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Biomedical subjects

J L Lewis

Publications and source records attributed to J L Lewis.

At least 217 records · Page 12Linked to original sources
PubMed1987

Lesions of the middle cerebellar peduncle disrupt acquisition and retention of the rabbit's classically conditioned nictitating membrane response.

Rabbits were classically conditioned to emit a nictitating membrane response (NMR) to either a light or tone conditioned stimulus (CS) paired with an eye shock unconditioned stimulus (UCS). They then received lesions of the middle cerebellar peduncle (MCP) or served as unoperated controls. Following surgery, they were given separate presentations of tone, light, and vibratory CSs, each paired with the eye shock UCS. In this way, conditioned responses (CR) to the previously trained light or tone served as a test of retention, whereas CRs to the remaining two conditioned stimuli (tone and vibratory or light and vibratory) served as a test of acquisition. The results of the study revealed that rabbits with complete lesions of the MCP showed disrupted acquisition and retention of the conditioned NMR to all stimuli, rabbits with partial MCP lesions also showed disrupted acquisition and retention to all CSs, but to a lesser degree, and animals with lesions that missed the MCP and unoperated controls both showed normal acquisition and retention of the conditioned NMR. These data are consistent with the view that the cerebellum is an essential part of the circuit for classical conditioning of the NM response and that information about CSs in the auditory, visual, and tactile modalities reach the cerebellum by way of the MCP.

Afferent Pathways↗
PubMed1987

Enalapril and hydrochlorothiazide as antihypertensive agents in the elderly.

This randomized, double blind study compared the antihypertensive effects of enalapril to hydrochlorothiazide (HCTZ) in the elderly. One hundred seventy-four patients with diastolic blood pressures (DBP) of 90-120 mm Hg or isolated systolic hypertension (ISH) (systolic BP greater than 160 mm Hg and diastolic BP less than 90 mm Hg) were studied. After four weeks of placebo, patients received either enalapril 10 mg or HCTZ 12.5 mg once daily. If the BP was uncontrolled (DBP greater than 85 mm Hg or SBP greater than 140 mm Hg) after 4 weeks, the dose was doubled. At 8 weeks, if necessary, the other drug could be added at the lower dose, then doubled 4 weeks later. Two-thirds of the patients had essential hypertension (EH), the rest ISH; 68% were male and 80% Caucasian. The baseline BPs were 167/94 mm Hg in both groups, at 8 weeks the mean BPs were 148/85 mm Hg in both groups (p less than or equal to 0.01), and at the end of the study the BPs with enalapril were 144/83 mm Hg and with HCTZ they were 145/83 mm Hg (p less than or equal to 0.01). The Caucasians showed greater BP falls on enalapril than HCTZ after 4 weeks (p less than or equal to 0.05). The SBP falls for the ISH (-22 mm Hg) and EH (-23 mm Hg) groups were similar at the end of the study. Both drugs were generally well tolerated. Laboratory adverse experiences (AEs) were 9% more common in the HCTZ patients (n.s.). Enalapril and HCTZ both seem to be effective antihypertensive agents in the elderly.

Aged↗
PubMed1987

Cracks emanating from a fluid filled void loaded in compression: application to the bone-implant interface.

Loosening of orthopedic implants is believed to be caused, in part, by fracture at the bone-cement interface. This loosening occurs even in regions where the interfacial load is primarily compressive. A model is developed whereby cracks can radiate from an elliptical fluid filled void. The incompressible fluid is allowed to penetrate into the cracks when the system is loaded compressively. The mode I stress intensity factor is calculated to test the feasibility of crack growth, and a numerical scheme which uses piecewise quadratic polynomials is used to solve the resulting singular integral equations. The results show the combinations of parameters for which cracks are likely to grow.

Biomechanical Phenomena↗
PubMed1987

Mercury poisoning after disc-battery ingestion.

A case is described of a 2-year-old girl who swallowed an alkaline disc battery containing mercuric oxide. Two days after ingestion it disintegrated in the stomach necessitating laparotomy to remove the battery casing and most of its contents. Postoperatively her blood mercury concentration rose to 340 micrograms/l and subsequently she developed small bowel obstruction due to adhesions. She was treated with dimercaprol but blood mercury concentrations did not fall until after a second laparotomy to relieve the obstruction and to remove residual mercury salts from the colon. The corrosive effects of swallowed disc batteries are well documented. The maximum blood concentration of mercury reported in this case is 17 times the 'acceptable level of mercury in the blood' and nearly double the highest level recorded previously after disc-battery ingestion. A policy for management of swallowed batteries is suggested.

Child, Preschool↗
PubMed1987

Clear-cell adenocarcinoma of the lower genital tract: Memorial Hospital 1974-1984.

Seventeen previously unreported cases of clear-cell adenocarcinoma originating in the vagina (13) and cervix (four) are presented. The mean age of the patients was 23.6 years. Four patients with cervical tumors and four patients with vaginal tumors underwent radical hysterectomy, bilateral pelvic lymphadenectomy, and partial vaginectomy. A total vaginectomy, with replacement of the excised vagina with a split-thickness skin graft or a segment of sigmoid colon, was added to the above procedure in five patients with vaginal cancer. In four patients, definitive treatment was radiation. All of the patients in the present series are without evidence of disease, with follow-up ranging from 21 months to more than ten years.

Adenocarcinoma↗
PubMed1986

Prognostic factors in adenocarcinoma of the uterine cervix.

A group of 136 female patients with adenocarcinoma of the uterine cervix, treated at Memorial Sloan-Kettering Cancer Center between 1949 and 1981, with slides available for review, formed the basis for this study. They ranged in age from 10 to 91 years. Most (73%) had abnormal bleeding, either alone or in combination with other symptoms; 15% were asymptomatic. Eighty percent had a visible abnormality, most commonly an exophytic mass. Clinical stages were: 0 (3%), IB (61%), IIA (14%), IIB (10%), III (4%). There were four major histologic subtypes: mucinous (47%), endometrioid (24%), adenosquamous (15%), and clear cell (9%) carcinoma. Of the many clinicopathologic variables evaluated for prognosis, the most significant was stage of disease (P less than 0.0001). Those with Stage IB disease had a survival probability of 76% at 5 years compared with 49% for those with Stage IIA and 34% with Stage IIB. The endometrioid pattern was associated with a more favorable prognosis than any other histologic subtype (P = 0.02). The presence of lymphatic tumor emboli and/or metastatic carcinoma in any lymph node group was associated with a less favorable prognosis for patients with Stage IB and IIA disease (P less than 0.0001).

Adenocarcinoma↗
PubMed1986

A review of second-look laparotomy for ovarian cancer.

One hundred twenty-seven patients underwent second-look laparotomies from July 1969 to June 1982. To be included in this report they must have met the following criteria: a documented ovarian neoplasm; previous surgery; adequate chemotherapy for cessation if no disease was found; and no X-ray, chemical, or clinical evidence of disease including an exam under anesthesia. Forty-one percent had residual disease at second-look laparotomy. The original stage and the percentage of tumor debulked at initial surgery were inversely related to the likelihood of finding residual disease. Age, histologic type and grade, and type of chemotherapy did not show a significant relationship with the likelihood of disease persisting. Recurrent tumor was subsequently detected in 16% of patients who had been found to be free of disease at second-look laparotomy. Of thirty stage III and IV patients treated with combinations containing cis-platinum, 10 (33%) had recurrences. This rate of recurrence was significantly greater than the 17.6% recurrence rate in 17 patients with Stage III and IV disease whose chemotherapy consisted of single alkylating agents or with combinations without cis-platinum. Twenty patients underwent a third-look laparotomy after completion of additional chemotherapy. Nine were found to have no residual disease. Two of the nine (22%) subsequently had recurrence of disease. Three of the eleven patients with persistent disease at the time of a third-look laparotomy underwent a fourth-look laparotomy. All were found free of disease and none have recurred. Six (55%) of those with persistent disease at the third-look laparotomy have died despite continued therapy. The ability to successfully treat some patients with persistent disease continues to be a justification for the use of a second-look laparotomy. However, the high rate of recurrence after cessation of treatment following the finding of no residual disease raises the question of whether it is appropriate to discontinue all therapy at this time.

Alkylating Agents↗
PubMed1986

Diagnostic conization of the cervix: review of 460 consecutive cases.

During a five-year period, 460 patients underwent cervical conization on the Gynecology Service at Memorial Hospital. The pertinent medical history of the 393 patients was reviewed as it related to the diagnosis of cervical intraepithelial neoplasia. All patients had repeat Papanicolaou smears and 94.4% had complete colposcopic examination using standard colposcopic procedures, endocervical curettage, and directed biopsies. For the purpose of this review, patients were separated into seven groups according to the primary and most significant indication for conization. The indications for the procedure and the histopathologic findings are discussed for each category. The usefulness of conization in the authors' institution varied according to the indication for which it was carried out. In this series of 393 patients, 18 patients (4.7%) initially diagnosed to have only intraepithelial disease, were found to have invasive carcinoma.

Adenocarcinoma↗
PubMed1986

Characteristics of synergic relations during isometric contractions of human elbow muscles.

We studied the patterns of EMG activity in elbow muscles in three normal human subjects. The myoelectrical activity of 7-10 muscles that act across the human elbow joint was simultaneously recorded with intramuscular electrodes during isometric joint torques exerted over a range of directions. These directions included flexion, extension, varus (internal humeral rotation), valgus (external humeral rotation), and several intermediate directions. The forces developed at the wrist covered a range of 360 degrees, all orthogonal to the long axis of the forearm. The levels of EMG activity were observed to increase with increasing joint torque in an approximately linear manner. All muscles were active for ranges less than 360 degrees and most were active for less than 180 degrees. The EMG activity was observed to vary in a systematic manner with changes in torque direction and, when examined over the full angular range at a variety of torque levels, is simply scaled with increasing torque magnitude. There were no torque directions or torque magnitudes for which a single muscle was observed to be active alone. In all cases, joint torque appeared to be produced by a combination of muscles. The direction for which the EMG of a muscle reached a maximum value was observed to correspond to the direction of greatest mechanical advantage as predicted by a simple mechanical model of the elbow and relevant muscles. Muscles were relatively inactive during varus torques. This implies that the muscles were not acting to stabilize the joint in this direction and could have been allowing ligaments to carry the load. Plots of EMG activity in one muscle against EMG activity in another demonstrate some instances of pure synergies, but patterns of coactivation for most muscles are more complicated and vary with torque direction. The complexity of these patterns raises the possibility that synergies are determined by the task and may have no independent existence. Activity in two heads of triceps brachii (medial head--a single-joint muscle and long head--a two-joint muscle) covaried closely for a range of torque magnitudes and directions, though shoulder torque and hence the forces experienced by the long head of the triceps undoubtedly varied. The similarity of activation patterns indicates that elbow torque was the principal determining factor. The origins of muscle synergies are discussed. It is suggested that they are best understood on the basis of a model which encodes limb torque in premotor neurons.(ABSTRACT TRUNCATED AT 400 WORDS)

Elbow Joint↗
PubMed1985

Risk of localized and widespread endometrial cancer in relation to recent and discontinued use of conjugated estrogens.

In a case-control study of the risk of adenocarcinoma of the endometrium in relation to conjugated-estrogen use, we found that 31 per cent of 425 women with endometrial cancer and 15 per cent of 792 controls reported having used conjugated estrogens; the rate-ratio estimate was 3.5 with a 95 per cent confidence interval of 2.6 to 4.7. For use that lasted at least one year, the rate-ratio estimate for Stage I or II cancer was 5.2 (95 per cent confidence interval, 3.7 to 7.2), and for Stages III and IV combined it was 3.1 (1.5 to 6.4). Among women who had used estrogen for at least one year and then discontinued it, the risk of endometrial cancer remained significantly elevated even after estrogen-free intervals of over 10 years. The findings suggest that long-term use of conjugated estrogen increases the risk of both localized and widespread endometrial cancer. The data also suggest that women who have taken conjugated estrogen for one or more years remain at increased risk for at least 10 years after they discontinue use. Such women should be considered for long-term gynecologic surveillance.

Adenocarcinoma↗
PubMed1985

Cell surface antigens of human trophoblast and choriocarcinoma defined by monoclonal antibodies.

Six distinct cell surface antigens of human trophoblast and choriocarcinoma were defined with MAbs. The distribution of the antigens was determined by MHA assays on 150 tumor cell lines and normal cell cultures and by immunofluorescence tests with a wide range of normal adult and fetal tissues and a tumor panel. Antigen LK26 is expressed on all cultured choriocarcinoma, teratocarcinoma and renal cancer lines but is absent from most cell lines derived from other tumor types and from cultures of normal kidney epithelium and fibroblasts. LK26 expression in normal tissues is restricted to the trophoblast. No other adult or fetal tissue was found to express the antigen, but choriocarcinoma and teratocarcinoma tissues were LK26+. SV19 is expressed on cultured choriocarcinomas and teratocarcinomas and on subsets of breast and colon cancer lines, but not on 120 additional cultures tested. In tissues, SV19 is detected in normal placenta, mammary gland and colon epithelium as well as in tumors of breast, colon and lung. Two antibodies, AbSV63 and AbK8, react with PLAP and AbSV63 also reacts with the intestinal form of the enzyme. AbLK24 defines a heat-stable determinant present on choriocarcinoma and breast cancer cell lines but absent from most other cultured cells. It is expressed on a small range of normal and malignant epithelial tissues, including normal trophoblast, normal breast epithelium and urothelium and tumors derived from these tissues. One antigen, K66, showed a wide distribution on cultured epithelial cells but was not found in any normal or malignant tissue. Finally, S4, a previously described marker of normal and malignant kidney epithelial cells, was also expressed on the choriocarcinoma cell lines. Four of the antigens are glycoproteins that could be immunoprecipitated from radiolabelled extracts of choriocarcinoma cells: LK26 (Mr 35,000), SV19 (Mr 40,000), PLAP (Mr 68,000) and S4 (Mr 160,000). The highly restricted distribution of LK26, SV19, S4, and PLAP in normal tissues and their expression in tumors make these antigens potential diagnostic markers of gestational choriocarcinoma and germ-cell tumors and, possibly, targets for immunotherapy.

Alkaline Phosphatase↗
PubMed1985

Workshop on the bone-joint implant interface.

A workshop on the bone-implant interface, as related to loosening of total joint implants, was held in Chicago on September 14-16, 1983. More than 60 orthopaedic clinicians and researchers and basic connective tissue biologists met to review problems and potential solutions to joint implant loosening. The following is a synopsis of the presentations and discussions.

Bone Cements↗
PubMed1985

Late recurrence of gestational trophoblastic disease.

Persistent normal human chorionic gonadotrophin (hCG) levels for a period of 1 year after treatment is considered to be a reliable criterion of complete and sustained remission in patients with gestational trophoblastic disease. This is because such patients rarely require further therapy. Two patients are presented who developed recurrent disease after being in remission for 18 and 21 months. One of the patients initially had metastatic disease in the lungs; the other had tumor in the lungs and brain. Both of the patients have remained clinically free of disease after retreatment; one patient for 31 months and the other patient for more than 4 years. The management of the patients is presented with an emphasis on the requirement for long-term surveillance. Possible mechanisms to account for the reactivation of disease after a prolonged latency period are considered.

Adult↗
PubMed1985

Immunopathologic analysis of a panel of mouse monoclonal antibodies reacting with human ovarian carcinomas and other human tumors.

The reactivity of a panel of five mouse monoclonal antibodies (mAb) produced to human ovarian and endometrial cancer cell lines was analyzed on frozen sections of normal adult and fetal tissues and on tumor sections using immunofluorescence and immunoperoxidase procedures. mAb MH99 was reactive with almost all types of epithelial cells and stained all epithelial tumors examined. mAb MH94 reacted mainly with secretory epithelia and was unreactive with the epithelial cell layer of normal ovaries. In contrast, approximately 50% of epithelial ovarian tumors and the lining cells of inclusion cysts were positive. mAb MF61 was positive only on the endometrium and noncellular follicular secretions or colloid of the thyroid among normal tissues examined. A subset of ovarian tumors was positive with this antibody. mAb MF116 gave no reactivity with normal tissues within the sensitivity of the assay. MF116 was expressed on a proportion (44%) of ovarian carcinomas of various histological types. These antibodies provide an initial panel for the immunohistological analysis of ovarian cancer.

Animals↗
PubMed1985

A model of tension and compression cracks with cohesive zone at a bone-cement interface.

This paper gives an insight about compression and tension cracks as encountered at a bone-cement interface. Within the context of continuum theory of fracture, an analytical solution is presented for the problem of a bimaterial interface edge crack under uniaxial tension or compression, assuming no tangential slip along the crack faces since cement pedicles penetrate into the cancellous bone several millimeters. Also essential to the solution are cohesive zone effects that account for a strengthening mechanism over the crack faces. The solution provides a methodological framework for quantifying the influence of the cohesive zone on the magnitude of the stress singularity. Mode I crack tip stress intensity factors are calculated at different stages of the loading and unloading phases under uniaxial tension or compression. Finally, an inelastic mechanism is presented that gives theoretical support to explain the formation of interfacial compression cracks, a phenomenon that was not previously appreciated and that arises from the rigid cement being forced into the more compliant cancellous bone.

Biomechanical Phenomena↗