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Biomedical subjects

L Katz

Publications and source records attributed to L Katz.

At least 55 records · Page 3Linked to original sources
PubMed1996

Saturation mutagenesis of the WSXWS motif of the erythropoietin receptor.

The WSXWS motif in the extracellular domain defines members of the cytokine receptor family, yet its role in receptor structure and function remains unresolved. To address this question we have generated a panel of 100 mutants within the WSXWS motif of the erythropoietin receptor, which represents all single amino acid substitutions of these five amino acids. All mutants were synthesized at the same level; however, their passage from the endoplasmic reticulum to the Golgi apparatus differed. Because of this, expression of mutant receptors at the cell surface varied more than 300-fold. The tolerance of the tryptophan and serine residues to substitution was quite narrow; as a result, most of these mutants were retained in the endoplasmic reticulum and showed no cell surface expression or reduced cell surface expression. Although many mutants with substitutions at the middle residue of the motif reached the cell surface, it was notable that one mutant, A234E, was processed more efficiently than the wild type receptor and was expressed in elevated numbers at the cell surface. Despite this variation, all mutant receptors that reached the cell surface appeared able to bind erythropoietin and transduce a proliferative signal normally. These results are discussed in terms of a general model for WSXWS function in which the motif contributes to efficient receptor folding.

Amino Acid Sequence↗
PubMed1996

Pilomatricoma-like endometrioid adenosquamous carcinoma of the ovary with neuroendocrine differentiation.

A case of high-grade endometrioid adenosquamous carcinoma of the ovary showing pilomatricoma-like areas and neuroendocrine differentiation is presented. The pilomatricoma-like areas were strongly positive for cytokeratin and vimentin, whereas the poorly differentiated areas of the tumor were positive for cytokeratin, synaptophysin, and neuron-specific enolase. Review of the literature did not show any published report of adenosquamous carcinoma with pilomatricoma-like areas either in the ovary or in the uterus.

Carcinoma, Adenosquamous↗
PubMed1996

Auditory selective attention: an fMRI investigation.

In the present experiment, 25 adult subjects discriminated speech tokens ([ba]/[da]) or made pitch judgments on tone stimuli (rising/falling) under both binaural and dichotic listening conditions. We observed that when listeners performed tasks under the dichotic conditions, during which greater demands are made on auditory selective attention, activation within the posterior (parietal) attention system and at primary processing sites in the superior temporal and inferior frontal regions was increased. The cingulate gyrus within the anterior attention system was not influenced by this manipulation. Hemispheric differences between speech and nonspeech tasks were also observed, both at Broca's Area within the inferior frontal gyrus and in the middle temporal gyrus.

Adult↗
PubMed1996

Erythromycin production in Saccharopolyspora erythraea does not require a functional propionyl-CoA carboxylase.

Using an oligonucleotide corresponding to the consensus sequence for the biotin-binding motif, two unlinked genetic loci, bpl1 and bpl2, were cloned from the erythromycin producer Saccharopolyspora erythraea and the nucleotide sequences of a c. 4 kb segment from each determined. The two loci share a virtually identical segment of 1746 nucleotides, coinciding with most of the genes designated bcpA1 and bcpA2 present in bpl1 and bpl2, respectively. The deduced sequences of these genes are highly similar to that of the alpha-chain of mammalian propionyl-CoA carboxylase. Upstream of bcpA2 lies pccB, the gene encoding the beta-chain of this enzyme. Mutant strains carrying frameshift mutations in bcpA1 and pccB were constructed, but we failed to isolate insertional mutants in bcpA2. Propionyl-CoA carboxylase activity was undetectable in the pccB mutant, but was unaffected in the bcpA1-defective strain. These results indicate that pccB encodes the beta-chain of propionyl-CoA carboxylases, and suggest that the alpha-chain of this enzyme, which is likely to be encoded by bcpA2, is shared with some other essential biotin-dependent enzyme. The pccB mutation had no impact on erythromycin production in complex medium.

Base Sequence↗
PubMed1996

Cerebral organization of component processes in reading.

The cerebral organization of word identification processes in reading was examined using functional magnetic resonance imaging (fMRI). Changes in fMRI signal intensities were measured in 38 subjects (19 males and 19 females) during visual (line judgement), orthographic (letter case judgement), phonological (nonword rhyme judgement) and semantic (semantic category judgement) tasks. A strategy of multiple subtractions was employed in order to validate relationships between structure and function. Orthographic processing made maximum demands on extrastriate sites, phonological processing on a number of frontal and temporal sites, and lexical-semantic processing was most strongly associated with middle and superior temporal sites. Significant sex differences in the cerebral organization of reading-related processes were also observed.

Adult↗
PubMed1996

A review of the psychobiology and pharmacotherapy of posttraumatic stress disorder.

OBJECTIVE: To review the literature on certain psychobiologic elements of posttraumatic stress disorder (PTSD) as they pertain to possible pharmacotherapeutic interventions. METHOD: The literature pertaining to the neuroanatomical, neurochemical, and cellular elements was reviewed. As well, both controlled and uncontrolled studies of pharmacotherapy in PTSD were analyzed. RESULTS: The literature suggests that the stress response triggers certain neuromodulators with subsequent psychoneurological restructuring; that various antidepressants have been demonstrated to be effective for treatment of criterion B symptoms; that, to date, a single antidepressant has been demonstrated to be effective in a controlled trial for criterion C symptoms; and that, to date, in controlled trials, antidepressants and a benzodiazepine have proved effective for criterion D symptoms. CONCLUSION: Currently, a comprehensive approach requires multimodel understanding and multimodal treatment.

Antidepressive Agents↗
PubMed1995

Enhancing physician adoption of practice guidelines. Dissemination of influenza vaccination guideline using a small-group consensus process.

BACKGROUND: A dissemination intervention to facilitate adoption of a preventive practice guideline (influenza vaccination for older adults) in group practices was developed and evaluated. The intervention, small-group consensus process, started with a physician expert presenting the guideline and followed with the group participating in a structured discussion of ways to implement the guideline that culminated in a public commitment (ie, "buy in") to adopt the guideline. METHODS: Thirteen group practices and their primary care physicians (mean size, 5) were assigned randomly to intervention or control arms. In each group practice, physicians in the intervention arm met for 1 hour. Control physicians participated in an unrelated discussion (non-steroidal drug use). Guideline adoption was determined by changes in physicians' vaccination rates that were obtained through prechart and postchart reviews of 51 physicians. Prequestionnaires and postquestionnaires measured influenza knowledge and prevention attitudes. RESULTS: Using analysis of covariance, the small-group consensus process was found to increase physician vaccination rates by 34% compared with the control arm (F (1,48) = 19.49). All intervention arm physicians increased vaccination rates from before to after compared with 54% of control arm physicians. Attitudes and knowledge did not change and were unrelated to increased vaccination rates. CONCLUSIONS: A case is made for the small-group consensus process as an effective utilization-focused dissemination method. Interventions based on group dynamics and sensitive to local practice contexts can be useful in facilitating adoption of guidelines by physicians in group practices.

Decision Making↗
PubMed1995

Sex differences in the functional organization of the brain for language.

A much debated question is whether sex differences exist in the functional organization of the brain for language. A long-held hypothesis posits that language functions are more likely to be highly lateralized in males and to be represented in both cerebral hemispheres in females, but attempts to demonstrate this have been inconclusive. Here we use echo-planar functional magnetic resonance imaging to study 38 right-handed subjects (19 males and 19 females) during orthographic (letter recognition), phonological (rhyme) and semantic (semantic category) tasks. During phonological tasks, brain activation in males is lateralized to the left inferior frontal gyrus regions; in females the pattern of activation is very different, engaging more diffuse neural systems that involve both the left and right inferior frontal gyrus. Our data provide clear evidence for a sex difference in the functional organization of the brain for language and indicate that these variations exist at the level of phonological processing.

Adult↗
PubMed1995

Overproduction and characterization of the erythromycin C-12 hydroxylase, EryK.

Hydroxylation of C-12 is one of the final steps in the biosynthesis of erythromycin A (ErA). A point of uncertainty in the erythromycin pathway has been whether the C-12 hydroxylase operates on each of two possible substrates, erythromycin B (ErB) and erythromycin D (ErD). Stassi et al. have cloned the gene, designated eryK, which encodes the P-450 monooxygenase responsible for erythromycin C-12 hydroxylation in Saccharopolyspora erythraea [Stassi, D., Donadio, S., Staver, M. J., & Katz, L. (1993) J. Bacteriol. 175, 182-189]. We report the overproduction of EryK in Escherichia coli as insoluble inclusion bodies; the solubilization, refolding, and reconstitution of active holo-EryK; and kinetic confirmation of a 1200-1900-fold preference of the enzyme for ErD over the alternative C-12 hydroxylase substrate ErB. Our results indicate that ErB is a shunt metabolite in the erythromycin biosynthetic pathway.

Amino Acid Sequence↗
PubMed1995

Epinephrine and sodium bicarbonate during CPR following asphyxial cardiac arrest in rats.

Although high-dose epinephrine during CPR improves coronary perfusion pressure (CoPP) and rate of return of spontaneous circulation (ROSC) in some models, its impact on long term outcome (> or = 72 h) has not been evaluated. Previous studies of sodium bicarbonate (NaHCO3) therapy during CPR indicate that beneficial effects may be dependent on epinephrine (EPI) dose. We hypothesized that EPI and NaHCO3 given during CPR have a significant impact on long term outcome. One hundred male Sprague-Dawley rats were prospectively studied in a block randomized placebo controlled trial. Rats were anesthetized, paralyzed, mechanically ventilated, instrumented, and each underwent 10 min of asphyxia, resulting in 6.8 +/- 0.4 min of circulatory arrest. Resuscitation was performed by mechanical ventilation and manual external chest compressions. EPI 0.0 (placebo), 0.01, 0.1, or 1.0 mg/kg IV was given at the onset of CPR, followed by NaHCO3 0.0 (placebo) or 1.0 mEq/kg IV. Successfully resuscitated rats were monitored and ventilated for 1 h without hemodynamic support. Neurologic deficit scores (NDS), cerebral histopathologic damage scores (CHDS) and myocardial histopathologic damage scores (MHDS) were determined in rats that survived 72 h. EPI improved CoPP and ROSC in a dose-dependent manner up to 0.1 mg/kg. Rats receiving EPI 0.1 and 1.0 mg/kg during CPR exhibited prolonged post-ROSC hypertension and metabolic acidemia, increased A-a O2 gradient, and an increased incidence of post-ROSC ventricular tachycardia or fibrillation. Overall survival was lower with EPI 0.1 and 1.0 mg/kg compared to 0.01 mg/kg. Although NDS was significantly less with EPI 0.1 mg/kg compared to placebo, there was no difference in CHDS between groups. In contrast, MDS was significantly higher with EPI 0.1 mg/kg compared to placebo or EPI 0.01 mg/kg. There was an overall trend toward improved survival at 72 h in rats that received NaHCO3 which was most evident in the EPI 0.1 mg/kg group. We conclude that (1) EPI during CPR has a biphasic dose/response curve in terms of survival, when post-resuscitation effects are left untreated and (2) NaHCO3 doses greater than 1.0 mEq/kg may be necessary to treat the side-effects of high-dose EPI. Further work is needed to determine if treating the immediate post-resuscitation effects of high-dose EPI can prevent detrimental effects on long-term outcome.

Animals↗
PubMed1995

Insulin-like growth factor binding protein (IGFBP) proteases: functional regulators of cell growth.

The IGFBP proteases were first described in pregnancy serum as a proteolytic activity against IGFBP-3. Since then, IGFBP proteases have been described in many other clinical situations, in various body fluids, and have been shown to cleave IGFBP-2 to -6 with varying specificity. The molecular nature of some of these proteases is being unraveled and three classes of IGFBP proteases have been recognized. These include kallikreins, cathepsins and matrix metalloproteinases (MMPs). We utilized two cellular systems to demonstrate the significance of IGFBP proteases in cellular growth regulation. In primary cultures of prostatic cells, we have shown that prostate-specific antigen (PSA) has the ability to enhance IGF mitogenic action by reducing the effects of IGFBPs. Similar kallikreins such as gamma nerve growth factor (NGF) share this activity. Within the prostatic milieu, we have also demonstrated epithelial production of the acid-activated IGFBP protease, cathepsin D, and its secretion into seminal plasma, as well as the serum of patients with prostate malignancy. We have also identified MMPs in prostatic cells and fluids. Using cultured airway smooth muscle (ASM) cells, we have demonstrated the synergism between IGFs and inflammatory agents in mediating ASM cell proliferation. Examination of this phenomenon revealed that these agents (e.g. leukotriene D4 and interleukin1-beta) induce the secretion of an IGFBP protease which cleaves the IGFBPs secreted by ASM cells, allowing IGFs to stimulate proliferation. Using several methods, including immunoblotting and immunodepletion techniques, we have identified this protease as MMP-1. These two pathophysiological systems demonstrate the importance of IGFBP proteases as autocrine paracrine growth regulators. Furthermore, IGFBP proteases may be critical elements in malignant and benign proliferative diseases, including prostate cancer and the ASM hyperplasia of long-standing asthma.

Animals↗
PubMed1995

Macrolides.

Explore the source record for details and available documents.

Actinomycetales↗
PubMed1995

Outcome model of asphyxial cardiac arrest in rats.

An outcome model with asphyxial cardiac arrest in rats has been developed for quantifying brain damage. Twenty-two rats were randomized into three groups. Control group I was normal, was conscious, and had no asphyxia (n = 6). Sham group II had anesthesia and surgery but no asphyxia (n = 6). All 12 rats in groups I and II survived to 72 h and were functionally and histologically normal. Arrest group III (the model; n = 10) had light anesthesia and apneic asphyxia of 8 min, which led to cessation of circulation at 3-4 min of apnea, resulting in cardiac arrest (no flow) of 4-5 min. All 10 rats had spontaneous circulation restored by standard external cardiopulmonary resuscitation. Nine rats survived controlled ventilation for 1 h and observation to 72 h, while one rat died before extubation. All nine survivors were conscious at 72 h, with neurologic deficit scores (0% = best; 100% = worst) of 7 +/- 6% (2-16%). All brain regions at five coronal levels were examined for ischemic neurons. The prevalence of ischemic neurons in five regions was categorically scored. The average total brain histopathologic damage score in group III (n = 9) was 2.1 (p < 0.05 vs. group I or II). A reproducible outcome model of cardiac arrest in rats was documented. It provides a tool for investigating pathophysiological mechanisms of neuronal death caused by a transient global hypoxic-ischemic brain insult.

Animals↗
PubMed1995

Substrate requirements for ErmC' methyltransferase activity.

ErmC' is a methyltransferase that confers resistance to the macrolide-lincosamide-streptogramin B group of antibiotics by catalyzing the methylation of 23S rRNA at a specific adenine residue (A-2085 in Bacillus subtilis; A-2058 in Escherichia coli). The gene for ErmC' was cloned and expressed to a high level in E. coli, and the protein was purified to virtual homogeneity. Studies of substrate requirements of ErmC' have shown that a 262-nucleotide RNA fragment within domain V of B. subtilis 23S rRNA can be utilized efficiently as a substrate for methylation at A-2085. Kinetic studies of the monomethylation reaction showed that the apparent Km of this 262-nucleotide RNA oligonucleotide was 26-fold greater than the value determined for full-size and domain V 23S rRNA. In addition, the Vmax for this fragment also rose sevenfold. A model of RNA-ErmC' interaction involving multiple binding sites is proposed from the kinetic data presented.

Bacillus subtilis↗
PubMed1995

Erythromycin biosynthesis. Highly efficient incorporation of polyketide chain elongation intermediates into 6-deoxyerythronolide B in an engineered Streptomyces host.

Feeding of (2S,3R)-[2,3-13C2]-2-methyl-3-hydroxypentanoyl NAC thioester (1a) to the recombinant organism Streptomyces coelicolor CH999/pCK7 harboring the complete set of eryA genes from Saccharopolyspora erythraea encoding the 6-deoxyerythronolide B synthase (DEBS) resulted in the formation of 6-deoxyerythronolide B (2a) labeled with 13C at C-12 and C-13, as evidenced by the appearance of a pair of enhanced and coupled doublets in the 13C NMR spectrum. The level of 13C enrichment was 15-20 atom% 13C, as much as 100 times higher than the usually observed efficiency of incorporation of NAC thioesters into polyketide metabolites. Similar incorporation of (2S,3R)-[3-2H,3-13C]-2-methyl-3-hydroxypentanoyl NAC thioester (1b) gave 6-deoxyerythronolide B (2b) labeled with both 13C and deuterium at C-13. The intact incorporation of both precursors confirms the normal functioning of the recombinant DEBS proteins in the heterologous host.

DNA, Recombinant↗
PubMed1995

Use of hysteroscopy in addition to laparoscopy for evaluating chronic pelvic pain.

This study assessed whether hysteroscopy can provide information concerning the cause of chronic pelvic pain. We prospectively evaluated the findings in 547 consecutive patients who had laparoscopy to evaluate chronic pelvic pain at a large, referral-based clinic and outpatient suite of a suburban hospital. Forty-eight had previous hysterectomies. The remaining 499 had hysteroscopy during the same surgery and met the following qualifications: chronic pelvic pain, dysmenorrhea, dyspareunia, dysuria, back pain, pelvic pressure or dyschezia for a duration greater than six months and previous failed medical therapy. When endometriosis was the primary diagnosis at laparoscopy, hysteroscopy revealed abnormalities in 62 (32.5%) of 191 patients. At hysteroscopy, 46 of 105 patients (43.8%) with single or multiple leiomyomas of significant sizes diagnosed laparoscopically were noted to have pathology within the uterine cavity. Ten of 11 patients (90.9%) found to have ovarian cysts underwent hysteroscopy. Four (40%) had uterine abnormalities; the most common was cervical stenosis. Pelvic adhesions were found in 118 patients (21.6%). Eighty-nine underwent hysteroscopy, and 24 (27%) had intrauterine abnormalities. Ninety-six patients (17.5%) who underwent laparoscopic evaluation had endometriosis and pelvic adhesions. Ninety-three of these underwent hysteroscopy, and abnormalities were noted in 26 (28.0%). In eight women (1.5%) no abnormality was found at laparoscopy. Two underwent hysteroscopy, and no abnormality was noted in either woman. Hysteroscopy provides useful, adjunctive information and may improve the diagnosis and treatment of chronic pelvic pain.

Chronic Disease↗
PubMed1994

Characterization of the macromolecular synthesis (MMS) operon from Listeria monocytogenes.

The macromolecular synthesis (MMS) operon consists of three genes: rpsU, which encodes the S21 ribosomal protein in Bacillus subtilis (Bs), rpsU is replaced by orfP23 which encodes a protein of unknown function), dnaG, encoding the DNA primase involved in the initiation of chromosome replication, and rpoD, which encodes the principal sigma subunit of RNA polymerase. The operon was cloned in three segments from Listeria monocytogenes (Lm), initially using a probe designed from a highly conserved region of RpoD. Analysis of the nucleotide sequence revealed three genes: orfP17 (whose product, P17, is homologous to Bs P23), dnaG and rpoD. The Lm DnaG resembles the primase from Escherichia coli through the first two-thirds of the sequence. C-terminal similarity was observed between DnaG from Lm and Bs. Lm RpoD is similar to Bs SigA, shares identical DNA-binding domains with SigA, and is a member of the sigma 43 subgroup of the sigma 70 family.

Amino Acid Sequence↗