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Biomedical subjects

L D Hudson

Publications and source records attributed to L D Hudson.

At least 73 records · Page 4Linked to original sources
PubMed1994

A novel heterodimerization partner for thyroid hormone receptor. Peroxisome proliferator-activated receptor.

Retinoid-like receptors play a central role in hormonal responses by forming heterodimers with other nuclear hormone receptors. In this study we have identified the peroxisome proliferator-activated receptor (PPAR) as a new thyroid hormone receptor (THR) auxiliary nuclear protein, heterodimerizing with THR in solution. Although these heterodimers do not recognize a classical thyroid hormone response element (TRE) characterized by direct repeat separated by four nucleotides (DR+4), PPAR behaves as a dominant negative regulator of thyroid hormone (TH) action. However, a TH-dependent positive effect is elicited by selective interaction of the THR beta-PPAR but not the THR alpha-PPAR heterodimer with a novel TRE (DR+2). The critical region of THR beta was mapped to 3 amino acids in the distal box of the DNA binding domain. Hence, PPAR can positively or negatively influence TH action depending on TRE structure and THR isotype.

3T3 Cells↗
PubMed1994

Concentric sclerosis (Baló): morphometric and in situ hybridization study of lesions in six patients.

Brain tissues from 6 patients with concentric sclerosis (Baló) were examined by in situ hybridization, immunocytochemistry, morphometry, and histological methods. The patients were 24 to 48 years old and had progressive cerebral symptoms and signs that lasted 15 to 100 days. Large demyelinative lesions, most frequent in the frontal white matter, contained alternating bands of demyelinated and partly myelinated white matter that were arranged in concentric or mosaic patterns. In the areas of demyelination, axons were relatively well preserved and there were perivascular inflammatory infiltrates. In 2 specimens, lesions contained regions with the characteristic appearance of actively demyelinating multiple sclerosis plaques. Oligodendroglial densities were highest in normal-appearing white matter, lower in partially myelinated areas, and lowest in demyelinated areas, which also contained many hypertrophic astrocytes closely associated with oligodendroglia. Messenger RNA levels for myelin-related proteins followed the same pattern; they were lowest in demyelinated areas, higher in partially myelinated areas, and highest in normal-appearing white matter beyond lesion margins. Our findings suggest that concentric sclerosis is a variant of multiple sclerosis, that oligodendroglial loss is important in the pathogenesis of demyelination, and that partially myelinated areas probably represent stages of ongoing myelin breakdown rather than remyelination of previously demyelinated areas.

Adult↗
PubMed1994

Astrocytes express insulin-like growth factor-I (IGF-I) and its binding protein, IGFBP-2, during demyelination induced by experimental autoimmune encephalomyelitis.

To assess the distribution of insulin-like growth-factor-related proteins during autoimmune CNS demyelination and remyelination, experimental autoimmune encephalomyelitis was produced by injecting Lewis rats with an emulsion containing guinea pig spinal cord and complete Freund's adjuvant. Tail weakness appeared at 10-12 days and was followed by hind and forelimb weakness. Paraplegia and incontinence were observed in some animals. From 8-40 days postinoculation (dpi), spinal cord sections were used to correlate lesion location and severity with mRNA distributions of insulin-like growth factor I (IGF-I), IGF-binding protein 2 (IGFBP-2), IGF-I-receptor (IGFR-I), glial fibrillary acidic protein (GFAP), and myelin basic protein (MBP). These were determined semiquantitatively by in situ hybridization. Fourteen dpi, there were inflammatory infiltrates and demyelination in both white matter (WM) and grey matter (GM). IGF-I and GFAP mRNAs were increased in these lesions and transcripts encoding myelin basic protein (MBP) were greatly reduced. Large lesions with extensive demyelination were evident in both WM and GM when mRNA levels of GFAP and IGF-I peaked 26 dpi. MBP mRNA levels began increasing 21 dpi and peaked 26 dpi, when a few thin regenerating myelin sheaths were found morphologically. Astrocytes, identified by their morphology and GFAP immunoreactivity, expressed very low levels of IGFBP-2 mRNA and peptide in normal controls; their levels were significantly higher 14 dpi, peaked 26 dpi, and then gradually decreased. Some neurons, as well as oligodendroglia in areas undergoing remyelination, expressed IGFR-I. Although levels of IGF-I, IGFBP-2, and GFAP mRNAs were highest in lesion areas, levels were also elevated around lesions and in some normal-appearing areas of WM and GM 14-40 dpi. The gene expression of both IGF-I and IGFBP-2 by hypertrophic GFAP-positive astrocytes was demonstrated 14-40 dpi by combined in situ hybridization and immunocytochemistry as well as by double immunostaining. Coexpression of IGF-I and IGFBP-2 in the same astrocyte was a frequent finding. Relative increases in both IGF-I, GFAP, IGFBP-2, IGFR-I, and MBP mRNAs peaked at about the same time. This suggests that during lesion progression and recovery, astrocytic expression of IGF-I-related peptides may reduce immune-mediated myelin injury. We also suggest that astrocytic IGFBP-2 in lesions may help target IGF-I to IGFR-I-expressing oligodendrocytes and promote remyelination of demyelinated axons.

Animals↗
PubMed1994

A combination of PLP and DM20 transgenes promotes partial myelination in the jimpy mouse.

Mutations in the myelin proteolipid protein (PLP) gene, such as that found in the jimpy mouse, result in an abnormal structure of the myelin, severe dysmyelination, and a reduction in the number of mature oligodendrocytes. To examine the functions of the two alternatively spliced isoforms of proteolipid protein, transgenic mice were generated that express either PLP or DM20 cDNAs placed under control of the PLP upstream regulatory region. The transgenes were bred into jimpy mice, and the effect of the transgenes on the dysmyelinating phenotype was analyzed. Neither the PLP transgene nor the DM20 transgene alone had an effect on myelination in the jimpy mice. Combining the two transgenes substantially increased the number of myelinated axons, suggesting that the two alternatively spliced products of the PLP locus perform distinct functions in oligodendrocytes. The enhanced myelination was not sufficient, however, for completely correcting the dysmyelinating phenotype of the jimpy mice, nor was it accompanied by the restoration of normal levels of myelin gene expression. The inability to rescue the jimpy phenotype is most likely attributable to a dominant negative action of the abnormal proteolipid proteins present in jimpy mice. These results demonstrate the complexity of proteolipid protein function in myelination.

Alternative Splicing↗
PubMed1994

Evolution of bronchoalveolar cell populations in the adult respiratory distress syndrome.

To characterize the evolution of inflammation in the adult respiratory distress syndrome (ARDS) and test the hypothesis that sustained alveolar inflammation is associated with a poor outcome in patients with ARDS, we performed fiberoptic bronchoscopy and bronchoalveolar lavage (BAL) in 125 patients and compared BAL cells and protein concentrations in survivors and nonsurvivors. ARDS followed sepsis syndrome in 35 patients, major trauma in 41, and other causes in 49. When possible, BAL was performed on Days 3, 7, and 14 after the onset of ARDS. Sixty-five patients (52%) had more than one BAL. We first performed analyses on each BAL day using information from all 212 BAL in the 125 patients (cross-sectional analysis). All patients had increased leukocytes and total protein in the first BAL (Day 3 after onset of ARDS). In patients with ARDS following sepsis, the percentage of BAL polymorphonuclear leukocytes (PMN) was higher on Day 7 (p = 0.11) and particularly Day 14 (p = 0.02) in patients who died; there was a consistent trend of a higher PMN concentration on all days in patients who died then in those who lived. In patients with ARDS following trauma and other risks, however, BAL PMN measures did not distinguish survivors from patients who died. Analysis of serial data from the patients with more than one BAL showed that alveolar macrophages (AM) increased in survivors of ARDS, both in absolute numbers and as a percentage of total cells; this pattern was most pronounced in the sepsis patients. The cross-sectional data analysis suggests that sustained alveolar inflammation occurs frequently in patients with ARDS following sepsis and is associated with a high mortality.

Adolescent↗
PubMed1994

Recovery of function in survivors of the acute respiratory distress syndrome.

We performed a prospective cohort analysis to determine the rate and extent of improvement in pulmonary function abnormalities and self-perceived health for 1 yr after surviving an episode of the acute respiratory distress syndrome (ARDS). We also examined the effect of ARDS severity and etiology, age, and sex on functional recovery. Patients were recruited from the intensive care units of one hospital and followed at regular time intervals from extubation to 1 yr. Fifty-two of 82 eligible adult survivors (63%) consented to participate; 37 of 82 (45%) had at least two examinations, and 20 (24%) had complete follow-up. Risk factors for ARDS included sepsis (n = 12), trauma (n = 15), and other (n = 10). Pulmonary function and self-perceived health scores improved considerably in the first 3 mo after extubation, with only slight additional improvement at 6 mo. No further changes were evident at 1 yr. Patients with more severe ARDS had significantly lower pulmonary function tests than did other survivors throughout follow-up. These observations should be useful for clinical follow-up of ARDS survivors and provide specific information concerning the expected rate of functional recovery in these patients.

Adult↗
PubMed1994

Changing use of intensive care for HIV-infected patients with Pneumocystis carinii pneumonia.

Clinicians' approach to acute respiratory failure from Pneumocystis carinii pneumonia (PCP) is hypothesized to have gone through three phases: aggressive management due to an absence of data on prognosis (1981-84), withholding of intensive care based on a few small studies showing high case fatality (1985-87), and an increase in intensive care to an intermediate level (1988 forward). Unfortunately, studies of survival from acute respiratory failure among such patients have been small and have been limited to patients in the intensive care unit. To determine whether this three-phase scenario has empirical support, we performed a retrospective chart review of all patients with human immunodeficiency virus (HIV) infection and PCP at a university-affiliated municipal hospital from 1983 to 1990. We identified 180 patients, representing 218 episodes of PCP. The previously hypothesized relationship between intensive care and year of diagnosis was confirmed: intubation rates were 30% before 1985, 0% in 1987, and 12% after 1988 (p = 0.03). Among all patients, the percentage dying in the hospital without intensive care had the opposite relationship with year of diagnosis, increasing from 0% in 1984 to 21% in 1987 and then declining to 0% in 1990 (p = 0.001). Overall mortality from an episode of PCP was 25% and did not change significantly over time. Disease severity also did not change significantly over time. In summary, the significant swings in the use of intensive care for HIV-infected patients with PCP suggest that judgments about the futility of intensive care were strongly influenced by incorrect perceptions of survival.

AIDS-Related Opportunistic Infections↗
PubMed1994

Emergent assessment and management of acute respiratory failure in COPD.

Acute respiratory failure in patients with COPD is a common cause of emergent medical intervention and can be difficult to assess and manage. Assessment is complicated by the imposition of acute respiratory failure on chronic respiratory failure and by the large number of problems that can tip a carefully compensated patient with COPD toward acute respiratory failure. Management must include correcting life-threatening hypoxemia and life-threatening acidosis, treating the underlying disease processes, and preventing and treating complications. Management can be enhanced by an understanding of the prognosis of acute respiratory failure in COPD and by incorporation of some ethical and societal issues.

Acidosis↗
PubMed1994

Outcome from respiratory failure.

A physician's assessment of the probable outcome of an episode of respiratory failure should be based on a combination of survival data from large studies and specific knowledge about the individual case in question. Clearly, mortality rates in cases of ARF are influenced by a number of factors. In general, only a minority of patients with ARF complicating COPD require mechanical ventilation. In these cases, mortality often is related to the nature of the precipitating illness and the severity of the patient's underlying chronic respiratory disease. The long-term prognosis in patients with COPD who survive an episode of ARF is related primarily to the severity of the patient's underlying disease. Acute mortality is higher in patients with ARDS than in patients with ARF complicating COPD. Although a significant number of ARDS patients die of their underlying illness, mortality in others more commonly appears to be related to sepsis and multiple organ failure rather than end-stage respiratory disease. Pulmonary function in survivors of ARDS is quite variable, and may be related to the severity of the acute episode. ARF has a particularly poor prognosis when associated with certain underlying illnesses such as hematologic malignancy.

Acute Disease↗
PubMed1993

Expression of the SmN splicing protein is developmentally regulated in the rodent brain but not in the rodent heart.

The SmN protein is a tissue-specific splicing factor which is closely related to the ubiquitous SmB splicing protein but which is expressed only in the adult brain and heart. SmN is also detectable albeit at a low level in both the embryonic brain and heart. During heart development, SmN levels remain constant while during rodent brain development the levels of SmN rise such that SmN replaces SmB as the predominant protein in adult brain. This increase in SmN levels is dependent upon a corresponding increase in the SmN mRNA which is detectable by in situ hybridization within neurons in virtually all areas of the adult brain.

Animals↗
PubMed1993

Immunohistochemistry of nitric oxide synthase demonstrates immunoreactive neurons in spinal cord and dorsal root ganglia of man and rat.

The presence of nitric oxide synthase in spinal cord and dorsal root ganglia was investigated by immunohistochemistry using antibodies against the constitutive neuronal form of nitric oxide synthase (NOS). NOS immunoreactivity was present in both man and rat with similar distribution, being present in primary sensory neurons of dorsal root ganglia and their afferent terminals in dorsal horn of spinal cord. NOS immunoreactive interneurons were found in the superficial layer of the dorsal horn, around the central canal and in the intermediolateral cell column. NOS immunoreactivity was also present in numerous motoneurons in the ventral horn. The widespread distribution of NOS in both sensory and motor nervous system is indicative of the involvement of nitric oxide in different neural functions.

Adult↗
PubMed1993

Safety of bronchoalveolar lavage in patients with adult respiratory distress syndrome.

Although shown to be safe in many other lung disorders, the safety of fiberoptic bronchoscopy (FOB) with bronchoalveolar lavage (BAL) in critically ill patients with adult respiratory distress syndrome (ARDS) remains unproven. We conducted a prospective study to evaluate the safety of BAL in patients with ARDS. There were 438 patients with ARDS at our institution during the study period. Of these, 110 underwent FOB and BAL for either research or clinical purposes. Data were collected at baseline, at 5-min intervals during the procedure, and 1 h after the procedure. We did not detect any statistically or clinically significant changes in PaO2/FlO2, mean arterial pressure, heart rate, peak inspiratory pressure, or static thoracic compliance after the procedure. A small decrease in SaO2 occurred after BAL. Although this change was statistically significant, the magnitude was not of clinical importance. Five patients (4.5%) had transient arterial oxygen desaturation to < 90% during FOB and one patient (0.9%) experienced desaturation to < 80%. There were no prolonged episodes of severe hypoxemia. No serious bleeding occurred. One pneumothorax developed during the procedure. No deaths occurred that were related to the procedure. We conclude that FOB and BAL can be performed safely and are reasonably well-tolerated in patients with ARDS.

Adolescent↗
PubMed1992

Identification of cis-regulatory elements in the myelin proteolipid protein (PLP) gene.

Regulatory elements of the proteolipid protein (PLP) gene were identified physically by footprinting and gel mobility shift assays and functionally by transfecting glial cell lines with PLP-chloramphenicol acetyltransferase chimeric genes. In both human and rat glial cells, only several hundred base pairs of upstream sequence were sufficient for high level activity of the human PLP promoter. This region contains five sites that contact nuclear proteins in vitro. More distal recognition sites may exist, as regions upstream of -524 displayed silencing activity indicative of a negative regulatory element. A series of site directed mutations revealed one essential positive element (ATGGA at -118) which is found in other genes encoding myelin proteins. Our combined biochemical and functional analyses indicate that the key cis sites for maximal tissue-specific expression of PLP in cultured glial cells are clustered near the promoter. Within this cluster are several conserved motifs that may coordinate the regulation of myelin-specific genes.

Animals↗