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Biomedical subjects

M Kahn

Publications and source records attributed to M Kahn.

At least 109 records · Page 6Linked to original sources
PubMed1984

Ligand inhibition studies on the role of Fc receptors in antibody-dependent cell-mediated cytotoxicity.

Subjection of human peripheral blood lymphocytes to a temp shift from 4 to 37 degrees C resulted in a shedding of Fc receptors (termed FcRI) from 40-50% of FcR-positive cells followed by their re-expression within 4 hr; a phenomenon which had no effect on the cells' antibody-dependent killing capacity. Removal of lymphocytes having an immobile form of the Fc receptor resistant to the effects of the temp shift (termed FcRII), or removal of lymphocytes bearing both FcRI and FcRII, resulted in a similar amount of reduction in ADCC activity. This was attributed, therefore, to the loss of FcRII-positive cells. The influence of isolated (shedded) FcRI and Clq on ADCC activity was investigated. Soluble FcRI was shown to inhibit ADCC mediated through the immobile Fc receptors (FcRII), despite its lack of an ability to block EA rosette formation through these receptors. Clq also had a dose-dependent inhibitory effect on ADCC. These observations are consistent with earlier findings that FcRII possesses two active binding sites; and suggest that a prerequisite for killing in ADCC is the interaction of these with the C gamma 2 and C gamma 3 domains. The ability of synthetic peptides representative of human gamma 1-chain sequences to inhibit ADCC was determined, in an attempt to locate those sites within the IgG antibody Fc region involved in interaction with two FcR binding sites. Preliminary evidence was obtained to suggest that one of these is situated within the C gamma 2 domain, in the region of residues 274 (Lys)-294 (Glu).

Antibody-Dependent Cell Cytotoxicity↗
PubMed1984

Prolactin response to single and multiple doses of haloperidol in schizophrenic patients.

Serum prolactin and blood levels of haloperidol were assessed in schizophrenic patients after single acute oral doses of haloperidol and during fixed dose treatment with this medication. Although significant intrapatient correlations between prolactin responses to different doses of haloperidol were found, no statistically significant interpatient relationship between haloperidol dose and prolactin response emerged. There were statistically significant relationships between steady-state plasma and red cell haloperidol levels (measured by radioreceptor or gas liquid chromatographic techniques) and serum prolactin response, but not between blood levels after the acute haloperidol dose and prolactin response.

Adolescent↗
PubMed1984

Management of acute subdural hematomas from aneurysmal rupture.

Subdural hematomas (SDH) from ruptured aneurysm (RA) are much less common than intracerebral (ICH) hematomas or subarachnoid (SAH) or intraventricular hemorrhage (IVH). With computerized tomography, preoperative diagnosis is now made more often. The authors have collected 18 such cases from a review of 897 cases of RA admitted to eleven medical centers in 1980 and 1981. Nine (50%) of these patients died prior to discharge from hospital. Four (22%) had surgery and died postoperatively and 9 (50%) were operated upon and survived. Thirteen (72%) of the patients showed anisocoria, decreased consciousness and unilateral weakness prior to surgery. Eight (89%) of the fatalities had shown preoperative herniation as opposed to only 5 (56%) of the survivors. The overall incidence of delayed ischemia due to vasospasm was 11% (2 cases). Those who died had greater midline shift and larger SDH on the admission CT scan. Sixteen (89%) of these patients were female. Thirteen (72%) had ruptured aneurysms on the internal carotid artery. All of these hematomas were unilateral and uniformly hyperdense, and the convexity hematomas were crescentic in shape. Seventeen (94%) had evidence of blood in locations other than the subdural space. If the patient is potentially salvageable and has a midline shift, the SDH should probably be evacuated immediately and the aneurysm clipped at the same operation since the development of a tentorial herniation has such an adverse effect on outcome.

Acute Disease↗
PubMed1984

Biodegradation and aneurysm formation in umbilical vein grafts. Observations and a realistic strategy.

In a series of 756 glutaraldehyde-stabilized umbilical vein grafts implanted over a 7 1/2-year period, aneurysms were identified in seven cases. The earliest aneurysm was seen at 31 months after implantation and the remainder between 43 and 79 months after surgery. Corrective surgery was performed in five cases and succeeded in four. Although definite mechanisms have not been identified, mechanical fatigue, reversal of aldehyde crosslinks, and immunologic factors may be operative. The pathologic changes include: (1) actual dilation of both graft and mesh with or without intraluminal thrombus and, (2) maintenance of graft diameter with erosion of the umbilical vein and polyester mesh rupture leading to perigraft hematoma and false aneurysm formation. Microscopic examination and infrared spectral analysis confirmed the presence of host-contributed lipid in some specimens. Although this is a low incidence of aneurysm formation, umbilical vein grafts should be selected primarily for patients with limited life expectancy or for whom alternative materials with comparable or superior patency rates are not available or acceptable. Periodic angiography, particularly after 3 or 4 years, is recommended as a routine part of follow-up examinations. Improved graft materials and control of host environmental factors are potential means to reduce the noted degradation.

Aneurysm↗
PubMed1984

Atherosclerosis and cerebral ischemic attacks: intakes of cerebrography with xenon133 inhaled and platelet tests in the diagnosis, clinical and therapeutic monitoring; the preventive role of dipyridamole.

A study of patients to develop the significance of the role of the blood platelets in the recurrence of transient cerebral ischemic attacks in patients with cerebral atheromatous, develop the effectiveness of dipyridamole in the prophylactic therapeutic regimen. In the group treated with dipyridamole, a 76.3% clinical improvement was recorded (mean increases of 11.2 ml/min. and 11.4 ml/min. of the cerebral hemispheric flows), 15.8% of cases stabilized (mean increases of 1.7 ml/min. and 1.2 ml/min.) and 7.9% failures (mean decreases of 10.4 ml/min. and 14.3 ml/min.) of these same flows. The cerebrography with xenon133 inhaled as well as the platelet tests used, constitute unfailing means of diagnosing and monitoring the clinical development.

Adult↗
PubMed1984

Lysis of arterial clot by intravenous or intra-arterial administration of streptokinase.

Intra-arterial thrombolysis with streptokinase was studied in 38 patients. The indications were peripheral thromboembolism in nine patients (group 1), postreconstruction graft thrombosis in 26 patients (group 2) and renal artery thrombosis in three patients (group 3). The intra-arterial route was used for the first and third groups and in 16 of the second group. The intravenous route was used in the remaining ten patients. Lysis was achieved in all of the group 1 and 3 patients. The latter were also treated with percutaneous transluminal angioplasty after dissolution of thrombus of the renal artery. In group 2 patients, lysis was achieved in eight of 16 patients in whom lytic therapy was instituted within seven days of graft closure. There was no lysis in all ten patients in whom elapsed time was more than seven days. Postlytic angiographic visualization of etiologic mechanisms for thrombosis enabled subsequent successful correction in three of five patients in group 2. Attempts to correct graft failure by surgical treatment when lysis had failed were often unsuccessful (12 of 17). Lytic therapy is most effective for acute embolic occlusion and for thrombosis of less than seven days duration. Although there is no difference in drug efficacy by route of administration, a lesser number of complications (such as, fever and hematoma) occurred with intra-arterial infusion. The effectiveness of lysis is also directly related to the collateral circulation and runoff beyond the occlusion. Lysis is not indicated for severe acute ischemia if surgical treatment is an alternative or if it may cause distal embolism as with complete axillofemoral graft thrombosis. Lytic therapy is least effective for graft thrombosis with pre-existent poor runoff.

Aged↗
PubMed1983

Distal arteriovenous fistula as an adjunct to maintaining arterial and graft patency for limb salvage.

Sixty-one distal arteriovenous fistulas (dAVFs) were constructed as adjuncts to tibial and peroneal vascular reconstructive procedures in 58 patients threatened with imminent limb loss. Specific indications for dAVF construction were absent or deficient pedal arches, usually associated with small, calcareous crural vessels. Conventional bypasses had been previously performed in 35 patients. Cumulative graft patency rates were 56%, 39%, and 18% at 6, 12, and 24 months, respectively. For the same intervals, the figures were 56%, 52%, and 52% (P less than 0.001 at 24 months) for nonAVF reconstructions (n = 49). The corresponding cumulative limb salvage rates were 62%, 52%, and 40% for the dAVF group and 78%, 72%, and 72% for the nonAVF group (P less than 0.05 at 24 months). The perioperative mortality rate was 7% (four of 61). Twenty-four amputations were required, of which 16 were below the knee and six despite patent grafts. There was no significant morbidity attributable directly to the dAVF. Cardiac output showed no deviations from normal values. Primary causes of early failure were infection (n = 4), absence of satisfactory veins (n = 6), and inappropriate case selection (n = 7). Intimal hyperplasia led to dAVF closure and graft failure in 13 patients. This study shows that dAVFs can maintain graft patency by diversion of the overload on a high-resistance vascular bed and, secondarily, by augmentation of inflow. Immediate survival of the limb still depends on the arterial runoff, as retrograde venous flow caused by venous valvular incompetence is a delayed development. Adjunctive dAVF is justified in selected cases where conventional bypass failure has occurred or is predictable by increased pedal vascular resistance.

Adult↗
PubMed1983

[Discrete distal gangrene].

The authors present their statistical findings from 114 cases of discrete distal gangrene. They stress the importance of a rigorous methodology to detect mechanical causes from the thoracic outlet syndrome and immunological causes, predominantly scleroderma, especially in women. It is important not to overlook blood diseases nor those cases which are a presentation of underlying cancer. Finally, the iatrogenic cause is now well known. Treatment depends on the causes of this distal lesion. However, in cases of severe connective tissue disease, the use of plasmapheresis is beginning to give interesting results.

Adult↗
PubMed1982

Acute leukemia as a transformation after polycythemia vera.

The development of acute leukemia as a natural progression of polycythemia vera is very rare. We have described a patient who had acute leukemia within one month after the diagnosis of polycythemia vera, which was treated only with phlebotomy on three occasions. Chromosomal study in the leukemic phase showed no abnormality, and the terminal deoxynucleotidyl transferase was positive. There was an initial brief response to vincristine and prednisone before the patient's death.

Aged↗
PubMed1982

Influence of failed vascular bypass procedures on conversion of below-knee to above-knee amputation levels.

From 1975 to 1980, 79 major limb amputations were performed from a group of 552 lower extremity vascular reconstructions with glutaraldehyde-stabilized umbilical vein grafts. All amputations were performed in instances in which limb salvage had been the indication for the attempted bypass (n = 520)--an incidence of 15.2%. Twelve of 51 below-knee (BK) amputations were converted to above-knee (AK) levels (crude failure rate, 23.5%). The highest crude failure rate occurred after failed bypass to the popliteal artery (33.3%); the lowest occurred after failed tibial bypass (16.7%), and the peroneal arteries were intermediate (22.2%). In addition to these 12, 28 primary AK amputations were performed. Excluding nine cases judged to require AK amputations before the attempted vascular reconstruction, success/failure rates for the entire series and each of the reconstruction types were calculated. Success, defined as a healed BK stump, occurred least after failed popliteal bypass, 44.5%, compared to 71.4% and 53.8% for the tibial and peroneal groups, respectively. Thus, failure of a popliteal bypass was more apt to lead to an AK amputation (56.5%) than failure of a distal bypass. In fact, tibial bypass failure leading to an AK stump occurred at a frequency (28.6%) almost similar to that obtained by other investigators when no previous bypass had been performed. Comparative cumulative graft patency and limb salvage rate data confirm the value of reconstructive vascular surgery, particularly in the peroneal group where negativism with regard to its clinical usefulness persists. With improved case selectivity and surgical expertise, increasing limb salvage rates can be secured while minimizing the definite morbidity of conversion of BK to AK amputation with failed vascular bypass.

Aged↗
PubMed1981

The nucleotide sequence of IS5 from Escherichia coli.

A 3-kb fragment of Haemophilus haemolyticus DNA which carries the HhaII restriction (r) and modification (m) genes has been cloned into the PstI site of pBR322 (Mann et al., 1978). When propagated in Escherichia coli, it was observed that spontaneous insertions of IS5 inactivated the restriction gene, producing r- mutants at a frequency of 10(-6). Electron microscopy, restriction-site mapping and sequence analysis of two r- plasmids have demonstrated the presence of IS5 at a single target site in both possible orientations. The complete nucleotide sequence of IS5 has been determined. It is 1195 bp long and has inverted terminal repeats of 16 bp. The target site for IS5 in this plasmid is 5'-CTAG. Approx. ten copies of IS5 were found to be present at about the same locations on the E. coli chromosome in various K-12 strains, using Southern hybridization analysis.

Base Sequence↗
PubMed1981

Rheumatic diseases other than rheumatic fever.

A total of 101 cases of rheumatic diseases collected during a period of six months from a hospital population have been analysed. These did not include rheumatic fever. Paediatric age group up to age of 12 years was not included in the series. Rheumatoid arthritis has been found to be the commonest condition, constituting 60 cases. Cervical spondylosis was next in common (24 cases). Ankylosing spondylitis and osteoarthritis constituted nine and six cases respectively. Emphasis has been laid on the bizarre manifestation of cervical spondylosis. The study, in spite of limitations throws some light on the relative frequency of rheumatic diseases other than rheumatic fever in Bangladesh.

Adolescent↗
PubMed1981

Morphologic structure of the pedal arch and its relationship to patency of crural vascular reconstruction.

Pedal arch integrity can be determined morphologically and functionally. The former is accessible by contrast studies and intraoperative catheterization, the latter, by flow studies and observation of graft patency. The roengten image of an intact pedal arch corresponds to the anatomic plantar arch. Sixty-four arch studies obtained by adequate intraoperative arteriography were categorized as intact, deficient or inadequate or absent. Patency of crural reconstructions was obtained in 18 of 24 patients with intact arches as compared with 15 of 32, p<0.06, when the arch was deficient. Crural reconstruction in the face of an inadequate or absent arch resulted in predictable graft closure. Qualitative factors, that is, size, calcium and stenotic lesions, are integrally related to over-all graft performance even with intact arches. The deficient arch for tibial and peroneal reconstruction continues as a challenge to the vascular surgeon.

Angiography↗
PubMed1981

Tibial arteriovenous fistula: successful use for limb salvage.

Embolization of atheromatous material from abdominal aortic aneurysms to the distal arterial circuit is a well-recognized clinical entity causing the "blue toe syndrome." A case is presented in which this phenomenon resulted in obliteration of the pedal arch and thrombosis of the tibial arteries. As a result, forefoot gangrene, severe leg ischemia and anterior and posterior compartment syndromes occurred. Salvage of the extremity required an extraordinary approach with the construction of an arteriovenous fistula between the posterior tibial vessels. The literature on the use of therapeutic and adjunctive arteriovenous fistulas and their physiology is discussed.

Aortic Aneurysm↗