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Biomedical subjects

L B Cohen

Publications and source records attributed to L B Cohen.

At least 55 records · Page 3Linked to original sources
PubMed1989

Transient esophageal obstruction after pneumatic dilation for achalasia.

We report what we believe to be the first patient in whom an esophagram immediately after a routine, uncomplicated pneumatic dilation revealed complete esophageal obstruction. With conservative medical therapy, the obstruction spontaneously resolved within 48 h, and total relief of dysphagia followed. Other reports have told of distal narrowing and slow emptying of the esophagus after pneumatic dilation. Most of these patients had a good therapeutic result. Hence, partial or complete esophageal obstruction after pneumatic dilation does not by itself represent evidence of treatment failure.

Barium Sulfate↗
PubMed1989

Optical recordings of the cortical response to whisker stimulation before and after the addition of an epileptogenic agent.

Optical recording methods using voltage-sensitive dyes were used to monitor activity in rat somatosensory cortex. We measured evoked signals in response to whisker stimulation before (control) and after the addition of the epileptogenic agent, bicuculline, and also detected spontaneous interictal events that occurred after bicuculline. Bicuculline led to an increase in the size, duration, cortical extent, and, surprisingly, the latency of the evoked responses. These enhanced evoked responses appeared to originate in the region of the control response and propagate outward. In contrast, the spontaneous signals appeared to originate at random cortical positions and had a more variable cortical extent. A transition signal measured just after the addition of bicuculline was larger than the control response but localized and rapid in time course. In most cases, there was a good correlation between the optical recordings and field potential measurements made with a ball electrode on the cortical surface, but there were occasional instances where the optical signal disappeared while the ball electrode signal was unchanged.

Animals↗
PubMed1989

Hundreds of neurons in the Aplysia abdominal ganglion are active during the gill-withdrawal reflex.

A combination of optical and electrode recording methods was used to obtain an overview of the neuron activity in the Aplysia abdominal ganglion in response to a light touch to the siphon skin. Spike activity was detected in up to 150 different neurons. Habituation and sensitization of the gill-withdrawal reflex was accompanied by large changes in the number of activated neurons. It is likely that these recordings are incomplete; the actual number of activated neurons is estimated to be about 300 in the acutely sensitized preparation. While we presume that not all 300 of these neurons are involved in the gill-withdrawal reflex, the number of neurons is so large that it may be difficult to determine the role of each activated neuron with presently available experimental tools.

Abdomen↗
PubMed1988

Optical monitoring of activity of many neurons in invertebrate ganglia during behaviors.

Optical methods for monitoring neuron activity were developed because these methods lend themselves to simultaneous multiple-site measurements. With the use of new voltage-sensitive dyes, the dye-related pharmacology and photodynamic damage appear to be relatively unimportant. Using multiple-site measurements made with a 124-element photodiode array, we estimated that approximately 30 of the 200 neurons present in the Navanax buccal ganglion make action potentials during feeding and that approximately 300 of the 1100 neurons present in the Aplysia abdominal ganglion are active during the gill-withdrawal reflex. The fact that a light mechanical touch to the siphon skin activated such a large number of neurons in the abdominal ganglion suggests that understanding the neuronal basis of the gill-withdrawal reflex and its behavioral plasticity may be forbiddingly difficult.

Animals↗
PubMed1988

Choriocarcinoma of the stomach: pathogenesis and clinical characteristics.

A patient with primary choriocarcinoma of the stomach is reported. Abdominal pain, weight loss, a palpable epigastric mass, and gastrointestinal bleeding are the most common clinical features of this germ cell tumor, making it difficult to distinguish choriocarcinoma from primary adenocarcinoma of the stomach. The unique aspect of this case is the mixed histology of this rare neoplasm, containing both adenomatous and embryonal carcinoma, in addition to the choriocarcinoma. We believe that this unusual tumor probably results from dedifferentiation of primary adenocarcinoma of the stomach. On the average, patients with this disease live less than 2 months from the time of diagnosis, and treatment with combination chemotherapy has not improved the survival.

Adenocarcinoma↗
PubMed1987

Odor-elicited activity monitored simultaneously from 124 regions of the salamander olfactory bulb using a voltage-sensitive dye.

In response to controlled, odor pulse stimulation of the olfactory receptor mucosa, large fluorescence signals were recorded simultaneously from 124 contiguous anatomical regions of the salamander olfactory bulb using the potentiometric probe RH 414. The amplitudes and waveforms of the signals varied systematically across the bulbar surface in apparent correspondence with the laminae of the bulbar neurons. Qualitatively similar results were obtained using both intact and decorporate preparations, although fluorescence signals obtained from intact animals were distorted by optical noise generated by mechanical disturbances related to the functioning cardiovascular system. These results indicate that multiple site optical recording can be used to obtain information about spatio-temporal patterning of bulbar electrical activity evoked by physiological odor stimulation of the receptor mucosa. This is the first demonstration that activity elicited by a single, one second odor stimulus at physiological concentration and duration can be measured across many elements in the olfactory bulb. Information provided by this approach, in combination with complementary data derived from 2-deoxyglucose and single unit studies, may yield a better understanding of how the vertebrate central nervous system extracts quality and concentration information from olfactory afferent input.

Action Potentials↗
PubMed1987

Optical recording of action potential propagation in demyelinated frog nerve.

Conduction in focally demyelinated frog nerves has been measured optically using potential-sensitive dyes. Absorption changes were recorded with an array of photodiodes positioned in the image plane of a microscope. Both the amplitude and conduction velocity of the optical signals decreased in the demyelinated region. Conduction was improved after exposure to the potassium channel blocking agent 4-aminopyridine.

Action Potentials↗
PubMed1987

Simultaneous optical recording of activity from many neurons during feeding in Navanax.

Optical methods for monitoring changes in membrane potential have been used to measure action potential activity in the buccal ganglion of an opisthobranch mollusc, Navanax inermis, while the animal was feeding. During feeding activity was detected in 10-15% of the approximately 200 neurons present in the ganglion. Control experiments carried out to determine the completeness of the optical recording showed that activity in at least 70% of the neurons could be detected. Thus, in certain invertebrate ganglia, it is possible to make a reasonably complete recording of the neuron activity responsible for generating relatively complex behaviors.

Animals↗
PubMed1986

Erythrocytic sedimentation rate as a measure of clinical activity in inflammatory bowel disease.

To assess the reliability of the erythrocytic sedimentation rate (ESR) as a measure of clinical activity in inflammatory bowel disease, we analyzed the correlations of ESR with a global assessment of clinical activity in 77 patients with varying extents of Crohn's disease and ulcerative colitis. Analysis of all 141 ESR determinations in all 77 patients showed a highly significant correlation between mean ESR and clinical activity score (r = 0.54, p less than 0.001). Analysis of 133 ESR determinations in these 77 patients when their disease activity was either mild, moderate, or severe showed some significant differences among certain disease categories. The highest mean ESRs were in patients with the most extensive colon involvement (Crohn's colitis 40.7 +/- 3.3, universal ulcerative colitis 31.0 +/- 3.9), whereas the lowest mean ESRs were in patients with the most limited disease (ulcerative proctitis and proctosigmoiditis 19.2 +/- 2.1). The rate of increase in ESR with progressively increasing clinical activity from mild to moderate was the same in all disease categories, with the exception of Crohn's disease limited to the small bowel (ileitis or jejunoileitis), in which the ESR was relatively unchanged in a small sample of patients. By the time clinical activity became severe, however, patients in all disease categories manifested similarly high ESRs, with the exception of ulcerative proctitis in which the ESR remained low in the single patient tested.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Sedimentation↗
PubMed1986

Simultaneous monitoring of activity of many neurons from invertebrate ganglia using a multielement detecting system.

The optical monitoring system has reached a level of sophistication where activity from a network of cells can be recorded in a minimally dissected behaving animal. We monitored activity in the buccal ganglion of the mollusk, Navanax inermis, during spontaneous expansions and during feeding. Deleterious pharmacological effects and photodynamic damage appear to be negligible in this preparation. The S/N is large enough to detect individual cell's activity without signal averaging, provided the cell soma is of sufficient size (greater than 20 microns). Indeed, if the S/N is large enough, it is possible to see graded or subthreshold potentials without the use of signal averaging. The activity of adjacent cells in the same focal plane could be detected as different cells by a single detector. In addition, cells that were out of focus but whose projected images fell on a detector also have their activity recorded as a significant signal by that detector. This finding suggested that recording from all the cells in a ganglion was possible. Preliminary evidence suggests that our recordings from Navanax buccal ganglia are at least 70% complete. It appears that the assumption that most of the cells' activity is being recorded is reasonable. A problem that could prevent correct identification of activity was the effect of light scattering on the signal. A signal dispersed owing to light scattering could give an erroneous estimate as to the cell size. However, the effect of light scattering on Navanax signals is small, and we feel that our estimates of cell size are accurate.

Animals↗
PubMed1986

Developmental change in infants' perception of correlations among attributes.

The perception of relational information such as the correlation or co-occurrence among features should play a central role in abilities ranging from the perception and recognition of a simple pattern or object to the formation of a category. 4 experiments were conducted to examine developmental change in 4-, 7-, and 10-month-old infants' perception of correlations among attributes. The results suggested a developmental progression in infants' processing of simple correlational information, ranging from the processing of independent featural information only at 4 months, the perception of relations among features of a single pattern at 7 months, to the abstraction of invariant relations from a category at 10 months.

Child Development↗
PubMed1986

Treatment of colonic polyps--practical considerations.

The adenomatous colonic polyp, a neoplastic lesion, is the precursor of most if not all carcinomas of the colon and rectum. Confirmatory evidence is derived from epidemiological, histological and clinical data demonstrating a close parallelism between adenomas and cancer of the colon. Based on current knowledge, all colonic polyps should be removed to prevent the development of colonic cancer. However, since the risk of malignancy within an adenoma is related to its size, histology and the degree of dysplasia, practical considerations dictate that all polyps 1 cm in diameter or larger should be removed upon their detection by barium enema or colonoscopy since such adenomas are the ones most likely to contain malignancy. The endoscopic removal of colon polyps can be efficiently and safely accomplished when established principles of colonoscopy and electrosurgery are followed. This technique requires the proper equipment, a skilled endoscopy assistant, and an experienced endoscopist with the ability to adeptly perform colonoscopy, an understanding of the basic concepts of electrocautery and knowledge of the various structural configurations of colonic polyps. Colonoscopic polypectomy will avoid the need for surgical resection in most instances. Management of the malignant colonic polyp remains controversial. The patient with a sessile or pseudo-pedunculated polyp containing invasive cancer should undergo colonic resection. Surgery is not necessary for the majority of patients whose pedunculated adenomas contain invasive cancer, unless the malignancy is poorly differentiated, the cancer invades lymphatics or vascular channels, or tumour is seen at or near the resection margin. Surveillance colonoscopy after endoscopic polypectomy should be performed in most instances within one year to look for recurrent tumour, missed polyps or a metachronous adenoma. Subsequently, colonoscopy should be performed every two years in patients with multiple index polyps, and every three years after removal of a single index adenoma.

Adenoma↗
PubMed1985

The clinical effectiveness and safety of chronic plasmapheresis in patients with primary biliary cirrhosis.

Primary biliary cirrhosis (PBC) is a chronic nonsuppurative, destructive cholangitis, whose etiology is unknown. Morbidity arises early from pruritus and later from hypercholesterolemia with xanthoma formation. Therapy is supportive and directed at the complications of cholestasis. Plasmapheresis has been reported to benefit patients with hyperlipidemia and PBC; thus a pilot study of plasmapheresis utilizing the Haemonetics Model 30 with replacement by albumin and saline was conducted. Five patients (four female and one male) with a mean age of 43 (range 29-58) and a mean duration of illness of 9.5 years (range 6-21) with marked jaundice, xanthomas, xanthelasma, hepatomegaly, fatigability, anorexia, and pruritus, as well as mild nausea were studied. Peripheral neuropathy was present in two patients. Two patients had splenomegaly. Two patients had an associated Sjogren syndrome. All patients had high serum bilirubin, alkaline phosphatase, and cholesterol levels and mild elevations in aspartate amino transferase and alanine amino transferase activities. Immune complexes measured in four patients were present. Antimitochondrial antibody titers were significant in all patients. Patients underwent a mean of 63 plasmapheresis procedures over a mean of 112 weeks removing a mean of 94.7 liters of plasma. No serious toxicity was seen. All patients showed a reduction in pruritus, xanthomas, xanthelasmas, and serum cholesterol values. The two patients who had evidence of Sjogren syndrome noted subjective improvement. All patients who had fatigue, anorexia and nausea also noted moderate improvement. There was no change in hepatomegaly or splenomegaly in patients demonstrating such organomegaly. Liver function did not change significantly. Overall, four patients had improvement in their condition and one patient achieved stability.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1985

Esophageal motility and symptoms after endoscopic injection sclerotherapy.

Endoscopic injection sclerotherapy is known to cause a variety of motility abnormalities, but the correlation between these changes and symptomatology has not been clearly defined. To assess the effects of endoscopic sclerosis of varices on esophageal function and symptoms, we prospectively studied esophageal motility in 25 patients undergoing sclerotherapy (group I). Thirteen patients underwent studies before and after sclerosis, and 12 patients were studied after completion of therapy. Acid clearance was studied in five patients (group I). Twenty-four of the 25 patients (group I) completed a course of sclerosis without the development of persistent dysphagia. We found that endoscopic sclerotherapy did not significantly alter the velocity of peristalsis or lower esophageal sphincter pressure, amplitude of contraction, or the duration of contraction. Acid clearance was diminished in three of five patients. Four patients who developed an esophageal stricture following sclerotherapy were studied manometrically (group II). Three of these four patients had a manometric pattern characterized by repetitive, nonperistaltic contractions, and all four patients experienced dysphagia which was relieved by bougienage. We conclude that esophageal motility is generally well preserved following endoscopic injection sclerotherapy and does not result in a long-lasting disturbance of swallowing. Dysphagia and disordered esophageal motility do occur after sclerotherapy when a sufficient fibrotic response has resulted in an esophageal stricture.

Esophageal Stenosis↗
PubMed1985

Charge-shift probes of membrane potential. Characterization of aminostyrylpyridinium dyes on the squid giant axon.

The characteristics of transmittance and fluorescence changes of 4-(p-aminostyryl)-1-pyridinium dyes in response to voltage-clamp pulses on the squid giant axon were examined. A zwitterionic styryl dye displays transmittance and excitation spectra on the voltage-clamped squid axon with shapes similar to those previously measured on a model membrane system and consistent with a postulated electrochromic mechanism. The speed of the transmittance response is faster than 1.2 microseconds. The size of the fluorescence change is a factor of 40 lower than on the model membrane; this diminution can be rationalized in terms of the background fluorescence from Schwann cells and the nonoptimal geometric arrangement of the axon membrane. When the emission spectrum is dissected from the excitation response, a nonelectrochromic component is found. This component might result from molecular motion during the excited state lifetime. A positively charged dye permeates the axon membrane and displays complex response waveforms dependent on the method of application and the axon holding potential. This contrasts markedly with model membrane results where the behavior of the cationic and zwitterionic dyes were indistinguishable.

Animals↗