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Biomedical subjects

R Garcia

Publications and source records attributed to R Garcia.

At least 109 records · Page 6Linked to original sources
PubMed1999

Preventing human rabies before and after exposure.

Rabies is a viral disease that can be transmitted from animals to humans. Recently, most human deaths from rabies have been caused by transmission from bats, in many cases without a documented bite or exposure. Rabies is fatal if untreated prior to onset of symptoms. Deaths from human rabies in the United States are rare, largely because of animal control measures and postexposure prophylaxis of people who have been bitten or exposed to the virus. Primary care providers play a pivotal role in the prevention of rabies. Preexposure prevention involves education and immunization of persons at high risk for rabies exposure. Rabies is difficult to diagnose antemortem because of the nonspecific presentation of signs and symptoms that may mimic those of respiratory or abdominal infections. Diagnosing rabies once symptoms begin will not save the victim's life but will help to minimize exposure to others, allow for identification and prophylaxis of those who may have been exposed, and identify the animal vector.

Animals↗
PubMed1999

Fever following total knee arthroplasty.

This study investigated the incidence and clinical significance of postoperative fever in 118 consecutive patients undergoing 141 total knee arthroplasties (TKAs). A postoperative fever was recorded in 63 (66%) of 95 unilateral and 17 (74%) of 23 bilateral TKA patients. Nine of the unilateral and five bilateral TKA patients developed positive clinical or laboratory findings to explain the pyrexia. Unilateral TKA patients who experienced postoperative fever were statistically more likely to have a complication in the immediate postoperative period. None of the surgical variables examined had any predictive value on the incidence of postoperative fever. Aggressive pulmonary toilet, repeated physical examinations, and urine analysis are recommended when evaluating TKA patients with postoperative fever. Fever following TKA was common and was not necessarily a contraindication to discharge.

Aged↗
PubMed1999

Thyroid transcription factor-1: immunohistochemical evaluation in pulmonary neuroendocrine tumors.

Thyroid transcription factor-1 (TTF-1), a nuclear transcription protein selectively expressed in the thyroid, the diencephalon, and respiratory epithelium, is expressed in more than 90% of pulmonary small cell carcinomas (SCLCs) and in almost 75% of pulmonary non-small cell carcinomas (NSCLCs), but it is absent in typical pulmonary carcinoids (TCs). Therefore, it was thought that SCLC and NSCLC might share a common lineage, different from that of TC. TTF-1 expression in atypical pulmonary carcinoids (ACs) and large-cell neuroendocrine carcinomas (LCNECs) was not studied previously. We examined TTF-1 expression in 51 TCs, 9 ACs, 8 LCNECs, and 21 SCLCs with use of formalin-fixed material and heat-induced epitope retrieval. TTF-1 expression was seen in 18 (35%) of 51 TCs, all of the 9 ACs, 6 (75%) of the 8 LCNECs, and 20 (95%) of the 21 SCLCs. These results reinforce earlier findings of the excellent sensitivity of TTF-1 for SCLC, and they show similar sensitivity for AC and LCNEC, but they argue against the hypothesis that SCLC and TC are of different cell lineages. The ubiquity of TTF-1 expression in pulmonary NECs demonstrated in this study also argues against its use in their subclassification.

Carcinoid Tumor↗
PubMed1998

Relation between variation in copy number of ribosomal RNA encoding genes and size of harbouring chromosomes in Leishmania of subgenus Viannia.

Chromosomal size polymorphism in Leishmania of subgenus Viannia has been correlated with eco-geography. The sizes of chromosomes bearing rDNA genes were determined in 69 isolates. A considerable size-variation was observed, ranging from 1100 to 1500 kb. Chromosomes of L.(V.). braziliensis, L.(V.)guyanensis and L.(V.) peruviana from northern Peru were significantly larger (200 kb) than those of L.(V.) peruviana from southern Peru. In addition, 31 out of 69 isolates presented each two different-sized homologues of the rDNA chromosome. Long range restriction mapping of three different-sized rDNA chromosomes from L.(V.)braziliensis M2903 and L.(V.)peruviana HB31 (north) and LC106 (south) each revealed three fragments delimited by PmeI restriction sites: two constant in size (the centre and one extremity of the chromosome) and one variable (the other extremity, containing a single cluster of rDNA genes). Further analysis of the M2903 rDNA chromosome allowed the localization of its 140 kb rDNA cluster at 85 kb from the telomeric end. Two arguments indicated that size-variation of the rDNA chromosome is partially due to amplification/deletion of the clustered rDNA genes: (i) size-variation of the cluster-containing fragment was proportional to the size-variation of the whole chromosome, and (ii) hybridization signal intensity of the rDNA chromosome with a small subunit rDNA probe strongly correlated with chromosomal size. Nevertheless, DNA sequences present between the rDNA cluster and the telomere might also play a role in chromosomal size polymorphism. In addition, our data suggest that rDNA gene copy number (20-40 copies cell(-1) under a diploid hypothesis) in subgenus Viannia is lower than reported previously.

Animals↗
PubMed1998

Influences of the bed nucleus of the stria terminalis and of the paraventricular nucleus of the hypothalamus on the excitability of hippocampal-lateral septal synapses in mice.

Previous experiments have shown that conditioning in aversive situations is associated with specific changes in excitability of hippocampal-septal synaptic transmission and that these changes might be related to a modulation of this synaptic transmission by afferents originating from the bed nucleus of the stria terminalis (BNST) and from the paraventricular nucleus (PVN) of the hypothalamus. Accordingly, the aim of the present experiment was to assess changes in excitability of hippocampal-septal synapses by varying the interval between the application of a conditioning pulse in either the BNST or the PVN, and a test pulse in fimbria fibers (FF). Electrical stimulation of FF, induces in the lateral septum (LS) a field potential characterized by two negative waves (N2 and N3) the magnitude of which is an index of excitability of two populations of target cells located in the ventral and dorsal lateral septum, respectively. Results showed that prestimulation of both the BNST and the PVN produced an increase in the amplitude of the N3 wave, although the optimal interpulse interval required for producing maximal increase was different as a function of the two structures. Only prestimulation of the BNST induced a significant increase in the amplitude of the N2 wave. These results suggest that the PVN projects mainly to the dorsal aspect of the LS, while the BNST projects to both dorsal and ventral parts of the LS. Together with results from previous experiments conducted in behaving mice exposed to conditioned aversive stimuli, it is concluded that these projections might play a role in the relief of contextual conditioned fear.

Animals↗
PubMed1998

Mechanical strain increases protein tyrosine phosphorylation in airway smooth muscle cells.

Mechanical stress contributes to normal structure and function of the lung as well as pathology in such diseases as bronchopulmonary dysplasia and adult respiratory distress syndrome. Stress-related increases in airway smooth muscle (ASM) quantity are reflected in vitro where cultured ASM cells respond to cyclic deformational strain with increased proliferation, cell reorientation, protein production, stress fibers, and focal adhesions. To understand the mechanisms of mechanical signaling in ASM cells, we investigated whether strain increased tyrosine phosphorylation of focal adhesion-related proteins. ASM cells were grown to confluence on collagen type I and subjected to 30 min of cyclic deformation strain (2 s of 25% deformation of the substratum, 2 s relaxation) and compared at various time points with identical cells not subjected to strain for phosphotyrosine content of three focal adhesion-concentrated proteins (pp125FAK, paxillin, and talin) by Western blotting. Strain caused a rapid increase in tyrosine phosphorylation of pp125FAK and paxillin. Tyrosine phosphorylation decreased by 4 h in pp125FAK after discontinuing strain but remained elevated in paxillin at 24 h. Increases in tyrosine phosphorylation of talin were not found. In separate studies, when cells were strained in the presence of tyrosine kinase inhibitors (genistein and herbimycin A), strain-induced reorientation and elongation were inhibited. Mechanochemical signal transduction appears to mediate cell morphologic changes through quantitative and possibly qualitative changes in tyrosine phosphorylation of adhesion-related proteins.

Animals↗
PubMed1998

Evidence for intracellular generation of angiotensin II in rat juxtaglomerular cells.

The formation of the vasoactive peptide angiotensin II (AII) is dependent on the sequential action of two enzymes, renin and angiotensin converting enzyme (ACE), on the substrate angiotensinogen. Although the renin-producing cells of the kidney do not express angiotensinogen, they contain large amounts of AII in the same storage granules that contain renin. When renin expression is suppressed in these cells, AII also disappears. In the current study, we have tested whether the renin-associated disappearance of AII in renal juxtaglomerular (JG) cells is due to a renin-dependent down-regulation of granule biosynthesis and whether receptor-mediated internalization of AII could account for its concentration in these cells. Our results support a model whereby AII peptides are generated within JG cells, presumably by a mechanism which involves the action of endogenous renin on internalized, exogenous angiotensinogen.

Angiotensin II↗
PubMed1998

Differential modulation of changes in hippocampal-septal synaptic excitability by the amygdala as a function of either elemental or contextual fear conditioning in mice.

Recent data obtained using a classic fear conditioning paradigm showed a dissociation between the retention of associations relative to contextual information (dependent on the hippocampal formation) and the retention of elemental associations (dependent on the amygdala). Furthermore, it was reported that conditioned emotional responses (CERs) could be dissociated from the recollection of the learning experience (declarative memory) in humans and from modifications of the hippocampal-septal excitability in animals. Our aim was to determine whether these two systems ("behavioral expression" system and "factual memory" system) interact by examining the consequences of amygdalar lesions (1) on the modifications of hippocampal-septal excitability and (2) on the behavioral expression of fear (freezing) resulting from an aversive conditioning during reexposure to conditional stimuli (CSs). During conditioning, to modulate the predictive nature of the context and of a discrete stimulus (tone) on the unconditional stimulus (US) occurrence, the phasic discrete CS was paired with the US or randomly distributed with regard to the US. After the lesion, the CER was dramatically reduced during reexposure to the CSs, whatever the type of acquisition. However, the changes in hippocampal-septal excitability persisted but were altered. For controls, a decrease in septal excitability was observed during reexposure to the conditioning context only for the "unpaired group" (predictive context case). Conversely, among lesioned subjects this decrease was observed in the "paired group" (predictive discrete CS case), whereas this decrease was significantly reduced in the unpaired group with respect to the matched control group. The amplitude and the direction of these modifications suggest a differential modulation of hippocampal-septal excitability by the amygdala to amplify the contribution of the more predictive association signaling the occurrence of the aversive event.

Acoustic Stimulation↗
PubMed1998

Clinical and radiological features of pulmonary disease caused by rapidly growing mycobacteria in cancer patients.

The role of rapidly growing mycobacteria in the pathogenesis of pulmonary disease is being increasingly recognized; however, the clinical significance of these mycobacteria in patients with underlying malignancy has not been well studied. Over a 6-year period, 37 cancer patients with rapidly growing mycobacteria isolated from respiratory specimens were identified at our center. Mycobacterium chelonae group was isolated in 24 cases and Mycobacterium fortuitum in 13 cases. Of the 24 cases with cultures yielding Mycobacterium chelonae group, eight met the study criteria for infection and were determined to be clinically significant, whereas only one of the Mycobacterium fortuitum isolates was determined to represent infection. An average of two antimicrobial agents were used for treatment, most commonly clarithromycin, ciprofloxacin, and trimethoprim/sulfamethoxazole. Although the isolation of rapidly growing mycobacteria represents colonization in most cases, these bacteria, especially the Mycobacterium chelonae group, may cause pulmonary disease in cancer patients. The clinical and radiological findings are usually non-specific in this population, and patients with respiratory cultures yielding rapidly growing mycobacteria should be assessed carefully to distinguish infection from colonization. Effective therapy can be provided with oral regimens that include at least two antibiotics to which the organism is susceptible.

Adolescent↗
PubMed1998

Activation of STAT transcription factors in oncogenic tyrosine kinase signaling.

Signal transducers and activators of transcription (STATs) are cytoplasmic transcription factors that translocate to the nucleus and regulate gene expression in response to cytokine and growth factor stimulation. Emerging evidence indicates that STAT signaling is also frequently activated by oncogenes and in tumor cells. Constitutive activation of STAT proteins has been reported in cell lines stably transformed by diverse oncoproteins that directly or indirectly activate specific tyrosine kinase signaling pathways. In addition, STAT activation has been detected in a variety of human tumors and tumor cell lines, many of which are known to harbor activated tyrosine kinases. Recent findings support a model in which activation of STAT signaling in the context of oncogenesis induces gene expression that participates in malignant transformation.

Animals↗
PubMed1998

An association between periodontal disease and peripheral vascular disease.

BACKGROUND: Periodontal disease has been shown to be associated with increased risk of coronary heart disease. Because coronary heart disease and peripheral vascular disease (PVD) have similar pathophysiologies, we hypothesized that periodontal disease might be a risk factor for PVD. METHODS: Using the combined data from the Normative Aging Study and Dental Longitudinal Study of the US Department of Veterans Affairs, we examined the relationship between PVD and periodontal disease. Multivariate logistic regression analysis was used. RESULTS: Over the 25 to 30 years of follow-up, 80 of these initially healthy subjects developed PVD. Compared with controls (n = 1,030), subjects with clinically significant periodontal disease at baseline had a 2.27 increment in the risk of developing PVD (95% confidence interval 1.32 to 3.9, P value = 0.003). CONCLUSIONS: Periodontal disease emerged as a significant independent risk factor for PVD in a multivariate analysis that adjusted for other established risk factors.

Adult↗
PubMed1998

Exposure to a conditioned aversive environment interferes with long-term potentiation induction in the fimbria-CA3 pathway.

The effect of re-exposure of rats to an aversive environment on the induction of long-term potentiation was investigated in the CA3 region 3 and 12 h after contextual conditioning. Electro-physiological recordings showed that re-exposure of rats to the conditioning chamber produced a significant and long-lasting decrease in population spike amplitude at both post-conditioning delays. High-frequency stimulation of the fimbria induced a large and persistent increase in CA3 population spike amplitude (about 400% of baseline) in animals of control groups and shocked animals that were not re-exposed to the conditioning environment. However, high-frequency stimulation applied during re-exposure of shocked subjects 3 h after the initial exposure resulted in a small and transient increase in population spike amplitude (about 140% of baseline); when applied 12 h after the initial exposure, it produced a persistent depression of the response (-30% of baseline). Behavioural testing indicated that re-exposure of shocked animals to the conditioning environment elicited a qualitatively and quantitatively similar freezing behaviour at both post-conditioning delays (3 or 12 h). In contrast to the long-lasting decrease in CA3 population spike amplitude produced by re-exposure to the aversive environment, the level of freezing behaviour diminished rapidly within 10 min of exposure. These results suggest that, during exposure to a conditioned aversive environment, alterations in fimbria-CA3 neural processing may be dissociated from contextual fear-induced freezing behaviour. In addition, processes underlying long-term potentiation induction in fimbria-CA3 pathway may be opposite to those taking place during hippocampal processing of conditioned aversive contexts.

Animals↗
PubMed1998

Opposite effects of lateral septal LTP and lateral septal lesions on contextual fear conditioning in mice.

The effect of fimbrial high-frequency stimulation (HFS)-induced long-term potentiation (LTP) in the lateral septum (LS) on contextual fear conditioning was studied in mice. Mice were conditioned for fear toward a novel context through the use of footshocks. The 1st experiment showed that pretraining HFS reduced significantly conditional freezing to contextual stimuli. The 2nd experiment was designed to determine whether the reduction of freezing produced by fimbrial HFS resulted from LTP in the LS rather than from LTP in other brain structures. Accordingly, mice with lesions of the LS were used and submitted to the same protocol as in the 1st experiment. Results showed that LS lesions completely abolished the impairing effect of fimbrial HFS and, as a whole, potentiated the freezing response. These data suggest that contextual fear conditioning is strongly modulated by the level of hippocampal-LS synaptic neurotransmission.

Analysis of Variance↗
PubMed1998

Footshock stress but not contextual fear conditioning induces long-term enhancement of auditory-evoked potentials in the basolateral amygdala of the freely behaving rat.

In this study, rats were bilaterally implanted with electrodes in the amygdala for chronic recording. Auditory click stimulation evoked in the basolateral nucleus a field potential characterized by three positive components: P1, P2 and P3 (peak latencies around: 10, 20 and 30 ms, respectively) which were each followed by three negative components: N1, N2 and N3 (peak latencies around: 13, 30 and 50 ms, respectively). Animals were divided into three groups (context-same, context-different and control). Following footshock administration, animals were either re-exposed to the same conditioning chamber (context-same group) or placed in a different context (context-different group) for electrophysiological and behavioural (evaluation of freezing response) recordings. The two early positive-negative complexes (P1-N1 and P2-N2) increased in amplitude from 2 min to 24 h following footshock in both context-same and context-different groups. No significant difference was observed between these two groups. The demonstration of significantly larger freezing responses in context-same subjects on exposure to the aversive conditioned environment indicated that this similarity of effects was not due to lack of conditioning of context under the experimental conditions chosen. We conclude that footshock stress produces general long-lasting changes in amygdala auditory field potentials that are not significantly affected by contextual fear conditioning.

Acoustic Stimulation↗
PubMed1998

Elastase is the only human neutrophil granule protein that alone is responsible for in vitro killing of Borrelia burgdorferi.

Phagocytosis of Borrelia burgdorferi by human polymorphonuclear leukocytes triggers oxygen-dependent and -independent mechanisms of potentially cidal outcome. Nevertheless, no factor or process has yet been singled out as being borreliacidal. We have studied the B. burgdorferi-killing ability of the myeloperoxidase-H2O2-chloride system and that of primary and secondary granule components in an in vitro assay. We found that neither secondary granule acid extracts nor the chlorinating system could kill these microorganisms, while primary granule extracts were effective. The Borrelia-killing factor was purified to homogeneity and demonstrated to be elastase. Its cidal activity was found to be independent of its proteolytic activity.

Amino Acid Sequence↗