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Biomedical subjects

A D Schwartz

Publications and source records attributed to A D Schwartz.

At least 19 recordsLinked to original sources
PubMed1999

Do ryanodine receptors regulate transmitter release at the neuromuscular junction of rat?

It has been suggested that calcium that is stored in nerve terminals can be released via activation of ryanodine receptors and this source of calcium could serve to modulate evoked transmitter release. Calcium influx via voltage dependent calcium channels could lead to calcium induced calcium release via ryanodine receptors in neuronal tissue. This additional source of calcium could contribute to the total calcium that is available for transmitter release or it could result in having a negative feedback action on calcium influx and transmitter release. We examined the effect of blocking and activating the ryanodine receptors on quantal transmitter release at the rat neuromuscular junction. Intracellular recording techniques were used to monitor end-plate potentials and miniature end-plate potentials. The data supports the view that intracellular calcium released via ryanodine receptors suppresses calcium influx leading to depressed quantal release.

Animals↗
PubMed1996

Placental echolucencies: does their presence influence outcome following genetic amniocentesis?

Women undergoing genetic amniocentesis procedures were evaluated for the presence of ultrasonographic echolucencies within the placenta. Non-calcified sonolucencies < 4 to 5 cm were classified as subchorionic hematomas (SH). Of the 1,000 pregnancies evaluated, 153 (15%) pregnancies manifested SH prior to amniocentesis (study group). The indications for referral were similar in the study and control groups. There were 13 (1.3%) losses: 3 and 10 in the study and control groups, respectively, with no statistical difference in fetal losses between the groups: RR 1.52 (95% confidence interval 0.56-4.14; p = 0.32). Placental sonolucencies < 4 to 5 cm in diameter appear to be incidental ultrasound findings not associated with increased fetal loss following genetic amniocentesis. Complications following invasive prenatal diagnosis cannot be attributed to the presence of these common ultrasound findings.

Adult↗
PubMed1995

Factor XI deficiency in an Ashkenazi Jewish child, causing severe postoperative hemorrhage.

Although inherited coagulation factor deficiencies with negative bleeding histories are rare, cases such as the one presented herein may not be diagnosed at the time of surgery and may experience severe hemostatic problems postoperatively. It may be prudent to obtain an activated partial thromboplastin time preoperatively for all Ashkenazi Jews, including those with a negative history for a hemostatic disorder, because of the high incidence of factor XI deficiency in their population. Surgeons and anesthesiologists should be aware of the existence of this and other uncommon hemostatic disorders and their treatment when faced with serious, apparently unexplained postoperative hemorrhage.

Adenoidectomy↗
PubMed1993

Infection in major sickle hemoglobinopathies: should management strategies change?

Four children with major sickle hemoglobinopathies developed severe pneumococcal infection. Three had sickle cell hemoglobin C (Hb SC) disease and one had sickle cell anemia (Hb SS). In three instances, there was a fatal outcome. The authors' experience with these cases leads them to question whether any patient with a major sickle hemoglobinopathy should be excluded from receiving prophylactic penicillin or if outpatient management with long-acting cephalosporin treatment in the sickle cell patient with suspected sepsis is appropriate therapy.

Adolescent↗
PubMed1992

Thalassemia screening in Baltimore.

An education and screening program for beta-thalassemia was offered to members of the Greek and Italian communities in the Baltimore area to allow for educated decisions regarding childbearing. Similar programs have been effective in decreasing the incidence of beta-thalassemia major in other countries.

Baltimore↗
PubMed1991

Inflammatory pseudotumor of the retroperitoneum.

A child presenting with the findings of inflammatory disease was found to have a pseudotumor of the retroperitoneum. Following surgical removal, all signs of the systemic inflammatory process resolved. These rare, benign tumors of unknown etiology must not only be differentiated from locally invasive malignant lesions, but may present with findings suggesting a chronic inflammatory disorder.

Child, Preschool↗
PubMed1986

Gonadal failure following busulfan therapy in an adolescent girl.

A girl with Philadelphia chromosome-positive CML (Ph1-positive CML) was treated with busulfan from the age of 10 years 11 months to 16 years. Before treatment she had no evidence of pubertal development and no sexual development has occurred over the ensuing 5 years. Endocrine evaluation revealed that the child had ovarian failure. The pubescent female appears to be prone to develop gonadal failure with resultant lack of sexual development when treated with busulfan during this period in her life.

Adolescent↗
PubMed1985

Adjuvant chemotherapy for medulloblastoma.

The use of adjuvant chemotherapy for cerebellar medulloblastoma is controversial. Twenty-one children and adolescents were treated with adjuvant low-dose cyclophosphamide and vincristine following surgery and radiotherapy. With a mean observation period of 6 years, the disease-free survival is 81%.

Adolescent↗
PubMed1985

Neonatal screening and genetic counseling for sickle cell trait.

In a newborn screening program for abnormal hemoglobins, 91 infants were found to have hemoglobin AS or AC. Their parents were informed and offered genetic counseling, but only 35% accepted. We tested parents' knowledge of sickle disorders before and after the session. The tests were repeated when their babies were 4 to 8 months old; parents of babies with normal hemoglobin and those with sickle trait who had not been counseled were also tested at this time. Parents who received counseling showed an increase in knowledge and retained it until the second interview although 27% did not recall the original session. Uncounseled parents of "trait families" also had knowledge of the condition; in general, trait families knew more about the condition than normals' families. Newborn hemoglobin screening programs prove helpful for certain families but not necessarily for all who may be eligible.

Anemia, Sickle Cell↗
PubMed1985

Neuroblastoma.

Neuroblastoma originates in the adrenal medulla or anywhere in the body that sympathetic tissue normally is present. It may present with a variety of symptoms due to primary tumor, metastatic disease, or unusual signs and symptoms such as opsoclonus-myoclonus or severe diarrhea. Despite the fact that this neoplasm responds to a variety of therapeutic modalities, it remains one of the most frustrating and difficult childhood tumors to treat and cure.

Abdomen↗
PubMed1984

Positive gallium scan in the syndrome of opsoclonus-myoclonus treated with adrenocorticotropic hormone.

The syndrome of opsoclonus and myoclonus may be the first presenting symptom of neuroblastoma. The disorder is often controlled by treatment with adrenocorticotropic hormone (ACTH). A child with this disorder and treated with ACTH gel had abnormal uptake of 67Ga in both adrenal glands during studies to attempt to detect an occult neuroblastoma. Repeat 67Ga scans proved to be normal once the ACTH was discontinued and the patient was treated with prednisone. It is concluded that ACTH stimulation of normal adrenal tissue was responsible for these abnormal findings.

Adrenal Glands↗
PubMed1984

Cholelithiasis in patients with major sickle hemoglobinopathies.

Cholelithiasis is a common complication of homozygous sickle cell disease. The frequency of gallstones appearing in patients with heterozygous sickle hemoglobinopathies is unknown. We performed sonographic tests on 65 unselected patients with major sickle hemoglobinopathies. Cholelithiasis was found in 11 (26%) of the 42 patients with hemoglobin SS, in three (20%) of the 15 with Hb SC, and in one (12.5%) of the eight with Hb S-beta-thalassemia. There was a correlation between the presence of gallstones and increasing age. All patients with major sickle hemoglobinopathies are at risk for the development of biliary tract disease.

Adolescent↗
PubMed1982

Cat-scratch disease simulating malignant lymphoma.

A six-year-old girl with induration, swelling and discoloration of the lower eyelid, a temporal mass, preauricular adenopathy and enlarged parotid gland, underwent biopsy, She was initially diagnosed as having a malignant disorder of histiocytic origin. All lesions resolved without therapy. Further evaluation revealed that the child had oculoglandular cat-scratch disease. Cat-scratch disease should be added to the list of nonmalignant disorders which may simulate a malignant neoplasm in its clinical and histologic appearance. Recognition of this fact is important in order to avoid erroneous diagnosis, unnecessary procedures and hazardous therapy.

Cat-Scratch Disease↗
PubMed1981

The protection of small amounts of splenic tissue against intravenous pneumococcal challenge following subtotal splenectomy.

The asplenic state increases susceptibility to overwhelming bacterial infection. We studied the ability of small amounts of splenic tissue to protect against intravenous pneumococcal challenge following subtotal splenectomy in which approximately 75% of the spleen was removed. Animals that had undergone subtotal splenectomy were more resistant to challenge than were asplenic animals, but were not as resistant as were control animals. The small amount of residual splenic tissue confers some degree of protection against intravenous bacterial challenge.

Animals↗
PubMed1980

67Ga scintigraphy in granulocytic sarcoma.

Several granulocytic sarcomas (chloromas) developed in a patient with acute myelogenous leukemia while in hematologic remission. A positive diagnosis of the symptomatic lesion was made by means of open biopsy examination. The other lesions, which were unsuspected, were detected with a 67Ga-citrate scan. Subsequent 67Ga-citrate scans indicated a favorable response to treatment. The incidence and significance of silent granulocytic sarcomas in patients in hematologic remission is not known. Documentation of such lesions might prove valuable for diagnosing extramedullary relapse or for delivering intensive local therapy.

Adolescent↗
PubMed1980

Hematology of beta-thalassemia trait--age-related developmental aspects and intrafamilial correlations.

Beta-thalassemia trait is a frequent cause of microcytic anemia in Mediterranean children. Because striking age-related changes occur in hemoglobin and mean corpuscular volume during childhood, we assessed developmental hematologic characteristics of 132 patients less than or equal to 18 years of age with beta-thalassemia trait. Thirty-nine kindred were studied to examine intrafamilial correlations of hematologic abnormalities. Patients with beta-thalassemia trait demonstrated Hgb values about 2 gm/dl below normal standards, with a progressive rise with age paralleling normal trends. Thalassemic MCV values showed a far greater deviation from normal than Hgb levels. In contrast to normal developmental trends which show a sharp increase in the first five years of life, the MCV in thalassemia trait showed no age-related increase prior to adolescence. No age-related changes in hemoglobin A2 levels were noted. Kindred studies demonstrate a correlation of the degree of anemia, microcytosis, and elevated hemoglobin A2 levels in affected family members (r = 0.318 P < 0.004, r = 0.525 P < 0.001, r = 0.416 P < 0.0015, respectively). Our findings support the use of electronically determined MCV values as an initial screening procedure for children with beta-thalassemia trait. Values of < 70 fl prior to adolescence and < 75 fl during adolescence were present in nearly all thalassemic subjects. Intrafamilial correlations of Hgb, MCV, and hemoglobin A2 levels suggest that these characteristics are genetically determined.

Adolescent↗