Search PubMed⌕ Search

Biomedical subjects

L Katz

Publications and source records attributed to L Katz.

At least 109 records · Page 6Linked to original sources
PubMed1990

Mutation and cloning of eryG, the structural gene for erythromycin O-methyltransferase from Saccharopolyspora erythraea, and expression of eryG in Escherichia coli.

A mutant strain derived by chemical mutagenesis of Saccharopolyspora erythraea (formerly known as Streptomyces erythreus) was isolated that accumulated erythromycin C and, to a lesser extent, its precursor, erythromycin D, with little or no production of erythromycin A or erythromycin B (the 3"-O-methylation products of erythromycin C and D, respectively). This mutant lacked detectable erythromycin O-methyltransferase activity with erythromycin C, erythromycin D, or the analogs 2-norerythromycin C and 2-norerythromycin D as substrates. A 4.5-kilobase DNA fragment from S. erythraea originating approximately 5 kilobases from the erythromycin resistance gene ermE was identified that regenerated the parental phenotype and restored erythromycin O-methyltransferase activity when transformed into the erythromycin O-methyltransferase-negative mutant. Erythromycin O-methyltransferase activity was detected when the 4.5-kilobase fragment was fused to the lacZ promoter and introduced into Escherichia coli. The activity was dependent on the orientation of the DNA relative to lacZ. We have designated this genotype eryG in agreement with Weber et al. (J.M. Weber, B. Schoner, and R. Losick, Gene 75:235-241, 1989). It thus appears that a single enzyme catalyzes all of the 3"-O-methylation reactions of the erythromycin biosynthetic pathway in S. erythraea and that eryG codes for the structural gene of this enzyme.

Chromatography, High Pressure Liquid↗
PubMed1990

Cancer incidence in young offspring of Jewish immigrants to Israel. A methodological study. I. Nasopharyngeal malignancies and Ewing sarcoma.

Differences in cancer incidence among various immigrant groups in Israel raised the question of persistence in their descendants. The methodological problems of identification of both parents and their origins, the choice of the denominator, and the long period of observation necessary for the rare childhood tumors have been examined. From 22-years data of the Israel Cancer Registry (ICR), three malignancies were chosen as examples: epithelial carcinoma of nasopharynx (31 cases), non-Hodgkin's lymphoma of nasopharynx (14 cases), and Ewing sarcoma (55 cases). The actual number of cases, in spite of the long period of incidence, is small and the computed significance must be accepted with reservation. There are two outstanding findings: the higher incidence in males as well as in females for nasopharynx carcinoma corresponds to that of their African-born parents; an increasing trend in the second 11-years period for Ewing sarcoma. Similar studies on leukemias, lymphomas, and others with a greater number of cases can be expected to have more reliable results. This survey relied on the majority of patients with immigrant parents, mostly of the same origin. In the following years, second and later generations of Israel-born and an increasing part of intermarriages will severely impede similar studies.

Adolescent↗
PubMed1989

Gene dosage effect on the expression of the delta-endotoxin genes of Bacillus thuringiensis subsp. kurstaki in Bacillus subtilis and Bacillus megaterium.

Significant differences in expression of the delta-endotoxin genes cryA1 and cryA2 of Bacillus thuringiensis subsp. kurstaki were observed in B. subtilis and B. megaterium. The cryA1 gene was expressed when present on a high-copy-number (hcn) vector in B. megaterium but not in B. subtilis. The cryA2 gene was expressed in both hosts, but at a higher level in B. megaterium. Expression of the cryA2 gene in B. megaterium was better from a hcn vector than from a low copy number vector. Inhibition of sporulation was observed when the toxin genes were present on hcn plasmids in B. subtilis while no such effect was evident in B. megaterium. In addition, there was a significant reduction in copy numbers in both B. subtilis and B. megaterium when delta-endotoxin genes or a spoVG promoter-containing fragment of DNA were cloned into hcn plasmids.

Bacillus↗
PubMed1989

Increased risk of breast cancer after low-dose irradiation.

A significant increase in the risk of breast cancer has been found for the most recent 5-year period of a long-term follow-up study of children subjected to scalp irradiation, in whom a carcinogenic effect was previously only apparent in the head and neck. This increased risk was found among women aged 5 to 9 years at exposure. The breast had been exposed to a low radiation dose of approximately 16 mGy.

Adolescent↗
PubMed1989

Brain enzyme changes as markers of brain damage in rat cardiac arrest model. Effects of corticosteroid therapy.

Apneic asphyxia to cardiac arrest (CA) in rats of 10 min was reversed by cardiopulmonary resuscitation (CPR), and after controlled ventilation and controlled normotension for 20 min, was followed by decapitation and brain freezing, and determination of brain concentrations of cytosolic and lysosomal enzymes. Normal values came from a control group of 10 rats without CA. In 20 rats with CA brain cytosolic enzymes CK, LD, and ASAT decreased post-arrest, while lysosomal enzyme changes were variable (Table I). Brain lactate increased 8-10-fold post-CA. To test the model, effect of methylprednisolone (MP) was studied. The 20 rats with CA were divided into 4 groups: Group I, received placebo pre-CA; Group II, MP 30 mg/kg i.v. pre-CA; Group III, placebo post-CA; and Group IV, MP post-CA. The post-CA MP Group IV was the only one without norepinephrine requirement and with return of EEG activity at 20 min. Brain CK, LD, and ASAT losses post-CA were not different between groups; and showed no differences between MP groups II and IV vs. placebo Groups I and III. When comparing both pre-CA Groups (I and II) with both post-CA Groups (III and IV), post-CA CK and ASAT levels were the same, but LD was higher in the post-CA treatment group. The lysosomal enzymes acid phosphatase, mannosidase, beta-glucuronidase and hexosaminidase showed variable concentration changes post-CA in the four groups, with a trend toward a lesser increase of some after MP or after post-treatment. Brain enzyme changes in our asphyxial CA rat model can serve as markers of brain damage. MP post-CA might enhance cardiovascular and EEG recovery, but does not seem to influence brain enzyme levels at 20 min post-CA.

Animals↗
PubMed1989

Orthographic depth and the interaction of visual and auditory processing in word recognition.

We studied the influence of word frequency and orthographic depth on the interaction of orthographic and phonetic information in word perception. Native speakers of English and Serbo-Croatian were presented with simultaneous printed and spoken verbal stimuli and had to decide whether they were equivalent. Decision reaction time was measured in three experimental conditions: Clear print and clear speech, degraded print and clear speech, and clear print and degraded speech. Within each language, the effects of visual and auditory degradation were measured, relative to the undegraded presentation. Both effects of degradation were much stronger in English than in Serbo-Croatian. Moreover, they were the same for high- and low-frequency words in both languages. These results can be accounted for by a parallel interactive processing model that assumes lateral connections between the orthographic and phonological systems at all of their levels. The structure of these lateral connections is independent of word frequency and is determined by the relationship between spelling and phonology in the language: simple isomorphic connections between graphemes and phonemes in Serbo-Croatian, but more complex, many-to-one, connections in English.

Form Perception↗
PubMed1988

Tumors of the brain and nervous system after radiotherapy in childhood.

We investigated the relation between radiotherapy in childhood for tinea capitis and the later development of tumors of the brain and nervous system among 10,834 patients treated between 1948 and 1960 in Israel. Benign and malignant tumors were identified from the pathology records of all Israeli hospitals and from Israeli national cancer and death registries. Doses of radiation to the neural tissue were retrospectively estimated for each patient (mean, 1.5 Gy). Sixty neural tumors developed in the patients exposed as children, and the 30-year cumulative risk (+/- SE) was 0.8 +/- 0.2 percent. The incidence of tumors was 1.8 per 10,000 persons per year. The estimated relative risk as compared with that for 10,834 matched general-population controls and 5392 siblings who had not been irradiated was 6.9 (95 percent confidence interval, 4.1 to 11.6) for all tumors and 8.4 (confidence interval, 4.8 to 14.8) when the analysis was restricted to neural tumors of the head and neck. Increased risks were apparent for meningiomas (relative risk, 9.5; n = 19), gliomas (relative risk, 2.6; n = 7), nerve-sheath tumors (relative risk, 18.8; n = 25), and other neural tumors (relative risk, 3.4; n = 9). A strong dose--response relation was found, with the relative risk approaching 20 after estimated doses of approximately 2.5 Gy. Our study confirms that radiation doses on the order of 1 to 2 Gy can significantly increase the risk of neural tumors.

Adolescent↗
PubMed1988

Substrate specificities of 5'-deoxy-5'-methylthioadenosine phosphorylase from Trypanosoma brucei brucei and mammalian cells.

The separation by chromatofocusing of two distinct purine nucleoside cleaving activities from crude extracts of Trypanosoma brucei brucei is described. One catalyzes the reversible phosphorolysis of 5'-deoxy-5'-methylthioadenosine (MeSAdo) and adenosine (Ado) and was designated an MeSAdo/Ado phosphorylase, while the other catalyzes the hydrolysis of adenosine, inosine, and guanosine but not MeSAdo. The substrate specificity of trypanosomal MeSAdo/Ado phosphorylase differed from that of a mammalian MeSAdo phosphorylase (derived from murine Sarcoma 180 cells) in that it was able to phosphorolyze 2'-deoxyadenosine, 3'-deoxyadenosine and 2',3'-dideoxyadenosine. In addition, the trypanosomal phosphorylase was able to utilize the nucleoside analog, 6-methylpurine 2'-deoxyribonucleoside, as an alternative substrate, whereas the mammalian enzyme could not. Because of these differences, cytotoxic analogs of MeSAdo may be designed that are selectively activated by the trypanosomal MeSAdo/Ado phosphorylase.

Adenosine↗
PubMed1988

Lung cancer in Israel, 1962-1982. I. Jews and Arabs.

The magnitude and dynamics of lung cancer incidence in Jews and Arabs in Israel between the years 1962 and 1982 were studied. In general, age-standardized incidence rates increased consistently between the years 1962 and 1976 among Jewish (24% increase) and Arab (39%) males, and to a lesser degree among Jewish females (15%). Arab females had the highest (77%) increase. From 1977 to 1982 a general decrease in incidence rates, which was largest among Arab males (19%) and females (15%), was noted. Rates among Jewish males are currently 26% higher than among Arab males, and are 162% higher among Jewish females than in Arab females. Lung cancer rates in both males and females in Israel (Jews and Arabs) are lower than in most developed countries in the world. Among the possible reasons are differences in the population risk factors profile, availability of health care and the level of diagnosis and ascertainment of cases.

Adolescent↗
PubMed1988

Characterization of bacteriophage phi C69 of Saccharopolyspora erythraea and demonstration of heterologous actinophage propagation by transfection of Streptomyces and Saccharopolyspora.

A bacteriophage, designated phi C69, isolated from a culture of Saccharopolyspora erythraea was characterized. The phage propagates on Sac. erythraea NRRL 2338 but does not infect 10 Streptomyces or 3 Micromonospora species tested. It infects Sac. erythraea NRRL 2359 but does not produce infectious phage particles in this host. phi C69 is approximately 40 kb in length and contains cohesive ends. A cos fragment containing ligated phage DNA ends was cloned in Escherichia coli. Restriction maps of the phage DNA and the cos fragment for several enzymes are shown. Transfection of both Sac. erythraea and Streptomyces lividans with phi C69 resulted in approximately equal titres of infectious phage particles produced from approximately the same number of regenerating cells. Transfection of Sac. erythraea with DNA from Streptomyces phages SH10 and KC404 also resulted in the production of infectious phage particles. The basis for differences among hosts in susceptibility to infection by various actinophages is discussed.

Bacteriophages↗
PubMed1988

Site-specific integration in Saccharopolyspora erythraea and multisite integration in Streptomyces lividans of actinomycete plasmid pSE101.

An 11.3-kilobase-pair plasmid, designated pSE101, exists in Saccharopolyspora erythraea NRRL 2338 as an integrated sequence (pSE101int) at a unique chromosomal location and in the free form in less than an average of 1 copy per 10 chromosomes. The plasmid sequence is missing from S. erythraea NRRL 2359. Restriction maps of the free and integrated forms of pSE101 showed point-to-point correspondence. Plasmid pECT2 was constructed by ligation of pSE101, pBR322, and the gene for thiostrepton resistance (tsr). When introduced by polyethylene glycol-mediated transformation into protoplasts of S. erythraea NRRL 2359, all thiostrepton-resistant regenerants examined were found to carry a single copy of pECT2 in the integrated state at a single chromosomal site. The chromosomal site of pECT2 integration in strain NRRL 2359 (attB) corresponded to the chromosomal location of pSE101int in strain NRRL 2338. The plasmid crossover site (attP) was mapped to the plasmid site that corresponded to the site of interruption of the plasmid sequence in the host carrying pSE101int, indicating that site-specific integrative recombination had occurred. An additional 2.8-kilobase-pair chromosomal sequence homologous to a segment of pSE101 was also observed in strains NRRL 2338 and NRRL 2359. After introduction of pECT2 into Streptomyces lividans, approximately half of the transformants examined were found to carry the plasmid as a stable, autonomously replicating element. The other half carried a single copy of pECT2 as an integrated sequence, but the location of pECT2int in Streptomyces lividans varied from one transformant to another. In each case, integrative crossover used the attP site. A model is proposed to account for the determination of the particular state of pSE101 in Streptomyces lividans.

Actinomycetales↗
PubMed1988

Renal function studies during intravenous acyclovir treatment of immune suppressed patients including renal transplantation.

We assessed the effect of acyclovir therapy on renal function during a course of therapy for herpesvirus disease. Renal function was assessed by measuring the clearances of inulin, albumin, and beta 2-microglobulin at the beginning and end of acyclovir therapy. Thirty-two patients had valid paired inulin clearances and 21 had valid paired albumin and beta 2-microglobulin clearances. No significant mean decrement of renal function was observed; however, 2 patients had a reversible renal dysfunction associated with acyclovir therapy which disappeared soon after discontinuation of the drug and was unassociated with a prior or recurrent renal dysfunction in short-term follow-up.

Acyclovir↗
PubMed1987

Familial colon cancer in the Tel-Aviv area and the influence of ethnic origin.

The family history of colon cancer was investigated in 38,823 individuals (2,129 families) who comprised a control and an oncology patient series from Tel-Aviv and nearby areas. A significant increased risk for colon cancer was observed among first-degree relatives of colon cancer patients when compared to controls. When the patient sample was divided into two groups based on country and continent of birth--European (Ashkenazim) and other (nonAshkenazim)--the relatives of the nonAshkenazi subjects showed a greater relative risk for colon cancer (P less than 0.05). Colon cancer was found to be less frequent in nonAshkenazim than in Ashkenazim controls. These findings suggest that although the colon cancer frequency in the nonAshkenazi group is lower, the genetic component may be more important than for the Ashkenazi sample. The nonAshkenazi Jews may represent distinct subgroups that differ with respect to either primary genetic susceptibility to colorectal cancer and/or they may have been subjected to peculiar, environmental carcinogenic exposures when compared to their Ashkenazim brethren.

Adult↗
PubMed1987

The prepiriform cortex in dementia of the Alzheimer type.

Histopathologic examination of the prepiriform cortex (PPC) in four documented cases of dementia of the Alzheimer type revealed increased numbers of neurofibrillary tangles and neuritic plaques. These findings indicate that some early- and late-onset cases of Alzheimer's disease may be associated with significant damage to the PPC, a relay center of the mammalian olfactory system that has extensive connections with structures concerned with cognitive and behavioral functions. Involvement of the PPC may be related to the complex neuropsychiatric manifestations observed in this disorder.

Aged↗