Search PubMed⌕ Search

Biomedical subjects

A Katz

Publications and source records attributed to A Katz.

At least 91 records · Page 5Linked to original sources
PubMed2000

Seasonal variation in sudden death in the Negev desert region of Israel.

BACKGROUND: Previous studies have documented an increased incidence of cardiac mortality and sudden death during winter months. OBJECTIVES: To evaluate seasonal variation in sudden death in a hot climate such as the desert region of southern Israel. METHODS: We analyzed the files of 243 consecutive patients treated for out-of-hospital sudden death by the Beer Sheva Mobile Intensive Care Unit during 1989-90. Daily, monthly and seasonal incidence of sudden death was correlated with meteorological data, including temperature, heat stress, relative humidity and barometric pressure. RESULTS: The seasonal distribution of sudden death was 23% in spring, 21% in summer, 25% in autumn and 31% in winter (not significant). In patients with known heart disease there were more episodes of sudden death in cold weather (< 15.4 degrees C) than hot (> 34.2 degrees C) (16 vs. 3, P < 0.05). Resuscitation was less successful in cold compared with hot weather (28 vs. 11, P < 0.05). Of patients older than 65 years, 11 sustained sudden death when heat stress was below 12.4 degrees C compared to 2 patients when heat stress was above 27.5 degrees C (P = 0.05). CONCLUSION: Despite the warm desert climate, there were more cases of sudden death in older patients and in those with known heart disease during the winter season and on particularly cold days.

Adult↗
PubMed1999

Indexing approximants of icosahedral quasicrystals.

It is well known that the crystallography of approxi-mants is directly related to that of the parent quasicrystal, once its unit-cell vectors are identified as parallel projections of certain N-dimensional lattice nodes A(i). Derived here are explicit simple relations for calculating the shear matrices varepsilon and the related crystallographic properties of the corresponding approximants, including diffraction indexing and the determination of the lattice in perpendicular space. Applied to low-dimensional approximants, the derivation shows that the systematic 'accidental' extinction rules observed in the pentagonal phases are generic extinctions that are due to the geometrical properties of the projected 1D lattice and are independent of the actual model of the quasicrystal.

Journal Article↗
PubMed1999

[Dose-intensive chemotherapy with continuous infusion 5-fluorouracil].

54 patients with advanced malignancy refractory to chemotherapy were studied to evaluate efficacy and toxicity of continuous infusion of 5-fluorouracil (5FU) given for 3 weeks. We report results of the first 156 courses given in combination with other drugs. 19 (37%) of the 54 responded, including 3 (6%) with complete response. Toxicity was acceptable, with mucositis in 13 (26%) and 3 (6%) with grade II-III toxicity. Results and toxicity profile were compatible with further disease-oriented studies using this dose-intensive program.

Adolescent↗
PubMed1999

Relation of atrial refractoriness to upper and lower limits of vulnerability for atrial fibrillation/flutter following implantable ventricular defibrillator shocks.

BACKGROUND: Implantable ventricular cardioverter defibrillator (ICD) shocks can cause atrial fibrillation/flutter (AF). This study investigated the pathogenesis of AF after ICD shocks in a canine model. METHODS AND RESULTS: The study was conducted in 8 dogs. In 5 dogs (group 1), truncated exponential (8 ms, 78% tilt) monophasic and biphasic shocks were delivered through a bipolar epicardial (patch) or endocardial lead. After the last S1 of atrial pacing at a cycle length of 350 ms, shocks of 0.1 to 7.6 A (0.005 to 27.7 J) were delivered, timed to the atrial effective refractory period (AERP). Ventricular defibrillation thresholds were also determined. In 3 dogs (group 2), the effect of the open versus closed chest technique on AF induction was tested in the endocardial biphasic shock configuration. AF was induced in all 8 dogs and in all waveforms and configurations. Mean AF duration was 11.5+/-6 s, with a mean ventricular rate of 184+/-37 bpm. Ventricular shocks could induce AF only if they were timed between an AERP of -60 to 40 ms, -40 to 60 ms, -40 to 60 ms, and -20 to 60 ms in the epicardial monophasic, epicardial biphasic, endocardial monophasic, and endocardial biphasic configurations, respectively. The mean+/-SD of the upper limit of vulnerability (ULV) for AF induction (in J) was 5. 2+/-0.6, 3.5+/-0.4, 5.2+/-1.2, and 2.5+/-0.1 for the epicardial monophasic, epicardial biphasic, endocardial monophasic, and endocardial biphasic configurations, respectively (P<0.05). The lower limit of vulnerability (LLV) was 0.8+/-0.1, 0.8+/-0.1, 0.9+/-0, and 0.6+/-0 for the epicardial monophasic, epicardial biphasic, endocardial monophasic, and endocardial biphasic configurations, respectively (P=NS). The ventricular defibrillation threshold (in J) for all wave forms and configurations was higher than the ULV (P<0. 05). CONCLUSIONS: (1) An atrial LLV and ULV exist for ventricular ICD shock-induced AF; (2) the shock-induced AF is related to both shock intensity and its timing to AERP; and (3) avoiding this atrial window of vulnerability may minimize the risk of post-ICD shock AF.

Animals↗
PubMed1999

Insulin stimulates both endothelin and nitric oxide activity in the human forearm.

BACKGROUND: The mechanism of the hemodynamic effect of insulin in the skeletal muscle circulation has not been fully elucidated. The purpose of this study was to assess whether the hemodynamic response to insulin involves the concurrent release of endothelin (ET-1) and nitric oxide (NO), 2 substances with opposing vasoactive properties. METHODS AND RESULTS: Bioactivity of ET-1 and NO was assessed without insulin and during insulin infusion in the forearm circulation of healthy subjects by use of blockers of ET-1 receptors and by NO synthesis inhibition. In the absence of hyperinsulinemia, ET-1 receptor blockade did not result in any significant change in forearm blood flow from baseline (P=0.29). Intra-arterial insulin administration did not significantly modify forearm blood flow (P=0. 88). However, in the presence of hyperinsulinemia, ET-1 receptor antagonism was associated with a significant vasodilator response (P<0.001). In the presence of ET-1 receptor blockade, the vasoconstrictor response to NO inhibition by N(G)-monomethyl-L-arginine was significantly higher after insulin infusion than in the absence of hyperinsulinemia (P=0.006). CONCLUSIONS: These findings suggest that in the skeletal muscle circulation, insulin stimulates both ET-1 and NO activity. An imbalance between the release of these 2 substances may be involved in the pathophysiology of hypertension and atherosclerosis in insulin-resistant states associated with endothelial dysfunction.

Endothelin-1↗
PubMed1999

Control of fertilization-independent endosperm development by the MEDEA polycomb gene in Arabidopsis.

Higher plant reproduction is unique because two cells are fertilized in the haploid female gametophyte. Egg and sperm nuclei fuse to form the embryo. A second sperm nucleus fuses with the central cell nucleus that replicates to generate the endosperm, a tissue that supports embryo development. To understand mechanisms that initiate reproduction, we isolated a mutation in Arabidopsis, f644, that allows for replication of the central cell and subsequent endosperm development without fertilization. When mutant f644 egg and central cells are fertilized by wild-type sperm, embryo development is inhibited, and endosperm is overproduced. By using a map-based strategy, we cloned and sequenced the F644 gene and showed that it encodes a SET-domain polycomb protein. Subsequently, we found that F644 is identical to MEDEA (MEA), a gene whose maternal-derived allele is required for embryogenesis [Grossniklaus, U., Vielle-Calzada, J.-P., Hoeppner, M. A. & Gagliano, W. B. (1998) Science 280, 446-450]. Together, these results reveal functions for plant polycomb proteins in the suppression of central cell proliferation and endosperm development. We discuss models to explain how polycomb proteins function to suppress endosperm and promote embryo development.

Arabidopsis↗
PubMed1999

Insulin increases near-membrane but not global Ca2+ in isolated skeletal muscle.

It has long been debated whether changes in Ca2+ are involved in insulin-stimulated glucose uptake in skeletal muscle. We have now investigated the effect of insulin on the global free myoplasmic Ca2+ concentration and the near-membrane free Ca2+ concentration ([Ca2+]mem) in intact, single skeletal muscle fibers from mice by using fluorescent Ca2+ indicators. Insulin has no effect on the global free myoplasmic Ca2+ concentration. However, insulin increases [Ca2+]mem by approximately 70% and the half-maximal increase in [Ca2+]mem occurs at an insulin concentration of 110 microunits per ml. The increase in [Ca2+]mem by insulin persists when sarcoplasmic reticulum Ca2+ release is inhibited but is lost by perfusing the fiber with a low Ca2+ medium or by addition of L-type Ca2+ channel inhibitors. Thus, insulin appears to stimulate Ca2+ entry into muscle cells via L-type Ca2+ channels. Wortmannin, which inhibits insulin-mediated activation of glucose transport in isolated skeletal muscle, also inhibits the insulin-mediated increase in [Ca2+]mem. These data demonstrate a new facet of insulin signaling and indicate that insulin-mediated increases in [Ca2+]mem in skeletal muscle may underlie important actions of the hormone.

Androstadienes↗
PubMed1999

Manganese sulfate-dependent glycosylation of endogenous glycoproteins in human skeletal muscle is catalyzed by a nonglucose 6-P-dependent glycogen synthase and not glycogenin.

Glycogenin, a Mn2+-dependent, self-glucosylating protein, is considered to catalyze the initial glucosyl transfer steps in glycogen biogenesis. To study the physiologic significance of this enzyme, measurements of glycogenin mediated glucose transfer to endogenous trichloroacetic acid precipitable material (protein-bound glycogen, i.e., glycoproteins) in human skeletal muscle were attempted. Although glycogenin protein was detected in muscle extracts, activity was not, even after exercise that resulted in marked glycogen depletion. Instead, a MnSO4-dependent glucose transfer to glycoproteins, inhibited by glycogen and UDP-pyridoxal (which do not affect glycogenin), and unaffected by CDP (a potent inhibitor of glycogenin), was consistently detected. MnSO4-dependent activity increased in concert with glycogen synthase fractional activity after prolonged exercise, and the MnSO4-dependent enzyme stimulated glucosylation of glycoproteins with molecular masses lower than those glucosylated by glucose 6-P-dependent glycogen synthase. Addition of purified glucose 6-P-dependent glycogen synthase to the muscle extract did not affect MnSO4-dependent glucose transfer, whereas glycogen synthase antibody completely abolished MnSO4-dependent activity. It is concluded that: (1) MnSO4-dependent glucose transfer to glycoproteins is catalyzed by a nonglucose 6-P-dependent form of glycogen synthase; (2) MnSO4-dependent glycogen synthase has a greater affinity for low molecular mass glycoproteins and may thus play a more important role than glucose 6-P-dependent glycogen synthase in the initial stages of glycogen biogenesis; and (3) glycogenin is generally inactive in human muscle in vivo.

Acarbose↗
PubMed1999

Patterns of radiotherapy practice for patients with squamous carcinoma of the uterine cervix: patterns of care study.

PURPOSE: To determine the impact of research findings and evolving technology on the patterns of radiotherapy practice for patients with carcinoma of the uterine cervix. METHODS AND MATERIALS: Sixty-two radiation therapy facilities participated in the study after having been selected from a random sample, proportionally stratified according to practice type, of all United States facilities. Each facility submitted a list of patients treated during 1992-1994 with radiation for squamous carcinoma of the cervix. Cases for review were randomly selected from each institution after excluding those of patients who had distant metastases or initial hysterectomy. A total of 471 patients' records were reviewed in the treating institutions to obtain information about patients' characteristics, diagnostic evaluation, tumor extent, treatment approach, and radiotherapy techniques. RESULTS: Of the 61 facilities that treated eligible cases of intact cervical cancer during the 3-year survey period, 35 (57%) treated fewer than three eligible patients per year. Thirty-four (83%) of 41 non-academic facilities vs. 1 (5%) of 20 academic facilities treated fewer than three patients per year. FIGO stages were I, II, III, and IV in 32%, 40%, 24%, and 3% of patients, respectively. Computed tomography (CT) was the most common method of lymph node evaluation, but surgical evaluation, which was performed in 76 (16%) patients, had increased from previous surveys. Fields were designed using a dedicated simulator in 95% of patients; a dedicated CT unit was used for treatment planning in 119 (30%) cases. External beam irradiation was most often given using a four-field technique at 180 cGy per day on a 10-20 MV linear accelerator. The average daily fraction size had decreased from previous surveys, and 13% of patients were treated with daily doses of 170 cGy or less. Most patients were treated with a combination of external beam and low dose-rate (LDR) intracavitary irradiation. Of 425 patients who had treatment with curative intent that included brachytherapy, 362 (85%) had LDR brachytherapy, 45 (11%) had high dose-rate (HDR) brachytherapy, 3 had a combination of HDR and LDR, and 15 had incomplete information about the brachytherapy dose-rate. Forty-six (23%) of 197 patients with Stages I-IIA disease were treated with radiation followed by extrafascial hysterectomy. Of 111 patients treated with curative intent for Stage III-IV disease, 72 (65%) had a combination of external beam and intracavitary radiation therapy, 22 (20%) had external beam plus interstitial brachytherapy, and 17 (15%) were treated with external beam irradiation only. For patients who completed treatment with curative intent and did not have adjuvant hysterectomy or HDR brachytherapy, the median total dose at point A was 82.5 Gy. For all patients who completed treatment with radiation alone, the median total duration of treatment was 63 days; more than 70 days were taken to complete treatment in 33% of cases. Twenty-nine percent of patients received chemotherapy, usually concurrent with their radiation therapy. Only 27% of these patients were on investigational protocols. CONCLUSIONS: Greater participation in well-designed prospective trials might help clinicians address important clinical questions and reduce current inconsistencies in the use of adjuvant treatments. Radiation oncologists should take steps to avoid unnecessary treatment protraction and to improve patient compliance. Future studies will be needed to determine whether the small number of cases being treated in most nonacademic facilities will influence the outcome for patients with invasive cervical carcinoma.

Adult↗
PubMed1999

Autonomous megakaryocyte growth in essential thrombocythemia and idiopathic myelofibrosis is not related to a c-mpl mutation or to an autocrine stimulation by Mpl-L.

Essential thrombocythemia (ET) and idiopathic myelofibrosis (PMF) are two myeloproliferative diseases characterized by a marked megakaryocytic (MK) involvement. The pathogenesis of these two diseases is unknown. Recently it has been shown that overexpression of Mpl-ligand (Mpl-L) in mice induces thrombocytosis and myelofibrosis. In this study, we investigated whether Mpl-L was responsible for the pathogenesis of ET and PMF. Using in vitro cultures of blood or marrow CD34(+) cells, we investigated whether MK growth was abnormal in these two diseases. Spontaneous MK growth involving only a fraction (20%) of the MK progenitors, as compared with growth in the presence of pegylated recombinant human megakaryocyte growth and development factor (PEG-rhuMGDF), was found in both diseases (21ET and 14PMF) using serum-free semisolid and liquid cultures, including cultures at one cell per well. We first searched for a c-mpl mutation/deletion by sequencing the entire coding region of the gene by polymerase chain reaction (PCR) in nine ET patients and five PMF patients, but no mutation was found. We subsequently investigated whether an autocrine stimulation by Mpl-L could explain the autonomous MK growth. Addition of different preparations of soluble Mpl receptor (sMpl) containing a Fc domain of IgG1 (sMpl-Fc) markedly inhibited MK spontaneous growth in both ET and PMF patients. This effect was specific for sMpl because a control soluble receptor (s4-1BB-Fc) had no inhibitory effect and an sMpl devoid of the Fc fragment had the same inhibitory efficacy as the sMpl-Fc. This inhibition was reversed by addition of PEG-rhuMGDF or a combination of cytokines. The sMpl-Fc markedly altered the entry into cell cycle of the CD34(+) cells and increased the apoptosis that occurs in most patient CD34(+) cells in the absence of exogenous cytokine, suggesting an autocrine stimulation. In contrast, a neutralizing antibody against Mpl-L did not alter the spontaneous MK growth, whereas it totally abolished the effects of 10 ng/mL PEG-rhuMGDF on patient or normal CD34(+) cells. Mpl-L transcripts were detected at a very low level in the patient CD34(+)cells and MK and only when a highly sensitive fluorescent PCR technique was used. By quantitative reverse-transcription (RT)-PCR, the number of Mpl-L transcripts per actin transcripts was lower than detected in human Mpl-L-dependent cell lines, suggesting that this synthesis of Mpl-L was not biologically significant. In favor of this hypothesis, the Mpl-L protein was not detected in culture supernatants using either an enzyme-linked immunosorbent assay (ELISA) or a biological (Ba/F3hu c-mpl) assay, except in one PMF patient. Investigation of Mpl-L signaling showed an absence of constitutive activation of STATs in spontaneously growing patient MKs. Addition of PEG-rhuMGDF to these MKs activated STATs 3 and 5. This result further suggests that spontaneous growth is neither related to a stimulation by Mpl-L nor to a c-mpl mutation. In conclusion, our results show that Mpl-L or Mpl are not directly implicated in the abnormal proliferation of MK cells from ET and PMF. The mechanisms by which the sMpl mediates a growth inhibition will require further experiments.

Adult↗
PubMed1999

A simple bedside test of 1-minute heart rate variability during deep breathing as a prognostic index after myocardial infarction.

BACKGROUND: We evaluate a simple, bedside test that measures 1-minute heart rate variability in deep breathing as a predictor of death after myocardial infarction. METHODS: Bedside heart rate variability was assessed in 185 consecutive patients 5.1 +/- 2.5 days after a first myocardial infarction. Patients were instructed to take 6 deep respirations in 1 minute while changes in heart rate were measured and calculated by an electrocardiographic recorder. An abnormal test result was defined as a difference of less than 10 beats/min between the shortest and longest heart rate interval. RESULTS: Heart rate variability <10 beats/min was found in 65 patients (35%) and was significantly lower (P <.05) in women, patients >60 years of age, patients with diabetes, patients with congestive heart failure, and patients taking angiotensin-converting enzyme inhibitors. Mean follow-up period was 16 months. Ten patients died during follow-up: 9 of cardiac causes and 1 of stroke. Nine of these 10 patients had heart rate variability <10 beats/min (P =.004). The sensitivity and specificity of this test for cardiovascular mortality is 90.0% and 68.0%, respectively. The negative predictive value is 99.2% and the relative risk is 16.6. Heart rate variability <10 beats/min remained a significant predictor of death after adjusting for clinical, demographic, and left ventricular function with an odds ratio of 1.38 (95% confidence interval, 1.13-1.63). CONCLUSIONS: This simple, brief bedside deep breathing test of heart rate variability in patients after myocardial infarction appears to be a good predictor for all-cause mortality and sudden death. It may be used as a clinical test for risk stratification after myocardial infarction.

Death, Sudden, Cardiac↗
PubMed1999

Perineural invasion on prostate needle biopsy: an independent predictor of final pathologic stage.

OBJECTIVES: To examine the significance of perineural invasion (PNI) in predicting pathologic findings in patients treated by radical prostatectomy, because a recent study concluded that PNI on needle biopsy has no independent predictive value. METHODS: Between 1993 and 1998, radical prostatectomy was performed in 319 consecutive patients. Prostate needle biopsies were reviewed in all cases. We compared PNI with other preoperative parameters, including digital rectal examination, PSA, and biopsy Gleason score, for the ability to predict tumor stage. Clinical records and pathologic findings were reviewed for all cases. Tumor stage was defined as either pT2 (organ confined) or pT3 (extraprostatic extension and/or seminal vesicle invasion). RESULTS: The median age was 61.4 years (range 40 to 75.6). Seventy-two percent of the 95 men with nonpalpable disease and 67% of the 224 men with palpable disease had organ-confined prostate cancer on final pathologic staging. Of 205 men with a Gleason score on biopsy of 6 or less, 159 (78%) had organ-confined disease compared with 59 (52%) of 114 with a Gleason score of 7 to 9 (P <0.001, chi-square test). PNI was identified in 77 (24%) of 319 patients, with 83% specificity and 40% sensitivity for Stage pT3 disease (odds ratio 3.49). Of men with pT3 disease on final pathologic staging, 18%, 27%, and 56% had preoperative PSA levels of 0 to 4, more than 4 to 10, and greater than 10 ng/mL, respectively (P <0.001, Mantel-Haenszel chi-square test). On multivariate analysis, PNI (P = 0.0031), PSA (P = 0.0004), and Gleason score (P = 0.0003) independently predicted stage (pT3 disease). CONCLUSIONS: PNI is an important preoperative predictor of pathologic stage and should be reported when adenocarcinoma is diagnosed on prostate needle biopsies.

Adult↗
PubMed1999

Isolation of norditerpenoid alkaloids from flowers of aconitum lycoctonum

The structures of two new lycoctonine-type alkaloids having an acetoxy group at C-6, 6-O-acetyldemethylenedelcorine (1) and 6-O-acetyl-14-O-methyldelphinifoline (2), isolated from the flowers of Aconitum lycoctonum, were determined by spectroscopic analysis. In addition, 14-O-methyldelphinifoline (4), gigactonine (5), and lycoctonine (6) were obtained.

Journal Article↗
PubMed1999

Effect of a mineral salt diet on 24-h blood pressure monitoring in elderly hypertensive patients.

The influence of a mineral salt on 24-h ambulatory blood pressure (BP) monitoring was studied in 20 elderly hypertensive subjects residing in an old peoples home. Ordinary table and cooking salt was substituted with a special Na-reduced, K-, Mg-, and l-lysine HCl-enriched mineral salt (Pansalt(R)) for 6 months. Antihypertensive therapy was uninterrupted. An ambulatory BP monitor (Suntech Accutracker) measured BP every 20 min during the day and every 30 min at night, before and 6 months after starting the diet. Nine patients (45%) decreased both systolic and diastolic BP significantly: systolic BP fell from 154.92 +/- 33.67 mm Hg to 143. 45 +/- 53.1 mm Hg (P < or = 0.01) during the daytime from 6 am to midnight; and from 139.80 +/- 32.84 mm Hg to 137.87 +/- 31.17 mm Hg (P < or = 0.01) from midnight to 6 am. Diastolic BP fell from 85.34 +/- 24.85 mm Hg to 70.29 +/- 18.31 mm Hg (P < or = 0.01) during the daytime from 6 am to midnight; and from 77.1 +/- 22.92 mm Hg to 67.76 +/- 15. 63 mm Hg (P < or = 0.01) at night. Blood pressure in the other 11 subjects showed no improvement. Heart rate also fell in the subjects, from 69.44 +/- 21.62 beats per minute (bpm) to 66.94 +/- 11.51 bpm (< or = 0.01) during the day, and from 61.28 +/- 12.82 bpm to 60.43 +/- 10.33 bpm (P < or = 0.01) during the night. It is concluded that decreased intake of Na and increased intake of both K and Mg can be useful in controlling high BP.

Aged↗