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Biomedical subjects

M Katz

Publications and source records attributed to M Katz.

At least 181 records · Page 10Linked to original sources
PubMed1994

Apparent image quality of magnifiers depends on amplitude of accommodation.

We investigated the importance of the role of amplitude of accommodation in assessing the usefulness of magnifiers. Accommodation must be exerted to scan across the image produced by a magnifier that exhibits astigmatism and curvature of field. In general, increasing amounts of negative accommodation are required to scan from the center to the edge of the image field of view (FOV) when a simple magnifier is set for nominal magnification. It is necessary to refocus the magnifier (move it closer to the object plane) to convert the demand to positive accomodation. We used the OSLO program to design and evaluate the oblique astigmatism of four common types of magnifiers: Equiconvex, Best-form, Aspheric, and the Steinheil triplet, in powers of 10, 20, 40, 60, and 80 D. We found that the circle of least confusion (CLC), produced by the Equiconvex and Best-form lenses set at nominal magnification, lie on a surface that demands as much as 2.75 D of negative accommodation to view the CLC at the edge of a 30 degrees FOV. By refocusing the magnifier, the CLC at the edge of the field can be imaged at infinity, i.e., have zero vergence, and the demand for negative accommodation may be eliminated, but then about 2.4 D of positive accommodation is required to scan to the center of the field. The Aspheric and Steinheil magnifiers largely corrected the astigmatic errors and flattened the field. Less than 0.75 D of accommodation was sufficient to scan from the edge to the center of the object. Depending on the degree of uncorrected astigmatism and field curvature, presbyopic patients, lacking accommodative ability, will perceive constricted in-focus zones in the image field. They will continuously have to refocus the magnifier to bring adjacent zones into best-focus. This condition may cause a presbyope to reject a magnifier thought to be of good quality by a young clinician who can accommodate for best-focus across the entire FOV.

Accommodation, Ocular↗
PubMed1994

Effect of different treatment regimes on linear growth and final height in beta-thalassaemia major.

OBJECTIVE: The clinical picture of thalassaemia major has changed progressively over the years. Our study is a retrospective analysis of data on growth in a group of patients who have completed puberty spontaneously and have attained their adult height. Our objective was to evaluate the effect of different transfusion regimes and desferrioxamine administration on the growth pattern in beta-thalassaemia major. DESIGN AND PATIENTS: We studied 64 patients (28 males and 36 females). The patients were divided into three groups (A, B and C) according to the different transfusion regimes and the schedules of chelating therapy. Group A consisted of 16 patients who were transfused regularly at low haemoglobin levels (on average 8.5 g/dl) from an early age and started subcutaneous chelation therapy during adolescence. Group B consisted of 19 patients who were transfused regularly at high haemoglobin levels (on average 10 g/dl) from an early age and started subcutaneous therapy during childhood. Group C consisted of 29 patients who were transfused regularly at high haemoglobin levels (on average 10.5 g/dl) from an early age and started subcutaneous chelation therapy very early, at a mean age of 2 years. Standard auxological measurements were made at 3-monthly intervals throughout childhood and puberty until adult height was achieved. For group C patients the data on linear growth are provided only until the age of 12 years. RESULTS: Our study indicates that group A male and female patients did not grow significantly better than those in group B. Group C male and female patients, surprisingly, grew no faster than those who started chelation therapy late in childhood (group A). The most striking feature in the majority of both group A and B patients was reduced spurt in height at puberty. In addition, in both groups, a reduced sitting height due to spinal growth abnormality was found. An inverse correlation between sitting height and serum ferritin levels was observed in group A patients (r = -0.55, P < 0.05), whereas there was a direct correlation in group B patients (r = 0.42, P < 0.05). CONCLUSIONS: These data suggest that an ideal therapeutic regime has yet to be found which avoids the toxic effect of iron overload and on the other hand avoids interference with growth, secondary to desferrioxamine. Therefore we recommend that the growth of thalassaemia patients be monitored routinely at every follow-up visit and documented on growth velocity charts in order to detect early changes in their growth pattern and to establish an appropriate protocol for investigation and treatment.

Adult↗
PubMed1994

Leisure activities of young adults not receiving mental handicap services who were in a special school for mental handicap as children.

The subjects of this study were 22-year-old adults who had attended a special school for children with mental handicap. Since leaving school, they had dropped out of the mental handicap services. The subjects' leisure activities were compared with peers who had always attended regular classes as children. The subjects engaged in fewer types of activities than the comparisons and had fewer activities that involved interpersonal relations, especially with non-family peers. The size of these differences was influenced by marital status.

Adult↗
PubMed1994

Allogeneic marrow transplantation for myelodysplastic syndrome complicating autologous bone marrow transplantation.

A patient with refractory relapsed Hodgkin's disease underwent an autologous bone marrow transplant in July 1987 and achieved remission of Hodgkin's disease. He had complete hematological recovery but developed pancytopenia 3 years post bone marrow transplantation with morphological evidence of myelodysplasia. High-dose cyclophosphamide, 200 mg/kg, chemotherapy followed by an allogeneic bone marrow transplant from a HLA-matched sibling was performed in April 1991 with complete hematological recovery. Allogeneic bone marrow transplantation was thus used successfully to treat a potential complication of autologous bone marrow transplantation.

Adult↗
PubMed1994

High speed document imaging supports: HMO's rush of new members.

Today, Physicians Health Services Inc. (PHS), headquartered in Trumbull, Conn., is one of the nation's largest, publicly-held IPA model HMOs. But in 1977, when it became operational, only four percent of Americans were covered under HMOs, and file cabinets and manual processes were the status quo in healthcare operations. Fortunately for us, PHS has forward thinking directors and executives who saw the value of introducing an image-based operations management system into our organization.

Connecticut↗
PubMed1994

Acupressure for nausea and vomiting of pregnancy: a randomized, blinded study.

OBJECTIVE: To evaluate the effectiveness of acupressure in reducing nausea and vomiting of pregnancy. METHODS: Symptomatic pregnant women were randomized to one of two acupressure groups: one treatment group using an acupressure point (PC-6) and one sham control group using a placebo point. Subjects were blind to the group assignment. Each evening for 10 consecutive days, the subjects completed an assessment scale describing the severity and frequency of symptoms that occurred. Data from the first 3 days were used as pre-treatment scores. Beginning on the morning of the fourth day, each subject used acupressure at her assigned point for 10 minutes four times a day. Data from day 4 were discarded to allow 24 hours for the treatment to take effect. Data from days 5-7 were used to measure treatment effect. RESULTS: Sixty women completed the study. There were no differences between groups in attrition, parity, fetal number, maternal age, gestational age at entry, or pre-treatment nausea and emesis scores. Analysis of variance indicated that both groups improved significantly over time, but that nausea improved significantly more in the treatment group than in the sham control group (F1,58 = 10.4, P = .0021). There were no differences in the severity or frequency of emesis between the groups. There was a significant positive correlation (r = 0.261, P = .044) between maternal age and severity of nausea. CONCLUSIONS: Our results indicate that acupressure at the PC-6 anatomical site is effective in reducing symptoms of nausea but not frequency of vomiting in pregnant women.

Acupuncture Points↗
PubMed1994

Prospective study of pituitary-gonadal function to evaluate short-term effects of ablative chemotherapy or total body irradiation with autologous or allogenic marrow transplantation in post-menarcheal female patients.

Pituitary-gonadal (P-G) function was evaluated 0-3 months before and 3-4 months after bone marrow transplantation (BMT) in 15 post-menarcheal females aged 17-30 (21.6 +/- 0.34) years with haematological malignancies. All patients had evidence of gonadal insufficiency prior to BMT in that their basal and human menopausal gonadotrophin (HMG)-stimulated oestradiol (E2) levels were significantly lower than those of control subjects. The patients also had markedly higher basal FSH levels and exaggerated responses to 100 micrograms iv gonadotrophin release hormone bolus compared with those of control subjects. However, the conditioning regimens employed prior to BMT, i.e. cytotoxic chemotherapy (CT) and total body irradiation (TBI), acting either singly or in combination, caused further ovarian damage. As a result, their gonadotrophins rose further into the menopausal range. Their oestradiol secretion diminished and ovaries became almost unresponsive 3-4 months after BMT. Pelvic ultrasound undertaken in 5 patients before and after BMT demonstrated a reduction in ovarian size associated with follicular depletion. All patients developed menopausal symptoms and became amenorrhoeic during this period. Contrary to expectation, the hormonal changes occurring acutely were similar in patients undergoing radiation-based regimens and those conditioned with high-dose chemotherapy alone. Also, the severity of ovarian dysfunction appeared independent of age at transplantation, the nature of the conditioning-regimen or the type of transplant. Gonadotrophic, thyrotrophic, lactotrophic and adrenocorticotrophic secretions were unaffected. These data indicate that the ovary suffers an acute insult during short-term chemotherapy but the anterior pituitary gland retains its trophic hormone reserve and secretory capacity.

Adolescent↗
PubMed1994

Germ cell failure and Leydig cell insufficiency in post-pubertal males after autologous bone marrow transplantation with BEAM for lymphoma.

Thirteen post-pubertal male patients aged 17-25 years were assessed for pituitary-gonadal function 0-3 months prior to and 2-3 months post-bone marrow transplantation for haematological malignancy. All patients had multiagent cytotoxic treatment prior to transplantation and 30% were found to have germ cell dysfunction with abnormal semen parameters before high-dose therapy indicating damage to the germinal epithelium. They also had evidence of reduced Leydig cell reserve even before transplantation. During transplantation all patients sustained sustained gonadal injury, the effect on their germ cells being more pronounced than on the Leydig cells. Fifty per cent had reduction in testicular volume and all had azoospermia 2-3 months post-transplantation. Our results indicate that short-term chemoradiotherapy causes profound damage to the germ cell compartment of the testis, with less severe damage to the Leydig cells, but no overt injury to the anterior pituitary gland. The changes appeared to be identical in patients conditioned with total body irradiation-based protocols and those who received only high-dose chemotherapy prior to bone marrow transplantation.

Adolescent↗
PubMed1994

Human alpha 7 acetylcholine receptor: cloning of the alpha 7 subunit from the SH-SY5Y cell line and determination of pharmacological properties of native receptors and functional alpha 7 homomers expressed in Xenopus oocytes.

The alpha-bungarotoxin-binding acetylcholine receptors from the human neuroblastoma cell line SH-SY5Y were found to cross-react with some monoclonal antibodies to alpha 7 subunits of nicotinic acetylcholine receptors from chicken brain. The human alpha 7 subunit cDNA from SH-SY5Y was cloned, revealing 94% amino acid sequence identity to rat alpha 7 subunits and 92% identity to chicken alpha 7 subunits. Native human alpha 7 receptors showed affinities for some ligands similar to those previously observed with native chicken alpha 7 receptors, but for other ligands there were large species-specific differences in binding affinity. These results paralleled properties of alpha 7 homomers expressed in Xenopus oocytes. Human alpha 7 homomers exhibited rapidly desensitizing, inwardly rectifying, agonist-induced, cation currents that triggered Ca(2+)-sensitive Cl- channels in the oocytes. A change in efficacy from partial agonist for chicken alpha 7 homomers to full agonist for human alpha 7 homomers was exhibited by 1,1-dimethyl-4-phenylpiperazinium. This result reveals a large species-specific pharmacological difference, despite small differences in alpha 7 sequences. This is important for understanding the effects of these drugs in humans and for identifying amino acids that may contribute to the acetylcholine binding site, for analysis by in vitro mutagenesis. These results also characterize properties of native alpha 7 receptors and alpha 7 homomers that will provide criteria for functional properties expected of structural subunits, when these can be identified, cloned, and coexpressed with alpha 7 subunits.

Amino Acid Sequence↗
PubMed1993

Elevation of intracellular cAMP in human T lymphocytes by an anti-CD44 mAb.

Regulation of lymphocyte responses to activation of the CD3/TCR complex by other cell surface proteins expressed on lymphocytes is a well established phenomenon. CD44 is an example of such a cell surface protein. Anti-CD44 mAb have been identified which either stimulate or inhibit lymphocyte function. Certain anti-CD44 mAb augment proliferation and IL-2 production by T cells stimulated through the CD2 or CD3/TCR pathways. An anti-CD44 mAb with opposing properties has also been identified. This mAb inhibits activation of human T cells by preventing the rise in [Ca2+]i stimulated by OKT3. The purpose of experiments reported here was to further characterize this phenomenon. The results show that the anti-CD44 mAb, 212.3, does not inhibit inositol phosphate turnover stimulated by OKT3 but does inhibit elevation of intracellular [Ca2+]i in these same cells. Addition of 212.3 to purified human T cells results in a rapid increase in intracellular levels of cAMP. Elevation of cAMP by 212.3 is time- and concentration-dependent. Activation of adenylate cyclase by forskolin also results in elevation of intracellular cAMP and inhibition of the increase in [Ca2+]i stimulated by OKT3. Taken together, these data suggest that CD44 may be positively coupled to adenylate cyclase and that activation of adenylate cyclase by the anti-CD44 mAb, 212.3, may mediate the inhibition of the OKT3-stimulated elevation of [Ca2+]i.

Animals↗
PubMed1993

Prenatal ultrasound diagnosis of a rare occurrence of lethal multiple pterygium syndrome in two siblings.

We report two cases of prenatal ultrasound diagnosis of the lethal form of multiple pterygium syndrome in successive pregnancies in the same woman. This extremely rare entity is characterized by multiple pterygia, flexion contractures, facial anomalies and hypoplasia of heart and lungs. The appearance of the congenital cataract is unique and this finding was present in both abortuses. Prenatal detection of this syndrome is feasible, and an ultrasound survey should be offered during genetic counselling to previously affected couples.

Journal Article↗
PubMed1993

Urinary excretion of modified nucleosides as biological marker of RNA turnover in patients with cancer and AIDS.

Using boronate gel affinity chromatography and reversed-phase high-performance liquid chromatography (RP-HPLC), a method for the simultaneous determination of 12 urinary modified nucleosides has been developed. The RP-HPLC fractions were identified by gas chromatography/mass spectrometry analysis. The HPLC quantitation of urinary nucleoside levels before and after surgery of cancer patients suggested that urinary 5'-deoxy-5'-methylthioadenosine and N-[(9-beta-D-ribofuranosyl-9H-purine-6-yl) carbamoyl]-L-threonine (t6A) levels were helpful in monitoring therapeutic effects in cancer patients. From the fact that molar ratios of urinary N2,N2-dimethylguanosine (m2 2G)pseudouridine (psi) and t6A/psi in cancer patients were lower than those of normal or post-surgical cancer patients, the increase of rRNA content in cancer tissues growing rapidly was estimated using the stoichiometric relationship between the ratio of the number of residues of their modified nucleoside in RNAs and the proportion of rRNA to total RNAs in average tissues of whole body. Furthermore, from the estimation of RNA turnover using urinary nucleoside levels, it was found that the half-lives of rRNA rather than tRNA of patients with cancer and those of both RNAs in the case of acquired immunodeficiency syndrome (AIDS) were extremely short compared with those of the normal. Thus, we discovered that the selected urinary modified nucleosides were very useful as a biological marker of whole-body RNA turnover in patients with cancer and AIDS.

Acquired Immunodeficiency Syndrome↗
PubMed1993

[Early ultrasonic diagnosis of conjoined twins].

Conjoined twins is a rare congenital malformation occurring in 1:30,000-1:100,000 live births. Its early prenatal detection was extremely rare prior to the introduction of obstetric ultrasonography. We report 3 cases of early ultrasound diagnosis of conjoined twins at 9, 15 and 19 weeks of pregnancy, respectively. The diagnosis at 9 weeks of gestation was made via the transvaginal approach, and to the best of our knowledge is the earliest diagnosis reported in the English literature. In all 3 cases the fetuses were of the thoraco-omphalopagus type and had a shared heart. Pregnancy was discontinued in all 3 cases using methods appropriate for the first and second trimesters of pregnancy.

Abortion, Therapeutic↗
PubMed1993

Divergent age-associated patterns of high density lipoprotein cholesterol and its percentage in Jewish and Moslem Arab Israeli children and adolescents: the Petach Tikva Project.

We studied three groups of Israeli Jewish schoolchildren in and surrounding Petach Tikva, Israel, cross-sectionally, at ages 9-10, 13-14, and 16-18 years, and compared lipid and lipoprotein levels and age-associated lipoprotein patterns in the same age groups of boys and girls in neighboring Israeli Moslem Arab schools during 1986-1987. Moslem children displayed striking differences in the levels of lipids and age-associated patterns of lipoproteins compared with Jewish schoolchildren. The mean total cholesterol levels were lower in the Moslem children, in both sexes, in every age grouping. High density lipoprotein cholesterol (HDL-C) levels were significantly higher at age 16-18 in the Moslem boys than in the Jewish boys. While the Jewish boys displayed a previously reported "typical" pattern of lower HDL-C levels postpuberty compared with prepuberty, the Moslem boys had markedly higher mean HDL-C levels at age 16-18 compared with those at age 9-10. The Moslem girls also had higher HDL-C levels at age 16-18 than those observed in the age 9-10 group. Concomitantly higher HDL-C levels (HDL-C/total cholesterol (%)) were seen in the Moslem boys and girls, at age 16-18 compared with age 9-10, but were not observed in the Jewish children. The identification of an ethnic group in whom HDL-C appears to increase at or near puberty could provide opportunities to elucidate factors that may increase HDL-C in individuals or in populations.

Adolescent↗
PubMed1993

Evaluation of growth hormone in thalassaemic boys with failed puberty: spontaneous versus provocative test.

Growth hormone (GH) secretion was determined by evaluating ultradian GH profiles for 12 h and GH responses to insulin stimulated hypoglycaemia (ITT) in 28 stunted boys with beta-thalassaemia major aged 15.2-17.4 years, who presented with pubertal failure (FP). Healthy non thalassaemia prepubertal boys (n = 10) aged 7.5-8.8 years, were studied as controls. All patients had normal responses to ITT with peak GH levels > or = 15 mU/l. Basal GH concentrations (mean +/- sem) (1.65 +/- 0.03 mU/l vs 2.58 +/- 0.27 mU/l; P < 0.05) and the stimulated GH responses (peak GH = 15.4 +/- 0.20 mU/l vs 21.08 +/- 0.78 mU/l; P < 0.001) were significantly lower in the patients with failed puberty than in the controls, indicating that the FP patients had diminished GH reserve and secretory capacity. Moreover, all the GH peak parameters including the maximum spontaneous concentrations (MX-GH) and the area under the GH curve (AUC) were significantly lower in the thalassaemic patients than in the controls (MX-GH = 5.2 +/- 0.21 mU/l vs 20.42 +/- 0.14 mU/l; P < 0.001; AUCb = 421.22 +/- 4.31 mU/l vs 712.20 +/- 3.42 mU/l; P < 0.001). These observations suggest that the thalassaemic patients had endogenous neurosecretory GH deficiency (GHND). Priming with sex steroid did not cause any improvement in the spontaneous or stimulated GH secretory patterns in thalassaemic patients. It was noteworthy that in neither the patients nor the control subjects, was there a significant correlation between the maximum stimulated and the MX-GH concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗