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Biomedical subjects

J Kaufman

Publications and source records attributed to J Kaufman.

At least 19 recordsLinked to original sources
PubMed1996

Regulation of HIV-1 protease activity through cysteine modification.

The homodimeric protease of the human immunodeficiency virus 1 contains two cysteine residues per monomer which are highly conserved among viral isolates. However, these cysteine residues are not essential for catalytic activity which raises the question of why they are conserved. We have found previously that these cysteine residues are unusually susceptible to oxidation by metal ions, and this results in inhibition of protease activity. Recombinant protease mutants (C67A, C95A, and the double mutant C67A,C95A) were prepared to assess the possible role of these cysteines in redox regulation of the enzyme. Mixed disulfides were formed between the cysteine residues of the enzymes and low molecular weight thiols. Enzyme activity was lost when a mixed disulfide was formed between 5,5'-dithiobis(2-nitrobenzoic acid) and cysteine 95, while the same mixed disulfide at cysteine 67 reduced activity by 50%. This effect was reversible as normal activity could be restored when the enzyme was treated with dithiothreitol. The cysteines could also be modified with the common cellular thiol glutathione. Modification with glutathione was verified by mass spectrometry of the protein peaks obtained from HPLC separation. Glutathiolation of cysteine 95 abolished activity whereas modification at cysteine 67 increased the k(cat) by more than 2-fold with no effect on K(m). In addition, glutathiolation at cysteine 67 markedly stabilized the enzyme activity presumably by reducing autoproteolysis. These results demonstrate one possible mechanism for regulation of the HIV-1 protease through cysteine modification and identify additional targets for affecting protease activity other than the active site.

Catalysis↗
PubMed1996

Corticotropin-releasing hormone challenge in prepubertal major depression.

This study investigates cortisol and ACTH (corticotropin) responses to an infusion of human CRH (corticotropin-releasing hormone) in prepubertal children with major depressive disorder (MDD). Following a period of 24 hours of adaptation to the laboratory environment with an intravenous catheter in place, 34 children with MDD and 22 healthy controls received 1 microgram/kg of human CRH at 5:00 PM. Blood samples for cortisol and ACTH were measured at baseline and post-CRH. Overall, there were no significant differences between the MDD and the normal controls in baseline or post CRH stimulation values of either cortisol or ACTH. Melancholic (n = 4) patients had significantly higher baseline cortisol levels than nonmelancholic (n = 24) patients. Compared with the outpatients and the nonmelancholics, the inpatients (n = 10) and the melancholics showed significantly lower total ACTH secretion (effect size: 0.9 and 1.4, respectively) after CRH infusion. These results are consistent with a broad literature suggesting that the HPA axis abnormalities occur less frequently in early-onset depression than reported in adult studies. The pattern of results in the subgroups of inpatients and in melancholic children, however, raise questions about possible continuities with adult studies.

Adolescent↗
PubMed1996

The chicken beta 2-microglobulin gene is located on a non-major histocompatibility complex microchromosome: a small, G+C-rich gene with X and Y boxes in the promoter.

beta 2-Microglobulin is an essential subunit of major histocompatibility complex (Mhc) class I molecules, which present antigenic peptides to T lymphocytes. We sequenced a number of cDNAs and two genomic clones corresponding to chicken beta 2-microglobulin. The chicken beta 2-microglobulin gene has a similar genomic organization but smaller introns and higher G+C content than mammalian beta 2-microglobulin genes. The promoter region is particularly G+C-rich and contains, in addition to interferon regulatory elements, potential S/W, X, and Y boxes that were originally described for mammalian class II but not class I alpha or beta 2-microglobulin genes. There is a single chicken beta 2-microglobulin gene that has little polymorphism in the coding region. Restriction fragment length polymorphisms from Mhc homozygous lines, Mhc congenic lines, and backcross families, as well as in situ hybridization, show that the beta 2-microglobulin gene is located on a microchromosome different from the one that contains the chicken Mhc. We propose that the structural similarities between the beta 2-microglobulin and Mhc genes in the chicken are due to their presence on microchromosomes and suggest that these features and the microchromosomes appeared by deletion of DNA in the lineage leading to the birds.

Amino Acid Sequence↗
PubMed1996

T2 relaxation times of hypervascular and non-hypervascular liver lesions: do hypervascular lesions mimic haemangiomas on heavily T2-weighted MR images?

AIM: To correlate the T2 relaxation times of liver lesions with their vascularity at angiography and to determine whether hypervascular lesions have similar signal intensity to haemangiomas on heavily T2-weighted MR images. PATIENTS AND METHODS: Thirty-four patients with histologically proven malignant liver lesions had both angiography and T2W (SE 3000/80,160) MR imaging (1.5 T) of the liver. Angiographically, the lesions were hypervascular in 15 and non-hypervascular in 19 patients. Fifteen additional patients with proven haemangioma also had MR imaging during the same time period. The T2 relaxation time of a representative lesion was calculated for each patient and the results compared. RESULTS: The mean T2 time for hypervascular lesions was 76 +/- 21 ms compared with 79 +/- 18 ms for non-hypervascular lesions (P = 0.61). The mean T2 relaxation time for haemangiomas was significantly longer than either group: 147 +/- 46 ms (P = 0.0001). CONCLUSION: The T2 relaxation times of hypervascular and non-hypervascular liver lesions are similar and are significantly shorter than those of haemangiomas. Therefore, hypervascular lesions should not mimic haemangiomas on heavily T2-weighted images.

Carcinoma, Hepatocellular↗
PubMed1996

The solution structure of HIV-1 Nef reveals an unexpected fold and permits delineation of the binding surface for the SH3 domain of Hck tyrosine protein kinase.

The solution structure of HIV-1 Nef has been solved by multidimensional heteronuclear NMR spectroscopy. The construct employed to circumvent problems associated with aggregation was a double-deletion mutant (delta2-39, delta159-173) in which conformationally disordered regions of the protein at the N terminus and in a long solvent-exposed flexible loop were removed, without affecting the properties or structural integrity of the remainder of the protein. Despite the absence of any sequence similarity, the overall fold of Nef is reminiscent of that of the family of winged helix-turn-helix DNA binding proteins. The binding surface of Nef for the SH3 domain of Hck tyrosine protein kinase has been mapped and reveals a non-contiguous (in terms of amino-acid sequence) interaction surface. This unique feature may suggest possible avenues for drug design aimed at inhibiting the interaction between Nef and SH3 domains.

Amino Acid Sequence↗
PubMed1996

Improving the process of care: the cost-quality value of interdisciplinary collaboration.

A multidisciplinary group of clinicians and administrators were convened to find innovative ways to contain costs and improve the quality of care on an inpatient orthopedic unit. This group was charged with examining all phases of care and recommending changes. The team proved to be a model of effective, successful collaboration and has enabled ambitious goals to be realized on this unit. The article outlines changes related to preoperative, intraoperative, and postoperative care and discusses the dynamics of effective interdisciplinary professional collaboration.

Boston↗
PubMed1995

High-yield production of diphtheria toxin mutants by high-density culture of C7 (beta)tox+ strains grown in a non-deferrated medium.

A high-density growth approach was utilized to produce mutated diphtheria toxin from two strains of Corynebacterium diphtheria: C7 (beta)(tox-201,tox-9) and C7 (beta)(tox-107). The cross-reacting mutants (CRM) of the diphtheria toxin are CRM9 and CRM107; both of them carry the mutation in their binding site and, as a result, have 1/300 of the systemic toxicity of the wild-type diphtheria toxin. Since iron inhibits diphtheria toxin production, the traditional approach has been to grow the bacteria in a very low iron concentration. The procedure described here involved the use of a modified, non-deferrated, growth medium that provided fast and high-density growth of the bacteria, and which, when associated with simultaneous depletion of glucose and iron, enhanced the toxin production. Oxygen-enriched air was supplied to enable the bacteria to grow to a cell density giving an absorbance of 70 at 600 nm (15-20 g/l dry weight). The maximum toxin concentration in the culture supernatant was 150 mg/l. The CRM products, which remained stable following microfiltration and ultrafiltration, could be easily purified using a two-step chromatography procedure.

Corynebacterium diphtheriae↗
PubMed1995

Oral versus repository corticosteroid therapy after hospitalization for treatment of asthma.

Tapering regimens of oral steroids may be difficult or confusing for some patients. Repository steroids have been shown to be as effective as tapering oral doses in preventing relapse after emergency treatment. This study was undertaken to determine whether repository steroids are as effective as tapering oral steroids in preventing relapse after hospitalization for treatment of asthma. Twenty-six patients with acute exacerbations of asthma requiring treatment for 24 to 72 hours with parenteral steroids were randomized into two groups. Both groups received oral prednisone, 60 mg daily, when parenteral steroids were discontinued. At discharge, one group received intramuscular placebo and oral prednisone tapered over 8 days, and the other received 80 mg intramuscular methylprednisolone sodium acetate and oral placebo. At discharge and 2-week follow-up, patients were interviewed and examined, and spirometry results were obtained. There was little difference between groups in ratings of symptoms at discharge or follow-up. Both groups had less wheezing at follow-up than at discharge, though the improvement was significant only in the repository steroid group (p < 0.05). Mean forced expiratory volume in 1 second, forced vital capacity, peak expiratory flow rate improved at follow-up in both groups. No significant differences in outcome were found between the oral and repository steroid groups.

Acute Disease↗
PubMed1995

Unipolar depression in adolescents: clinical outcome in adulthood.

OBJECTIVE: This study examined the longitudinal clinical course and adult sequelae of adolescent unipolar major depressive disorder (MDD) using a controlled longitudinal design. METHOD: Subjects were 28 adolescents (15.4 +/- 1.3 years) with systematically diagnosed unipolar MDD and 35 group-matched control subjects who participated in a cross-sectional electroencephalogram sleep and neuroendocrine study. Using standardized instruments, interviewers who were blind to subjects' initial diagnoses conducted follow-up clinical assessments 7.0 +/- 0.5 years later in 94% of the original cohort. RESULTS: The depressed group showed high rates of recurrence of MDD episodes during the interval period (69%). They also had elevated rates of new-onset bipolar disorder (19%). Twenty-three percent of subjects with an initial diagnosis of MDD had no additional depressive episodes after the index assessment. The rate of new onset of depression in the controls was 21%. Low socioeconomic status predicted recurrence of depressive episodes in the MDD group. MDD subjects with recurrence(s) and controls with new onset of depression during the follow-up period had significant psychosocial morbidity, as evidenced by disruption in interpersonal relationships and dissatisfaction with life and decrease in global functioning, compared with both MDD subjects with no further episodes and control subjects who had never been psychiatrically ill. These psychosocial deficits persisted remission from depressive episode(s). CONCLUSIONS: Adolescent unipolar MDD predicts continued risk for recurrences with persistence of depressive episodes and psychosocial morbidity into adulthood. A sizable minority, however, have sustained periods of remission associated with good social adjustment.

Adolescent↗
PubMed1995

A case-control family history study of depression in adolescents.

OBJECTIVE: To examine whether depression aggregates in the families of depressed adolescents and to determine whether clinical features and/or comorbid syndromes in the depressed adolescents change the risk of psychopathology in relatives. METHOD: Lifetime prevalence rates of psychopathology in the first-degree (n = 228) and second-degree (n = 736) relatives of 76 adolescents with major depressive disorder (MDD) and the first-degree (n = 107) and second-degree (n = 323) relatives of 34 normal control adolescents were assessed by the Family History-Research Diagnostic Criteria (FH-RDC) method using the parent/guardian as the family informant. RESULTS: Compared with the first-degree relatives of normal controls, the relatives of depressed adolescents had significantly higher lifetime rates of MDD (25% versus 13%) and "any" of the FH-RDC psychiatric disorders (53% versus 36%). The second-degree relatives of adolescents with MDD had significantly higher lifetime rates of FH-RDC "other" psychiatric disorder (12% versus 7%) and "any" of the FH-RDC psychiatric disorders (22% versus 15%) but not MDD (5% versus 6%) compared with the relatives of normal controls. The first-degree relatives of depressed adolescents who were also suicidal had increased lifetime rates of suicidal behavior which significantly cosegregated with MDD. Comorbid conduct disorder in the depressed adolescent was associated with increased rates of antisocial personality disorder in the first-degree relatives and also tended to cosegregate with MDD. CONCLUSIONS: The current study provides further evidence for the familial aggregation of depression in adolescent-onset MDD. This study also suggests that the familial aggregation of nonaffective psychiatric disorders depends on the clinical features and comorbid syndromes present in the depressed adolescent proband.

Adolescent↗
PubMed1995

Eosinophilic pleural effusion associated with valproic acid administration.

A case of eosinophilic pleural effusion with peripheral blood eosinophilia is presented. No cause of the pleural effusion was found, but on cessation of valproic acid therapy, both the pleural effusion and eosinophilia resolved. Valproic acid should be added to the list of drugs associated with pleural fluid eosinophilia.

Adult↗
PubMed1995

A "minimal essential Mhc" and an "unrecognized Mhc": two extremes in selection for polymorphism.

The high polymorphism of classical Mhc molecules found in mammals is not simply the result of strong selection for pathogen resistance in the recent past, since there are virtually no examples of diseases caused by infectious pathogens for which resistance is determined by particular Mhc haplotypes, and in the best-studied case, a particular aspect of malaria in humans, the selection is remarkably weak. We discuss three possibilities to explain high polymorphism in mammals: accumulating, merging and boosting. The mammalian Mhc is complicated and redundant, so that every Mhc haplotype may give some level of resistance due to multiple classical Mhc genes as well as other disease resistance genes; this frustrates the attempts to demonstrate selection for disease resistance. We have looked at two vertebrate groups that may represent two extreme examples of selection for Mhc polymorphism. Birds, like mammals, have highly a polymorphic Mhc that determines strong allograft rejection. However, chickens have a much smaller, compact and simpler Mhc than mammals, as though the Mhc has been stripped down to the essentials during evolution. The selection on a single Mhc gene should be much stronger than on a large multigene family and, in fact, there are a number of viral diseases for which resistance and susceptibility are determined by particular chicken Mhc haplotypes. We have determined the peptide motifs for the chicken class I molecules from a number of haplotypes, which may explain some disease associations quite simply. On the other hand, salamanders have very low Mhc polymorphism and slow allograft rejection. We have isolated axolotl Mhc molecules and shown that they cosegregate with the locus that determines graft rejection in the axolotl, have only a few alleles and only weakly stimulate axolotl T lymphocytes in mixed lymphocyte culture. We believe that salamanders have classical Mhc molecules but most T cells do not recognize them, so that there is no strong selection for polymorphism.

Amino Acid Sequence↗
PubMed1995

Synergistic effect of basic fibroblast growth factor and methylprednisolone on neurological function after experimental spinal cord injury.

The authors evaluated the effects of exogenous basic fibroblast growth factor (bFGF) in combination with intravenous methylprednisolone on neurological function and cord angiogenesis in a model of spinal cord injury. Cord injury was produced by extradural clip compression through a T-1 laminectomy. Rats were randomized to one of six groups. Group A was given sham laminectomy without cord injury or treatment. The remaining animals were divided into five groups: untreated injury (Group B); injury treated with methylprednisolone (Group C); combined methylprednisolone and 1 microgram bFGF administered locally at the site of injury (Group D); methylprednisolone and 3 micrograms bFGF (Group E); or methylprednisolone and 3 micrograms heated bFGF (Group F). Groups C through F received treatment 1 hour after cord injury. At 1, 2, 3, and 4 weeks after surgery, neurological function of hindlimbs was assessed by blinded observers using an established multiple test method (toe spread, reflexes to extension, pain, and pressure as well as inclined plane and swim test) with tests graded and results expressed as a combined behavioral score. Animals were killed to study spinal cord angiogenesis in cord samples (2-mm sections proximal and distal to the injury site) by capillary density determination. Behavioral scores over time showed a significant difference among Groups B, C, D, E, and F (p = 0.0044), with Groups E and B maintaining highest and lowest scores, respectively. There was a linear dose effect of bFGF over time (p = 0.0187). At 4 weeks, scores showed a difference among the five groups (p = 0.006), with Group E showing higher scores than any other treatment group (for example, vs. group F: p = 0.035). There was a significant difference among the groups in gray matter capillary density counts: proximal (p = 0.0192) and distal (p = 0.024), whereas white matter capillary counts were similar across treatment groups. These results show: 1) possible synergism exists between methylprednisolone and bFGF, such that combinations of these drugs significantly enhance neurological recovery, 2) bFGF exhibits a dose-response effect in function but not in capillary density, and 3) heated, inactivated bFGF is not therapeutically effective.

Analysis of Variance↗