an extrapyramidal motor behavior. Whereas physostigmine produced powerful suppression of the stereotypy, the sulfonyl fluorides did not produce any clear behavioral effect. Biochemical experiments conducted with the behavioral tests demonstrated that the sulfonyl fluorides produced inhibition of whole brain, caudate, cortex, cerebellum, hippocampus and brain stem cholinesterate equal to that produced by physostigmine. The reason for the marked discrepancy between the behavioral effect of physostigmine and the sulfonyl fluorides is unknown. It is, however, clear that the effect of the various drugs on extrapyramidal motor behaviors is not a simple function of the degree to which each inhibited CNS cholinesterase.

Animals↗
PubMed1983

Climatological and genetic effects on milk composition and yield.

Results confirm most other research on milk composition and yield. All responses were affected by climate, some considerably more than others, if percent of error variance is the criterion. Jersey yields were less sensitive to climate than were Holstein, but Jersey milk composition appeared more sensitive. Somatic cell count (REF), a measure of mastitis, was affected by climate but less than all other variables except protein/fat and LM%. Needed are estimates of interactions between climatic effects and response surface models to quantify possible improvement in performance following environmental modification. Genetic correlations between milk yield and REF and chloride % suggest that single trait selection for milk yield might increase incidence of mastitis although phenotypic correlations indicate that high yields and absence of mastitis are correlated.

Animals↗